Heat-affected zone microstructure and mechanical properties evolution for laser remanufacturing LZ50 axle steel

In this article, the laser cladding on LZ50 axle steel was conducted to investigate the evolution of microstructure and mechanical property of HAZ. Based on the quality of cladding formation and thermal damage evaluation in the HAZ, the optimal process parameters was obtained as 7.8g/min powder feeding rate,420mm/min scanning rate and other constant settings. The microstructure of HAZ was characterized by means of OM and SEM. Meanwhile hardness distribution in HAZ and tensile property of cladding-HAZ-substrate samples were measured. The results indicate that, Two types of HAZs were observed under different cladding strategies: gradually changed microstructure during thin-layer cladding process and relatively uniform microstructure during multi-layer cladding process..Due to different maximum temperature of thermal cycle, HAZ and substrate have partial surface hardening during the laser cladding process. The mechanism of hardening was discussed. The final microstructure after complex thermal cycles result hardening behavior in both HAZ and substrate.