Influence of SiC morphology and distribution on the ablation behavior of Ta0.8Hf0.2C-SiC coating for C/C composites

To enhance the ablation resistance of carbon/carbon (C/C) composites under extreme thermal environments, Ta_0.8Hf_0.2C-SiC coatings were fabricated via pack cementation, with the morphology and distribution of SiC precisely tuned by adjusting the fabrication temperature. The influence of SiC characteristics on coating microstructure, oxide evolution, and ablation behavior was systematically investigated. Coatings with optimally sized (∼30–40 μm), well-dispersed SiC exhibited the highest spectral emissivity (2.5–3 μm), enabling efficient thermal radiation and surface temperature reduction. During oxyacetylene ablation at 2130 ℃ for 300 s, the optimized coating formed a dense, low-volatility Ta-Hf-Si-O oxide layer and achieved a near-zero linear ablation rate (0.103 μm/s). In contrast, coatings with underdeveloped or overgrown SiC led to porous structures, phase segregation, and inferior thermal protection. This study demonstrates the key role of SiC morphology in controlling oxide phase evolution and provides a promising strategy for the design of advanced carbide-based coatings for ultra-high-temperature aerospace applications.