Design the compositions and microstructure of low friction coefficient bimodal coatings for heavy load component

Abstract To get low friction coefficient and low wear rate coatings, three kinds of bimodal coatings were prepared using high-velocity oxygen-fuel (HVOF). After heat treatment, the WO₃ and CoWO₄ are detected. The friction coefficient decrease due to the lubricating WO₃ and CoWO₄. The minimum friction coefficient is 0.47±0.023 and wear rate is 3.95±0.42 ×10^-6 mm³N^-1m^-1 for the coating heat treated at 450℃ for 4h. The bimodal WC-Co coatings with Cu doping can improve tribological properties. The best doping content is 4wt%, and the friction coefficient and wear rate are 0.47±0.021 and 3.38±×10^-6 mm³N^-1m^-1, respectively. For the textured coatings, the Cu embedded in the coating can form a thin self-lubricating Cu film. Soft Cu fills the gap of the hard WC islands. During friction, The wear debris can form lubricant film on the surface of Cu phase. The Cu phase can form self-lubrication film on the WC islands. The friction film on the wear surface can decrease the friction coefficient and wear rate, which reduces by 32.8% and 25.7%, respectively.