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Fedina, T., Sundqvist, J. & Kaplan, A. F. .. (2022). The role of powder morphology in particle movement behavior in laser powder bed fusion with an emphasis on fluid drag. Powder Technology, 395, 720-731
Open this publication in new window or tab >>The role of powder morphology in particle movement behavior in laser powder bed fusion with an emphasis on fluid drag
2022 (English)In: Powder Technology, ISSN 0032-5910, E-ISSN 1873-328X, Vol. 395, p. 720-731Article in journal (Refereed) Published
Abstract [en]

This study investigates the movement behavior of particles of dissimilar morphology in the powder bed in Laser Powder Bed Fusion. Gas atomized (GA) and water atomized (WA) low alloy steel powders were employed to study their motion around the laser scan path. Particle velocities, entrainment distances and denudation zones were measured for both powders using high-speed imaging. The entrainment of GA powder particles in front of the laser beam towards the process area was initiated 1.6 mm from the edge of the melt pool, whereas the distance was 0.6–0.8 mm for the WA powder. The differences in observed behavior were related to the variations in particle shape of the two types of powder. The processing of WA powder resulted in a 16% narrower denudation zone (for a low volumetric energy density) compared to GA powder. However, the denudation width difference decreased with increasing volumetric energy density, most likely due to a steeper pressure gradient in the process area which diminishes the impact of powder shape. X-ray computed microtomography was utilized to estimate the drag force acting on the powder particles of various morphologies. The results showed that the radial drag force exerted on GA powder was 64% greater than when using WA powder. Moreover, if the WA powder particles were of elongated shape the drag force decreased by almost an order of magnitude, demonstrating the importance of the particle's morphology in the process dynamics.

Place, publisher, year, edition, pages
Elsevier, 2022
Keywords
Water atomized powder, Particle movement, Dissimilar morphology, Drag force, Laser powder bed fusion, Additive manufacturing
National Category
Manufacturing, Surface and Joining Technology
Research subject
Manufacturing Systems Engineering
Identifiers
urn:nbn:se:ltu:diva-87583 (URN)10.1016/j.powtec.2021.10.020 (DOI)000718001100004 ()2-s2.0-85117723002 (Scopus ID)
Funder
Interreg Nord, 304-7463-2018
Note

Validerad;2021;Nivå 2;2021-10-25 (beamah);

Funder: EIT Raw Materials (No.17070)

2022-03-02: Dubblettpost PID: 1554744 har raderats. (sofila)

Available from: 2021-10-21 Created: 2021-10-21 Last updated: 2023-03-02Bibliographically approved
Fedina, T., Sundqvist, J. & Kaplan, A. F. .. (2021). Spattering and oxidation phenomena during recycling of low alloy steel powder in Laser Powder Bed Fusion. Materials Today Communications, 27, Article ID 102241.
Open this publication in new window or tab >>Spattering and oxidation phenomena during recycling of low alloy steel powder in Laser Powder Bed Fusion
2021 (English)In: Materials Today Communications, ISSN 2352-4928, Vol. 27, article id 102241Article in journal (Refereed) Published
Abstract [en]

This study reports on the impact of repeated powder recycling on the degradation of low alloy steel powder in Laser Powder Bed Fusion. The average powder particle size increased slightly upon recycling due to powder agglomeration and the presence of spatters and other ejecta from the process zone. The oxygen content showed a continuous growth after each recycle, while the other chemical elements of the recycled powder remained largely unchanged. A map of ejecta classification is presented, featuring various ejecta types formed during laser processing. Ejecta of increased diameter and different shapes were observed in the recycled powder, using high-speed imaging and Scanning Electron Microscopy. The ejecta were collected after each powder recycle to enable the calculation of the ejecta mass generated during the process. The result showed a direct correlation between oxygen content in the powder and spatter/ejecta formation with the number of recycling events. It is likely that the increase in oxygen contributes to powder spattering.

Place, publisher, year, edition, pages
Elsevier, 2021
Keywords
Low alloy steel, Spattering, Powder degradation, Recycling, Laser Powder Bed Fusion, Additive manufacturing
National Category
Manufacturing, Surface and Joining Technology
Research subject
Manufacturing Systems Engineering
Identifiers
urn:nbn:se:ltu:diva-83247 (URN)10.1016/j.mtcomm.2021.102241 (DOI)000683034600006 ()2-s2.0-85102510106 (Scopus ID)
Funder
Interreg Nord, 304-7463-2018
Note

Validerad;2021;Nivå 2;2021-03-23 (johcin);

Finansiär: EIT Raw Materials Knowledge and Innovation Community (17070)

Available from: 2021-03-12 Created: 2021-03-12 Last updated: 2023-03-02Bibliographically approved
Fedina, T., Sundqvist, J. & Kaplan, A. F. H. (2021). The use of non-spherical powder particles in Laser Powder Bed Fusion. In: IOP Conference Series: Materials Science and Engineering: . Paper presented at 18th Nordic Laser Materials Processing Conference (18th NOLAMP), Luleå, Sweden, January 18-20, 2022. Institute of Physics (IOP), 1135, Article ID 012018.
Open this publication in new window or tab >>The use of non-spherical powder particles in Laser Powder Bed Fusion
2021 (English)In: IOP Conference Series: Materials Science and Engineering, Institute of Physics (IOP), 2021, Vol. 1135, article id 012018Conference paper, Published paper (Refereed)
Abstract [en]

Laser powder bed fusion (LPBF) generally involves the use of near-spherical powders due to their smooth morphology and enhanced flowability that allow for easier powder layering and laser processing. Non-spherical powders, on the other hand, are more cost-efficient to manufacture, however, the underlying mechanisms of their movement and interparticle interaction on the powder bed are still unclear. Thus, this study reports on the use of irregular iron-based powder material in LPBF, with a specific focus on particle motion and interaction behavior on the powder bed. The powder morphology, sphericity and particle size were analysed using X-ray computed microtomography and scanning electron microscopy. Based on the acquired data and by using a simplified analytical calculation, the influence of the particle shape/size on the particle movement in LPBF was established. High-speed imaging was employed to investigate the particle flow dynamics in the process zone, as well as the powder entrainment phenomenon. Particle entrainment and entrainment distances along the scanning direction were measured for near-spherical and non-spherical powders. The obtained results were compared between the powders, revealing a dissimilar particle transfer behavior. Non-spherical powder had a shorter entrainment distance partly attributed to the weaker drag force acting on these particles.

Place, publisher, year, edition, pages
Institute of Physics (IOP), 2021
Series
IOP Conference Series: Materials Science and Engineering, ISSN 1757-8981, E-ISSN 1757-899X
National Category
Manufacturing, Surface and Joining Technology
Research subject
Manufacturing Systems Engineering
Identifiers
urn:nbn:se:ltu:diva-89960 (URN)10.1088/1757-899X/1135/1/012018 (DOI)000766307500018 ()
Conference
18th Nordic Laser Materials Processing Conference (18th NOLAMP), Luleå, Sweden, January 18-20, 2022
Note

Funder: EIT Raw Materials (17070); EU-ERDF Interreg Nord program (304-7463-2018)

Available from: 2022-03-31 Created: 2022-03-31 Last updated: 2022-04-11Bibliographically approved
Fedina, T., Sundqvist, J., Powell, J. & Kaplan, A. F. . (2020). A comparative study of water and gas atomized low alloy steel powders for additive manufacturing. Additive Manufacturing, 36, Article ID 101675.
Open this publication in new window or tab >>A comparative study of water and gas atomized low alloy steel powders for additive manufacturing
2020 (English)In: Additive Manufacturing, ISSN 2214-8604, E-ISSN 2214-7810, Vol. 36, article id 101675Article in journal (Refereed) Published
Abstract [en]

This work reports a study of the differences between laser processing of water and gas atomized low alloy steel powders with a focus on powder behavior and performance in additive manufacturing. Material packing densities were measured to establish a relationship between powder packing and track formation. The results showed that the track height when using water atomized powder was 15% lower than the value achieved for the gas atomized powder. High-speed imaging was utilized to observe the material behavior and analyze the powder particle movement under laser irradiation. It was found that water atomized powder has less particle entrainment due to its tendency towards mechanical interlocking. The occurrence of powder spattering and melt pool instabilities was also studied. More frequent spatter ejection is believed to be due to the higher amount of oxygen in the water atomized powder.

Place, publisher, year, edition, pages
Elsevier, 2020
Keywords
Additive manufacturing, Laser powder bed fusion, Water atomized powder, Packing density, Low alloy steel, High-speed imaging
National Category
Manufacturing, Surface and Joining Technology
Research subject
Manufacturing Systems Engineering
Identifiers
urn:nbn:se:ltu:diva-81523 (URN)10.1016/j.addma.2020.101675 (DOI)000600807800194 ()2-s2.0-85095580581 (Scopus ID)
Funder
Interreg Nord, 304–7463-2018
Note

Validerad;2021;Nivå 2;2021-01-04 (alebob);

Finansiär: EIT Raw Materials Knowledge and Innovation Community, Europe (17070)

Available from: 2020-11-23 Created: 2020-11-23 Last updated: 2023-09-06Bibliographically approved
Sundqvist, J. & Kaplan, A. F. H. (2019). Analysis of inter-granular corrosion susceptibility stemming from laser-induced thermal cycles. In: Stefan Kaierle; Stefan W. Heinemann (Ed.), High-Power Laser Materials Processing: Applications, Diagnostics, and Systems VIII. Paper presented at High-Power Laser Materials Processing: Applications, Diagnostics, and Systems VIII, San Francisco, United States, February 5-7, 2019. SPIE - International Society for Optical Engineering, Article ID 1091107.
Open this publication in new window or tab >>Analysis of inter-granular corrosion susceptibility stemming from laser-induced thermal cycles
2019 (English)In: High-Power Laser Materials Processing: Applications, Diagnostics, and Systems VIII / [ed] Stefan Kaierle; Stefan W. Heinemann, SPIE - International Society for Optical Engineering, 2019, article id 1091107Conference paper, Published paper (Refereed)
Abstract [en]

Low-chromium ferritic stainless steel that is subjected to a second laser-induced thermal cycle is susceptible to intergranular corrosion. Precipitation of carbides and nitrides depletes the adjacent regions of chromium. For this material, despite its low carbon content of 0.007%, laser transformation hardening has achieved a considerable increase in hardness. For certain thermal conditions during overlapping of tracks the above precipitation mechanism can take place. Numerical modelling was applied to analyse the laser parameters that could be critical for precipitation to take place. The results are compared to experiments that were screened with a standardised test method. Avoiding susceptibility to intergranular corrosion when laser transformation hardening was shown to be difficult during a second thermal cycle of an overlapping pass that passes a critical though narrow temperature range. Based on this, measures to mitigate the susceptibility was introduced, in the form of heating the material above melting temperature. When melting the material, even during the first pass, corrosion behaviour changes. It is shown that the risk of corrosion can be avoided during subsequent passes. Different thermal cycles are analysed to find limits for avoiding susceptibility to intergranular corrosion. By laser treating and mapping the critical thermal cycles, the material can be used in a wider range of applications.

Place, publisher, year, edition, pages
SPIE - International Society for Optical Engineering, 2019
Series
Proceedings of SPIE, ISSN 0277-786X, E-ISSN 1996-756X ; 10911
Keywords
Laser hardening, sensitisation, numerical modelling, corrosion, stainless steel
National Category
Manufacturing, Surface and Joining Technology
Research subject
Manufacturing Systems Engineering
Identifiers
urn:nbn:se:ltu:diva-86213 (URN)10.1117/12.2506912 (DOI)000473302200005 ()2-s2.0-85065768931 (Scopus ID)
Conference
High-Power Laser Materials Processing: Applications, Diagnostics, and Systems VIII, San Francisco, United States, February 5-7, 2019
Funder
Interreg NordEuropean Regional Development Fund (ERDF), 304-15588-2015
Note

ISBN för värdpublikation: 9781510624641; 9781510624658;

Finansiär: CINEMA project (20201655); EC Research Fund for Coal and Steel (754155); EC EIT-KIC RawMaterials; SPAcEMAN project (17070)

Available from: 2021-07-01 Created: 2021-07-01 Last updated: 2021-09-07Bibliographically approved
Sundqvist, J. & Samarjy, R. S. (2019). High-speed imaging of droplet behaviour during the CYCLAM drop-deposition technique. Paper presented at 17th Nordic Laser Materials Processing Conference (NOLAMP17), 27-29 August, 2019, Trondheim, Norway. Procedia Manufacturing, 36, 208-215
Open this publication in new window or tab >>High-speed imaging of droplet behaviour during the CYCLAM drop-deposition technique
2019 (English)In: Procedia Manufacturing, E-ISSN 2351-9789, Vol. 36, p. 208-215Article in journal (Refereed) Published
Abstract [en]

The material in laser additive manufacturing is traditionally supplied in the form of powder or sometimes wire. A technique called CYCLAM was recently presented which is a fast and direct recycling technique which lowers the number of steps that need to be taken in typical recycling, allowing for a more circular economy. The CYCLAM technique proposes that waste metal is directly recycled through laser cutting or laser ablation of one sheet and the molten droplet is directly deposited onto a new product and can be used for additive manufacturing or cladding. The technique also can also use materials that otherwise are not available as powder or wires. Because of the novelty of the technique, it is still scarcely studied, and many aspects still needs to be understood. This paper focusses on high-speed imaging of the technique to understand the droplet behaviour. The material removal of the feeding sheet was done with Remote Fusion Cutting. Different power levels lead to different drop geometry and flight pattern of the drops where the drops at higher power are pushed further forward. The influence of the laser power on the shape of the deposited track can be seen from cross sections of the cladded track where higher power means that more power is transmitted through the feeding sheet and onto the substrate which creates a smoother surface

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
laser additive manufacturing, circular economy, high-speed imaging, laser cladding, recycling
National Category
Manufacturing, Surface and Joining Technology
Research subject
Manufacturing Systems Engineering
Identifiers
urn:nbn:se:ltu:diva-75729 (URN)10.1016/j.promfg.2019.08.027 (DOI)000610364700026 ()2-s2.0-85072522395 (Scopus ID)
Conference
17th Nordic Laser Materials Processing Conference (NOLAMP17), 27-29 August, 2019, Trondheim, Norway
Note

Konferensartikel i tidskrift

Available from: 2019-08-28 Created: 2019-08-28 Last updated: 2021-12-13Bibliographically approved
Sundqvist, J., Manninen, T., Heikkinen, H.-P., Anttila, S. & Kaplan, A. F. H. (2018). Laser surface hardening of 11% Cr ferritic stainless steel and its sensitisation behaviour. Surface & Coatings Technology, 344, 673-679
Open this publication in new window or tab >>Laser surface hardening of 11% Cr ferritic stainless steel and its sensitisation behaviour
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2018 (English)In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 344, p. 673-679Article in journal (Refereed) Published
Abstract [en]

11% Cr ferritic stainless steel conforming to EN 1.4003 standard was surface hardened by a continuous-wave fibre laser beam. Both single-pass and multi-pass laser hardening was investigated. Different laser parameters were compared and their influence on hardness, microstructure, geometry of the hardened zone and sensitisation was investigated, especially for overlapping passes. The experiments showed that a surface hardness which is double that of the base material hardness was obtainable via martensitic phase transformation and high cooling rate, in spite of the low carbon and nitrogen content. This behaviour could be predicted from the chemical composition using the Kaltenhauser Ferrite Factor. Hardening at higher power levels gives more coarse-grained lath martensite but does not increase the hardness. Sensitisation was not a problem in single-pass hardening. However, the production of overlapping tracks could be detrimental to corrosion resistance in 11% Cr steel due to the formation of chromium carbides and nitrides.

Place, publisher, year, edition, pages
Elsevier, 2018
Keywords
Laser surface hardening, Ferritic stainless steel, Sensitisation
National Category
Mechanical Engineering Manufacturing, Surface and Joining Technology
Research subject
Manufacturing Systems Engineering
Identifiers
urn:nbn:se:ltu:diva-67581 (URN)10.1016/j.surfcoat.2018.04.002 (DOI)000437391300077 ()2-s2.0-85044924333 (Scopus ID)
Note

Validerad;2018;Nivå 2;2018-04-06 (andbra)

Available from: 2018-02-09 Created: 2018-02-09 Last updated: 2022-06-30Bibliographically approved
Sundqvist, J., Kim, K., Bang, H.-S., Bang, H. & Kaplan, A. (2018). Numerical simulation of laser preheating of friction stir welding of dissimilar metals. Science and technology of welding and joining, 23(4), 351-356
Open this publication in new window or tab >>Numerical simulation of laser preheating of friction stir welding of dissimilar metals
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2018 (English)In: Science and technology of welding and joining, ISSN 1362-1718, E-ISSN 1743-2936, Vol. 23, no 4, p. 351-356Article in journal (Refereed) Published
Abstract [en]

Friction stir welding, FSW, of harder metal alloys is difficult to perform, like here dissimilar welding of titanium alloy to stainless steel in butt joint configuration. One major limitation is tool wear which can be reduced by preheating with a laser beam. A mathematical model to calculate the tool forces during FSW was developed further. The calculations show that the laser beam reduces forces at the pin and shoulder of the FSW-tool, accompanied by reduced heat generation through the tool. Within its operating limits, the process has low sensitivity on the lateral position of the leading laser beam. The model supports the understanding and optimisation of the complex interaction zone of forces and heat around the FSW-tool.

Place, publisher, year, edition, pages
Taylor & Francis, 2018
National Category
Manufacturing, Surface and Joining Technology
Research subject
Manufacturing Systems Engineering
Identifiers
urn:nbn:se:ltu:diva-66366 (URN)10.1080/13621718.2017.1391936 (DOI)000435470000009 ()2-s2.0-85032491421 (Scopus ID)
Note

Validerad;2018;Nivå 2;2018-03-14 (andbra)

Available from: 2017-11-02 Created: 2017-11-02 Last updated: 2018-07-26Bibliographically approved
Sundqvist, J. & Kaplan, A. (2018). Sensitisation behaviour of drop-deposited 11% Cr ferritic stainless steel. Optics and Laser Technology, 487-495
Open this publication in new window or tab >>Sensitisation behaviour of drop-deposited 11% Cr ferritic stainless steel
2018 (English)In: Optics and Laser Technology, ISSN 0030-3992, E-ISSN 1879-2545, p. 487-495Article in journal (Refereed) Published
Abstract [en]

For low-chromium ferritic stainless steel, a recently developed laser-driven drop-deposition technique enabled the building of three adjacent tracks on a substrate sheet of the same alloy, to study its risk for sensitisation from certain sequences of thermal cycles. The process was recorded by high-speed imaging to understand the drop-deposition mechanisms. Higher beam power resulted in a smoother track. The added layer was fully martensitic, achieving an elevated hardness of 320 HV. For a temperature peak just below austenitisation, the thermal cycle from a subsequent track affected the former track through tempering. Etching revealed a continuous region of ditched grain boundaries around the interface between the melted and heat affected zones. In the melted zone, the network became discontinuous approaching the surface, meaning that the specimen was immune to sensitisation, in contrast to transformation hardening results in the solid state. Additive manufacturing can induce manifold sequences of thermal cycles, but from the here generalized knowledge, strategies against sensitisation can be derived.

Place, publisher, year, edition, pages
Elsevier, 2018
National Category
Mechanical Engineering Manufacturing, Surface and Joining Technology
Research subject
Manufacturing Systems Engineering
Identifiers
urn:nbn:se:ltu:diva-70218 (URN)10.1016/j.optlastec.2018.07.031 (DOI)000443664100059 ()2-s2.0-85050526410 (Scopus ID)
Note

Validerad;2018;Nivå 2;2018-08-06 (andbra)

Available from: 2018-08-06 Created: 2018-08-06 Last updated: 2018-10-08Bibliographically approved
Sundqvist, J., Kaplan, A., Shachaf, L. & Kong, C. Y. (2017). Analytical heat conduction modelling for shaped laser beams. Journal of Materials Processing Technology, 247, 48-54
Open this publication in new window or tab >>Analytical heat conduction modelling for shaped laser beams
2017 (English)In: Journal of Materials Processing Technology, ISSN 0924-0136, E-ISSN 1873-4774, Vol. 247, p. 48-54Article in journal (Refereed) Published
Abstract [en]

Conduction mode laser spot welding and laser spot hardening usually employ Gaussian or top-hat-like beam modes. One main requirement of these techniques is the avoidance of overheating in the centre of the laser-material interaction zone. Process flexibility can be improved by spatially and/or temporally shaping the beam, which can enable higher process quality, robustness or speed. A desired spatial beam shape can be achieved by a suitably designed diffractive optical element. However, the prediction of a suitable beam shape for a particular process can be complex. A simplified analytical heat conduction model has been developed that can rapidly calculate the temperature field and cooling behaviour for almost any spatial and temporal beam shape. The potential and limits of the model are demonstrated and discussed by calculating and analysing temperature profiles for several cases of multi-spot welding

Place, publisher, year, edition, pages
Elsevier, 2017
National Category
Manufacturing, Surface and Joining Technology
Research subject
Manufacturing Systems Engineering
Identifiers
urn:nbn:se:ltu:diva-63056 (URN)10.1016/j.jmatprotec.2017.04.011 (DOI)000403133400006 ()2-s2.0-85018469004 (Scopus ID)
Note

Validerad; 2017; Nivå 2; 2017-05-11 (andbra)

Available from: 2017-04-18 Created: 2017-04-18 Last updated: 2018-07-10Bibliographically approved
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