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  • 1.
    Brandau, Benedikt
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling. JENOPTIK Optical Systems GmbH, System Development Advanced Manufacturing, Göschwitzerstraße 25, 07745 Jena, Germany.
    Brueckner, Frank
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling. Fraunhofer Institute for Material and Beam Technology IWS, Winterbergstraße 28, 01277 Dresden, Germany.
    Kaplan, Alexander F. H.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Absorbance determination of a powder bed by high resolution coaxial multispectral imaging in laser powder bed fusion2024Inngår i: Optics and Laser Technology, ISSN 0030-3992, E-ISSN 1879-2545, Vol. 168, artikkel-id 109780Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This study presents an approach for in-situ monitoring of laser powder bed fusion. Using standard laser optics, coaxial high-resolution multispectral images of powder beds are acquired in a pre-objective scanning configuration. A continuous overview image of the entire 114 × 114 mm powder bed can be generated, detecting objects down to 20 µm in diameter with a maximum offset of 22–49 µm. Multispectral information is obtained by capturing images at 6 different wavelengths from 405 nm to 850 nm. This allows in-line determination of the absorbance of the powder bed with a maximum deviation of 2.5% compared to the absorbance spectra of established methods. For the qualification of this method, ray tracing simulations on powder surfaces and tests with 20 different powders have been carried out. These included different particle sizes, aged and oxidized powders.

    Fulltekst (pdf)
    fulltext
  • 2.
    Brandau, Benedikt
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling. JENOPTIK Optical Systems GmbH, System Development Advanced Manufacturing, Göschwitzerstraße 25, 07745 Jena, Germany.
    Brückner, Frank
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling. Fraunhofer Institute for Material and Beam Technology IWS, Winterbergstraße 28, 01277 Dresden, Germany.
    Kaplan, Alexander
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Proof-of-concept of an absorbance determination of a powder bed by high resolution coaxial multispectral imaging in laser material processingInngår i: Additive Manufacturing, ISSN 2214-8604, E-ISSN 2214-7810Artikkel i tidsskrift (Annet vitenskapelig)
    Abstract [en]

    Imaging techniques are very popular for process monitoring in laser material processing due to their high information content. At the same time, coaxial systems focused by passive laser optics still present a major challenge, because most laser optics cause imaging errors for the monitoring channel. In this paper, the design, methodology and procedure are shown to be able to acquire coaxial image data by standard laser components, which is demonstrated by components for a laser powder bed fusion system and their use on a powder bed. The focus is on the correction of the image data to produce a high-resolution, geometrically accurate and gap-free overview image of the entire processing area. For this purpose, optical simulations of the system are performed to detect aberrations, distortions and chromatic errors and to correct them by hardware elements or in software post-processing. Over the entire 114 mm by 114 mm working area, objects can be captured geometrically accurate with a maximum deviation of 22 μm - 49 μm, depending on the detection wavelength. By capturing images atPaper C: Coaxial multispectral imaging Benedikt Brandau148wavelengths of 405 nm, 450 nm, 520 nm, 580 nm, 625 nm and 850 nm, multispectral information is gained over the entire working area. In addition, an absorbance of the powder bed is derived from the images. To qualify this methodology, tests are performed on 20 different powders. These include different particle sizes, aged and oxidized powders of different metals. The ability to determine absorbance is simulated by ray tracing powder surfaces. This allows the determination of in-line absorbances from the powder bed with a maximum deviation of 2.5 % compared to absorbance spectra of established methods. The origins of component defects such as foreign particles, powder oxidation, spatter and uncoated areas were able to be identified down to a diameter of 20 μm.

  • 3.
    Brandau, Benedikt
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling. JENOPTIK Optical Systems GmbH, System Development Advanced Manufacturing, Göschwitzerstraße 25, 07745 Jena, Germany.
    Da Silva, Adrien
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Wilsnack, Christoph
    Fraunhofer, Institute for Material and Beam Technology IWS, Winterbergstraße 28, 01277 Dresden, Germany.
    Brueckner, Frank
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling. Fraunhofer, Institute for Material and Beam Technology IWS, Winterbergstraße 28, 01277 Dresden, Germany.
    Kaplan, Alexander F.H.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Absorbance study of powder conditions for laser additive manufacturing2022Inngår i: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 216, artikkel-id 110591Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Absorbance is often used for simulations or validation of process parameters for powder-based laser materials processing. In this work, the absorbance of 39 metal powders for additive manufacturing is determined at 20 laser wavelengths. Different grain sizes and aging states for: steels, aluminum alloys, titanium alloys, Nitinol, high entropy alloy, chromium, copper, brass and iron ore were analyzed. For this purpose, the absorbance spectrum of the powders was determined via a dual-beam spectrometer in the range of λ = 330 - 1560 nm. At the laser wavelengths of λ = 450 nm, 633 nm and 650 nm, the absorbance averaged over all materials was found to increase by a factor of 2.4 up to 3.3 compared to the usual wavelength of λ = 1070 nm, with minimal variations in absorbance between materials. In the investigation of the aged or used powders, a loss of absorbance was detectable. Almost no changes from the point of view of processing aged and new AlSi10Mg powders, is expected for laser sources with λ = 450 nm. The resulting measurements provide a good basis for process parameters for a variety of laser wavelengths and materials, as well as a data set for improved absorbance simulations.

    Fulltekst (pdf)
    fulltext
  • 4.
    Brandau, Benedikt
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling. JENOPTIK Optical Systems GmbH, System Development Advanced Manufacturing, Göschwitzerstraße 25, 07745 Jena, Germany.
    Mai, Torsten
    JENOPTIK Optical Systems GmbH, System Development Advanced Manufacturing, Göschwitzerstraße 25, 07745 Jena, Germany.
    Brueckner, Frank
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling. Fraunhofer Institute for Material and Beam Technology IWS, Winterbergstraße 28, 01277 Dresden, Germany.
    Kaplan, Alexander F. H.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Angular dependence of coaxial and quasi-coaxial monitoring systems for process radiation analysis in laser materials processing2022Inngår i: Optics and lasers in engineering, ISSN 0143-8166, E-ISSN 1873-0302, Vol. 155, artikkel-id 107050Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Process monitoring is becoming increasingly important in laser-based manufacturing and is of particular importance in the field of additive manufacturing [e.g. Laser Powder Bed Fusion (LPBF)]. Process monitoring enables a reduction of production costs and a lower time-to-market. Furthermore, the data can be used to create a digital twin of the workpiece. There are already many established processing head-integrated monitoring systems for such applications as the multispectral analysis of process radiation. However, the monitoring of complex signals in systems with F-Theta scanner lenses is very challenging and requires specially adapted optics or measuring sensors.

    In this paper a potential arrangement for spectroscopy-based process monitoring in pre-objective scanning is presented. The process radiation was monitored using a coaxial and a quasi-coaxial observation system. The measurements were carried out on both a solid and a powder coated sample of 2.4668 (Inconel 718) to show the potential use of these systems in laser-based additive manufacturing. In order to obtain comprehensive data about the process signal, the process zone was analyzed at different angles of incidence (AOI) of the laser using a high-speed camera (HSI) and a spectrometer. The connection between the HSI and the spectral measurements is discussed. The ionization of the material and the formation of a plasma was observed and found to lose intensity as the angle of incidence increases. A model of the system that demonstrates the intensity of the emitted radiation of the plasma was created. It enables the measured values to be corrected. The corrected measurement data can be used to detect impurities or a non-ideal energy input across the entire processing field, which is a move towards robust process monitoring.

    Fulltekst (pdf)
    fulltext
  • 5.
    Brueckner, Frank
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling. Fraunhofer Institute for Material and Beam Technology IWS Dresden.
    Riede, Mirko
    Fraunhofer Institute for Material and Beam Technology IWS Dresden.
    Mueller, Michael
    Fraunhofer Institute for Material and Beam Technology IWS Dresden.
    Marquardt, Franz
    Fraunhofer Institute for Material and Beam Technology IWS Dresden; Technische Universität Dresden.
    Knoll, Matthias
    Fraunhofer Institute for Material and Beam Technology IWS Dresden.
    Willner, Robin
    Fraunhofer Institute for Material and Beam Technology IWS Dresden; Technische Universität Dresden.
    Seidel, André
    Fraunhofer Institute for Material and Beam Technology IWS Dresden; Technische Universität Dresden.
    Lopéz, Elena
    Fraunhofer Institute for Material and Beam Technology IWS Dresden.
    Leyens, Christoph
    Fraunhofer Institute for Material and Beam Technology IWS Dresden; Technische Universität Dresden.
    Beyer, Eckhard
    Fraunhofer Institute for Material and Beam Technology IWS Dresden; Technische Universität Dresden.
    Fabrication of metallic multi-material components using Laser Metal Deposition2017Inngår i: Solid Freeform Fabrication 2017: Proceedings of the 28th Annual International Solid Freeform Fabrication Symposium – An Additive Manufacturing Conference, The University of Texas at Austin , 2017, s. 2530-2538Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    Meanwhile, Laser Metal Deposition (LMD) is a well-known Additive Manufacturing technology used in various industrial branches as energy, tooling or aerospace. It can be used for the fabrication of new components but also repair applications. So far, volume build-ups were mostly carried out with one single material only. However, loading conditions may strongly vary and, hence, the use of more than one material in a component would yield major benefits. By means of multi-material build-ups, cost-intensive alloys could be used in highly-loaded areas of the part, whereas the remaining part could be fabricated with cheaper compositions. The selection of combined materials strongly depends on the requested thermo-physical and mechanical properties. Within this contribution, possibilities of material combinations by LMD and selected examples of beneficial multi-material use are presented.

  • 6.
    Brueckner, Frank
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling. Fraunhofer Institute for Material and Beam Technology, Winterbergstraße 28, 01277 Dresden, Germany.
    Schab, Johannes C.
    Fraunhofer Institute for Material and Beam Technology, Winterbergstraße 28, 01277 Dresden, Germany.
    Marquardt, Franz
    Fraunhofer Institute for Material and Beam Technology, Winterbergstraße 28, 01277 Dresden, Germany.
    Müller, Michael
    Fraunhofer Institute for Material and Beam Technology, Winterbergstraße 28, 01277 Dresden, Germany; Technische Universität Dresden, Faculty of Mechanical Engineering, Inst. of Materials Science, 01069 Dresden, Germany.
    Phenomena in multi-material fabrication using laser metal deposition2019Inngår i: Laser 3D Manufacturing VI / [ed] Bo Gu; Henry Helvajian; Hongqiang Chen, SPIE - International Society for Optical Engineering, 2019, artikkel-id 109090HKonferansepaper (Fagfellevurdert)
    Abstract [en]

    Additive Manufacturing (AM) processes as Laser Metal Deposition (LMD) addresses various benefits such as the build-up of complex shaped parts, the possibility of functional integration, reduced lead times or the use of difficult machinable materials compared to conventional manufacturing possibilities. Beside mentioned advantages, the use of more than one material in a component strongly increases the field of applications. Similar to structures in nature, multi-material arrangements can be realized by (I) sharp intersections from one material to the other (e. g. in the case of a thin corrosion protection), (II) graded structures enabling smoother material transitions (e. g. dissimilar materials joined together without defects), (III) composite structures with enclosed particles in a matrix material as well as by (IV) in-situ alloying of different material compositions. Due to varying material properties (e.g. thermo-physical, mechanical, optical), the combination of materials often requires a detailed investigation of occurring process phenomena and well-chosen modifications of the process regimes. Within this paper, (a) the right material feeding as well as powder interaction between various materials in Laser Metal Deposition, (b) the suitable selection of laser wavelengths for different materials, (c) process window adjustments by means of additional sensor equipment, (d) limitations of material combinations as well as (e) results and material characterization of multi-material parts are discussed. Phenomena are discussed by means of exemplary industrial applications, e.g. from the jet engine or medical business. 

  • 7.
    Eberle, Sebastian
    et al.
    Kampf Telescope Optics GmbH, Alois-Gilg-Weg 7, 81373 Munich, Germany.
    Reutlinger, Arnd
    Kampf Telescope Optics GmbH, Alois-Gilg-Weg 7, 81373 Munich, Germany.
    Curzadd, Bailey
    Kampf Telescope Optics GmbH, Alois-Gilg-Weg 7, 81373 Munich, Germany.
    Mueller, Michael
    Fraunhofer Institute for Material and Beam Technology, Winterbergstraße 28, Dresden, Germany; Technische Universität Dresden, Helmholtzstr. 7, 01069 Dresden, Germany.
    Riede, Mirko
    Fraunhofer Institute for Material and Beam Technology, Winterbergstraße 28, Dresden, Germany.
    Wilsnack, Christoph
    Fraunhofer Institute for Material and Beam Technology, Winterbergstraße 28, Dresden, Germany.
    Brandão, Ana
    European Space Research and Technology Centre – ESTEC, Noordwijk, Netherlands .
    Pambaguian, Laurent
    European Space Research and Technology Centre – ESTEC, Noordwijk, Netherlands.
    Seidel, André
    Fraunhofer Institute for Material and Beam Technology, Winterbergstraße 28, Dresden, Germany.
    López, Elena
    Fraunhofer Institute for Material and Beam Technology, Winterbergstraße 28, Dresden, Germany.
    Brueckner, Frank
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling. Fraunhofer Institute for Material and Beam Technology, Winterbergstraße 28, Dresden, Germany.
    Beyer, Eckhard
    Fraunhofer Institute for Material and Beam Technology, Winterbergstraße 28, Dresden, Germany; Technische Universität Dresden, Helmholtzstr. 7, 01069 Dresden, Germany .
    Leyens, Christoph
    Fraunhofer Institute for Material and Beam Technology, Winterbergstraße 28, Dresden, Germany; Technische Universität Dresden, Helmholtzstr. 7, 01069 Dresden, Germany.
    Additive manufacturing of an AlSi40 mirror coated with electroless nickel for cryogenic space applications2018Inngår i: International Conference on Space Optics—ICSO 2018: Chania, Greece 9–12 October 2018 / [ed] Zoran Sodnik; Nikos Karafolas; Bruno Cugny, SPIE - International Society for Optical Engineering, 2018, artikkel-id 1118015Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Advanced Manufacturing (AM) has the potential to improve existing technologies and applications in terms of performance, light-weighting and costs. In the context of the SME4ALM initiative, launched by DLR and ESA, the company Kampf Telescope Optics GmbH (KTO) in cooperation with the Fraunhofer Institute for Material and Beam Technology (IWS) have assessed the feasibility of AM to build a high-performance optical mirror for space applications. 

    For the assessment of the AM potentials, a mirror design concept for cryogenic instruments for observations in the IR and NIR range was baselined. In a second step, Nickel-Phosphorus (NiP) was selected as optical coating. The combination of coating and mirror material is a primary design driver for optical performance. Both materials must have a very similar CTE as well as be compliant to modern optical manufacturing (diamond turning, polishing). As a promising candidate for NiP coating the AlSi40 was selected for the mirror structure. 

    The potential advantages of AM for optical mirrors in terms of mechanical performance, cost, and manufacturing time were exploited. The achievement of those objectives was / will be demonstrated by:

    1. verifying AM material properties and manufacturability of AM mirrors by material sample tests and subcomponent tests

    2. designing AM mirror demonstrator by structural, thermal, and optical performance analysis

    3. applying and elaborating AM specific design methods (topology optimization, sandwich structures with internal microstructures, monolithic design, etc.)

    4. manufacturing, assembling, and testing AM mirror demonstrator to verify manufacturability and optical performance

    5. comparing optical and mechanical performance of the AM mirror demonstrator to a conventional mirror by numerical analysis to exploit potential advantages of AM

  • 8.
    Fedina, Tatiana
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Belelli, Filippo
    Politecnico di Milano, Department of Mechanical Engineering, Via G. La Masa 1, 20156, Milano, Italy.
    Lupi, Giorgia
    Politecnico di Milano, Department of Mechanical Engineering, Via G. La Masa 1, 20156, Milano, Italy.
    Brandau, Benedikt
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling. Jenoptik Optical Systems GmbH, Göschwitzersrasse 25, 07745 Jena, Germany.
    Casati, Riccardo
    Politecnico di Milano, Department of Mechanical Engineering, Via G. La Masa 1, 20156, Milano, Italy.
    Berneth, Raphael
    Fraunhofer IWS, Winterbergstrasse 28, 01277, Dresden, Germany.
    Brueckner, Frank
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling. Fraunhofer IWS, Winterbergstrasse 28, 01277, Dresden, Germany.
    Kaplan, Alexander F.H.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Influence of AlSi10Mg powder aging on the material degradation and its processing in laser powder bed fusion2022Inngår i: Powder Technology, ISSN 0032-5910, E-ISSN 1873-328X, Vol. 412, artikkel-id 118024Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This study investigates the impact of powder aging on the degradation of AlSi10Mg powder during processing in laser powder bed fusion. Powder aging as result of handling, continuous storage and recycling is a fundamental concern for aluminum alloys as it introduces oxygen to the feedstock material. In this work, the analysis of the powder properties, affected by laser exposure and the aging procedure, showed a change of chemical and morphological characteristics of the powders in virgin and aged conditions. The oxygen content in the powders appeared to have a significant effect on the powders' surface appearance and light absorbance, gradually deteriorating the processability of the powders with the increase of oxygen level. Optical microscopy and X-ray computed tomography were used to analyze the porosity distribution in the printed part samples, identifying the origin, size and location of the pores. A direct relationship between the pore occurrence in final parts and the oxygen content in the powders was observed, revealing a higher degree of porosity in the aged powder sample (6.5%) in comparison with the virgin state (3.16%). The evolution of mechanical properties in the part samples after laser processing and powder aging was also studied, demonstrating a rapid decrease of ultimate tensile strength and elongation from virgin condition to aged.

  • 9.
    Fedina, Tatiana
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Brueckner, Frank
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling. Fraunhofer IWS, Winterbergstrasse 28, 01277 Dresden, Germany.
    Kaplan, Alexander F. H.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Wilsnack, Christoph
    Fraunhofer IWS, Winterbergstrasse 28, 01277 Dresden, Germany.
    Laser-assisted reduction of iron ore using aluminum powder2023Inngår i: Journal of laser applications, ISSN 1042-346X, E-ISSN 1938-1387, Vol. 35, nr 2, artikkel-id 022007Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This study reports on the laser-assisted reduction of iron ore waste using Al powder as areducing agent. Due to climate change and the global warming situation, it has become ofparamount importance to search for and/or develop green and sustainable processes for ironand steel production. In this regard, a new method for iron ore utilization is proposed in thiswork, investigating the possibility of iron ore waste reduction via metallothermic reaction withAl powder. Laser processing of iron ore fines was performed, focusing on the Fe2O3-Alinteraction behavior and extent of the iron ore reduction. The reaction between the materialsproceeded in a rather intense uncontrolled manner which led to a formation of Fe-rich domainsand alumina as two separate phases. In addition, a combination of Al2O3 and Fe2O3 melts aswell as transitional areas such as intermetallics were observed, suggesting the occurrence ofincomplete reduction reaction in isolated regions. The reduced iron droplets were prone toacquire a sphere-like shape and concentrated mainly near the surface of the Al2O3 melt or at theinterface with the iron oxide. Both SEM, EDS and WDS analyses were employed to analyzechemical composition, microstructure and morphological appearances of the reaction products.High-speed imaging was used to study the process phenomena and observe differences in themovement behavior of the particles. Furthermore, the measurements acquired from X-raycomputed microtomography revealed that approximately 2.4 % of iron was reduced during thelaser processing of Fe2O3-Al powder bed, most likely due to insufficient reaction time orinappropriate equivalence ratio of the two components.

    Fulltekst (pdf)
    fulltext
  • 10.
    Frostevarg, Jan
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Volpp, Jöerg
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Thompson, Cassidy
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik.
    Prasad, Himani Siva
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Fedina, Tatiana
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Brückner, Frank
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling. Fraunhofer Institute for Material and Beam Technology, Dresden, Germany.
    Influence of the vapour channel on processing in laser powder bed fusion2019Inngår i: Procedia Manufacturing, E-ISSN 2351-9789, Vol. 36, s. 80-87Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Additive Manufacturing provides many opportunities to design and manufacture parts that are difficult or not possible to produce with conventional methods. In Selective Laser Melting (SLM) in powder bed fusion (PBF), melt pool dynamics and stability is dependent on a large number of factors, e.g. laser power output, power density, travel speed, reflectivity of powder bed, rapid heating and vaporization. Since travel speeds are often very fast and the laser interaction zone is small, the physical events become difficult to predict but also to observe. This work aims to describe the formation and geometrical characteristics of the vaporization zone during processing. Using a combination of theoretical descriptions, resulting material structures and a comprehensive analysis of high-speed images of the processing zone for different heat inputs and travel speeds, explanations for the dynamic melt pool behaviour are derived. The melting and pressures from processing involved moves powder particles next to it, changing the conditions for neighbouring tracks due to lack of material. These findings can provide a basis for creating more efficient and stable SLM processing, with fewer imperfections.

  • 11.
    Greifzu, Moritz
    et al.
    Additive Manufacturing and Printing, Fraunhofer-Institut für Werkstoff- und Strahltechnik, Dresden, Germany.
    Tkachov, Roman
    Additive Manufacturing and Printing, Fraunhofer-Institut für Werkstoff- und Strahltechnik, Dresden, Germany; Institute of Materials Science, Technische Universität Dresden, Dresden, Germany.
    Stepien, Lukas
    Additive Manufacturing and Printing, Fraunhofer-Institut für Werkstoff- und Strahltechnik, Dresden, Germany.
    López, Elena
    Additive Manufacturing and Printing, Fraunhofer-Institut für Werkstoff- und Strahltechnik, Dresden, Germany.
    Brückner, Frank
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Leyens, Christoph
    Additive Manufacturing and Printing, Fraunhofer-Institut für Werkstoff- und Strahltechnik, Dresden, Germany; Institute of Materials Science, Technische Universität Dresden, Dresden, Germany.
    Laser Treatment as Sintering Process for Dispenser Printed Bismuth Telluride Based Paste2019Inngår i: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 12, nr 20, artikkel-id 3453Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Laser sintering as a thermal post treatment method for dispenser printed p- and n-type bismuth telluride based thermoelectric paste materials was investigated. A high-power fiber laser (600 W, 1064 nm) was used in combination with a scanning system to achieve high processing speed. A Design of Experiment (DoE) approach was used to identify the most relevant processing parameters. Printed layers were laser treated with different process parameters and the achieved sheet resistance, electrical conductivity, and Seebeck coefficient are compared to tube furnace processed reference specimen. For p-type material, electrical conductivity of 22 S/cm was achieved, compared to 15 S/cm in tube furnace process. For n-type material, conductivity achieved by laser process was much lower (7 S/cm) compared to 88 S/cm in furnace process. Also, Seebeck coefficient decreases during laser processing (40–70 µV/K and −110 µV/K) compared to the oven process (251 µV/K and −142 µV/K) for p- and n-type material. DoE did not yet deliver a set of optimum processing parameters, but supports doubts about the applicability of area specific laser energy density as a single parameter to optimize laser sintering process.

  • 12.
    Gruber, Samira
    et al.
    Fraunhofer Institute for Material and Beam Technology, IWS, Dresden, Germany. Institute of Materials Science, Technische Universität Dresden,Dresden, Germany.
    Grunert, Christian
    Fraunhofer Institute for Material and Beam Technology, IWS, Dresden, Germany.
    Riede, Mirko
    Fraunhofer Institute for Material and Beam Technology, IWS, Dresden, Germany.
    López, Elena
    Fraunhofer Institute for Material and Beam Technology, IWS, Dresden, Germany.
    Marquardt, Axel
    Institute of Materials Science, Technische Universität Dresden, Dresden, Germany.
    Brückner, Frank
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling. Fraunhofer Institute for Material and Beam Technology, IWS, Dresden, Germany.
    Leyens, Christoph
    Fraunhofer Institute for Material and Beam Technology, IWS, Dresden, Germany. Institute of Materials Science, Technische Universität Dresden,Dresden, Germany.
    Comparison of dimensional accuracy and tolerances of powder bed based and nozzle based additive manufacturing processes2020Inngår i: Journal of laser applications, ISSN 1042-346X, E-ISSN 1938-1387, Vol. 32, nr 3, artikkel-id 032016Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Additive manufacturing processes have the potential to produce near-net shaped complex final parts in various industries such as aerospace, medicine, or automotive. Powder bed based and nozzle based processes like laser metal deposition (LMD), laser powder bed fusion (LPBF), and electron beam melting (EBM) are commercially available, but selecting the most suitable process for a specific application remains difficult and mainly depends on the individual know-how within a certain company. Factors such as the material used, part dimension, geometrical features, as well as tolerance requirements contribute to the overall manufacturing costs that need to be economically reasonable compared to conventional processes. Within this contribution, the quantitative analysis of basic geometrical features such as cylinders, thin walls, holes, and cooling channels of a special designed benchmark demonstrator manufactured by LMD; LPBF and EBM are presented to compare the geometrical accuracy within and between these processes to verify existing guidelines, connect the part quality to the process parameters, and demonstrate process-specific limitations. The fabricated specimens are investigated in a comprehensive manner with 3D laser scanning and CT scanning with regard to dimensional and geometrical accuracy of outer and inner features. The obtained results will be discussed and achievable as-built tolerances for assessed demonstrator parts will be classified according to general tolerance classes described [DIN ISO 2768-1,Allgemeintoleranzen-Teil 1: Toleranzen fur Langen- und Winkelmasse ohne einzelne Toleranzeintragung(1991). Accessed 26 February 2018; DIN ISO 2768-2,Allgemeintoleranzen-Teil 2: Toleranzen fur Form und Lage ohne einzelne Toleranzeintragung(1991). Accessed 26 February 2018].

  • 13.
    Gruber, Samira
    et al.
    Fraunhofer Institute for Material and Beam Technology IWS, 01277, Dresden, Germany.
    Stepien, Lukas
    Fraunhofer Institute for Material and Beam Technology IWS, 01277, Dresden, Germany.
    Gerdt, Leonid
    Fraunhofer Institute for Material and Beam Technology IWS, 01277, Dresden, Germany.
    Lopez, Elena
    Fraunhofer Institute for Material and Beam Technology IWS, 01277, Dresden, Germany.
    Kieser, Jan
    Fraunhofer Institute for Material and Beam Technology IWS, 01277, Dresden, Germany.
    Brueckner, Frank
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling. Fraunhofer Institute for Material and Beam Technology IWS, 01277, Dresden, Germany.
    Leyens, Christoph
    Fraunhofer Institute for Material and Beam Technology IWS, 01277, Dresden, Germany; TUD Dresden University of Technology, Institute of Materials Science, 01069, Dresden, Germany.
    Bratt, Craig
    Fraunhofer USA—Center Midwest, Laser Applications Division, Plymouth, Michigan 48170, United States.
    Process development for laser powder bed fusion of GRCop-42 using a 515 nm laser source2023Inngår i: Journal of laser applications, ISSN 1042-346X, E-ISSN 1938-1387, Vol. 35, nr 4, artikkel-id 042078Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Copper is widely used in high heat flux and electrical applications because of its excellent electrical and thermal conductivity properties. Alloying elements such as chromium or nickel are added to strengthen the material, especially for higher temperatures. Cu4Cr2Nb, also known as GRCop-42, is a dispersion-strengthened copper-chromium-niobium alloy developed by NASA for high-temperature applications with high thermal and mechanical stresses such as rocket engines. Additive manufacturing (AM) enables applications with complex functionalized geometries and is particularly promising in the aerospace industry. In this contribution, a parametric study was performed for GRCop-42 and the AM process laser powder bed fusion (PBF-LB/M) using a green laser source for two-layer thicknesses of 30 and 60 µm. Density, electrical conductivity, hardness, microstructure, and static mechanical properties were analyzed. Various heat treatments ranging from 400 to 1000 °C and 30 min to 4 h were tested to increase the electrical conductivity and hardness. For both layer thicknesses, dense parameter sets could be obtained with resulting relative densities above 99.8%. Hardness and electrical conductivity could be tailored in the range of 103-219 HV2 and 24%-88% International Annealed Copper Standard (IACS) depending on the heat treatment. The highest ultimate tensile strength (UTS) obtained was 493 MPa. An aging temperature of 700 °C for 30 min showed the best combination of room temperature properties such as electrical conductivity of 83.76%IACS, UTS of 481 MPa, elongation at break (A) at 24%, and hardness of 125 HV2.

    Fulltekst (pdf)
    fulltext
  • 14.
    Gruber, Samira
    et al.
    Fraunhofer Institute for Material and Beam Technology, IWS, Winterbergstraße 28, 01277 Dresden, Germany.
    Stepien, Lukas
    Fraunhofer Institute for Material and Beam Technology, IWS, Winterbergstraße 28, 01277 Dresden, Germany.
    López, Elena
    Fraunhofer Institute for Material and Beam Technology, IWS, Winterbergstraße 28, 01277 Dresden, Germany.
    Brueckner, Frank
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling. Fraunhofer Institute for Material and Beam Technology, IWS, Winterbergstraße 28, 01277 Dresden, Germany.
    Leyens, Christoph
    Fraunhofer Institute for Material and Beam Technology, IWS, Winterbergstraße 28, 01277 Dresden, Germany; Institute of Materials Science, Technische Universität Dresden, Helmholtzstr. 7, 01069 Dresden, Germany.
    Physical and Geometrical Properties of Additively Manufactured Pure Copper Samples Using a Green Laser Source2021Inngår i: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 14, nr 13, artikkel-id 3642Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    So far, copper has been difficult to process via laser powder bed fusion due to low absorption with the frequently used laser systems in the infrared wavelength range. However, green laser systems have emerged recently and offer new opportunities in processing highly reflective materials like pure copper through higher absorptivity. In this study, pure copper powders from two suppliers were tested using the same machine parameter sets to investigate the influence of the powder properties on the material properties such as density, microstructure, and electrical conductivity. Samples of different wall thicknesses were investigated with the eddy-current method to analyze the influence of the sample thickness and surface quality on the measured electrical conductivity. The mechanical properties in three building directions were investigated and the geometrical accuracy of selected geometrical features was analyzed using a benchmark geometry. It could be shown that the generated parts have a relative density of above 99.95% and an electrical conductivity as high as 100% International Annealed Copper Standard (IACS) for both powders could be achieved. Furthermore, the negative influence of a rough surface on the measured eddy-current method was confirmed.

  • 15.
    Haack, M
    et al.
    Fraunhofer Institute for Material and Beam Technology, Dresden, Germany.
    Kuczyk, M
    Fraunhofer Institute for Material and Beam Technology, Dresden, Germany.
    Seidel, A
    Fraunhofer Institute for Material and Beam Technology, Dresden, Germany.
    Lopéz, E
    Fraunhofer Institute for Material and Beam Technology, Dresden, Germany.
    Brückner, Frank
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling. Fraunhofer Institute for Material and Beam Technology, Dresden, Germany. Department of Production Technologies.
    Leyens, C
    Fraunhofer Institute for Material and Beam Technology, Dresden, Germany. Institute/Department of Material Science, Technische Universität Dresden, Dresden, Germany.
    Investigation on the formation of grain boundary serrations in additively manufactured superalloy Haynes 2302020Inngår i: Journal of laser applications, ISSN 1042-346X, E-ISSN 1938-1387, Vol. 32, nr 3, artikkel-id 032014Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Solid-solution and carbide-strengthened superalloys such as Haynes 230 are the materials of choice for the hot-section components of gas turbines, e.g., combustion cans and transition ducts. Under severe thermal conditions, to which those parts are exposed, creep strength is a crucial property of the related materials during their lifetime. Recently, the introduction of serrated grain boundaries in Haynes 230 has been intensively studied [J. G. Yoon, H. W. Jeong, Y. S. Yoo, and H. U. Hong, "Influence of initial microstructure on creep deformation behaviors and fracture characteristics of Haynes 230 superalloy at 900 °C,"Mater. Charact. 101, 49-57 (2015); L. Jiang, R. Hu, H. Kou, J. Li, G. Bai, and H. Fu, "The effect of M23C6 carbides on the formation of grain boundary serrations in a wrought Ni-based superalloy,"Mater. Sci. Eng. A 536, 37-44 (2012)], and nearly a triplication of the time to creep failure at high temperature and low stress conditions has been observed [J. G. Yoon, H. W. Jeong, Y. S. Yoo, and H. U. Hong, "Influence of initial microstructure on creep deformation behaviors and fracture characteristics of Haynes 230 superalloy at 900 °C,"Mater. Charact. 101, 49-57 (2015)]. The aim of this paper is to achieve serrated grain boundaries in Haynes 230 through an appropriate thermal process chain including the intrinsic heat treatments of the laser metal deposition (LMD) process, subsequent hot isostatic pressing and suitable heat treatments. The formation of serrations is a relatively new technique for Haynes 230 (i.e., first paper in 2012), and similar alloys and thus serrations have only been introduced in conventionally cast or wrought alloys so far. Optical and scanning electron microscopies are employed in this work to investigate the created microstructures, whose grain and carbide structure is finer compared to the recently studied conventionally processed alloys. Within the LMD samples, serrations were already found on almost all of the observed grain boundaries even in the as-build condition. This result was rather unexpected, as literature reports slow-cooling to be responsible for the formation of serrations, while fast-cooling is prevalent in LMD. Some authors associated the formation of serrations to the precipitation of M23C6-carbides at the grain boundaries during slow cooling conditions [L. Jiang, R. Hu, H. Kou, J. Li, G. Bai, and H. Fu, "The effect of M23C6 carbides on the formation of grain boundary serrations in a wrought Ni-based superalloy,"Mater. Sci. Eng. A 536, 37-44 (2012)]. The lower density of carbides along grain boundaries in the as-build state, however, makes this mechanism seem unlikely. Other authors attributed the emergence of serrations to a phenomenon similar to the faceting mechanism [J. G. Yoon, H. W. Jeong, Y. S. Yoo, and H. U. Hong, "Influence of initial microstructure on creep deformation behaviors and fracture characteristics of Haynes 230 superalloy at 900 °C,"Mater. Charact. 101, 49-57 (2015)]. It can be said that no uniform theory for the emergence of grain boundary serrations exists as of now. The electron backscatter diffraction (EBSD) investigations performed in this work indicated a correlation between serrated grain boundary segments, the {111}-directions of the crystal lattice, and possibly segregations along dendritic subgrain boundaries for a two-dimensional case. Serial sectioning in combination with EBSD analysis confirmed an agreement between the three-dimensional orientation of serrated grain boundary segments and the {111}-direction of adjacent grains. Hence, a mechanism different from the ones described in previous works is proposed for the formation of grain boundary serrations in the additively manufactured Haynes 230 alloy.

  • 16.
    Haack, Maximilian
    et al.
    Fraunhofer Institute for Material and Beam Technology IWS, Dresden, Germany.
    Kuczyk, Martin
    Fraunhofer Institute for Material and Beam Technology IWS, Dresden, Germany.
    Seidel, André
    Fraunhofer Institute for Material and Beam Technology IWS, Dresden, Germany.
    López, Elena
    Fraunhofer Institute for Material and Beam Technology IWS, Dresden, Germany.
    Brueckner, Frank
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling. Fraunhofer Institute for Material and Beam Technology IWS, Dresden, Germany.
    Leyens, Christoph
    Fraunhofer Institute for Material and Beam Technology IWS, Dresden, Germany. Dresden University of Technology, Institute of Materials Science, Dresden, Germany.
    Comprehensive study on the formation of grain boundary serrations in additively manufactured Haynes 230 alloy2020Inngår i: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 160, artikkel-id 110092Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Recently, grain boundary serrations have been introduced in conventionally processed Haynes 230 through a slow-cooling heat treatment. The aim of this work was to utilize these heat treatments to introduce serrations in additively manufactured (Laser Metal Deposition) Haynes 230. Contrary to expectations, serrations already formed during the fast-cooling of the Laser Metal Deposition process. Electron Backscatter Diffraction was used to elucidate the underlying phenomenon for the emergence of serrations during fast-cooling. As a result, a hypothesis regarding a new mechanism responsible for the formation of grain boundary serrations was formulated. Additionally, specific characteristics of the Laser Metal Deposition process have been identified. This includes a columnar-to-equiaxed transition (CET) for slower feed rates, leading to smaller grains despite lower cooling rates; the observation of an abrupt increase in grain growth for a raised solution annealing temperature; the fact that serrations hinder uncontrolled grain growth and finally that the LMD-process leads to a finer carbide morphology compared to conventional manufacturing methods, potentially leading to an increased precipitation strengthening effect.

  • 17.
    Heidowitzsch, Maximilian
    et al.
    Fraunhofer Institute for Material and Beam Technology IWS, Winterbergstr. 28, Dresden, Saxony 01277, Germany.
    Gerdt, Leonid
    Fraunhofer Institute for Material and Beam Technology IWS, Winterbergstr. 28, Dresden, Saxony 01277, Germany.
    Samuel, Conrad
    Fraunhofer Institute for Material and Beam Technology IWS, Winterbergstr. 28, Dresden, Saxony 01277, Germany.
    Maetje, Jacob-Florian
    Fraunhofer Institute for Material and Beam Technology IWS, Winterbergstr. 28, Dresden, Saxony 01277, Germany.
    Kaspar, Jörg
    Fraunhofer Institute for Material and Beam Technology IWS, Winterbergstr. 28, Dresden, Saxony 01277, Germany.
    Riede, Mirko
    Fraunhofer Institute for Material and Beam Technology IWS, Winterbergstr. 28, Dresden, Saxony 01277, Germany.
    López, Elena
    Fraunhofer Institute for Material and Beam Technology IWS, Winterbergstr. 28, Dresden, Saxony 01277, Germany.
    Brueckner, Frank
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling. Fraunhofer Institute for Material and Beam Technology IWS, Winterbergstr. 28, Dresden, Saxony 01277, Germany.
    Leyens, Christoph
    Fraunhofer Institute for Material and Beam Technology IWS, Winterbergstr. 28, Dresden, Saxony 01277, Germany; Chair of Materials Technology (IfWW), Institute of Materials Science, TU Dresden, Helmholtzstr. 7, Dresden, Saxony 01069, Germany.
    Grain size manipulation by wire laser direct energy deposition of 316L with ultrasonic assistance2023Inngår i: Journal of laser applications, ISSN 1042-346X, E-ISSN 1938-1387, Vol. 35, nr 3, artikkel-id 032017Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The epitaxial growth of coarse and columnar grain structures along the build direction of additive manufactured metals is a usual phenomenon. As a result, as-built components often exhibit pronounced anisotropic mechanical properties, reduced ductility, and, hence, a high cracking susceptibility. To enhance the mechanical properties and processability of additive manufactured parts, the formation of equiaxed and fine grained structures is thought to be most beneficial. In this study, the potential of grain refinement by ultrasonic excitation of the melt pool during laser wire additive manufacturing has been investigated. An ultrasound system was developed and integrated in a laser wire deposition machine. AISI 316L steel was used as a substrate and feedstock material. A conversion of coarse, columnar grains (d(m) = 284.5 mu m) into fine, equiaxed grains (d(m) = 130.4 mu m) and a weakening of typical -fiber texture with increasing amplitude were verified by means of light microscopy, scanning electron microscopy, and electron backscatter diffraction analysis. It was demonstrated that the degree of grain refinement could be controlled by the regulation of ultrasound amplitude. No significant changes in the dendritic structure have been observed. The combination of sonotrode/melt pool direct coupling and the laser wire deposition process represents a pioneering approach and promising strategy to investigate the influence of ultrasound on grain refinement and microstructural tailoring.

    Fulltekst (pdf)
    fulltext
  • 18.
    Hendl, Julius
    et al.
    Institute of Materials Science, Technische Universität Dresden, Helmholtzstr. 7, 01069 Dresden, Germany; Fraunhofer—Institute for Material and Beam Technology (IWS—Dresden), Winterbergstraße 28, 01069 Dresden, Germany.
    Daubner, Sina
    Institute of Materials Science, Technische Universität Dresden, Helmholtzstr. 7, 01069 Dresden, Germany.
    Marquardt, Axel
    Institute of Materials Science, Technische Universität Dresden, Helmholtzstr. 7, 01069 Dresden, Germany; Fraunhofer—Institute for Material and Beam Technology (IWS—Dresden), Winterbergstraße 28, 01069 Dresden, Germany.
    Stepien, Lukas
    Fraunhofer—Institute for Material and Beam Technology (IWS—Dresden), Winterbergstraße 28, 01069 Dresden, Germany.
    Lopez, Elena
    Fraunhofer—Institute for Material and Beam Technology (IWS—Dresden), Winterbergstraße 28, 01069 Dresden, Germany.
    Brückner, Frank
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling. Fraunhofer—Institute for Material and Beam Technology (IWS—Dresden), Winterbergstraße 28, 01069 Dresden, Germany.
    Leyens, Christoph
    Institute of Materials Science, Technische Universität Dresden, Helmholtzstr. 7, 01069 Dresden, Germany; Fraunhofer—Institute for Material and Beam Technology (IWS—Dresden), Winterbergstraße 28, 01069 Dresden, Germany.
    In Situ CT Tensile Testing of an Additively Manufactured and Heat-Treated Metastable ß-Titanium Alloy (Ti-5Al-5Mo-5V-3Cr)2021Inngår i: Applied Sciences, E-ISSN 2076-3417, Vol. 11, nr 21, artikkel-id 9875Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Additive manufacturing has been considered a suitable process for developing high-performance parts of medical or aerospace industries. The electron beam powder bed fusion process, EB-PBF, is a powder bed fusion process carried out in a vacuum, in which the parts are melted using a highly focused electron beam. The material class of metastable β-titanium alloys, and especially Ti-5Al-5Mo-5V-3Cr, show great potential for use as small and highly complex load-bearing parts. Specimens were additively manufactured with optimised process parameters and different heat treatments used in order to create tailored mechanical properties. These heat-treated specimens were analysed with regard to their microstructure (SEM) and their mechanical strength (tensile testing). Furthermore, in situ tensile tests, using a Deben CT5000 and a YXLON ff35 industrial µ-CT, were performed and failure-critical defects were detected, analysed and monitored. Experimental results indicate that, if EB-PBF-manufactured Ti-5553 is heat-treated differently, a variety of mechanical properties are possible. Regarding their fracture mechanisms, failure-critical defects can be detected at different stages of the tensile test and defect growth behaviour can be analysed.

  • 19.
    Hendl, Julius
    et al.
    Institute for Materials Science, Technische Universität Dresden, Dresden, Germany; Fraunhofer Institute for Material and Beam Technology IWS, Dresden, Germany.
    Marquardt, Axel
    Institute for Materials Science, Technische Universität Dresden, Dresden, Germany; Fraunhofer Institute for Material and Beam Technology IWS, Dresden, Germany.
    Willner, Robin
    Fraunhofer Institute for Material and Beam Technology IWS, Dresden, Germany.
    Lopez, Elena
    Fraunhofer Institute for Material and Beam Technology IWS, Dresden, Germany.
    Brückner, Frank
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling. Fraunhofer Institute for Material and Beam Technology IWS, Dresden, Germany.
    Leyens, Christoph
    Institute for Materials Science, Technische Universität Dresden, Dresden, Germany; Fraunhofer Institute for Material and Beam Technology IWS, Dresden, Germany.
    NDE for Additive Manufacturing2022Inngår i: Handbook of Nondestructive Evaluation 4.0 / [ed] Norbert Meyendorf, Nathan Ida, Ripudaman Singh, Johannes Vrana, Springer, 2022, 1, s. 665-696Kapittel i bok, del av antologi (Annet vitenskapelig)
    Abstract [en]

    By means of additive manufacturing (AM) complex-shaped parts can be manufactured using a broad range of different materials. The latter can be supplied in the form of powder, wire, paste material, or even as foil. Various technologies are covered by the term “Additive Manufacturing,” for example, direct energy deposition (DED), laser powder bed fusion (LPBF), fused filament fabrication (FFF), or binder jetting printing (BJP). In all varieties, parts are manufactured layer by layer which results in changed material properties compared to conventional manufacturing routes, for example, mechanical properties or fatigue life. To reach a conformal material deposition without defects such as lack of fusion, delamination or cracking, an optimal process window with well-chosen parameters (e.g., beam power, spot size, scanning speed) has to be identified.

    For nondestructive evaluation (NDE), different approaches can be used to classify AM manufactured parts regarding their defect structure and consequentially their performance:

    1.Process optimization and understanding of defect formation in order to prevent defects 2.In situ measurements by a variety of integrated sensors and (IR) cameras for direct process observations 3.Post-processing NDE methods such as ultrasonic testing, X-ray, or computer tomography (CT)

    If the three approaches are simultaneously executed, a prediction of the effect of defects can be made for certain cases.

  • 20.
    Kaplan, Alexander F. H.
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Fedina, Tatiana
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling. SWERIM AB, Box 7047, 164 07 Kista, Sweden.
    Brückner, Frank
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling. Fraunhofer IWS, Winterbergstrasse 28, 01277 Dresden, Germany.
    Powell, John
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling. Laser Expertise Ltd., Nottingham, UK.
    Laser induced reduction of iron ore by silicon2023Inngår i: Journal of Alloys and Metallurgical Systems, ISSN 2949-9178, Vol. 4, artikkel-id 100039Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Iron ore powder accompanied by Si-powder as a reducing agent, was melted using a high-power laser beam. During laser melting of the two different powder beds placed next to each other, silicon merged and diffused into the iron ore, forming a ternary melt phase Fe-O-Si of around 30–60–10 at%. High speed imaging of the laser melting process as well as subsequent SEM-analysis of the generated nuggets showed the formation of droplets that merge with the surrounding Si- or ore-powder and form distinct domains. Under certain circumstances, the solidifying nuggets, of the order of 0.5–5 mm in size, generated numerous small domains, up to 25 µm, of high purity iron, 90 + at%, surrounded by a matrix of the above mentioned slag. Many of these Fe-domains were created in the vicinity of regions of high Si-content.

    Fulltekst (pdf)
    fulltext
  • 21.
    Kaplan, Alexander F.H.
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Fedina, Tatiana
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Brückner, Frank
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling. Fraunhofer IWS, Winterbergstrasse 28, 01277, Dresden, Germany.
    Study of Si-domains enabling local reduction of laser-melted iron ore for iron-making during 3D-printing2022Inngår i: 12th CIRP Conference on Photonic Technologies [LANE 2022] / [ed] M. Schmidt, F. Vollertsen, B.M. Colosimo, Elsevier, 2022, Vol. 111, s. 377-380Konferansepaper (Fagfellevurdert)
    Abstract [en]

    One main issue for global warming are CO2-emissions from iron ore reduction during steelmaking. This study presents a new approach, to merge iron ore powder with a suitable reducing agent, here silicon powder. By laser melting of the powders, some of the generated grains are composed of homogeneous slag, O-Fe-Si about 60-30-10 at.-%. However, other grains indeed contain small domains with high iron content, 90-100 at.-%. Manifold appearances of the iron particles were identified, surrounded preferably by slag but also by accompanying domains of high Si-content. These appearances indicate how ore reduction took place, like spherical growth or irregular drop conglomeration. If the iron particles can be extracted as drops, direct 3D-printing from ore can be enabled, including tailored alloying of iron to steel. Such short value chain would not only be efficient but also aims to cause solely environment-friendly by-products, for example SiO2 instead of CO2.

  • 22.
    Kledwig, Christian
    et al.
    Development Department, Sauer GmbH LASERTEC, DMG MORI AG, Pfronten, 87459, Germany.
    Hofer, Markus
    Development Department, Sauer GmbH LASERTEC, DMG MORI AG, Pfronten, 87459, Germany.
    Reisacher, Martin
    Development Department, Sauer GmbH LASERTEC, DMG MORI AG, Pfronten, 87459, Germany.
    Brückner, Frank
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling. Additive Manufacturing and Printing, Fraunhofer Institute for Material and Beam Technology IWS, Dresden, 01277, Germany.
    Bliedtner, Jens
    SciTec Department, Ernst-Abbe-Hochschule Jena, Jena, 07745, Germany.
    Leyens, Christoph
    Additive Manufacturing and Printing, Fraunhofer Institute for Material and Beam Technology IWS, Dresden, 01277, Germany. Institute of Materials Science, Technische Universität Dresden, Dresden, 01062, Germany.
    A Study on the accuracy of Thermography-based Temperature measurement in Powder-fed directed energy deposition2020Inngår i: 20th CIRP Conference on Electro Physical and Chemical Machining / [ed] Konrad Wegener, Moritz Wiessner, Elsevier, 2020, s. 35-41Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Due to continuous development and increasingly deep understanding of the additive process, directed-energy deposition (DED) is becoming more and more interesting for industrial use. However, both the number of influencing factors and the process complexity, still require well-trained operators who can monitor and understand the machine tools. In order to facilitate the operators and to enable longer unattended processes, higher process safety, reliable monitoring systems and closed-loop controller are required. For example, despite a large number of investigations, the monitoring and control of the temperature distribution within the work piece still poses a big challenge.

    This study focusses on workpiece temperature measurement using a thermal imaging camera that observes the entire machining area. In order examine the measurement error caused by different viewing angles (φ = 0 … 75°), object temperatures (T = 333 … 1073K), surface conditions (welded and milled) and materials (316L, Inconel 718 and CuAl10) commonly used in DED, several approaches were followed using a thermal camera.

    It was found that surface condition and material cause the greatest measuring errors (up to +325K |−453K).). However, the measuring errors can be significantly reduced by suitable selection of the emissivity, so that it is possible to measure even the milled CuAl10 surface at a known viewing angle with a measuring error of +13.3% |−10.9%.

  • 23.
    Kledwig, Christian
    et al.
    Development Department, Sauer GmbH LASERTEC, DMG MORI AG, Pfronten, Germany.
    Perfahl, Holger
    Development Department, Sauer GmbH LASERTEC, DMG MORI AG, Pfronten, Germany.
    Reisacher, Martin
    Development Department, Sauer GmbH LASERTEC, DMG MORI AG, Pfronten, Germany.
    Brueckner, Frank
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling. Additive Manufacturing and Printing, Fraunhofer Institute for Material and Beam Technology IWS, Dresden, Germany.
    Bliedtner, Jens
    SciTec Department, Ernst-Abbe-Hochschule Jena, Jena, Germany.
    Leyens, Christoph
    Additive Manufacturing and Printing, Fraunhofer Institute for Material and Beam Technology IWS, Dresden, Germany; Institute of Materials Science, Technische Universität Dresden, Dresden, Germany.
    Analysis of Melt Pool Characteristics and Process Parameters Using a Coaxial Monitoring System during Directed Energy Deposition in Additive Manufacturing2019Inngår i: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 12, nr 2, artikkel-id 308Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The growing number of commercially available machines for laser deposition welding show the growing acceptance and importance of this technology for industrial applications. Their increasing usage in research and production requires process stability and user-friendly handling. A commercially available DMG MORI LT 65 3D hybrid machine used in combination with a CCD-based coaxial temperature measurement system was utilized in this work to investigate what information relating to the intensity distribution of melt pool surfaces could be appropriate to draw conclusions about process conditions. In this study it is shown how the minimal required specific energy for a stable process can be determined, and it is indicated that the evolution of a plasma plume depends on thermal energy within the base material. An estimated melt pool area—calculated by the number of pixels (NOP) with intensities larger than a fixed, predefined threshold—builds the main measure in analysing images from the process camera. The melt pool area and its temporal variance can also serve as an indicator for an increased working distance

  • 24.
    Kledwig, Christian
    et al.
    Development Department, Sauer GmbH LASERTEC, DMG MORI AG, Pfronten 87459, Germany.
    Perfahl, Holger
    Development Department, Sauer GmbH LASERTEC, DMG MORI AG, Pfronten 87459, Germany.
    Reisacher, Martin
    Development Department, Sauer GmbH LASERTEC, DMG MORI AG, Pfronten 87459, Germany.
    Brückner, Frank
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling. Additive Manufacturing and Printing, Fraunhofer Institute for Material and Beam Technology IWS, Dresden 01277, Germany.
    Bliedtner, Jens
    SciTec Department, Ernst-Abbe-Hochschule Jena, Jena 07745, Germany.
    Leyens, Christoph
    Additive Manufacturing and Printing, Fraunhofer Institute for Material and Beam Technology IWS, Dresden 01277, Germany. Institute of Materials Science, Technische Universität Dresden, Dresden 01062, Germany.
    Image-based algorithm for nozzle adhesion detection in powder-fed directed-energy deposition2020Inngår i: Journal of laser applications, ISSN 1042-346X, E-ISSN 1938-1387, Vol. 32, nr 2, artikkel-id 022021Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The rapidly growing technological innovation of directed energy deposition leads to an increase in part complexity as well as quality and mechanical properties of manufacturable components. However, the variety of process parameters and influencing factors still requires skilled operators, who observe the machine tools. For an unobserved use of deposition welding machines, well parametrized and validated monitoring systems have to analyze the process to detect irregularities and finally initiate a machine stop. This study focuses on nozzle adhesions that frequently occur when tool or high-speed steels are processed. This effect leads to decreasing quality or ultimately to a failure of the whole welding process. In this work, the authors present an algorithm and the corresponding parametrization to automatically detect nozzle adhesions based on images from a coaxial camera, integrated in the laser head. The algorithm is based on a detailed image analysis from which temporal and spatial patterns are derived. In particular, the algorithm calculates a nozzle adhesion indicator based on the heat intensity distribution in an experimentally derived shaped area on the inner nozzle boundary. It is parametrized in such a way that process-critical adhesions are detected. The algorithm was parametrized using an experimental setup with four materials: stainless steel (X2CrNiMo17-12-2), tool steel (X35CrMoMn7-2-1), high-speed steel (HS6-5-2C), and the nickel-based alloy NiCr19NbMo.

  • 25.
    Kolsch, N.
    et al.
    Fraunhofer Institute for Material and Beam Technology, Dresden, Germany.
    Seidel, A.
    Fraunhofer Institute for Material and Beam Technology, Dresden, Germany.
    Finaske, T.
    Fraunhofer Institute for Material and Beam Technology , Winterbergstraße 28, 01277 Dresden, Germany.
    Brueckner, Frank
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling. Fraunhofer Institute for Material and Beam Technology, Dresden, Germany.
    Gumpinger, J.
    European Space Research and Technology Centre—ESTEC, Noordwijk, Netherlands.
    Bavdaz, M.
    European Space Research and Technology Centre—ESTEC, Noordwijk, Netherlands.
    Rohr, T.
    European Space Research and Technology Centre—ESTEC, Noordwijk, Netherlands.
    Ghidini, T.
    European Space Research and Technology Centre—ESTEC, Noordwijk, Netherlands.
    Leyens, C.
    Fraunhofer Institute for Material and Beam Technology , Winterbergstraße 28, 01277 Dresden, Germany; Institute of Materials Science, Technische Universität Dresden, Helmholtzstr. 7, 01069 Dresden, Germany.
    Novel local shielding approach for the laser welding based additive manufacturing of large structural space components from titanium2020Inngår i: Journal of laser applications, ISSN 1042-346X, E-ISSN 1938-1387, Vol. 32, nr 2, artikkel-id 022075Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The Advanced Telescope for High-ENergy Astrophysics (ATHENA) will observe “the hot and energetic universe,” which was determined as one of the most urgent scientific topics for a major future space mission by The European Space Agency (ESA). One of its three main components is the optical bench, a monolithic titanium structure that accommodates 678 mirror modules and keeps them accurately aligned. The immense but slender structure in the range of 2.5–3 m diameter at a height of 300 mm proves a challenge to manufacturing. A hybrid robot cell is developed using additive buildup via laser welding, combined with high-performance machining and the state of the art process and metrology monitoring and control. The present work focuses on the shielding of the laser induced melt pool, a key concern when processing titanium. The sensitive metal with unusual low heat conductivity requires a large area of high purity atmosphere to prevent embrittlement. However, the large hybrid system prohibits the use of a sealed enclosure, and therefore, a local shielding system is developed for the challenging case of the ATHENA optical bench’s hollow-chamber design. Since the present thin wall design poses a worst-case scenario in terms of heat dissipation and shielding flow for the shielding system, its effectiveness here can be applied to most other geometries enabling the flexibility for lot size one. The key features of the novel approach are the prevention of turbulence while keeping operation economical despite the large shielding area. The first is achieved by means of an integrated honeycomb screen and the latter by employing a layered flow with a higher velocity outer curtain and an air deflecting coflow. This system was numerically optimized, tested, and effectiveness proven by means of visual inspection, microstructural analysis, and measurement of material properties.

  • 26.
    Moritz, J.
    et al.
    Fraunhofer Institute for Material and Beam Technology, Dresden, Germany.
    Seidel, A.
    Fraunhofer Institute for Material and Beam Technology, Dresden, Germany.
    Braun, B.
    Space Structures GmbH, Berlin, Germany.
    Brandao, A.
    European Space Research and Technology Centre, ESTEC, Noordwijk, Netherlands.
    Pambaguian, L.
    European Space Research and Technology Centre, ESTEC, Noordwijk, Netherlands.
    Köhler, B.
    Fraunhofer Institute for Ceramic Technologies and Systems, Dresden, Germany.
    Barth, M.
    Fraunhofer Institute for Ceramic Technologies and Systems, Dresden, Germany.
    Riede, M.
    Fraunhofer Institute for Material and Beam Technology, Dresden, Germany.
    Lopéz, E.
    Fraunhofer Institute for Material and Beam Technology, Dresden, Germany.
    Brückner, Frank
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling. Fraunhofer Institute for Material and Beam Technology, Dresden, Germany.
    Leyens, C.
    Fraunhofer Institute for Material and Beam Technology, Dresden, Germany.Institute of Materials Science IfWW, Technische Universität Dresden, Dresden, Germany.
    Functional integration approaches via laser powder bed processing2019Inngår i: Journal of laser applications, ISSN 1042-346X, E-ISSN 1938-1387, Vol. 31, nr 2, artikkel-id 022319Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Additive manufacturing design rules are different from those of conventional fabrication techniques. These allow geometries that would not be possible to achieve otherwise. One example of application is the integration of functional parts as part of the manufacturing process. Conceivable applications range from mechanical functions like integration of moving parts or thermodynamic functions, for example, cooling channels or incorporation of electric circuits for electrical functionalization [J. Glasschroeder, E. Prager, and M. F. Zaeh, Rapid Prototyping J. 21, 207–215 (2015)]. Nevertheless, the potential of functional integration using powder-bed processes is far from being exhausted. The present approach addresses the generation of inner cavities and internal structures of titanium-based parts or components by the use of selective laser melting. This paper focusses on the investigation of voids and cavities regarding their capabilities to add new functions to the material. To this end, comprehensive characterization is performed using destructive as well as nondestructive testing methods. These include 3D scanning, computed tomography, and surface roughness measurements as well as microscopic analysis. Voids and cavities were filled with different thermoplastic materials, followed by the qualitative assessment of the mold filling and resulting material properties. Finally, applications are derived and evaluated with respect to the field of lightweight design or damping structures.

  • 27.
    Moritz, Juliane
    et al.
    Institute of Materials Science (IfWW), Technische Universität Dresden, Helmholtzstr. 7, 01069 Dresden, Germany. Fraunhofer Institute for Material and Beam Technology IWS, Winterbergstraße 28, 01277 Dresden, Germany.
    Götze, Philipp
    Fraunhofer Institute for Material and Beam Technology IWS, Winterbergstraße 28, 01277 Dresden, Germany.
    Schiefer, Tom
    Fraunhofer Institute for Material and Beam Technology IWS, Winterbergstraße 28, 01277 Dresden, Germany.
    Stepien, Lukas
    Fraunhofer Institute for Material and Beam Technology IWS, Winterbergstraße 28, 01277 Dresden, Germany.
    Klotzbach, Annett
    Fraunhofer Institute for Material and Beam Technology IWS, Winterbergstraße 28, 01277 Dresden, Germany.
    Standfuß, Jens
    Fraunhofer Institute for Material and Beam Technology IWS, Winterbergstraße 28, 01277 Dresden, Germany.
    López, Elena
    Fraunhofer Institute for Material and Beam Technology IWS, Winterbergstraße 28, 01277 Dresden, Germany.
    Brückner, Frank
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling. Fraunhofer Institute for Material and Beam Technology IWS, Winterbergstraße 28, 01277 Dresden, Germany.
    Leyens, Christoph
    Institute of Materials Science (IfWW), Technische Universität Dresden, Helmholtzstr. 7, 01069 Dresden, Germany. Fraunhofer Institute for Material and Beam Technology IWS, Winterbergstraße 28, 01277 Dresden, Germany.
    Additive Manufacturing of Titanium with Different Surface Structures for Adhesive Bonding and Thermal Direct Joining with Fiber-Reinforced Polyether-Ether-Ketone (PEEK) for Lightweight Design Applications2021Inngår i: Metals, ISSN 2075-4701, Vol. 11, nr 2, artikkel-id 265Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Hybrid joints consisting of metals and fiber-reinforced polymer composites exhibit highly desirable properties for many lightweight design applications. This study investigates the potential of additively manufactured surface structures for enhancing the bond strength of such joints in comparison to face milled and laser structured surfaces. Titanium samples with different surface structures (as-built surface, groove-, and pin-shaped structures) were manufactured via electron beam melting and joined to carbon fiber-reinforced polyether-ether-ketone (PEEK) via adhesive bonding and thermal direct joining, respectively. Bond strength was evaluated by tensile shear testing. Samples were exposed to salt spray testing for 1000 h for studying bond stability under harsh environmental conditions. The initial tensile shear strengths of the additively manufactured samples were competitive to or in some cases even exceeded the values achieved with laser surface structuring for both investigated joining methods. The most promising results were found for pin-shaped surface structures. However, the hybrid joints with additively manufactured structures tended to be more susceptible to degradation during salt spray exposure. It is concluded that additively manufactured structures can be a viable alternative to laser surface structuring for both adhesive bonding and thermal direct joining of metal-polymer hybrid joints, thus opening up new potentials in lightweight design.

  • 28.
    Moritz, Juliane
    et al.
    Fraunhofer Institute for Material and Beam Technology, Winterbergstraße 28, Dresden, Germany.
    Seidel, André
    Fraunhofer Institute for Material and Beam Technology, Winterbergstraße 28, Dresden, Germany.
    Kopper, Michael
    Westsächsische Hochschule Zwickau, Dr.-Friedrichs-Ring 2A, 08056, Zwickau, Germany.
    Bretschneider, Jörg
    Fraunhofer Institute for Material and Beam Technology, Winterbergstraße 28, Dresden, Germany.
    Gumpinger, Johannes
    ESA/ESTEC, European Space Research and Technology Center, 2201, Noordwijk, AZ, Netherlands.
    Finaske, Thomas
    Fraunhofer Institute for Material and Beam Technology, Winterbergstraße 28, Dresden, Germany.
    Riede, Mirko
    Fraunhofer Institute for Material and Beam Technology, Winterbergstraße 28, Dresden, Germany.
    Schneeweiß, Michael
    Westsächsische Hochschule Zwickau, Dr.-Friedrichs-Ring 2A, 08056, Zwickau, Germany.
    López, Elena
    Fraunhofer Institute for Material and Beam Technology, Winterbergstraße 28, Dresden, Germany.
    Brückner, Frank
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling. Fraunhofer Institute for Material and Beam Technology, Winterbergstraße 28, Dresden, Germany.
    Leyens, Christoph
    Fraunhofer Institute for Material and Beam Technology, Winterbergstraße 28, Dresden, Germany. Technische Universität Dresden, Helmholtzstr. 7, 01069, Dresden, Germany.
    Rohr, Thomas
    ESA/ESTEC, European Space Research and Technology Center, 2201, Noordwijk, AZ, Netherlands.
    Ghidini, Tommaso
    ESA/ESTEC, European Space Research and Technology Center, 2201, Noordwijk, AZ, Netherlands.
    Hybrid manufacturing of titanium Ti-6Al-4V combining laser metal deposition and cryogenic milling2020Inngår i: The International Journal of Advanced Manufacturing Technology, ISSN 0268-3768, E-ISSN 1433-3015, Vol. 107, nr 7-8, s. 2995-3009Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Hybrid manufacturing, which, e.g., combines additive manufacturing with conventional machining processes, can be a way of overcoming limitations currently encountered in additive manufacturing. Cryogenic milling might be a viable option for hard-to-cut materials, as it leaves a contamination-free surface and can increase surface quality and tool life compared to conventional cooling concepts. In this study, the influence of cryogenic milling with carbon dioxide on titanium Ti-6Al-4V specimens manufactured with laser metal deposition (LMD) was investigated regarding tool wear and surface integrity in comparison to dry machining and machining with cooling lubricants. Moreover, additional layers of material were deposited on top of conventionally and cryogenically machined surfaces by means of LMD. The interface zone was then examined for defects. The milling process was closely monitored by means of thermal and high-speed imaging. Optical and tactile surface analysis provided evidence that lower roughness values and improved surface qualities could be obtained with cryogenic machining in comparison to dry machining. Moreover, significantly less tool wear was observed when a cryogenic cooling medium was applied. Although the utilization of conventional cooling lubricants resulted in satisfying surface qualities, substantial residual contamination on the milled surface was detected by means of fluorescence analysis. These contaminants are suspected to cause defects when the next layer of material is deposited. This is supported by the fact that pores were found in the weld bead applied on top of the milled specimens by means of LMD. Conversely, cryogenic machining resulted in very clean surfaces due to the residue-free evaporation of the coolant. Hence, a good metallurgical bonding between the weld bead and the milled substrate could be achieved. The results indicate the great potential of cryogenic milling in hybrid manufacturing, especially in terms of intermediate machining, as it provides residue-free surfaces for subsequent material deposition without an additional cleaning step and can significantly prolongate tool life.

  • 29.
    Moritz, Juliane
    et al.
    Technische Universität Dresden, Institute of Materials Science (IfWW), 01069, Dresden, Germany; Technology Field Additive Manufacturing and Surface Technologies, Fraunhofer Institute for Material and Beam Technology IWS, 01277, Dresden, Germany.
    Teschke, Mirko
    Chair of Materials Test Engineering (WPT), TU Dortmund University, 44227, Dortmund, Germany.
    Marquardt, Axel
    Technische Universität Dresden, Institute of Materials Science (IfWW), 01069, Dresden, Germany; Technology Field Additive Manufacturing and Surface Technologies, Fraunhofer Institute for Material and Beam Technology IWS, 01277, Dresden, Germany.
    Heinze, Stefan
    Technische Universität Dresden, Institute of Materials Science (IfWW), 01069, Dresden, Germany.
    Heckert, Mirko
    Technische Universität Dresden, Institute of Materials Science (IfWW), 01069, Dresden, Germany.
    Stepien, Lukas
    Technology Field Additive Manufacturing and Surface Technologies, Fraunhofer Institute for Material and Beam Technology IWS, 01277, Dresden, Germany.
    López, Elena
    Technology Field Additive Manufacturing and Surface Technologies, Fraunhofer Institute for Material and Beam Technology IWS, 01277, Dresden, Germany.
    Brueckner, Frank
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling. Technology Field Additive Manufacturing and Surface Technologies, Fraunhofer Institute for Material and Beam Technology IWS, 01277 Dresden, Germany.
    Walther, Frank
    Chair of Materials Test Engineering (WPT), TU Dortmund University, 44227, Dortmund, Germany.
    Leyens, Christoph
    Technische Universität Dresden, Institute of Materials Science (IfWW), 01069, Dresden, Germany; Technology Field Additive Manufacturing and Surface Technologies, Fraunhofer Institute for Material and Beam Technology IWS, 01277, Dresden, Germany.
    Influence of Two-Step Heat Treatments on Microstructure and Mechanical Properties of a β-Solidifying Titanium Aluminide Alloy Fabricated via Electron Beam Powder Bed Fusion2023Inngår i: Advanced Engineering Materials, ISSN 1438-1656, E-ISSN 1527-2648, Vol. 25, nr 2, artikkel-id 2200931Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Additive manufacturing technologies, particularly electron beam powder bed fusion (PBF-EB/M), are becoming increasingly important for the processing of intermetallic titanium aluminides. This study presents the effects of hot isostatic pressing (HIP) and subsequent two-step heat treatments on the microstructure and mechanical properties of the TNM-B1 alloy (Ti–43.5Al–4Nb–1Mo–0.1B) fabricated via PBF-EB/M. Adequate solution heat treatment temperatures allow the adjustment of fully lamellar (FL) and nearly lamellar (NL-β) microstructures. The specimens are characterized by optical microscopy and scanning electron microscopy (SEM), X-ray computed tomography (CT), X-ray diffraction (XRD), and electron backscatter diffraction (EBSD). The mechanical properties at ambient temperatures are evaluated via tensile testing and subsequent fractography. While lack-of-fusion defects are the main causes of failure in the as-built condition, the mechanical properties in the heat-treated conditions are predominantly controlled by the microstructure. The highest ultimate tensile strength is achieved after HIP due to the elimination of lack-of-fusion defects. The results reveal challenges originating from the PBF-EB/M process, for example, local variations in chemical composition due to aluminum evaporation, which in turn affect the microstructures after heat treatment. For designing suitable heat treatment strategies, particular attention should therefore be paid to the microstructural characteristics associated with additive manufacturing.

    Fulltekst (pdf)
    fulltext
  • 30.
    Moritz, Juliane
    et al.
    Institute of Materials Science (IfWW), Technische Universität Dresden, 01069, Dresden, Germany; Fraunhofer Institute for Material and Beam Technology IWS, 01277, Dresden, Germany.
    Teschke, Mirko
    Chair of Materials Test Engineering (WPT), TU Dortmund University, 44227, Dortmund, Germany.
    Marquardt, Axel
    Institute of Materials Science (IfWW), Technische Universität Dresden, 01069, Dresden, Germany; Fraunhofer Institute for Material and Beam Technology IWS, 01277, Dresden, Germany.
    Stepien, Lukas
    Fraunhofer Institute for Material and Beam Technology IWS, 01277, Dresden, Germany.
    López, Elena
    Fraunhofer Institute for Material and Beam Technology IWS, 01277, Dresden, Germany.
    Brueckner, Frank
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling. Fraunhofer Institute for Material and Beam Technology IWS, 01277 Dresden, Germany.
    Walther, Frank
    Chair of Materials Test Engineering (WPT), TU Dortmund University, 44227, Dortmund, Germany.
    Leyens, Christoph
    Institute of Materials Science (IfWW), Technische Universität Dresden, 01069, Dresden, Germany; Fraunhofer Institute for Material and Beam Technology IWS, 01277, Dresden, Germany.
    Influence of Electron Beam Powder Bed Fusion Process Parameters at Constant Volumetric Energy Density on Surface Topography and Microstructural Homogeneity of a Titanium Aluminide Alloy2023Inngår i: Advanced Engineering Materials, ISSN 1438-1656, E-ISSN 1527-2648, Vol. 25, nr 15, artikkel-id 2201871Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In powder bed fusion additive manufacturing, the volumetric energy density E V is a commonly used parameter to quantify process energy input. However, recent results question the suitability of E V as a design parameter, as varying the contributing parameters may yield different part properties. Herein, beam current, scan velocity, and line offset in electron beam powder bed fusion (PBF-EB) of the titanium aluminide alloy TNM–B1 are systematically varied while maintaining an overall constant E V. The samples are evaluated regarding surface morphology, relative density, microstructure, hardness, and aluminum loss due to evaporation. Moreover, the specimens are subjected to two different heat treatments to obtain fully lamellar (FL) and nearly lamellar (NLγ) microstructures, respectively. With a combination of low beam currents, low-to-intermediate scan velocities, and low line offsets, parts with even surfaces, relative densities above 99.9%, and homogeneous microstructures are achieved. On the other hand, especially high beam currents promote the formation of surface bulges and pronounced aluminum evaporation, resulting in inhomogeneous banded microstructures after heat treatment. The results demonstrate the importance of considering the individual parameters instead of E V in process optimization for PBF-EB.

    Fulltekst (pdf)
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  • 31.
    Moritz, Juliane
    et al.
    Institute of Materials Science (IfWW), Technische Universität Dresden, 01069 Dresden, Germany; Technology Field Additive Manufacturing and Surface Technologies, Fraunhofer Institute for Material and Beam Technology IWS, 01277 Dresden, Germany.
    Teschke, Mirko
    Chair of Materials Test Engineering (WPT), TU Dortmund University, 44227 Dortmund, Germany.
    Marquardt, Axel
    Institute of Materials Science (IfWW), Technische Universität Dresden, 01069 Dresden, Germany; Technology Field Additive Manufacturing and Surface Technologies, Fraunhofer Institute for Material and Beam Technology IWS, 01277 Dresden, Germanyterial and Beam Technology IWS, 01277 Dresden, Germany.
    Stepien, Lukas
    Technology Field Additive Manufacturing and Surface Technologies, Fraunhofer Institute for Material and Beam Technology IWS, 01277 Dresden, Germany.
    López, Elena
    Technology Field Additive Manufacturing and Surface Technologies, Fraunhofer Institute for Material and Beam Technology IWS, 01277 Dresden, Germany.
    Brueckner, Frank
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling. Technology Field Additive Manufacturing and Surface Technologies, Fraunhofer Institute for Material and Beam Technology IWS, 01277 Dresden, Germany.
    Walther, Frank
    Chair of Materials Test Engineering (WPT), TU Dortmund University, 44227 Dortmund, Germany.
    Leyens, Christoph
    Institute of Materials Science (IfWW), Technische Universität Dresden, 01069 Dresden, Germany; Technology Field Additive Manufacturing and Surface Technologies, Fraunhofer Institute for Material and Beam Technology IWS, 01277 Dresden, Germany.
    Locally Adapted Microstructures in an Additively Manufactured Titanium Aluminide Alloy Through Process Parameter Variation and Heat Treatment2023Inngår i: Advanced Engineering Materials, ISSN 1438-1656, E-ISSN 1527-2648, Vol. 25, nr 2, artikkel-id 2200917Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Electron beam powder bed fusion (PBF-EB/M) has been attracting great research interest as a promising technology for additive manufacturing of titanium aluminide alloys. However, challenges often arise from the process-induced evaporation of aluminum, which is linked to the PBF-EB/M process parameters. This study applies different volumetric energy densities during PBF-EB/M processing to deliberately adjust the aluminum contents in additively manufactured Ti–43.5Al–4Nb–1Mo–0.1B (TNM-B1) samples. The specimens are subsequently subjected to hot isostatic pressing (HIP) and a two-step heat treatment. The influence of process parameter variation and heat treatments on microstructure and defect distribution are investigated using optical and scanning electron microscopy, as well as X-ray computed tomography (CT). Depending on the aluminum content, shifts in the phase transition temperatures can be identified via differential scanning calorimetry (DSC). It is confirmed that the microstructure after heat treatment is strongly linked to the PBF-EB/M parameters and the associated aluminum evaporation. The feasibility of producing locally adapted microstructures within one component through process parameter variation and subsequent heat treatment can be demonstrated. Thus, fully lamellar and nearly lamellar microstructures in two adjacent component areas can be adjusted, respectively.

    Fulltekst (pdf)
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  • 32.
    Moritz, Juliane
    et al.
    Institute of Materials Science (IfWW), Technische Universität Dresden, 01069 Dresden, Germany; Department of Additive Manufacturing and Printing, Fraunhofer Institute for Material and Beam Technology IWS, 01277 Dresden, Germany.
    Teschke, Mirko
    Department of Materials Test Engineering (WPT), TU Dortmund University, 44227 Dortmund, Germany.
    Marquardt, Axel
    Institute of Materials Science (IfWW), Technische Universität Dresden, 01069 Dresden, Germany; Department of Additive Manufacturing and Printing, Fraunhofer Institute for Material and Beam Technology IWS, 01277 Dresden, Germany.
    Stepien, Lukas
    Department of Additive Manufacturing and Printing, Fraunhofer Institute for Material and Beam Technology IWS, 01277 Dresden, Germany.
    López, Elena
    Department of Additive Manufacturing and Printing, Fraunhofer Institute for Material and Beam Technology IWS, 01277 Dresden, Germany.
    Brückner, Frank
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling. Department of Additive Manufacturing and Printing, Fraunhofer Institute for Material and Beam Technology IWS, 01277 Dresden, Germany.
    Macias Barrientos, Marina
    Department of Materials Test Engineering (WPT), TU Dortmund University, 44227 Dortmund, Germany.
    Walther, Frank
    Department of Materials Test Engineering (WPT), TU Dortmund University, 44227 Dortmund, Germany.
    Leyens, Christoph
    Institute of Materials Science (IfWW), Technische Universität Dresden, 01069 Dresden, Germany; Department of Additive Manufacturing and Printing, Fraunhofer Institute for Material and Beam Technology IWS, 01277 Dresden, Germany.
    Electron beam powder bed fusion of γ‐titanium aluminide: Effect of processing parameters on part density, surface characteristics and aluminum content2021Inngår i: Metals, ISSN 2075-4701, Vol. 11, nr 7, artikkel-id 1093Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Gamma titanium aluminides are very interesting for their use in high‐performance applications such as aircraft engines due to their low density, high stiffness and favorable hightemperature properties. However, the pronounced brittleness of these intermetallic alloys is a major challenge for their processing through conventional fabrication methods. Additive manufacturing by means of electron beam powder bed fusion (EB‐PBF) significantly improves the processability of titanium aluminides due to the high preheating temperatures and facilitates complex components. The objective of this study was to determine a suitable processing window for EB‐PBF of the TNM‐B1 alloy (Ti‐43.5Al‐4Nb‐1Mo‐0.1B), using an increased aluminum content in the powder raw material to compensate for evaporation losses during the process. Design of experiments was used to evaluate the effect of beam current, scan speed, focus offset, line offset and layer thickness on porosity. Top surface roughness was assessed through laser scanning confocal microscopy. Scanning electron microscopy, electron backscatter diffraction (EBSD) and energydispersive X‐ray spectroscopy (EDX) were used for microstructural investigation and to analyze aluminum loss depending on the volumetric energy density used in EB‐PBF. An optimized process parameter set for achieving part densities of 99.9% and smooth top surfaces was derived. The results regarding microstructures and aluminum evaporation suggest a solidification via the β‐phase.

  • 33.
    Mueller, M.
    et al.
    Fraunhofer IWS, Winterbergstraße 28, 01277, Dresden, Germany; Institute of Materials Science, Technische Universität Dresden, Helmholtzstr. 7, 01069, Dresden, Germany.
    Franz, K.
    Fraunhofer IWS, Winterbergstraße 28, 01277, Dresden, Germany.
    Riede, M.
    Fraunhofer IWS, Winterbergstraße 28, 01277, Dresden, Germany.
    López, E.
    Fraunhofer IWS, Winterbergstraße 28, 01277, Dresden, Germany.
    Brueckner, F.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling. Fraunhofer IWS, Winterbergstraße 28, 01277, Dresden, Germany.
    Leyens, C.
    Fraunhofer IWS, Winterbergstraße 28, 01277, Dresden, Germany; Institute of Materials Science, Technische Universität Dresden, Helmholtzstr. 7, 01069, Dresden, Germany.
    Influence of process parameter variation on the microstructure of thin walls made of Inconel 718 deposited via laser-based directed energy deposition with blown powder2023Inngår i: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 58, nr 27, s. 11310-11326Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In laser-based directed energy deposition (L-DED) of Inconel 718 the microstructure of the fabricated components strongly depends on the applied process parameters and the resulting solidification conditions. Numerous studies have shown that the process parameters deposition speed and laser power have a major influences on microstructural properties, such as dendrite morphology and segregation behavior. This study investigates how changes in these process parameters affect the microstructure and hardness when the line mass, and thus the resulting layer height, are kept constant. This enables the microstructural comparison of geometrically similar specimens that were manufactured with the same number of layers but severely different process parameters. This approach yields the benefit of almost identical geometrical boundary conditions, such as the layer-specific build-height and heat conducting cross section, for all specimens. For microstructural analysis scanning electron microscopy and energy dispersive X-ray spectroscopy were applied and the results evaluated in a quantitative manner. The microstructural features primary dendritic arm spacing, fraction and morphology of precipitated Laves phase as well as the spatially resolved chemical composition were measured along the build-up direction. The occurring cooling rates were calculated based on the primary dendritic arm spacing using semi-empirical models. Three different models used by others researchers were applied and evaluated with respect to their applicability for L-DED. Finally, microhardness measurements were performed for a baseline evaluation of the influence on the materials’ mechanical properties.

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  • 34.
    Mueller, Michael
    et al.
    Fraunhofer Institute for Material and Beam Technology, Dresden, Germany; Technische Universität Dresden, Dresden, Germany.
    Riede, Mirko
    Fraunhofer Institute for Material and Beam Technology, Dresden, Germany.
    Eberle, Sebastian
    Kampf Telescope Optics GmbH, Munich, Germany.
    Reutlinger, Arnd
    Kampf Telescope Optics GmbH, Munich, Germany.
    Brandão, Ana D.
    European Space Research and Technology Centre, ESTEC, Noordwijk, Netherlands.
    Pambaguian, Laurent
    European Space Research and Technology Centre, ESTEC, Noordwijk, Netherlands.
    Seidel, André
    Fraunhofer Institute for Material and Beam Technology, Dresden, Germany.
    Lopéz, Elena
    Fraunhofer Institute for Material and Beam Technology, Dresden, Germany.
    Brückner, Frank
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling. Fraunhofer Institute for Material and Beam Technology, Dresden, Germany.
    Beyer, Eckhard
    Fraunhofer Institute for Material and Beam Technology, Dresden, Germany; Technische Universität Dresden, Dresden, Germany.
    Leyens, Christoph
    Fraunhofer Institute for Material and Beam Technology, Dresden, Germany; Technische Universität Dresden, Dresden, Germany.
    Microstructural, mechanical, and thermo-physical characterization of hypereutectic AlSi40 fabricated by selective laser melting2019Inngår i: Journal of laser applications, ISSN 1042-346X, E-ISSN 1938-1387, Vol. 31, nr 2, artikkel-id 02232Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The powder bed additive manufacturing process selective laser melting (SLM) enables designers and engineers to overcome restrictions of conventional manufacturing technologies. The potential of fabricating complex lightweight structures and processing advanced materials is a key feature for enhancing further development of high performance components for space applications. Due to a high specific stiffness and a thermal expansion coefficient very close to electroless nickel, which is an advantageous optical coating material, the hypereutectic aluminum-silicon alloy AlSi40 shows great potential for the manufacturing of optical mirrors for space applications. In prior investigations, Hilpert et al.showed the feasibility to process AlSi40 by SLM [E. Hilpert and S. Risse, Materials Science & Technology Conference and Exhibition MS&T'15, Columbus, Ohio, 4–8 October 2015(Association for Iron & Steel Technology, Warrendale, PA, 2015) and E. Hilpert, “Struktur und Eigenschaften von additiv gefertigten hypereutektischen Aluminum-Siliciumlegierungen,” in Werkstoffwoche 2017, Dresden, Germany28 September 2017 (Deutsche Gesellschaft für Materialkunde e.V., Berlin, 2017)]. Nevertheless, in order to qualify this material for space applications, the manufacturing process and fabricated samples need to be thoroughly investigated in terms of microstructural, mechanical, as well as thermo-physical characterization. The authors present results of the SLM process development for manufacturing dense AlSi40 samples with a relative density above 99.50%. The effect of various process parameters, such as hatch distance, preheating, and scanning strategy, on the formation of defects was investigated by destructive [e.g., optical microscopy (OM)] and nondestructive (e.g., computed tomography) testing. In addition, the effect of several thermal post-treatments on the AlSi40 microstructure was profoundly analyzed by multiple methods such as OM, scanning electron microscopy, and energy dispersive x-ray spectroscopy analysis. Moreover, mechanical and thermo-physical testing of manufactured specimens was conducted to provide material characteristics for component design. In conclusion, the determined material properties of AlSi40 samples fabricated by SLM were compared to bulk material properties. The gained knowledge and testing data were evaluated in order to identify correlations and dependencies.

  • 35.
    Müller, M.
    et al.
    Fraunhofer IWS, Winterbergstraße 28, Dresden 01277, Germany; Technische Universität Dresden, Helmholtzstr. 7, 01069 Dresden, Germany.
    Labisch, C. C.
    Fraunhofer IWS, Winterbergstraße 28, Dresden 01277, Germany.
    Gerdt, L.
    Fraunhofer IWS, Winterbergstraße 28, Dresden 01277, Germany.
    Bach, L.
    Fraunhofer IWS, Winterbergstraße 28, Dresden 01277, Germany.
    Riede, M.
    Fraunhofer IWS, Winterbergstraße 28, Dresden 01277, Germany.
    Kaspar, J.
    Fraunhofer IWS, Winterbergstraße 28, Dresden 01277, Germany.
    López, Elena
    Fraunhofer IWS, Winterbergstraße 28, Dresden 01277, Germany.
    Brueckner, Frank
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling. Fraunhofer IWS, Winterbergstraße 28, Dresden 01277, Germany.
    Zimmermann, M.
    Fraunhofer IWS, Winterbergstraße 28, Dresden 01277, Germany; Technische Universität Dresden, Helmholtzstr. 7, 01069 Dresden, Germany.
    Leyens, C.
    Fraunhofer IWS, Winterbergstraße 28, Dresden 01277, Germany; Technische Universität Dresden, Helmholtzstr. 7, 01069 Dresden, Germany.
    Multimaterial direct energy deposition: From three-dimensionally graded components to rapid alloy development for advanced materials2023Inngår i: Journal of laser applications, ISSN 1042-346X, E-ISSN 1938-1387, Vol. 35, nr 1, artikkel-id 012006Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Laser-based direct energy deposition (L-DED) with blown powder enables the simultaneous or sequential processing of different powder materials within one component and, thus, offers the possibility of additive multimaterial manufacturing. Therefore, the process allows a spatially resolved material allocation and fabrication of sharp or even graded material transitions. Within this contribution, the latest results from two major research fields in multimaterial L-DED—(I) automation and (II) rapid alloy development of high entropy alloys (HEAs) by in situ synthesis—shall be presented. First, an automated multimaterial deposition process was developed, which enables the automated manufacturing of three-dimensionally graded specimens. For this, a characterization of the deposition system regarding powder feeding dynamics and resulting powder mixtures in the process zone was conducted. The obtained system characteristics were used to achieve a three-dimensional deposition of specified powder mixtures. The fabricated specimens were analyzed by energy-dispersive x-ray spectroscopy, scanning electron microscopy, and micro hardness measurement. The research demonstrates the increasing readiness of L-DED for the fabrication of multimaterial components. Second, the latest results from rapid alloy development for HEAs by DED are presented. By the simultaneous usage of up to four powder feeders, a vast range of alloy compositions within the Al–Ti–Co–Cr–Fe–Ni HEA system was investigated. For this, tailored measurement systems such as an in-house developed powder sensor were beneficially used. The study shows the influence of a variation of Al on the phase formation and resulting mechanical properties and demonstrates the potential of L-DED for reducing development times for new alloys.

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  • 36.
    Müller, Michael
    et al.
    Department of Additive Manufacturing and Printing, Fraunhofer Institute for Material and Beam Technology, Winterbergstraße 28, 01277 Dresden, Germany; Institute of Materials Science, Faculty of Mechanical Science and Engineering, TUD Dresden University of Technology, Helmholtzstr. 7, 01069 Dresden, Germany.
    Enghardt, Stefan
    Institute of Materials Science, Faculty of Mechanical Science and Engineering, TUD Dresden University of Technology, Helmholtzstr. 7, 01069 Dresden, Germany.
    Kuczyk, Martin
    Department of Additive Manufacturing and Printing, Fraunhofer Institute for Material and Beam Technology, Winterbergstraße 28, 01277 Dresden, Germany; Institute of Materials Science, Faculty of Mechanical Science and Engineering, TUD Dresden University of Technology, Helmholtzstr. 7, 01069 Dresden, Germany.
    Riede, Mirko
    Department of Additive Manufacturing and Printing, Fraunhofer Institute for Material and Beam Technology, Winterbergstraße 28, 01277 Dresden, Germany.
    López, Elena
    Department of Additive Manufacturing and Printing, Fraunhofer Institute for Material and Beam Technology, Winterbergstraße 28, 01277 Dresden, Germany.
    Brueckner, Frank
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling. Department of Additive Manufacturing and Printing, Fraunhofer Institute for Material and Beam Technology, Winterbergstraße 28, 01277 Dresden, Germany.
    Marquardt, Axel
    Department of Additive Manufacturing and Printing, Fraunhofer Institute for Material and Beam Technology, Winterbergstraße 28, 01277 Dresden, Germany; Institute of Materials Science, Faculty of Mechanical Science and Engineering, TUD Dresden University of Technology, Helmholtzstr. 7, 01069 Dresden, Germany.
    Leyens, Christoph
    Department of Additive Manufacturing and Printing, Fraunhofer Institute for Material and Beam Technology, Winterbergstraße 28, 01277 Dresden, Germany; Institute of Materials Science, Faculty of Mechanical Science and Engineering, TUD Dresden University of Technology, Helmholtzstr. 7, 01069 Dresden, Germany.
    Microstructure of NiAl-Ta-Cr in situ alloyed by induction-assisted laser-based directed energy deposition2024Inngår i: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 238, artikkel-id 112667Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The development of new high temperature materials for coatings as well as structural components is an important topic to contribute to a higher efficiency and sustainability of e.g. gas turbine engines. One promising new class of high temperature materials are NiAl-based alloys. Within this study, the microstructure and microhardness of NiAl-Ta-Cr alloys with varying Cr and Ta content were investigated. Graded specimens were fabricated by laser-based directed energy deposition utilizing an in situ alloying approach by mixing elemental Ta and Cr as well as pre-alloyed NiAl powder. Thermodynamic calculations were performed to design the alloy compositions beforehand. Inductive preheating of the substrate was used to counter the challenge of cracking due to the high brittleness. The results show that the cracking decreases with increasing preheating temperature. However, even at 700 °C, the cracking cannot be fully eliminated. Scanning electron microscopy, X-ray diffraction and electron backscatter diffraction revealed the formation of the phases B2-NiAl, A2-Cr and C14-NiAlTa within NiAl-Ta and NiAl-Cr alloys. For NiAl-Ta-Cr compositions, deviations regarding the phase formation between calculation and experiment were observed. Maximum hardness values were achieved within the NiAl-Ta and NiAl-Ta-Cr systems for the eutectic compositions at 14 at.-% Ta with maximum values above 900 HV0.1.

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  • 37.
    Müller, Michael
    et al.
    Department of Additive Manufacturing and Printing, Fraunhofer Institute for Material and Beam Technology, Winterbergstraβe 28, 01277 Dresden, Germany; Faculty of Mechanical Science and Engineering, Institute of Materials Science, Dresden University of Technology, Helmholtzstr. 7, 01069 Dresden, Germany .
    Heinen, Bastian
    Department of Additive Manufacturing and Printing, Fraunhofer Institute for Material and Beam Technology, Winterbergstraβe 28, 01277 Dresden, Germany.
    Riede, Mirko
    Department of Additive Manufacturing and Printing, Fraunhofer Institute for Material and Beam Technology, Winterbergstraβe 28, 01277 Dresden, Germany.
    López, Elena
    Department of Additive Manufacturing and Printing, Fraunhofer Institute for Material and Beam Technology, Winterbergstraβe 28, 01277 Dresden, Germany.
    Brückner, Frank
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling. Department of Additive Manufacturing and Printing, Fraunhofer Institute for Material and Beam Technology, Winterbergstraβe 28, 01277 Dresden, Germany.
    Leyens, Christoph
    Department of Additive Manufacturing and Printing, Fraunhofer Institute for Material and Beam Technology, Winterbergstraβe 28, 01277 Dresden, Germany; Faculty of Mechanical Science and Engineering, Institute of Materials Science, Dresden University of Technology, Helmholtzstr. 7, 01069 Dresden, Germany.
    Additive Manufacturing of β-NiAl by Means of Laser Metal Deposition of Pre-Alloyed and Elemental Powders2021Inngår i: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 14, nr 9, artikkel-id 2246Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The additive manufacturing (AM) technique, laser metal deposition (LMD), combines the advantages of near net shape manufacturing, tailored thermal process conditions and in situ alloy modification. This makes LMD a promising approach for the processing of advanced materials, such as intermetallics. Additionally, LMD allows the composition of a powder blend to be modified in situ. Hence, alloying and material build-up can be achieved simultaneously. Within this contribution, AM processing of the promising high-temperature material β-NiAl, by means of LMD, with elemental powder blends, as well as with pre-alloyed powders, was presented. The investigations showed that by applying a preheating temperature of 1100 °C, β-NiAl could be processed without cracking. Additionally, by using pre-alloyed, as well as elemental powders, a single phase β-NiAl microstructure can be achieved in multi-layer build-ups. Major differences between the approaches were found within substrate near regions. For in situ alloying of Ni and Al, these regions are characterized by an inhomogeneous elemental distribution in a layerwise manner. However, due to the remelting of preceding layers during deposition, a homogenization can be observed, leading to a single-phase structure. This shows the potential of high temperature preheating and in situ alloying to push the development of new high temperature materials for AM.

  • 38.
    Müller, Michael
    et al.
    Department of Additive Manufacturing, Fraunhofer Institute for Material and Beam Technology, Winterbergstraße 28, Dresden, 01277 Germany; Institute of Materials Science, Faculty of Mechanical Science and Engineering, Dresden University of Technology, Helmholtzstr. 7, Dresden, 01069 Germany.
    Stellmacher, André
    Department of Additive Manufacturing, Fraunhofer Institute for Material and Beam Technology, Winterbergstraße 28, Dresden, 01277 Germany.
    Riede, Mirko
    Department of Additive Manufacturing, Fraunhofer Institute for Material and Beam Technology, Winterbergstraße 28, Dresden, 01277 Germany.
    López, Elena
    Department of Additive Manufacturing, Fraunhofer Institute for Material and Beam Technology, Winterbergstraße 28, Dresden, 01277 Germany.
    Brueckner, Frank
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling. Department of Additive Manufacturing, Fraunhofer Institute for Material and Beam Technology, Winterbergstraße 28, Dresden, 01277 Germany.
    Leyens, Christoph
    Department of Additive Manufacturing, Fraunhofer Institute for Material and Beam Technology, Winterbergstraße 28, Dresden, 01277 Germany; Institute of Materials Science, Faculty of Mechanical Science and Engineering, Dresden University of Technology, Helmholtzstr. 7, Dresden, 01069 Germany.
    Multimaterial Additive Manufacturing of graded Laves phase reinforced NiAlTa structures by means of Laser Metal Deposition2022Inngår i: Advanced Engineering Materials, ISSN 1438-1656, E-ISSN 1527-2648, Vol. 24, nr 4, artikkel-id 2100993Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Recently, the Additive Manufacturing (AM) technology Laser Metal Deposition (LMD) has gained a lot of attention for processing crack prone high temperature materials such as nickel based superalloys or intermetallics. This contribution presents a feasibility study on LMD of a graded transition from binary ß-NiAl to Ni50Al42Ta8 with the aim to show the possibility of manufacturing ß-NiAl based structures with a spatially resolved microstructure and subsequently tailored mechanical properties. For achieving this the alloys Ni50Al50 and Ni50Al42Ta8 are co-injected into the process zone and the powder feeding rates are adapted in a layer-wise manner. Due to pre-heating temperatures of up to 1000 °C the transition can be manufactured with high relative density and a low degree of cold cracking. Scanning electron microscopy of the transition zone shows the formation of a fine dendritic microstructure consisting of ß-NiAl dendritic and NiAlTa interdendritic regions. Large area energy dispersive x-ray analysis reveals a gradient in NiAlTa Laves phase content with increasing build height. The observed volume fraction of Laves phase corresponds well to reported values from cast ingots. Finally, hardness measurements along the build-up direction show an increase in hardness from 300 HV0.1 to 680 HV0.1 indicating a tremendous increase in tensile strength.

  • 39.
    Naesstroem, Himani
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Brueckner, Frank
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling. Fraunhofer-Institut fur Werkstoff und Strahltechnik, Dresden, Germany.
    Kaplan, Alexander F.H.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    From mine to part: Directed energy deposition of iron ore2021Inngår i: Rapid prototyping journal, ISSN 1355-2546, E-ISSN 1758-7670, Vol. 27, nr 11, s. 37-42Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Purpose - This paper aims to gain an understanding of the behaviour of iron ore when melted by a laser beam in a continuous manner. This fundamental knowledge is essential to further develop additive manufacturing routes such as production of low cost parts and in-situ reduction of the ore during processing.

    Design/methodology/approach - Blown powder directed energy deposition was used as the processing method. The process was observed through high-speed imaging, and computed tomography was used to analyse the specimens.

    Findings - The experimental trials give preliminary results showing potential for the processability of iron ore for additive manufacturing. A large and stable melt pool is formed in spite of the inhomogeneous material used. Single and multilayer tracks could be deposited. Although smooth and even on the surface, the single layer tracks displayed porosity. In case of multilayered tracks, delamination from the substrate material and deformation can be seen. High-speed videos of the process reveal various process phenomena such as melting of ore powder during feeding, cloud formation, melt pool size, melt flow and spatter formation.

    Originality/value - Very little literature is available that studies the possible use of ore in additive manufacturing. Although the process studied here is not industrially useable as is, it is a step towards processing cheap unprocessed material with a laser beam.

  • 40.
    Naesstroem, Himani
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Brückner, Frank
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling. Fraunhofer IWS, Winterbergstrasse 28, 01277 Dresden, Germany.
    Kaplan, Alexander F. H.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Blown powder directed energy deposition on various substrate conditions2022Inngår i: Journal of Manufacturing Processes, ISSN 1526-6125, Vol. 73, s. 660-667Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Blown powder directed energy deposition of SS316L powder is carried out on various substrate surface conditions of SS304 such as cleaned, sand blasted, milled, oily, cold galvanised and painted to study their influence on the process. High-speed imaging is used for process observation and the deposited tracks are analysed qualitatively and quantitatively using surface images, cross sectional macrographs and x-ray images. Frames from high-speed imaging reveal the removal of additional material from the substrate surface such as paint and oil. The stages involved in their removal: peeling and evaporation are presented. EDS analysis showed that no additional elements other than powder and substrate material are found in the track volume. The quantitative results for all specimens show that the surface conditions had minor influences on track width, track height, wetting angle, dilution and deposited cross sectional area. Defects such as porosity, inclusions and cracking were not observed related to the surface conditions. These findings could significantly reduce processing time by skipping the cleaning step before directed energy deposition such as laser cladding or repair in industrial applications.

  • 41.
    Näsström, Jonas
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Brueckner, Frank
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Kaplan, Alexander
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    A near-vertical approach to Laser Narrow Gap Multi-Layer Welding2020Inngår i: Optics and Laser Technology, ISSN 0030-3992, E-ISSN 1879-2545, Vol. 121, artikkel-id 105798Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A novel, near-vertical approach to the usually horizontal laser Narrow Gap Multi-Layer Welding process is introduced. The process is applied to join X100 pipeline steel and studied through High Speed Imaging. The produced welded joints are compared to their horizontally welded counterparts using 3D scanning, longitudinal & perpendicular cross sections and Computed Tomography analysis. The near-vertical approach is found to be robust and produce welded joints with a uniform appearance. The top surface exhibits certain reoccurring morphological features, and variations in internal track melting boundaries are observed. Any observed cavities appear similar to those produced using the horizontal process, with the difference of their orientation. A combination of the horizontal and the near-vertical process could be beneficial; the near-vertical approach offers potential for shorter inter-layer time and the horizontal method for better surface finish than that of its counterpart. Potential benefits of, and improvements to, the near-vertical process are discussed.

  • 42.
    Näsström, Jonas
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Brueckner, Frank
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling. Fraunhofer Institute for Material and Beam Technology, IWS, Dresden, Germany.
    Kaplan, Alexander
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Laser enhancement of wire arc additive manufacturing2019Inngår i: Journal of laser applications, ISSN 1042-346X, E-ISSN 1938-1387, Vol. 31, nr 2, artikkel-id 022307Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Additive manufacturing (AM) can be used for the fabrication of large metal parts, e.g., aerospace/space applications. Wire arc additivemanufacturing (WAAM) can be a suitable process for this due to its high deposition rates and relatively low equipment and operationcosts. In WAAM, an electrical arc is used as a heat source and the material is supplied in the form of a metal wire. A known disadvantageof the process is the comparably low dimensional accuracy. This is usually compensated by generating larger structures than desired andmachining away excess materials. So far, using combinations of arc in atmospheric conditions with high precision laser heat sources forAM has not yet been widely researched. Properties of the comparable cheap arc-based process, such as melt pool stability and dimensionalaccuracy, can be improved with the addition of a laser source. Within this paper, impacts of adding a laser beam to the WAAMprocess are presented. Differences between having the beam in a leading or a trailing position, relative to the wire and arc, are alsorevealed. Structures generated using the arc-laser-hybrid processes are compared to ones made using only an arc as the heat source. Bothgeometrical and material aspects are studied to determine the influences of laser hybridization, applied techniques including x ray,energy-dispersive X-ray spectroscopy, and high precision 3D scanning. A trailing laser beam is found to best improve topological capabilitiesof WAAM. Having a leading laser beam, on the other hand, is shown to affect cold metal transfer synergy behavior, promotinghigher deposition rates but decreasing topological accuracy.

  • 43.
    Näsström, Jonas
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Brueckner, Frank
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling. Fraunhofer Institute for Material and Beam Technology, IWS, Dresden, Germany.
    Kaplan, Alexander
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Measuring the effects of a laser beam on melt pool fluctuation in arc additive manufacturing2019Inngår i: Rapid prototyping journal, ISSN 1355-2546, E-ISSN 1758-7670, Vol. 25, nr 3, s. 488-495Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Purpose

    The steadily growing popularity of additive manufacturing (AM) increases the demand for understanding fundamental behaviors of these processes. High-speed imaging (HSI) can be a useful tool to observe these behaviors, but many studies only present qualitative analysis. The purpose of this paper is to propose an algorithm-assisted method as an intermediate to rapidly quantify data from HSI. Here, the method is used to study melt pool surface profile movement in a cold metal transfer-based (CMT-based) AM process, and how it changes when the process is augmented with a laser beam.

    Design/methodology/approach

    Single-track wide walls are generated in multiple layers using only CMT, CMT with leading and with trailing laser beam while observing the processes using HSI. The studied features are manually traced in multiple HSI frames. Algorithms are then used for sorting measurement points and generating feature curves for easier comparison.

    Findings

    Using this method, it is found that the fluctuation of the melt surface in the chosen CMT AM process can be reduced by more than 35 per cent with the addition of a laser beam trailing behind the arc. This indicates that arc and laser can be a viable combination for AM.

    Originality/value

    The suggested quantification method was used successfully for the laser-arc hybrid process and can also be applied for studies of many other AM processes where HSI is implemented. This can help fortify and expand the understanding of many phenomena in AM that were previously too difficult to measure.

  • 44.
    Näsström, Jonas
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Brueckner, Frank
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling. Fraunhofer Institute for Material and Beam Technology, IWS, Germany.
    Kaplan, Alexander F.H.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Imperfections in narrow gap multi-layer welding: Potential causes and countermeasures2020Inngår i: Optics and lasers in engineering, ISSN 0143-8166, E-ISSN 1873-0302, Vol. 129, artikkel-id 106011Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Narrow Gap Multi-Layer Welding (NGMLW) using a laser as the main heat source and metal wire for material addition has been a growing topic of interest in the last decade. This is in part due to its potential for joining much thicker sheets of steel than what is usually considered possible when using autogenous laser welding. The process has shown great potential but improvements can still be made, e.g. through increased process control to decrease welding imperfections. Using closed-loop control, where the process is continuously monitored and regulated automatically, can help to account for variations during manufacturing. However, achieving functional closed loop control can be challenging due to limitations in data gathering and processing speeds. Important initial steps include identifying what data can be useful and how frequently this data has to be recorded. Too much data takes too long to process while too little causes risks of missing important details. In this study, 20 mm thick X80 pipeline steel sheets are joined together using this multi-layer approach; the samples are examined using 3D scanning and Computed Tomography (CT) analysis and the process is observed using High-Speed Imaging (HSI). The quality of the welded joint and welding imperfections are discussed and potential points of formation are identified. Suggestions on how to mitigate imperfections to improve the quality of the welded joint are presented, including the potential to use camera imaging for closed-loop process control and additional industrial uses of the HSI footage.

  • 45.
    Polenz, S.
    et al.
    Fraunhofer Institute for Material and Beam Technology, Dresden, Germany.
    Seidel, A.
    Fraunhofer Institute for Material and Beam Technology, Dresden, Germany.
    Moritz, J.
    Fraunhofer Institute for Material and Beam Technology, Dresden, Germany.
    Kunz, W.
    Fraunhofer Institute for Ceramic Technologies and Systems IKTS, Dresden, Germany.
    Riede, M.
    Fraunhofer Institute for Material and Beam Technology, Dresden, Germany.
    Lopéz, E.
    Fraunhofer Institute for Material and Beam Technology, Dresden, Germany.
    Brückner, Frank
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling. Fraunhofer Institute for Material and Beam Technology, Dresden, Germany.
    Leyens, C.
    Fraunhofer Institute for Material and Beam Technology, Dresden, Germany.Technische Universität Dresden, Dresden, Germany.
    Wavelength dependent laser material processing of ceramic materials2019Inngår i: Journal of laser applications, ISSN 1042-346X, E-ISSN 1938-1387, Vol. 31, nr 2, artikkel-id 022316Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In the future, ceramic materials will find even more applications in aerospace, energy, and drive technology. Reasons for this are the comparatively low density and good long-term stability at high temperatures for applications for components exposed to high temperatures, e.g., of engines. By using increasing combustion temperatures through the use of ceramics increases the efficiency of modern drive systems [Ohnabe, Masaki, Onozuka, Miyahara, and Sasa, Compos. Part A Appl. Sci. Manuf. 30, 489–496 (1999)]. Despite the high interest of the aviation industry to increase the use of ceramic materials, the time- and energy-consuming classical production of these materials and the concomitant limiting factors in terms of shape and size are still a drawback [Krenkel, Ceramic Matrix Composites Fiber Reinforced Ceramics and their Applications (WIY-VCH Verlag GmbH & Co. KGaA, Weinheim, 2008)]. This paper follows a new approach to producing ceramic matrix composites (CMCs). The laser material deposition (LMD) and selective laser melting techniques were used to investigate the coupling of different laser wavelengths into ceramic materials. By combining different energy sources and utilizing wavelength-dependent energy coupling, the additive manufacturing application of ceramic materials to metallic substrates was tested. With the knowledge gained from wavelength-dependent energy coupling, the potential for the production of CMCs should be demonstrated by means of LMD

  • 46.
    Polenz, Stefan
    et al.
    Fraunhofer Institute for Material and Beam Technology (IWS), Winterbergstr. 28, 01277 Dresden, Germany.
    Kolbe, Christian
    FKT Formenbau und Kunststofftechnik GmbH, Jahnstr. 2, 07819 Triptis, Germany.
    Bittner, Florian
    Fraunhofer Institute for Machine Tools and Forming Technology (IWU), Nöthnitzer Str. 44, 01187 Dresden, Germany.
    López, Elena
    Fraunhofer Institute for Material and Beam Technology (IWS), Winterbergstr. 28, 01277 Dresden, Germany.
    Brückner, Frank
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling. Fraunhofer Institute for Material and Beam Technology (IWS), Winterbergstr. 28, 01277 Dresden, Germany.
    Leyens, Christoph
    Fraunhofer Institute for Material and Beam Technology (IWS), Winterbergstr. 28, 01277 Dresden, Germany. Technische Universität Dresden, Helmholtzstr. 7, 01069 Dresden, Germany.
    Integration of pure copper to optimize heat dissipation in injection mould inserts using laser metal deposition2021Inngår i: Journal of laser applications, ISSN 1042-346X, E-ISSN 1938-1387, Vol. 33, nr 1, artikkel-id 012029Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Conventional infrared lasers (1070 nm) are not ideal for processing materials such as copper or gold. The reason for this is the corresponding high reflectivity of the aforementioned materials for infrared radiation. Since 2017, so-called “green lasers” {wavelengths around 500 nm [Kaliudis, see https://www.trumpf.com/de_DE/magazin/gruene-welle-fuers-kupferschweissen/ for “Grüne Welle fürs Kupferschweißen, TRUMPF Media Relations,” Press Release (2017)]} are available for welding processes and additive manufacturing technologies, viz., laser powder bed fusion (LPBF) and laser metal deposition (LMD). These lasers are specially designed for the processing of highly reflective materials and have been recently used for the fabrication of specimens from pure copper. Due to process reasons, only one alloy is typically used for the manufacturing of components if powder bed based methods (LPBF) are applied. For many components, however, it is the combination of different materials (differences in thermophysical properties) that leads to an improvement in the component performance. The LMD process, in contrast to LPBF, can be adjusted with relative low efforts for the processing of two or more different materials. This offers new possibilities for the functionalization of parts that are already fabricated through a combination of subtractive and additive technologies (hybrid manufacturing). A mould insert for polymer injection molding will be presented in this contribution. It was produced by using a combination of different processes (subtractive, additive) and materials (pure copper, steel 1.2764).2–5 For a conventionally manufactured basic body (1.2764), copper cores were integrated in the corner areas by means of LMD. The cladding of the cores with 1.2764 was carried out with regard to the basic body and guaranteed dimensional accuracy for further processing. In order to improve the flow of coolant to the copper cores in the later application, the upper part of the mould insert with conformal cooling channels was manufactured using LPBF. The entire tool insert demonstrator was then finished and case-hardened. Initial tests under real conditions on the overall component are intended to prove full functionality. Simultaneously, we discuss the added value of the hybrid manufacturing approach that was funded by the Federal Ministry of Education and Research (BMBF) in Germany as part of the AGENT-3D project IMProVe.

  • 47.
    Polenz, Stefan
    et al.
    Fraunhofer Institute for Material and Beam Technology (IWS), Dresden, 01277, Germany.
    Kunz, Willy
    Fraunhofer Institute for Ceramic Technologies and Systems (IKTS), Dresden, 01277, Germany.
    Braun, Benjamin
    Space Structures GmbH, Berlin, 12435, Germany.
    Franke, Andrea
    AXIAL Ingenieurgesellschaft für Maschinenbau mbH, Radebeul, 01445, Germany.
    López, Elena
    Fraunhofer Institute for Material and Beam Technology (IWS).
    Brückner, Frank
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling. Fraunhofer Institute for Material and Beam Technology (IWS), Dresden, 01277, Germany.
    Leyens, Cristoph
    Fraunhofer Institute for Material and Beam Technology (IWS), Dresden, 01277, Germany; Technische Universität Dresden, Dresden, 01069, Germany.
    Development of a system for additive manufacturing of ceramic matrix composite structures using laser technology2021Inngår i: Materials, E-ISSN 1996-1944, Vol. 14, nr 12, artikkel-id 3248Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Ceramic matrix composites (CMCs) are refractory ceramic materials with damage-tolerant behavior. Coming from the space industry, this class of materials is increasingly being used in other applications, such as automotive construction for high-performance brake discs, furnace technology, heat coatings for pipe systems and landing flaps on reusable rocket sections. In order to produce CMC faster and more cost-efficiently for the increasing demand, a new additive manufacturing process is being tested, which in the future should also be able to realize material joints and higher component wall thicknesses than conventional processes. The main features of the process are as follows. A ceramic fiber bundle is de-sized and infiltrated with ceramic suspension. The bundle infiltrated with matrix material is dried and then applied to a body form. During application, the matrix material is melted by laser radiation without damaging the fiber material. For the initial validation of the material system, samples are pressed and analyzed for their absorption properties using integrating sphere measurement. With the results, a suitable processing laser is selected, and initial melting tests of the matrix system are carried out. After the first validation of the process, a test system is set up, and the first test specimens are produced to determine the material parameters.

  • 48.
    Prasad, Himani Siva
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Brueckner, Frank
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Kaplan, Alexander F.H.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Powder incorporation and spatter formation in high deposition rate blown powder directed energy deposition2020Inngår i: Additive Manufacturing, E-ISSN 2214-8604, Vol. 35, artikkel-id 101413Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A high deposition rate blown powder directed energy deposition process is presented. Clad tracks are deposited and the process is observed by high-speed imaging. An island of unmelted powder forms inside the melt pool, in the centre of the laser spot, which can be attributed to the highly focussed powder flow and the laser beam configuration used. On contact with the melt pool, the powder grains melt to join the melt pool, or they overcome surface tension and are engulfed by the melt. Powder grains can also incorporate into a mushy zone that may be present on the powder island. The powder island appears to rotate in the melt pool and incorporates relatively slowly. The speed of rotation is connected to the size of the island, which also depends on the energy density used. Spatter can form from the edges of the melt pool or from areas around the island when molten metal droplets burst. Frames from high-speed videos are presented and reasons for the various phenomena observed are discussed.

  • 49.
    Prasad, Himani Siva
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Brueckner, Frank
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling. Fraunhofer IWS, Winterbergstrasse 28, 01277, Dresden, Germany.
    Volpp, Joerg
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Kaplan, Alexander F. H.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Laser metal deposition of copper on diverse metals using green laser sources2020Inngår i: The International Journal of Advanced Manufacturing Technology, ISSN 0268-3768, E-ISSN 1433-3015, Vol. 107, nr 3-4, s. 1559-1568