Microstructure and property of a selective laser melting process induced oxide dispersion strengthened 17-4 PH stainless steel

Abstract

Selective laser melting (SLM) process of 17-4 PH stainless steel has been a subject of research interest due to its complex microstructure-property correlation associated with SLM process. In this work, an oxide dispersion strengthened 17-4 PH stainless steel was successfully fabricated directly by SLM process with an oxygen content of 500 ppm in the chamber. It contained a matrix of ultrafine packet of martensite and reverted austenite with a dispersion of nano Mn-Si oxide particles that could provide strengthening by generation of geometrically necessary dislocations, making 17-4 PH an oxide dispersion strengthened material after the SLM process. Furthermore, post heat treatments could increase fractions of martensite and further induce either formation of ultrafine reverted austenite to promote significant transformation-induced plasticity during work hardening process or Cu-rich phase precipitation strengthening. This article not only describes a clear microstructure-property correlation for a SLM processed 17-4 PH, but also it shows the potential advantage of the SLM process in microstructure engineering.