Influences of the compositions and mechanical properties of HVOF sprayed bimodal WC-Co coating on its high temperature wear performance

In this work, the bimodal WC-Co coatings were sprayed by high-velocity oxygen-fuel (HVOF), and the conventional WC-Co coatings were also fabricated for comparison. The microstructure, mechanical properties and high temperature wear performance were investigated. The bimodal WC-Co coating presented denser structure (porosity lower than 1.0%), higher average hardness (1164HV0.1) and fracture toughness (11.5±1.4MPa·m1/2) than that of conventional coating. The Weibull analysis of microhardness data of the bimodal coating presents a mono-modal distribution. The friction coefficient and wear rate of the bimodal coating were 0.61 and 2.96×10−6mm3·N−1·m−1, respectively, which is lower than that of conventional coating at the test temperature of 450°C. The tribofilm could be formed on the worn surface of bimodal WC-Co coating, which is composed of WO3 and CoWO4. The formation of tribofilm could reduce friction and wear. •The bimodal WC-Co coating presented denser structure and higher average hardness and fracture toughness than that of conventional coating.•The bimodal coating presented lower friction coefficient and wear rate compared to the conventional coating at the test temperature of 450°C.•The tribofilm, composed of WO3 and CoWO4, could be formed on the worn surface of bimodal WC-Co coating. The formation of tribofilm could reduce friction and wear.