Tissue evolution and properties of plasma solid-state surface metallurgical TiCoCrNiWMo high-entropy alloy coatings

Using plasma solid-state surface metallurgy is a new method for preparing high-entropy alloy (HEA) coatings. In this paper, based on the experience in plasma solid-state surface metallurgy and the HEA, the TiCoCrNiWMo HEA coatings with metallurgical bonding and gradient structure were prepared by five-element co-infiltration of Co–Cr–Ni–W–Mo on the surface of a TC4 substrate for the first time. The tissue morphology evolution and properties of HEA coatings at different holding temperatures were investigated. The results show that the HEA coating at the holding temperature of 1000 °C consists of a deposited layer + diffusion layer. When the temperature exceeds the (α + β)/β transition temperature of TC4, only the deposited layer is formed on the surface of the substrate. Holding temperature does not affect the phase composition of the HEA coating. The best bonding performance of the HEA coating with the substrate was achieved at a holding temperature of 1000 °C, with a bonding force of about 63.81 N. All the HEA coatings showed different degrees of improvement in hardness, wear resistance, and corrosion resistance compared to the substrate. The HEA coatings prepared at 1000 °C had the best performance, with hardness and wear resistance 1.5 and 8.9 times higher than those of the substrate, respectively, and excellent corrosion resistance in acidic, alkaline, and salt solutions. The results show that the new TiCoCrNiWMo HEA coatings prepared by plasma solid-state surface metallurgy have good wear resistance and corrosion resistance and have good application prospects in the fields of automobile manufacturing and shipbuilding.