Microstructure and high-temperature properties of laser cladded AlCoCrFeNiTi0.5 high-entropy coating on Ti 6Al-4V alloy

Abstract In this study, AlCoCrFeNiTi0.5 high-entropy alloy (HEA) coating was deposited on Ti-6Al-4V alloy by laser cladding, aiming at enhancing the high-temperature wear and oxidation resistance. The microstructure, hardness, oxidation performance as well as high-temperature wear of the coating were characterized respectively. The results indicated that the coating was composed of dendrite (DR) and interdendrite (IR) phases. The DR phase had FCC structure being rich in Al, Co, Ni and Ti. The IR phases had BCC structure, for which, the IR1 was rich in Fe and Cr, and the IR2 was rich in Fe, Cr, Ti, Co and Ni. The coating possessed much better oxidation resistance than Ti-6Al-4V alloy at 600 °C due to a more compact oxide surface and the sluggish diffusion effect, which impeded the subsequent oxidation effectively. The average oxidation rate of the coating was about one tenth that of Ti-6Al-4V alloy. Moreover, the oxide scale was about one fifth that of Ti-6Al-4V alloy. The average micro-hardness of the coating was 706.3 HV about 2.32 times that of Ti-6Al-4V alloy. The HEA coating exhibited a mixture wear mechanism of adhesive and oxidative wear at 600 °C, having a wear volume loss about one thirteenth that of Ti-6Al-4V alloy.