Effect of solid oxidation products on the ablation mechanisms of ZrC and HfC based coatings above 2000°C

Solid and liquid oxidation products have been considered to be the key issues to influence the ablation resistance of UHTCs coatings. However, the effect of solid oxidation products on the ablation performance is not clear. In the present work, four kinds of UHTCs coatings (ZrC, ZrC-30vol.%SiC, HfC, HfC-30vol.%SiC) were selected to study the effect of different solid oxides on the ablation behaviors of UHTCs coatings. The results showed that the HfC-based coatings had thinner oxide scale and SiC-depleted layer, which shown better ablation resistance than the ZrC-based coatings. Based on the characterization of oxygen vacancy and density functional theory (DFT) calculation, it is thought that the solid oxidation products of HfO2 possesses higher defect formation energy compared with ZrO2, which can help to restrain the diffusion of oxygen and contribute to the better ablation resistance.