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The design of a new multilayer anti-ablation coating is inseparable from the performance assessment in multiple environments. This work investigates the effects of different ablation flux on the microstructure evolution and phase composition of multilayer TaC/HfC coating. The results show that the different temperature regions were generated on ablated coating surface, resulting in the formation of different oxidation products. At heat flux of 2.4 MW/m2, the formation of dense Hf-Ta-O solid solution phase tightly adhered on substrate. As heat flux increased to 4.2 MW/m2, a large amount of molten oxidation phase was produced in the central area, which caused secondary damage to the coating under the action of high-speed flame. • Different temperature regions were formed on the coating surface under different heat flux. • The generation of a large amount of molten oxide phase caused secondary damage to the coating. • The ablation process of the TaC/HfC multi-layer coating can be divided into two stages. [ABSTRACT FROM AUTHOR]

HfC-SiC coatings have promising applications in the field of ablation protection for carbon-carbon (C/C) composites. In this work, HfC-SiC coatings with different ratios were designed and successfully prepared by low pressure chemical vapor co-deposition using HfCl 4 -MTS-CH 4 -H 2 -Ar system under the guidance of thermodynamic calculations. The phase composition, microstructure, and ablation behavior of HfC-SiC coating with different phase proportions were investigated. The coating with HfC/SiC ratio of 1:1 showed the best ablation resistance after ablation for 90 s, and its mass and linear ablation rates of HfC-SiC coating was only 1.016 ± 0.12 mg/s and 0.998 ± 0.08 µm/s, respectively. [Display omitted] • HfC-SiC coatings were co-deposited on C/C composites by low pressure chemical vapor co-deposition using HfCl 4 -MTS-CH 4 -H 2 -Ar system. • The influences of process parameters on coating phase composition and content were investigated under the guidance of thermodynamic calculations. • The coating with the HfC/SiC ratio of 1:1 exhibited excellent ablation resistance after ablation for 90 s. [ABSTRACT FROM AUTHOR]

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]