Absorption of Nitrogen during Pulsed Wave L-PBF of 17-4 PH Steel

Ben Brown; Joseph Newkirk; Frank Liou

doi:10.3390/ma14030560

Absorption of Nitrogen during Pulsed Wave L-PBF of 17-4 PH Steel

Materials (Basel). 2021 Jan 25;14(3):560. doi: 10.3390/ma14030560.

Authors

Ben Brown¹, Joseph Newkirk², Frank Liou³

Affiliations

¹ Materials Engineering, Department of Energy's Kansas City National Security Campus, Kansas City, MO 64147, USA.
² Material Science and Engineering Department, Missouri University of Science and Technology, Rolla, MO 65401, USA.
³ Mechanical and Aerospace Engineering Department, Missouri University of Science and Technology, Rolla, MO 65401, USA.

Abstract

In the fabrication of 17-4 PH by laser powder bed fusion (L-PBF) the well-documented occurrence of large amounts of retained austenite can be attributed to an elevated concentration of nitrogen present in the material. While the effects of continuous wave (CW) laser processing on in-situ nitrogen absorption characteristics have been evaluated, power modulated pulsed wave (PW) laser processing effects have not. In this study the effects of PW L-PBF processing of 17-4 PH on nitrogen absorption, phase composition, and mechanical performance are explored using commercially available PW L-PBF equipment and compared to samples produced by CW L-PBF. PW L-PBF samples fabricated in cover gas conditions with varying amounts of nitrogen demonstrated reduced absorption levels compared to those produced by CW L-PBF with no effects on phase composition and minimal effects on mechanical performance.

Keywords: 17-4 PH; additive manufacturing; nitrogen absorption.