Chemical recovery of spent copper powder in laser powder bed fusion

Speidel, Alistair; Gargalis, Leonidas; Ye, Jianchao; Matthews, Manyalibo J.; Spierings, Adriaan; Hague, Richard; Clare, Adam T.; Murray, James W.

Abstract

In laser powder bed fusion (LPBF), recovered unfused powder from the powder bed often degrades upon sequential processing through mechanisms like thermal oxidation and particle satelliting from ejected weld spatters and particle-laser interactions. Given the sensitivity of LPBF performance and build quality to powder properties, spent powder is generally discarded after a few build cycles, especially for materials that are sensitive towards surface oxidation. This increases feedstock material costs, as well as costs associated with machine downtime during powder replacement. Here, a new method to chemically reprocess spent LPBF metal powder is demonstrated under ambient conditions, using a heavily oxidised Cu powder feedstock recovered from prior LPBF processing as a model material. This is compared to an equivalent virgin Cu powder. The near-surface powder chemistry has been analysed, and it is shown that surface oxide layers present on spent Cu powder can be effectively reset after rapid reprocessing (from 5 to 20 min). Diffuse reflectance changes on etching, reducing for gas-atomised virgin Cu powder due to the formation of anisotropic etch facets, and increasing for heavily oxidised spent Cu as the highly absorptive oxide layers are removed. The mechanism of powder degradation for moisture sensitive materials like Cu has been correlated to the degradation of LPBF deposits, which manifests as widespread and extensive porosity. This extensive porosity is largely eliminated after reprocessing the spent Cu powder. Chemically etched spent powder is therefore demonstrated as a practical feedstock in LPBF in which track density produced is comparable to virgin powder.

Citation

Speidel, A., Gargalis, L., Ye, J., Matthews, M. J., Spierings, A., Hague, R., …Murray, J. W. (2022). Chemical recovery of spent copper powder in laser powder bed fusion. Additive Manufacturing, 52, Article 102711. https://doi.org/10.1016/j.addma.2022.102711

• Journal Article Type: Article
• Acceptance Date: Feb 21, 2022
• Online Publication Date: Feb 26, 2022
• Publication Date: 2022-04
• Deposit Date: Apr 3, 2024
• Publicly Available Date: Apr 8, 2024
• Journal: Additive Manufacturing
• Print ISSN: 2214-7810
• Electronic ISSN: 2214-8604
• Publisher: Elsevier
• Peer Reviewed: Peer Reviewed
• Volume: 52
• Article Number: 102711
• DOI: https://doi.org/10.1016/j.addma.2022.102711
• Keywords: Laser powder bed fusion; Powder reprocessing; Powder recycling; Powder recovery; Chemical etching; Porosity
• Public URL: https://nottingham-repository.worktribe.com/output/31880409
• Additional Information: This article is maintained by: Elsevier; Article Title: Chemical recovery of spent copper powder in laser powder bed fusion; Journal Title: Additive Manufacturing; CrossRef DOI link to publisher maintained version: https://doi.org/10.1016/j.addma.2022.102711; Content Type: article; Copyright: © 2022 The Authors. Published by Elsevier B.V.