High‐temperature oxidation behavior of (Hf 0.2 Zr 0.2 Ta 0.2 Nb 0.2 Ti 0.2 )C high‐entropy ceramics in air

Abstract High‐entropy metal carbides have recently been arousing considerable interest. Nevertheless, their high‐temperature oxidation behavior is rarely studied. Herein the high‐temperature oxidation behavior of (Hf 0.2 Zr 0.2 Ta 0.2 Nb 0.2 Ti 0.2 )C high‐entropy metal carbide (HEC‐1) was investigated at 1573‐1773 K in air for 120 minutes. The results showed that HEC‐1 had good oxidation resistance and its oxidation obeyed a parabolic law at 1573‐1673 K, while HEC‐1 was completely oxidized after isothermal oxidation at 1773 K for 60 minutes and thereby its oxidation followed a parabolic‐linear law at 1773 K. An interesting triple‐layered structure was observed within the formed oxide layer at 1673 K, which was attributed to the inward diffusion of O 2 and the outward diffusion of Ti element and CO or CO 2 gaseous products.