Reuse of powder feedstock for directed energy deposition

The deposition efficiency of metal based additive manufacturing processes, particularly with directed energy deposition (DED) equipment which requires powder feedstock, is often <50%. While reuse of the remaining powder is common in industry, the precise effects on build quality resulting from possible morphological, microstructural, and chemical changes in the powder remain poorly understood. In this study, the reuse of 316L stainless steel powder in the Laser Engineered Net Shaping (LENS (R)) machine was investigated through multiple deposition cycles. Particular attention was paid to the influence of reusing powder on: particle morphology, flowability, agglomeration, chemical composition and microstructure, via scanning electron microscopy, particle size analysis and mechanical testing of deposited parts from select reuse cycles. Results show that, for the range of parameters studied in this investigation, the physical properties of powder particles vary over multiple deposition cycles without significantly effecting the build quality of deposited parts. (C) 2018 Elsevier B.V. All rights reserved.