Effect of Aluminum Content on the Tribological Properties of AlxCrTiMo Refractory High-Entropy Alloys

Refractory high-entropy alloys are a new type of alloy exhibiting good properties at high temperatures. In this study, AlxCrTiMo refractory high-entropy alloys were prepared by spark plasma sintering, and the mechanical and tribological properties of the alloys were investigated. The three-dimensional morphology and SEM image of the worn surface showed variation of wear marks, wherein the wear rate of the alloy decreased with increasing temperature, and the main wear mechanism changed from abrasive to adhesive wear. The results of Raman and x-ray diffraction spectroscopies of the phase structure of the oxidized glazed layer on the wear marks showed that the oxide layer on the surface of the Al0.25CrTiMo wear mark at 800°C contained oxides of MoO3 and MoO2. It can be concluded from these results that reduction of the aluminum content of the alloy will promote the formation of Cr and Mo oxides, which is important in the development of high-temperature wear resistance of AlxCrTiMo alloys.