Effect of different heat-treatment temperatures on the laser cladded M3:2 high-speed steel

Abstract

M3:2 high-speed steel (HSS) coating was fabricated on one austenitic stainless steel by laser cladding (LC). The cladded specimen (specimen A) was heat treated at 500°C (specimen B) and 800°C (specimen C). Microstructure, phase structure, residual stress, micro-hardness and wear behavior of the specimens were examined. Dry sliding wear was carried out on each specimen and lubricant sliding wear (emulsifier solution and water served as lubricant) was carried out on specimen C. Results show that the observed microstructure of specimen A is characterized by comparably fine equiaxial grains, dendrites and inter-dendritic network shaped eutectic carbides. This microstructure is composed of supersaturated martensite, retained austenite and MxCy type carbides. Heat treatment, carried out on specimens B and C, leads to the relief of residual stress and phase transformation. Retained austenite enriches and stabilizes in specimen B. Tempered sorbite forms in specimen C. Both specimens show the existence of Fe2O3. Residual stress changes from tensile to compressive stress after heat treatment. The maximum principal stress change rates of specimens B and C compared with that of specimen A are −1.04 and −2.53, respectively. Average micro-hardness of specimen A increases by 4.3% and decreases by 32.5% after heat treated at 500°C and 800°C, respectively. Dry sliding wear resistance shows similar variation tendency with the microhardness of the HSS coating. Wear resistance of specimen B is the best during the dry sliding wear, and that of specimen C is the worst. Addition of lubricant greatly improves the wear resistance of specimen C.