Characterization of a 17-4 PH stainless steel obtained through metal powder Hot Isostatic Pressing process for automotive application

Abstract

Abstract Steels of the family 17-4 Precipitation Hardening stainless steels are often considered as potential candidates for applications requiring high levels of strength (typically above 600 MPa in tensile strength) and a moderate ductility. The aim of this work is the characterization of a 17-4 precipitation hardening stainless steel obtained through metal powder Hot Isostatic Pressing process. The main purposes of using Hot Isostatic Pressing process are the better chemical composition and microstructure homogeneity, the finer grain size (allowing to higher mechanical properties), and the possibility to obtain net shape products, avoiding subsequent finishing operations. The Hot Isostatic Pressing process temperature does not seem to significantly influence the tensile properties, while, the aging temperature is a key factor: lower aging temperature brings to higher strength and lower ductility. However, a higher influence of the Hot Isostatic Pressing process temperature was detected on the toughness. Improved toughness both at room and at low temperature was obtained by optimizing the aging treatments. An improvement of 32 % in impact energy was obtained by the optimization of the aging process thanks to a higher austenite content, which has shown a nanosized shape between the martensite platelets, in the steel structure.