Microstructure and wear behavior of in situ boride and carbide particle reinforced composite coating by laser cladding and tempering treatment

In situ carbide and boride ceramic particle reinforced Ni60CuMoW composite coating was fabricated by laser cladding and the tempering treatment process on 45 medium carbon steel. The influence of tempering treatment on the wear mechanism of the coating was analyzed. The results show that the coating is mainly composed of γ (Ni, Fe), (Ni, Cu) solid solution, Fe3Ni3B, Fe3B, CrB borides, and M23C6 (M=Cr, Ni, Fe), W2C, MoC type carbides. After tempering, the carbide and boride particle reinforced phases in the coating are uniformly dense and have good metallurgical bonding with 45 medium carbon steel in the 1.3 mm thickness range. Compared with the 45 medium carbon steel, the average microhardness of coatings before and after tempering increased by 3.7 and 4.6 times, and the relative wear resistance increased by 1.0 and 2.89 times, respectively. The worn surface of the coating without tempering fails primarily by surface fatigue wear, accompanied by minor abrasive wear caused by fatigue-generated debris. But for the coating after tempering, the wear surface is relatively smooth and shows a shallow scratch, good adhesion, and small size of wear debris, belonging to the abrasive wear mechanism.