Evolution of AISI 304L stainless steel part properties due to powder recycling in laser powder-bed fusion

Abstract

Laser Powder-Bed Fusion (L-PBF), often called selective laser melting (SLM), is a powder-bed fusion process in Additive Manufacturing (AM) that uses a laser beam to selectively fuse layers of powder into near net-shape components with little porosity. However, inconsistencies in the part properties due to the presence of defects in as-built components have hindered the widespread adoption of L-PBF for industrial applications motivating researchers to study the sources of variation for quality control purposes. A critical area suspected of creating variation in the part properties is the feedstock, where batch-to-batch differences as well as changes in the powder properties with reuse have the potential to affect performance. During processing, laser spatter and condensate form and deposit into the powder-bed surrounding the built parts. These particulates, collectively known as ejecta, differ morphologically and chemically from the virgin powder, potentially compromising reusability. In this study, 304L stainless steel powder was recycled for a total of 5 times through a systematic approach aimed at accelerating powder reuse to reveal its influence on both the tensile properties and impact toughness. Through analysis of variance (ANOVA), it was found that tensile properties did not change with reuse, while the impact toughness showed a steady decline revealing the differences in static and dynamic part properties due to powder reuse.