Microstructure and wear properties of CuNiSiTiZr high-entropy alloy coatings on TC11 titanium alloy produced by electrospark - computer numerical control deposition process

An equiatomic 5-component alloy of CuNiSiTiZr was produced by vacuum arc melting. It was used as an electrode to prepare CuNiSiTiZr high-entropy alloy coatings (HEACs) on TC11 titanium alloy via electrospark - computer numerical control deposition (ES-CNCD) process with optimal process parameters. The resulting coating was analyzed by X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM) and X-ray energy-dispersive spectroscopy (EDS). The thermodynamic analysis of the HEAC was carried out based on a new concept of mixing enthalpy matrix (MEM) and a HEA-MEM-Calcu toolbox. The results showed that the coating is composed of BCC solid solution with micro/nanocrystallines. The hardness of the HEAC surface is more than 2.5 times that of the TC11 substrate. The wear resistance of the HEAC was more excellent than that of the TC11 substrate. The improvement of the hardness and wear resistance of the HEAC is attributed to the solid solution strengthening effect, precipitation strengthening effect, and nanocomposite strengthening effect. The wear mechanism of the HEAC is the cracking and chipping brittle mechanism.