The tribological properties of carbon doped Al0.2Co1.5CrFeNi1.5Ti0.5 high entropy alloys

High entropy alloys (HEAs) are expected to be applied at elevated temperatures. However, the tribological properties of the HEAs in a wide temperature range have not been studied systemically, especially at high temperatures. In this paper, the micro-hardness as well as the tribological properties of Al0.2Co1.5CrFeNi1.5Ti0.5+xCx (x = 0, 1.0 and 2.0) HEAs from 25°C to 800°C was investigated and compared with Inconel 718 superalloy. The results showed that the solid solution strengthening effect of the HEAs and the dispersion strengthening effect of in situ generated TiC resulted in a significantly higher high temperature microhardness of the carbon-doped HEAs than that of the Inconel 718. The friction coefficient of the HEAs increased with increasing carbon content at same temperature, but it decreased as the temperature increased. The wear resistance of carbon doped HEAs were superior than that of Inconel 718 and carbon-free HEAs from 25 to 800 °C. Below 600 °C, the wear rate of the HEAs which decreased monotonously with increasing carbon content was in the range of (0.31-12.56) × 10-5 mm3 N-1∙m-1, but above 600 °C, the wear rate of the HEAs was proportion to carbon content within (2.64-23.90) × 10-6 mm3 N-1∙m-1. The excellent high-temperature wear resistance of the HEAs was attributed to the synergistic effect of the good high temperature softening resistance and a nano-oxidized glaze layer with superior mechanical properties on the worn surface.