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 (1164 HV0.1) and fracture toughness (11.5 +/- 1.4 MPa.m(1/2)) 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 x 10(-6) MM(3)N(-1)m(-1), respectively, which is lower than that of conventional coating at the test temperature of 450 degrees 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.