Structure evolution and ablation behavior of ZrC coating on C/C composites under single and cyclic oxyacetylene torch environment

ZrC ablation resistance coating was prepared on carbon/carbon composites by low pressure chemical vapor deposition using the ZrCl4-C3H6-H2-Ar system. The structure evolution and ablation behavior of the coating under single and cyclic ablation were investigated in an oxyacetylene torch environment. Single ablation results show that the ablated coating consists of three layers (outer ZrO2 layer, transitional ZrCxOy layer and residual ZrC layer). An oxidation progress is inferred that ZrC is oxidized into ZrCxOy firstly and then into ZrO2 in the case of the continuous diffusion of oxygen. Cyclic ablation results show that the effect of crack growth inhibition and the oxygen diffusion limitation of ZrO2 and ZrCxOy layers dominate the ablation of the coating and result in two different ablation behaviors. Based on the role of the ZrO2 and ZrCxOy layers in the single and cyclic ablation, two different ablation modes of the coating are proposed.