Oxidation behavior of (Hf0.2Ta0.2Zr0.2Ti0.2Nb0.2)C-xSiC ceramics at high temperature

In this work, high-entropy carbide (Hf0.2Ta0.2Zr0.2Ti0.2Nb0.2)C (HEC) ceramics doped with different concentrations of SiC were prepared by spark plasma sintering at 2000 degrees C in vacuum. Oxidation behavior of HEC ceramics was studied in 1300-1500 degrees C temperature range. The addition of SiC enhances oxidation resistance of HEC ceramics through the formation of Hf(Zr)SiO4 and Hf(Zr)TiO4 protective oxide layer, with 20 vol% SiC-doped ceramics exhibiting the best oxidation resistance. Outward diffusion of TiO is suggested to be rate-controlling process in the oxidation of SiC-doped HEC ceramics. Although the SiC does not affect oxidation mechanism of HEC ceramics, its presence leads to a delay in outward diffusion of transit elements including Nb and Ta during oxidation. Thus, oxidation resistance of HEC at high temperatures could be improved by the addition of SiC.