Effect of heat treatment on the microstructure, impact toughness and wear resistance of Fe-based/B4C composite coating by vacuum cladding

The study focused on the effect of quenching and quenching-tempering processes on the microstructure, hardness, impact toughness and wear resistance of Fe-based/B4C composite coating on the surface of ASTM 1045 steel by vacuum cladding. The results revealed that the metallurgical bonding was realized between the coating and steel substrate. After quenching at 950/1000/1050 °C and quenching-tempering at 1000–490/1000–540/1000–590 °C, the hard phases (M2B and M23 (C, B) 6) in the coating remained unchanged in type, but their morphologies were broken and became more rounded. The coating matrix changed from pearlite to martensite, and granular secondary phases of M23(C, B)6 precipitated from coating matrix. After heat treatment, the impact energy of coated samples is significantly improved, which may be related to the evolution of the coating microstructure and the appearance of interfacial delamination fracture. The results of the wear test showed that the change of coating matrix and hard phase morphology, and the coordination between them were the main factors affecting the wear resistance of the coating. The best wear resistance of the coating was obtained at QT540, and the wear mechanisms were mainly fatigue spalling and brittle fracture.