The effect of configurational entropy and refractory elements on the oxidation behaviour of high entropy carbides containing up to eight elements

High entropy carbides (HECs) have attracted increasing attention due to their promising oxidation resistance properties. The oxidation behaviour of (Zr,Nb,Ta,Hf,Cr)C (HEC5-Cr), (Ti,V,Cr,Zr,Nb,Hf,Ta,W)C (HEC8-Cr), and (Ti,V,Zr,Nb,Mo,Hf,Ta,W)C (HEC8-Mo) powders was compared and studied from room temperature to 1200 degrees C. It was found that the oxidation onset temperatures (OOT) for the HEC5-Cr, HEC8-Cr, and HEC8-Mo powders were 790 degrees C, 688 degrees C, and 617 degrees C respectively. The high entropy effect benefits the structural stability of carbides and thus improves their oxidation resistance. However, there is no direct correlation between the configurational entropy value and the OOT of the studied HECs. Compared to the configurational entropy value, the refractory elements in HECs and the thermal stability of the produced oxides have a more significant impact on the oxidation resistance of HECs. Most of the group IV, V, and VI metals except W, Mo, and V have main oxides suitable for high-temperature applications, making them attractive candidates for oxidation-resistant HECs.