Enhanced Corrosion Resistance of Additively Manufactured 316L Stainless Steel After Heat Treatment

Abstract

The microstructures and passivation behavior of selective laser melted 316L stainless steel (SLM SS316L) after various heat treatments (500 °C, 950 °C, and 1100 °C) were investigated. The electrochemical results showed that the SLM SS316L sample that was heat treated at 950 °C exhibited the lowest passive current density. The microstructural characterization analysis indicated that the subgrain structures transformed from dislocation-rich subgrain boundaries into island-like cellular trace structures after heat treatment at 950 °C. This led to improved corrosion resistance due to the elimination of dislocations and the homogenization of the composition. Compositional analyses of the passive film indicated that there was no notable change in the passive film composition after heat treatment at 500 °C and 950 °C. However, heat treatment at 1100 °C promoted the formation of Cr(OH) 3 in the passive film, resulting in a reduced corrosion resistance. Based on these results, heat treatment at 950 °C appears to be an adequate post-process for SLM SS316L to optimize the microstructure, while also improving corrosion resistance.