Preparation and ablation properties of the SiC/ZrB₂-SiC gradient ceramic coating on C/C-ZrC-SiC composites

The SiC/ZrB₂-SiC gradient ceramic (S/ZS) coating and ZrB₂-SiC ceramic (ZS) coating were prepared via slurry brushing and liquid silicon infiltration methods. The microstructure evolution and ablation behaviors of the S/ZS and ZS coatings were systematically investigated and compared. The S/ZS coating and matrix were closely bonded due to the formation of SiC at the interfaces. Meanwhile, the ingredient gradient from the SiC transition coating reduced the coefficient of thermal expansion (CTE) mismatch between the matrix and the outer ceramic coating. Therefore, the adhesion strength of the S/ZS coating was 38.48 % higher than that of the ZS coating. After 90 s of ablation, the ZS coating exhibited obvious peeling, while the S/ZS coating still remained intact. Correspondingly, the mass and linear ablation rates of the ZS coating were 709.09 % and 274 % higher than those of the S/ZS coating, respectively. In this work, the SiC transition coating could improve the structural integrity of the oxide layer and enhance the ablation performance of the coating.