Oxidation behavior of high-entropy (Zr0.2Hf0.2Ta0.2Nb0.2Ti0.2)B2 ceramic with 20% SiC addition

Oxidation behaviors of (Zr0.2Hf0.2Ta0.2Nb0.2Ti0.2)B2 high-entropy boride (HEB) ceramic and its composite containing 20 vol.% SiC (HEB-20SiC) were studied at 1100-1400 oC in air for the first time. Compared with the HEB, the HEB-20SiC showed the significantly lower oxidation rate, the higher oxidation activation energy and the improved oxidation resistance, which could be attributed to the formation of stable and dense oxide scale containing SiO2. A layered oxidation structure was observed in the cross-section of HEB-20SiC, ascribing to the active oxidation, the generation of SiO and TiO gases, their subsequent outward diffusion and the re-oxidation at the surface.