Difference evaluation on ablation behaviors of ZrC-based and ZrB2-based UHTCs coatings

•The difference of ablation behavior for ZrC- and ZrB2-based coatings was firstly investigated and reported.•ZrB2-based coating showed better ablation resistance including lower surface temperature and superior oxidation resistance.•The ablation mechanism of ZrC- and ZrB2-based coatings was also analyzed based on thermodynamics predictions. In the present work, five kinds of UHTCs coatings (ZrC, ZrC-SiC, ZrB2, ZrB2-SiC, ZrB2-ZrC-SiC) were fabricated. The difference of ablation behavior between ZrB2- and ZrC-based coatings was evaluated and focused on. The microstructure evolution of resulted oxide layer were characterized in detail. The results showed that the ablation resistance of ZrB2-based coating was better than that of ZrC-based coating under the same environment, exhibiting lower surface temperature, thinner thickness of both the total oxide layer and the SiC-depleted layer. The possible reasons for the phenomena were supposed based on microstructure characters and thermodynamic analysis.