Structure and wear performance of the atmospheric heat-treated HVOF sprayed bimodal WC-co coating

In this study, the bimodal WC-Co coatings were prepared by high-velocity oxygen-fuel (HVOF). The coatings were then heat treated for 4 h at 350 °C, 450 °C and 550 °C in air atmosphere. The effect of the heat treatment on the composition, microstructure, mechanical property and wear performance were investigated. The results show that, after heat treatment, the coating shows dense microstructure at 450 °C and shows loose structure and cracks at 550 °C. the hardness first increases and then decreases with the increase of the heat-treated temperature, the maximum hardness is 1261 ± 61 HV after heat treatment at 450 °C. Testing at room and high temperature, the coating heat-treated at 450 °C for 4 h exhibits better wear resistance than the as-sprayed coating. The CoWO4 exhibits low shear strength and antifriction property and the friction promotes the formation of CoWO4.