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HfC coatings were deposited on the surface of carbon/carbon (C/C) composites and CVD-SiC coating by low-pressure chemical vapor deposition (CVD), respectively. The effects of two substrates on the microstructure, phase composition and preferred orientation of HfC coatings were investigated in detail. Results showed that HfC coatings deposited on two substrates inherit their own substrate surface characteristics. After ablation for 90 s, the HfC coating prepared on CVD-SiC coating has better ablation resistance under oxyacetylene flame with heat flux of 2.4 MW/m2, because the transition layer can effectively relieve the damage caused by thermal stress. • HfC coating was successfully deposited on the surface of CVD-SiC and C/C composite. • The influence of two substrates on the growth mechanism of CVD-HfC coatings was systematically discussed. • The ablation resistance of CVD-HfC coating on the surface of C/C composites and CVD-SiC coating was tested. [ABSTRACT FROM AUTHOR]

• In present study, a detailed investigation on the ablation behavior of the layered structure by computational and experimental methods. • The multilayer alternating structure HS coating performed better ablation resistance compared with single layer SiC and HfC coating. • The multi-layer structure can effectively inhibit the propagation of cracks in the coating during ablation. To improve the service life of carbon/carbon (C/C) composites under ultra-high temperature ablation environments (> 2200 ℃), SiC/HfC coating with multi-layer alternating structure was designed and prepared on C/C composites by low-pressure chemical vapor deposition (LPCVD). The microstructure and phase compositions of the as-prepared and ablated coatings were investigated, and the influence of the multi-layer structure on the ablation behavior and thermal stress distribution of the coatings were analyzed as well. After ablation for 120 s, the (SiC/HfC) 3 coating has better ablation resistance due to its multi-layer structure and the formation of Hf-Si-O sticky glass phase. [ABSTRACT FROM AUTHOR]