Microstructural evolution and mechanical behavior of Custom 465 precipitation hardening stainless steel fabricated via laser powder bed fusion

Abstract

Custom 465(C465), a precipitation hardening stainless steel (PHSS) combining high strength and excellent corrosion resistance, has found myriad applications in diverse industries, particularly serving as a candidate for next-generation landing gear materials. However, no work on the additive manufacturing of this steel has been reported in open literature to date. In this study, laser powder bed fusion (L-PBF) was employed for the first time to fabricate C465 to gain knowledge on its printability, microstructure features and mechanical performance. It is found that C465 is crack-sensitive, but the inner cracks can be closed through hot isostatic pressing at 1155 °C for 3 h. Furthermore, a finite element model was constructed to evaluate the effect of laser beam scanning parameters on the melt pool temperature profile. An equation was proposed to predict the austenite fraction (11.3%–19.1 %) in the as-built C465. The microstructure of the LPBF-processed C465 after heat treatment was featured with martensite lath with dispersed nano-sized Ni3Ti precipitates, as well as 5.7%–7.0 % austenite. Tensile tests demonstrated that the LPBF-processed C465 after heat treatment exhibits an excellent combination of strength (UTS = 1761 MPa, YS = 1691 MPa) and ductility (6 %), comparable to that of the conventionally wrought C465. This study demonstrates a practicable L-PBF approach for processing C465 parts with satisfactory mechanical properties, paving the way for the application of additively manufactured C465 components in diverse industries.