Effect of heat treatment on the microstructure and corrosion resistance of 316L stainless steel fabricated by hybrid in-situ rolled wire-arc additive manufacturing

Abstract

The effect of heat treatment on the microstructure and corrosion resistance of 316L stainless steel fabricated using the hybrid in-situ rolled wire-arc additive manufacturing (HRAM) technique was studied. The results showed that the as-built sample was composed of dendritic δ-ferrite and irregular austenite grains. With increasing annealing temperature (650–1200 °C), the corrosion resistance of HRAM 316L steel in a proton exchange membrane fuel cell environment showed a complex change trend of constant-increase-decrease-increase, attributing to the coupling effects of the variation in phase composition, grain characteristics, and texture. Particularly, after annealing at 1050 °C, the δ-ferrite transformed into the σ-phase with higher contents of Cr and Mo, which promoted the formation and stabilization of the passivation film in the steel, thereby resulting in superior corrosion resistance.