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Laser enhancement of wire arc additive manufacturing
Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.ORCID iD: 0000-0003-2596-5303
Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development. Fraunhofer Institute for Material and Beam Technology, IWS, Dresden, Germany.
Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.ORCID iD: 0000-0002-3569-6795
2019 (English)In: Journal of laser applications, ISSN 1042-346X, E-ISSN 1938-1387, Vol. 31, no 2, article id 022307Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
American Institute of Physics (AIP), 2019. Vol. 31, no 2, article id 022307
Keywords [en]
additive manufacturing, laser augmentation, gas metal arc, hybrid processing, wire arc additive manufacturing/WAAM
National Category
Manufacturing, Surface and Joining Technology
Research subject
Manufacturing Systems Engineering
Identifiers
URN: urn:nbn:se:ltu:diva-74233DOI: 10.2351/1.5096111ISI: 000484435200037OAI: oai:DiVA.org:ltu-74233DiVA, id: diva2:1321219
Conference
Proceedings of the International Congress of Applications of Lasers & Electro-Optics (ICALEO® 2018)
Funder
Interreg Nord, 20200060
Note

Konferensartikel i tidskrift

Available from: 2019-06-07 Created: 2019-06-07 Last updated: 2019-10-01Bibliographically approved
In thesis
1. Phenomena in wire based multi-layer laser welding and hybrid deposition
Open this publication in new window or tab >>Phenomena in wire based multi-layer laser welding and hybrid deposition
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Alternative title[sv]
Fenomen i trådbaserad, flerskiktad lasersvetsning och hybriddeposition
Abstract [en]

Several laser materials processing technologies using metal wire addition have been researched during the last decades. Especially in the field of joining, as well as in the field of Additive Manufacturing (AM), multiple major benefits have been reached, e.g. higher welding speeds and lower heat input. With laser and arc hybrid welding techniques, additional prospects become accessible. These can combine and improve both deep penetration of autogenous laser welding and gap bridging capabilities of traditional arc welding. In the field of AM, wire feed has been a much-appreciated way of supplying additional material. Reasons include clean and easy handling, high utilisation and availability. A high intensity heat source, e.g. a laser beam or an electrical arc, continuously melts a metal wire; the melt being deposited onto a substrate in one or multiple layers to generate a new surface or three dimensional structure. An alternative joining process is Narrow Gap Multi-Layer Welding (NGMLW). This technique utilises the former mentioned AM processes to fill a gap to join sheets together, instead of depositing on an open surface. NGMLW is a capable competitor to the above-mentioned joining processes due to its prospects of being able to join essentially any thickness of sheets, as long as the beam and wire can accurately reach the gap floor and a sufficient number of layers are used.

In this thesis, multiple types of NGMLW, Papers A – D, and hybrid material deposition, Papers E and F, using laser and hybrid heat sources with metal wire addition have been studied. Techniques such as High-Speed Imaging (HSI), 3D and Computed Tomography (CT) scanning have been used to gain greater insight into the workings of these modern manufacturing processes. The multi-layered way of material deposition within a gap to form a welded joint and onto a surface for AM have many similarities, e.g. wire melting behaviour and melt flow.

Paper A introduces the workings of NGMLW, highlighting possible welding imperfections and welded joint morphology. HSI of the process is analysed both qualitatively and quantitatively: qualitative analysis identifying possible causes for said imperfections; quantitative analysis highlighting the potential for using similar and lower frame rate camera footage for closed loop control to suppress the formation of such imperfections.

In Paper B, an alternative near-vertical building strategy for NGMLW is presented and compared to its more common horizontal counterpart. This upright strategy is found to be fully capable of producing sound welded joints, sporting less than 0.3% cavities. The near-vertical welded joints also have potential for unique material properties due to their much different thermal history.

Papers C and D return to the topic of horizontal NGMLW, but with resistance heating of the metal wire for easier processing, also referred to as Laser Hot-Wire Welding (LHWW). Process behaviour and the resulting morphology of welded joints are the main topics of Paper C. Theoretical reasoning for the formation of occasional centre-line cracks, relating to the shape of the melt pool during solidification, are presented. Arcing is observed in some of the experiments, although prior theory indicates that the applied wire voltage was too low for arcing to occur. This arcing phenomenon is further covered in Paper D, where HSI observations are used to correlate process parameters to arcing probability and a theoretical explanation of why arcing can occur is suggested.

Papers E and F take the step out of the gap, studying the impact of laser beam augmentation in different orientations on Wire-Arc Additive Manufacturing (WAAM). Paper E focuses on a method of quantifying melt pool movement. Fluctuations of the melt pool surface decreased by more than 35% with the introduction of a laser beam to the process. Paper F analyses the generated structures, evaluating the usable portion of the “as deposited” shapes and material composition. Surface irregularities decreased by more than 50% on application of a trailing laser beam. Additional aspects relating to the resulting morphology are also presented, including observations and reasoning for surface irregularities and sloping.

The knowledge gained and methods used in the presented work intertwine to form a strong insight into both laser and laser-hybrid materials processing with wire addition. They also introduce approaches for processing and quantifying HSI footage for process evaluation and improvement.

Place, publisher, year, edition, pages
Luleå: Luleå University of Technology, 2019
Series
Doctoral thesis / Luleå University of Technology 1 jan 1997 → …, ISSN 1402-1544
National Category
Manufacturing, Surface and Joining Technology
Research subject
Manufacturing Systems Engineering
Identifiers
urn:nbn:se:ltu:diva-74543 (URN)978-91-7790-407-6 (ISBN)978-91-7790-408-3 (ISBN)
Public defence
2019-10-23, E632, Luleå, 09:00 (English)
Opponent
Supervisors
Available from: 2019-06-19 Created: 2019-06-14 Last updated: 2019-10-01Bibliographically approved

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Näsström, JonasBrueckner, FrankKaplan, Alexander

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