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Blown powder directed energy deposition on various substrate conditions
Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.ORCID iD: 0000-0002-7213-0002
Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development. Fraunhofer IWS, Winterbergstrasse 28, 01277 Dresden, Germany.
Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.ORCID iD: 0000-0002-3569-6795
2022 (English)In: Journal of Manufacturing Processes, ISSN 1526-6125, Vol. 73, p. 660-667Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
Elsevier, 2022. Vol. 73, p. 660-667
Keywords [en]
Laser cladding, Laser metal deposition, Surface conditions, Contaminated surfaces, High-speed imaging
National Category
Manufacturing, Surface and Joining Technology
Research subject
Manufacturing Systems Engineering
Identifiers
URN: urn:nbn:se:ltu:diva-83612DOI: 10.1016/j.jmapro.2021.11.048ISI: 000740842200001Scopus ID: 2-s2.0-85120158320OAI: oai:DiVA.org:ltu-83612DiVA, id: diva2:1543825
Note

Validerad;2021;Nivå 2;2021-12-02 (johcin)

Available from: 2021-04-13 Created: 2021-04-13 Last updated: 2023-09-13Bibliographically approved
In thesis
1. Phenomena in laser based material deposition
Open this publication in new window or tab >>Phenomena in laser based material deposition
2021 (English)Doctoral thesis, comprehensive summary (Other academic)
Alternative title[sv]
Fenomen i laserbaserad materialdeponering
Abstract [en]

This thesis is regarding the use of a laser beam to deposit material. Phenomena in two processes, laser beam welding with filler wire and blown powder directed energy deposition (DED) also known as laser metal deposition (LMD)1, are discussed. High-speed imaging is used as a central tool, supported by cross-sectional macrographs, surface images, X-ray images, computed tomography scans and quantitative analysis of the acquired results to observe many phenomena. Several results generated could be used in the manufacturing industry.

A novel concept of feeding the filler wire off-axis to the joint in laser beam welding is presented. The formation of defects called undercuts depended mainly on the stability of the wire feed and irregular melting of its tip. Process parameters played a key role in the robustness of the process, with higher welding speeds and laser powers increasing the chance for formation of defects.

Powder catchment in DED, and the various influencing factors are discussed. The position of initial interaction between powder grains and the melt pool plays an important role in defining incorporation behaviour. Powder grains can float on the surface of melt pool and travel along the direction of surface tension driven melt flows before fully incorporating. In high-deposition rate DED, an island of unmelted powder can form in the melt pool, depending on the laser beam shape and powder feeding configuration used. This island could lead to formation of spatter from the melt pool and porosity in resulting clads. Solid oxide skins present on the melt pool in low temperature areas can act like a barrier preventing complete incorporation of powder grains or possibly causing localised boiling, forming spatter.

For the first time, near-unprocessed material was used as feedstock in the DED process. A single large melt pool is formed in the relatively calm process, and phenomena like cloud formation while feeding of material and spatter were observed. Single and multi-layered deposition resulted in porous tracks and delamination from the substrate. While the process is not industrially useable in its current state, it is a step towards processing cheap unprocessed material with a laser beam to manufacture low cost parts or for in-situ reduction. 

The roles of material composition and surface conditions of the substrate in DED are also presented. Both, the composition and surface condition affect the absorption of the laser radiation. Material composition influences the time taken for incorporation of powder grains. The size of the melt pool and dilution depends on the thermal conductivity of the substrate material. Surfaces that are rough or coated with (several sorts of) paint produce wider tracks, with better wetting angles as compared to milled or ground surfaces. Coatings like paints or cold-galvanising primers do not negatively affect the process. Deposition directly on rough or painted surfaces could significantly reduce processing time and the resources needed for cleaning before cladding or repair processes. 

Place, publisher, year, edition, pages
Luleå University of Technology, 2021
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-83613 (URN)978-91-7790-819-7 (ISBN)978-91-7790-820-3 (ISBN)
Public defence
2021-06-10, A109, Luleå tekniska universitet, Luleå, 09:00 (English)
Opponent
Supervisors
Available from: 2021-04-14 Created: 2021-04-13 Last updated: 2021-11-12Bibliographically approved

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Naesstroem, HimaniBrückner, FrankKaplan, Alexander F. H.

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