Effects of W contents on the oxidation resistance of (Zr, Hf, Nb, Ta, W)C high-entropy carbides at 800–1200 °C

Abstract

Oxidation resistance of high-entropy carbides is a critical property considering their possible applications in harsh environments. In this work, the oxidation resistance of non-equimolar (Zr, Hf, Nb, Ta, W)C high-entropy carbides (HECCs-W) containing different W content was studied. The results showed that the antioxidation property of the HECCs-W was affected by both W content and oxidation temperature. In-situ oxidation monitoring by high temperature X-ray diffractometer and theoretical calculation results found delayed oxidation effect of W atoms. Combining morphology analysis and phase compositions of the oxide layers, we concluded that the content of W and its oxidation rate at different temperature affected the content of (Nb, Ta, Zr, Hf)_xW_yO_z in the oxide layer, which substantially affected the morphology of the oxide layer, for (Nb, Ta, Zr, Hf)_xW_yO_z usually had a low or negative thermal expansion coefficient. And the morphology of the oxide layer consequently decided the oxidation resistance of the HECCs-W.