Effect of Mo on the high temperature oxidation behavior of Al19Fe20-xCo20-xNi41Mo2x high entropy alloys

The eutectic high-entropy alloys (EHEAs) are a promising family of alloys for high-temperature application, while their high-temperature oxidation and the effect of refractory elements are not well known. In this work, the high-temperature oxidation of the Al19Fe20-xCo20-xNi41Mo2x (x = 0, 1, 2) EHEAs is investigated. The EHEA with no Mo addition forms a porous oxides scale with three layers and shows the lowest oxidation resistance. With minor addition of Mo, which can facilitate the selective oxidation of Al, the EHEA forms a dense and continuous oxides scale and has a significantly improved high-temperature oxidation resistance. With more Mo addition, the EHEA shows lower oxidation resistance due to the formation of volatile Mo oxides, which can evaporate and leave channels for oxygen. These results could be helpful in understanding the oxidation resistance of the Mo-containing HEAs.