Mid Sweden University

miun.sePublications
Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Electron beam powder bed fusion processing of stainless steels
Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Mathematics, and Science Education (2023-). (Sports Tech Research Centre)ORCID iD: 0000-0002-2543-2809
2023 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Additive manufacturing (AM) is still a relatively new technology. In contrast to traditional machining where material is removed from a blank, AM is used to fuse a feedstock material into complex shapes, layer by layer, starting from an empty workspace. AM enables the manufacture of complex part geometries and part variations with little to no extra manufacturing cost. Manufacturing of geometries which was not previously possible, are now available as design options such as bent internal channels, intricate lattice structures and designed surface porosity - all of which can be produced repeatably. Electron beam powder bed fusion (PBF-EB) is an AM method in which an electron beam is used to process a fine-grained powder into parts. Since its conception, PBF-EB has been hampered by the number of materials available for processing. The aim of this thesis is to explore the possibilities for processing stainless steels using PBF-EB. The work is focused on the development of parameters for efficient processing with the aim of achieving high-density as-built materials and an understanding of the relationship between process parameters and the resulting microstructure and other quality aspects of the parts. Two stainless steel powders, 316LN (austenitic) and super duplex 2507 (austenitic / ferritic), are processed via a wide range of process parameters into solid parts using various melting strategies. Density, microstructural features, and mechanical properties are evaluated and assessed before selecting a set of parameters that produce high-quality parts at a high processing rate. This work concludes that stainless steels are well suited for PBF-EB processing, with a wide processing window. The studies also show that the material properties are highly influenced by the processing parameters used. In the case of super duplex stainless steel 2507 the built parts require post-build heat treatment to achieve the desired microstructure, phase-composition and tensile properties, while 316LN can to a larger extent be used as-built, provided that proper build preparation and processing parameters are used.

Place, publisher, year, edition, pages
Östersund: Mid Sweden University , 2023. , p. 85
Series
Mid Sweden University doctoral thesis, ISSN 1652-893X ; 396
Keywords [en]
Additive manufacturing, Electron beam powder bed fusion, PBF-EB, Stainless steel, Mechanical properties, Micro-structure, Nanoindentation
National Category
Mechanical Engineering
Identifiers
URN: urn:nbn:se:miun:diva-49338ISBN: 978-91-89786-31-8 (print)OAI: oai:DiVA.org:miun-49338DiVA, id: diva2:1798428
Public defence
2023-10-17, Q221, Akademigatan 1, 83140 Östersund, Östersund, 09:00 (English)
Opponent
Supervisors
Funder
Knowledge FoundationInterreg
Note

Vid tidpunkten för disputationen var följande delarbeten opublicerade: delarbete 5 under granskning och delarbete 6 manuskript.

At the time of the doctoral defence the following papers were unpublished: paper 5 under review and paper 6 in manuscript.

Available from: 2023-09-22 Created: 2023-09-19 Last updated: 2023-09-19Bibliographically approved
List of papers
1. Characterization of 316ln lattice structures fabricated via electron beam melting
Open this publication in new window or tab >>Characterization of 316ln lattice structures fabricated via electron beam melting
2017 (English)In: Materials Science and Technology Conference and Exhibition 2017, MS and T 2017, Association for Iron and Steel Technology, AISTECH , 2017, p. 336-343Conference paper, Published paper (Refereed)
Abstract [en]

One of the promising application areas of additive manufacturing (AM) relates to light weight structures, including complex near net shape geometries and lattices. So far one of the limiting factors hampering wider industrial usage of AM technologies is the limited availability of processed materials. The aim of present study was to expand the previous success in electron beam melting (EBM®) manufacturing of 316LN bulk materials into thinner lattice structures thus further widening the application areas available for the method. Present paper reports on the initial results where lattice structures with octagonal basic cells were manufactured using EBM® and characterized using microscopy and compression testing. 

Place, publisher, year, edition, pages
Association for Iron and Steel Technology, AISTECH, 2017
Keywords
316l, Additive manufacturing, Electron beam melting, Lattice, Net structures
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:miun:diva-32865 (URN)10.7449/2017/MST_2017_336_343 (DOI)2-s2.0-85041185273 (Scopus ID)9781510850583 (ISBN)
Conference
Materials Science and Technology Conference and Exhibition 2017, MS and T 2017, Pittsburgh, United States, 8 October 2017 through 12 October 2017
Available from: 2018-02-20 Created: 2018-02-20 Last updated: 2023-09-19Bibliographically approved
2. Macro- and Micromechanical Behavior of 316LN Lattice Structures Manufactured by Electron Beam Melting
Open this publication in new window or tab >>Macro- and Micromechanical Behavior of 316LN Lattice Structures Manufactured by Electron Beam Melting
Show others...
2019 (English)In: Journal of materials engineering and performance (Print), ISSN 1059-9495, E-ISSN 1544-1024, Vol. 28, no 12, p. 7290-7301Article in journal (Refereed) Published
Abstract [en]

This work focuses on the possibility of processing stainless steel 316LN powder into lightweight structures using electron beam melting and investigates mechanical and microstructural properties in the material of processed components. Lattice structures conforming to ISO13314:2011 were manufactured using varying process parameters. Microstructure was examined using a scanning electron microscope. Compression testing was used to understand the effect of process parameters on the lattice mechanical properties, and nanoindentation was used to determine the material hardness. Lattices manufactured from 316L using EBM show smooth compression characteristics without collapsing layers and shear planes. The material has uniform hardness in strut shear planes, a microstructure resembling that of solid 316LN material but with significantly finer grain size, although slightly coarser sub-grain size. Grains appear to be growing along the lattice struts (e.g., along the heat transfer direction) and not in the build direction. Energy-dispersive x-ray spectroscopy analysis reveals boundary precipitates with increased levels of chromium, molybdenum and silicon. Studies clearly show that the 316LN grains in the material microstructure are elongated along the dominating heat transfer paths, which may or may not coincide with the build direction. Lattices made from a relatively ductile material, like 316LN, are much less susceptible to catastrophic collapse and show an extended range of elastic and plastic deformation. Tests indicate that EBM process for 316LN is stable allowing for both solid and lightweight (lattice) structures.

Keywords
316L additive manufacturing electron beam melting ISO 13314:2011 lattice nanoindentation
National Category
Other Mechanical Engineering Other Mechanical Engineering
Identifiers
urn:nbn:se:miun:diva-37818 (URN)10.1007/s11665-019-04484-3 (DOI)000499641800002 ()2-s2.0-85075894379 (Scopus ID)
Available from: 2019-12-02 Created: 2019-12-02 Last updated: 2023-09-19Bibliographically approved
3. Process Window for Electron Beam Melting of 316LN Stainless Steel
Open this publication in new window or tab >>Process Window for Electron Beam Melting of 316LN Stainless Steel
2021 (English)In: Metals, ISSN 2075-4701, Vol. 11, no 137Article in journal (Refereed) Published
Abstract [en]

Electron beam melting (EBM) is currently hampered by the low number of materials available for processing. This work presents an experimental study of process parameter development related to EBM processing of stainless steel alloy 316LN. Area energy (AE) input and beam deflection rate were varied to produce a wide array of samples in order to determine which combination of process parameters produced dense (>99%) material. Both microstructure and tensile properties were studied. The aim was to determine a process window which results in dense material. The range of AE which produced dense materials was found to be wider for 316LN than for many other reported materials, especially at lower beam deflection rates. Tensile and microstructural analysis showed that increasing the beam deflection rate, and consequently lowering the AE, resulted in material with a smaller grain size, lower ductility, lower yield strength, and a narrower window for producing material that is neither porous nor swelling.

Place, publisher, year, edition, pages
Basel: , 2021
Keywords
powder bed fusion, electron beam melting (EBM), process window, stainless steel, 316LN
National Category
Mechanical Engineering Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:miun:diva-40899 (URN)10.3390/met11010137 (DOI)000610491600001 ()2-s2.0-85099315871 (Scopus ID)
Funder
Interreg Sweden-Norway
Available from: 2021-01-21 Created: 2021-01-21 Last updated: 2023-09-19Bibliographically approved
4. Electron beam powder bed fusion processing of 2507 super duplex stainless steel. as-built phase composition and microstructural properties
Open this publication in new window or tab >>Electron beam powder bed fusion processing of 2507 super duplex stainless steel. as-built phase composition and microstructural properties
2023 (English)In: Journal of Materials Research and Technology, ISSN 2238-7854, Vol. 24, p. 6473-6483Article in journal (Refereed) Published
Abstract [en]

This study focuses on adapting the Electron Beam Powder Bed Fusion (E-PBF) process for the manufacturing of parts from 2507 super duplex stainless steel, combining high strength and corrosion resistance, therefore presenting an interesting choice for E-PBF implementation. Samples manufactured using four sets of process parameters were characterized by scanning electron microscopy, tensile testing, X-ray diffraction analysis, energy dispersive X-ray spectroscopy and nanoindentation. The different E-PBF process temperatures investigated had the strongest influence on the phase characteristics and the resulting microstructure. The processability of the material was good, and high productivity rates were achieved, indicating good suitability for industrial transfer.

Place, publisher, year, edition, pages
Elsevier, 2023
Keywords
1.4410, 2507, Additive manufacturing, Electron beam powder bed fusion, Nanoindentation, Stainless steel
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:miun:diva-48320 (URN)10.1016/j.jmrt.2023.04.230 (DOI)001026745000001 ()2-s2.0-85156260914 (Scopus ID)
Available from: 2023-05-16 Created: 2023-05-16 Last updated: 2023-09-19Bibliographically approved

Open Access in DiVA

Stefan Roos - Powder bed fusion processing of stainless steels(1561 kB)233 downloads
File information
File name FULLTEXT01.pdfFile size 1561 kBChecksum SHA-512
5e5de73cb307f54e17d411f2ebc58b5cb567aad2caa732f69036e50e09188cfbd45973490bddbb240bc7ca62a95135df51c35b3526df28921c08413001e71945
Type fulltextMimetype application/pdf

Authority records

Roos, Stefan

Search in DiVA

By author/editor
Roos, Stefan
By organisation
Department of Engineering, Mathematics, and Science Education (2023-)
Mechanical Engineering

Search outside of DiVA

GoogleGoogle Scholar
Total: 234 downloads
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

isbn
urn-nbn

Altmetric score

isbn
urn-nbn
Total: 1415 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf