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Macro- and Micromechanical Behavior of 316LN Lattice Structures Manufactured by Electron Beam Melting
Mid Sweden University, Faculty of Science, Technology and Media, Department of Quality Management and Mechanical Engineering. (Sports Tech Research Centre)ORCID iD: 0000-0002-2543-2809
Mid Sweden University, Faculty of Science, Technology and Media, Department of Quality Management and Mechanical Engineering. (Sports Tech Research Centre)
Mid Sweden University, Faculty of Science, Technology and Media, Department of Quality Management and Mechanical Engineering. (Sports Tech Research Centre)ORCID iD: 0000-0002-9205-6807
Mid Sweden University, Faculty of Science, Technology and Media, Department of Quality Management and Mechanical Engineering. (Sports Tech Research Centre)ORCID iD: 0000-0003-2964-9500
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2019 (English)In: Journal of materials engineering and performance (Print), ISSN 1059-9495, E-ISSN 1544-1024Article 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.

Place, publisher, year, edition, pages
2019.
Keywords [en]
316L additive manufacturing electron beam melting ISO 13314:2011 lattice nanoindentation
National Category
Other Mechanical Engineering Other Mechanical Engineering
Identifiers
URN: urn:nbn:se:miun:diva-37818DOI: 10.1007/s11665-019-04484-3OAI: oai:DiVA.org:miun-37818DiVA, id: diva2:1374677
Available from: 2019-12-02 Created: 2019-12-02 Last updated: 2019-12-04Bibliographically approved
In thesis
1. Process Development for Electron Beam Melting of 316LN Stainless Steel
Open this publication in new window or tab >>Process Development for Electron Beam Melting of 316LN Stainless Steel
2019 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Additive manufacturing (AM) is a technology that inverts the procedure of traditional machining. Instead of starting with a billet of material and removing unwanted parts, the AM manufacturing process starts with an empty workspace and proceeds to fill this workspace with material where it is desired, often in a layer-by-layer fashion. Materials available for AM processing include polymers, concrete, metals, ceramics, paper, photopolymers, and resins. This thesis is concerned with electron beam melting (EBM), which is a powder bed fusion technology that uses an electron beam to selectively melt a feedstock of fine powder to form geometries based on a computer-aided design file input. There are significant differences between EBM and conventional machining. Apart from the process differences, the ability to manufacture extremely complex parts almost as easily as a square block of material gives engineers the freedom to disregard complexity as a cost-driving factor. The engineering benefits of AM also include manufacturing geometries which were previously almost impossible, such as curved internal channels and complex lattice structures. Lattices are lightweight structures comprising a network of thin beams built up by multiplication of a three-dimensional template cell, or unit cell. By altering the dimensions and type of the unit cell, one can tailor the properties of the lattice to give it the desired behavior. Lattices can be made stiff or elastic, brittle or ductile, and even anisotropic, with different properties in different directions. This thesis focuses on alleviating one of the problems with EBM and AM, namely the relatively few materials available for processing. The method is to take a closer look at the widely used stainless steel 316LN, and investigate the possibility of processing 316LN powder via the EBM process into both lattices and solid material. The results show that 316LN is suitable for EBM processing, and a processing window is presented. The results also show that some additional work is needed to optimize the process parameters for increased tensile strength if the EBM-processed material is to match the yield strength of additively laser-processed 316L material.

Place, publisher, year, edition, pages
Sundsvall: Mid Sweden University, 2019. p. 39
Series
Mid Sweden University licentiate thesis, ISSN 1652-8948 ; 164
Keywords
additive manufacturing, beam deflection rate, electron beam melting, energy input, material properties, microstructure, powder bed fusion, process parameters, 316LN stainless steel
National Category
Other Mechanical Engineering
Identifiers
urn:nbn:se:miun:diva-37840 (URN)978-91-88947-25-3 (ISBN)
Presentation
2019-12-18, Q221, Akademigatan 1, 831 25 Östersund, 09:00 (Swedish)
Opponent
Supervisors
Funder
Interreg Sweden-Norway, TROJAM3DC
Note

Vid tidpunkten för framläggningen av avhandlingen var följande delarbete opublicerat: delarbete 3 (inskickat).

At the time of the defence the following paper was unpublished: paper 3 (submitted).

Available from: 2019-12-04 Created: 2019-12-03 Last updated: 2019-12-04Bibliographically approved

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Roos, StefanBotero Vega, Carlos AlbertoDanvind, JonasKoptioug, AndreiRännar, Lars-Erik

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