Effects of heat treatment on microstructure, mechanical and corrosion properties of 15-5 PH stainless steel parts built by selective laser melting process

Abstract

With recent advancements in additive manufacturing, Selective Laser Melting (SLM) is emerging as an unconventional manufacturing process of exceptional flexibility capable to fabricating any complex part without requiring expensive fixtures, tooling, mold or any other additional auxiliary with a very short lead time from design conceptualization to fabrication. Very few reports are available on the effect of heat treatment on mechanical and corrosion properties of SLM 15-5 Precipitation Hardening (PH) stainless steel. Herein, micro-structural evolution and its correlation with various mechanical and corrosion properties of heat treated SLM 15-5 PH stainless steel are investigated to widen the application of SLM parts for industrial usages. Results show, standard aging condition (H900) increases yield strength, hardness and corrosion resistance through the formation of fine spherical ε-Cu-rich precipitates (∼15 nm), but makes the specimens brittle resulting in an increase in wear rate and a decrease in impact energy. Combined effects of coarsening of elliptical ε-Cu-rich precipitates and increase in reverted austenite phase in overaging (H1150) make the specimen ductile having relatively low yield strength, hardness, wear rate but high impact energy. Solution annealing was found to reduce anisotropy in mechanical properties through the homogenization of microstructure. Higher aging temperature and longer soaking time doesn’t have significant impact on different mechanical properties but deteriorates the corrosion properties. Solution annealing before aging is recommended for the homogeneity in microstructure. Present findings can be used as a guideline to select proper post heat treatment for SLM 15-5 PH stainless steel to impart application oriented mechanical and corrosion properties.