Ablation behavior of ZrB2–SiC protective coating for carbon/carbon composites

Abstract Ablation behavior of ZrB 2 –SiC protective coating for carbon/carbon composites during oxyacetylene flame test at 2500 °C was investigated by analyzing the microstructure differentiation caused by the increasing intensity of ablation from the border to the center of the surface. After ablation, a continuous SiO 2 scale, a porous SiO 2 layer inlaid with fine ZrO 2 nuclei, and a continuous ZrO 2 scale respectively emerged in the border region, the transitional region, and the center region. In order to investigate the ablation microstructure in the initial stage, the sub-layer microstructure was characterized and found to be mainly formed by coral-like structures of ZrO 2 , which showed huge difference with the continuous structure of ZrO 2 on the surface layer. A kinetic model concerning the thickness change induced by volatilization and oxidation during ablation was built to explain the different growth mechanisms of the continuous ZrO 2 scale and the coral-like ZrO 2 structure.