Effect of wide range of heat treatments on the corrosion resistance of additively manufactured 316L stainless steel (316L SS) via PBF-LB/M (powder bed fusion of metals using a laser beam)
摘要
The current study seeks to understand the influence of a variety of heat treatments at a range of temperatures from 800 °C to 1200 °C on microstructure evolution, and corrosion behaviour of as-built components of 316L stainless steel (316L SS) fabricated by powder bed fusion of metals using a laser beam (PBF-LB/M). Heat treatment is typically carried out in additively manufactured alloys to homogenise the microstructure and reduce defects, which leads to enhanced performance. Interfaces such as cell boundaries and melt pool boundaries produced during additive manufacturing are regions of elemental segregation and therefore expected to be an impediment to uniform concentration of desirable alloying additions. However, this study shows counterintuitive results. Electrochemical measurements showed that the as-built specimen exhibited the lowest corrosion rate (Icorr, ~ 1.9 × 10–7 A/cm2) and thus the best corrosion resistance amongst all conditions. The microstructural origins of this behaviour in terms of evolution of the interfaces during heat treatment are explored for the first time in the present study using detailed characterisation. The role of Cr and Mo in the hierarchical solidification structure is elucidated. The results will allow for an informed interface engineering of AM alloys, specifically for improved corrosion resistance in many applications such as chemical processing, pressurized water reactors and petrochemical industries.