Thermal ablation behavior of SiC coating for 3D braided carbon fiber reinforced ZrC-SiC composites in different heat fluxes

In this study, CVD-SiC coating was prepared on 3D braided carbon fiber reinforced ZrC-SiC (abbreviated as C_f/ZrC-SiC) composites, and the microstructure and morphology of the composites and coating were characterized by scanning electron microscopy coupled with energy dispersive spectrometry (SEM–EDS), X-ray diffraction (XRD). The effect and mechanism of CVD-SiC coating on the ablation properties of C_f/ZrC-SiC composites under different ablation conditions were studied in details. The results showed that the CVD-SiC coating could reduce the ablation temperature and improve the compactness, which will promote the ablation properties of the C_f/ZrC-SiC composites in the heat flux of 2.38 MW/m². But with the heat flux increasing to 4.18 MW/m², ablation properties of C_f/ZrC-SiC composites decreased significantly, it was mainly difficult to form dense and stable ZrO₂-SiO₂ protective oxides due to accelerated mechanical erosion which makes the CVD-SiC coating lose its protection for C_f/ZrC-SiC composites during ablation and higher ablation temperature which will aggravate active oxidation of SiC and the evaporation of SiO₂.