Effect of Y on the high-temperature oxidation behavior of CrMoTaTi refractory high entropy alloy

Abstract Refractory high-entropy alloys (RHEAs) usually exhibited good mechanical properties at high temperatures. Unfortunately, the very poor high-temperature oxidation resistance was still greatly limited their practical application space. In this work, the effect of the reactive element (RE) Y on the high temperature oxidation resistance of CrMoTaTi RHEA was systematically investigated. It was found that the addition of Y could significantly improve the high-temperature oxidation resistance of CrMoTaTi RHEA. For the Y-bearing RHEAs, they greatly reduced the critical concentration of Cr required for the formation of Cr2O3 on the alloy surface, which was conducive to the rapid formation of Cr2O3 reacting with Ta2O5, resulting the generation of CrTaO4 with a relatively dense and continuous protective layer. The Y-bearing RHEAs exhibited good oxidation resistance even when the alloys were oxidized at 1000 °C for 100 h. This work proposed a positive role of the reactive elements and new insights to improve the high-temperature oxidation resistance of RHEAs.