Microstructure and Wear Behavior of AlCoCrFeNiTi 0.5 High Entropy Alloy Coating Prepared by Electron Beam Cladding on Ti-6Al-4V Substrate

AlCoCrFeNiTi 0.5 high entropy alloy (HEA) coating with high hardness and excellent wear resistance was deposited on TC4 surface by electron beam cladding, and the process parameters, microstructure and properties of the coating were studied. The analysis shows that the microstructure of HEA coating is composed of dendritic (DR) and interdendritic (IR) phases. The IR phase, which is mainly composed of Fe and Cr, is confirmed to be BCC solid solution, while the DR phase is FCC solid solution with AlNi 2 Ti (or AlCo 2 Ti) structure. The grain orientation of the HEA coating is random, without obvious texture. Hardness gradually decreases from the upper part area of the HEA coating to the inner of the TC4 substrate. The hardness curve in the HEA coating region has some fluctuations, but the fluctuations are small, indicating a homogeneous microstructure. The average hardness of the HEA coating is 796.18 HV 0.2 , which is about 2.6 times that of the TC4 substrate. The HEA coating exhibits a higher coefficient of friction (COF) compared to the TC4 substrate. The average COF of HEA coating and TC4 substrate in the stable stage are 0.57 and 0.48, respectively. Wear loss of the HEA coating is 0.0657 mm 3 , about one tenth of that of TC4 substrate (0.6112 mm 3 ). The hardness of the HEA coating is high, no obvious furrow is found, and its wear mechanism is considered to be a mixture of adhesive wear and oxidation wear.