Water vapor oxidation behavior of high-entropy (Ti,Nb,Ta,Hf,W)C x at 1200 °C: the role of carbon vacancies.

The oxidation behavior of (Ti,Nb,Ta,Hf,W)C x in high-temperature water vapor was studied. The results indicate that the replacement of Zr with W enhances the oxidation resistance of high-entropy (Ti,Zr,Nb,Ta,Hf)C. Moreover, with increasing carbon vacancies, the oxidation resistance of (Ti,Nb,Ta,Hf,W)C x further increases, and (Ti,Nb,Ta,Hf,W)C0.8 displays optimal oxidation resistance. The weaker O atom adsorbing ability and the lower diffusion ability of W are among the main reasons for the superior oxidation resistance. Additionally, the decrease in residual carbon in the oxidation layer with increasing carbon vacancies and the disappearance of the (Nb,Ta)2O5 phase in the oxide scale on reaction with WO2 effectively inhibit the inward diffusion of water vapor.