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Materials Science in Additive Manufacturing Spheroidization of 304L SS powder for LPBF process

A B with the as-received powder. The more spherical geometry of
the spheroidized powder improved the powder’s flowability
compared to the as-received powder.

Acknowledgments
This work was funded by Honeywell Federal Manufacturing
& Technologies LLC under Contract No. DE-NA0002839
with the U.S. Department of Energy. The publisher, by
accepting the article for publication, acknowledges that the
C D United States Government retains a nonexclusive, paid-up,
irrevocable, worldwide license to publish or reproduce the
published form of this manuscript, or allow others to do so,
for the United States Government purposes.
Conflict of interest

The authors declare that they have no conflict of interest.
Author contributions
Figure 15. SEM micrographs of parts built with (A-B) as-received and
(C-D) spheroidized powder. The samples were electrolytically etched Conceptualization: M. Hossein Sehhat, Austin T. Sutton
using a 60%/40% nitric acid to water solution.
Data curation: M. Hossein Sehhat, Austin T. Sutton, Chia-
Hung Hung
during spheroidization, promoting delta ferrite formation.
Therefore, it is critical to assess if the change in powder Investigation: M. Hossein Sehhat, Austin T. Sutton,
chemistry leads to delta ferrite retention in the as-built Chia-Hung Hung, Ben Brown, Ronald J. O’Malley,
microstructure, which is a future work of this study. Jonghyun Park, Ming C. Leu

In addition to causing a difference in the resulting Formal analysis: M. Hossein Sehhat, Austin T. Sutton,
microstructure, a reduction in C and N can decrease the Chia-Hung Hung, Ben Brown
strength since the reduction of both alloying elements prevents Funding acquisition: Ming C. Leu
the material from solid solution strengthening. Moreover, the
removal of the dislocation-dense cellular structure through Supervision: Ming C. Leu
FA solidification will also reduce the strength. Thus, the lower Writing – original draft: M. Hossein Sehhat, Austin T.
strength of the parts produced with the spheroidized powder Sutton
compared to the as-received powder is expected.
Writing – review & editing: M. Hossein Sehhat, Austin
4. Conclusion T. Sutton, Chia-Hung Hung, Ben Brown, Ronald J.
O’Malley, Jonghyun Park, Ming C. Leu
After the plasma spheroidization process, the particles
reshaped to spheres while their particle size remained Availability of data and materials
essentially unchanged. This indicates the particles are only
reshaping in geometry but not changing in particle size. The The raw or processed data required to reproduce these
reduction of solid solution strengthening elements including findings cannot be shared at the time of article publication
carbon and nitrogen after the spheroidization process changed as the data also forms part of an ongoing study.
the solidification mode of powder particles and fabricated References
parts. The spheroidized powder contained partially ferritic
particles, increasing the powder’s overall ferrite content 1. Committee F42 on Additive Manufacturing Technologies.
compared to the as-received powder. The parts made with the Available from: https://www.astm.org/COMMITTEE/F42.
spheroidized powder exhibited a FA solidification mode. The htm [Last accessed on 2021 Jan 02].
reduction in solid solution strengthening elements including 2. Behdani B, Senter M, Mason L, et al., 2020, Numerical study
nitrogen and carbon, as well as oxygen content, accompanied on the temperature-dependent viscosity effect on the strand
by the changes in solidification mode influenced the properties shape in extrusion-based additive manufacturing. J Manuf
of parts built with the spheroidized powder, which exhibited Mater Process, 4: 46.
a lower strength but higher ductility than the parts fabricated https://doi.org/10.3390/jmmp4020046

Volume 1 Issue 1 (2022) 10 http://doi.org/10.18063/msam.v1i1.1