Characterization of AISI 304L stainless steel powder recycled in the laser powder-bed fusion process

• Published in: Additive manufacturing 2020-03, Vol.32, p.100981, Article 100981
• Main Authors: Sutton, Austin T., Kriewall, Caitlin S., Karnati, Sreekar, Leu, Ming C., Newkirk, Joseph W.
• Format: Article
• Language: English
• Subjects: Laser spatter; Powder characterization; Powder recycling; Selective laser melting
• ISSN: 2214-8604; 2214-7810
• DOI: 10.1016/j.addma.2019.100981

During part fabrication by laser powder-bed fusion (L-PBF), an Additive Manufacturing process, a large amount of energy is input from the laser into the melt pool, causing generation of spatter and condensate, both of which have the potential to settle in the surrounding powder-bed compromising its reusability. In this study, AISI 304 L stainless steel powder is subjected to seven reuses in the L-PBF process to assess the changes in powder properties that occur as a result of successive recycling. The powder was characterized morphologically by particle size and shape distribution measurements, chemically through inert gas fusion for evaluation of oxygen content, and microstructurally by X-ray diffraction for phase identification. The evolution in powder properties was used to explain observed performance differences obtained by the Hausner ratio and a Revolution Powder Analyzer for quantifying flowability. The results show that recycled powder coarsens and becomes more spherical, accrues oxygen, and accumulates delta ferrite as it is reused. Due to the change in powder morphology, recycled powder exhibited improved flowability in comparison to the virgin powder.