Tribological Properties of AlCoCrFeNi High Entropy Alloy at Elevated Temperature

AlCoCrFeNi high entropy alloy (HEA) is a potential candidate for the next-generation high temperature structural materials because of the excellent properties. However, the tribological properties of the HEA have been rarely reported. In this paper, the AlCoCrFeNi HEA was prepared by spark plasma sintering (SPS), and the microstructure, mechanical properties and tribological properties from room temperature (RT) to 800 ℃ of the HEA were studied. The SPSed AlCoCrFeNi consisted of a FCC phase, a disordered BCC phase and a little ordered BCC phase. The FCC phase with net-like structure enabled the HEA to have good ductility and fracture toughness, and the BCC phase with near-equiaxed shape made the HEA have excellent strength. The friction coefficients and wear rates of the HEA from RT to 800 ℃ were 0.43~0.51 and below 10^–5 mm³/(N·m), respectively. Abrasive wear was the main wear mechanism of the HEA from RT to medium temperatures. From medium temperatures to high temperatures, the main wear mechanism was the combined action of abrasive wear, adhesive wear and plastic deformation. At high temperatures, a oxides layer that mainly consisted of Al₂O₃ and Cr₂O₃ formed on the HEA surface, and the oxides layer played a key role in improving the wear resistance of the HEA.