Elucidating the impact of severe oxidation on the powder properties and laser melting behaviors

In this work, commercial 316L stainless steel (SS) powder was used to experimentally determine the impacts of severe oxidation on the powder characteristics and laser powder bed fusion (L-PBF) melting behaviors. The morphology, surface state, and laser absorptivity of both virgin and oxidized powders were systematically characterized. Their impacts on the flowability and powder bed quality were monitored by custom-designed recoating experiments and powder shear tests. The results of an in situ wetting analysis and microstructure evaluation were compared to establish a correlation between the powder characteristics and laser fusion. The powder oxidation enhanced L-PBF processability by improving the homogeneity of powder spreading and the formation of stable, consecutive laser beads. A thin ceramic layer-coated SS alloy reinforced with uniform (Si, Mn)-based oxides was synthesized by the LPBF processing of severely oxidized powders. The mechanical strength of this alloy was found to be similar to that processed using the virgin powders, whereas the elongation was slightly decreased, likely due to the amorphous oxide feature and the mechanical oxide-Fe interface. This study provides a systematic understanding of powder reuse and new insight into the potential for economically developing highperformance parts by the positive utilization of powder oxidation and the L-PBF process. CO 2022 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

Automated summary

This study experimentally determined the impacts of severe oxidation on the characteristics of 316L stainless steel powder and the melting behaviors in laser powder bed fusion (L-PBF). The results showed that powder oxidation can improve the L-PBF processability by enhancing the uniformity of powder spreading and the stability of laser fusion. A ceramic layer-coated SS alloy was synthesized by processing severely oxidized powders, and its mechanical strength was similar to that processed using virgin powders.