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The effect of powder recycling on the mechanical performance of laser powder bed fused stainless steel 316L

Rory Douglas, Nick Barnard, Nicholas Lavery Orcid Logo, James Sullivan Orcid Logo, Thomas Jones, Robert Lancaster Orcid Logo

Additive Manufacturing, Volume: 88, Start page: 104245

Swansea University Authors: Rory Douglas, Nick Barnard, Nicholas Lavery Orcid Logo, James Sullivan Orcid Logo, Robert Lancaster Orcid Logo

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Abstract

Powder recycling refers to the reuse of unused powder feedstock in the laser powder bed fusion (PBF-LB/M) process. This approach is crucial for the economic viability and sustainability of PBF-LB/M, as powder accounts for a large proportion of the total production cost. However, through powder recyc...

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Published in: Additive Manufacturing
ISSN: 2214-8604
Published: Elsevier BV 2024
Online Access: Check full text

URI: https://cronfa.swan.ac.uk/Record/cronfa66598
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Abstract: Powder recycling refers to the reuse of unused powder feedstock in the laser powder bed fusion (PBF-LB/M) process. This approach is crucial for the economic viability and sustainability of PBF-LB/M, as powder accounts for a large proportion of the total production cost. However, through powder recycling, the physical and chemical properties of powder are liable to change. This variation in powder properties can subsequently lead to knock-on effects on the mechanical properties of a fully built component.This research has investigated the changes that occur to stainless steel 316L (SS316L) powder as a result of recycling. This includes changes to powder size distribution (PSD), flowability, chemistry and phase composition. Likewise, the impact that these changes have will also be assessed in PBF-LB/M SS316L components manufactured from powders after different levels of recycling and subjected to alternative post processing routes such as hot isostatic pressing (HIP). This comprehensive investigation involves a thorough examination of both macro- and microstructures, encompassing detailed analyses of chemical composition, microstructural features, and defects. The study aims to elucidate differences in mechanical behaviour through a series of experiments, including uniaxial tensile tests, Charpy impact assessments, and low cycle fatigue (LCF) experiments. Additionally, the investigation will be complemented by pitting potential tests, providing a holistic understanding of the material's performance and characteristics.Although moderate changes to powder were observed for both PSD and chemistry, this was found to be negligible and not enough to result in any adverse changes to part performance. In addition, the microstructure of SS316L remained stable across differing levels of powder recycling. Whereas the porosity content increased marginally as the fine particle content of powder was reduced, this was not found to be sufficient to affect the LCF performance of the material. After powder recycling, increases in ductility and Young’s modulus were attributed to a reduction in oxides present in the microstructure, which were sources of localised damage and deformation.
Keywords: Laser powder bed fusion; Powder recycling; Low cycle fatigue; Stainless steel 316L
College: Faculty of Science and Engineering
Funders: The current research was funded under the EPSRC Industrial Case Award EP/T517537/1. The provision of a research bursary, materials, and supporting information from Rolls-Royce plc. is gratefully acknowledged. Mechanical tests were performed at Swansea Materials Research and Testing Ltd. (SMaRT).
Start Page: 104245