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HfC-TaC/HfC-SiC alternate coatings with different sublayer thicknesses were fabricated on SiC-coated carbon/carbon composites by supersonic atmosphere plasma spraying. Their ablation resistance was studied under oxyacetylene torch and compared with monolayered HfC-TaC coating. The alternate coating with 6 spray cycles of HfC-TaC and 3 spray cycles of HfC-SiC sublayers exhibited the best ablation performance as confirmed by the integral coating morphology and the lowest ablation rates. A dense oxide layer acting as an oxygen insulator and the release of thermal stress induced by the formation of dendritic cracks are thought to be responsible for its great ablation resistance. For the alternate coating with 4 spray cycles of HfC-TaC and 2 spray cycles of HfC-SiC sublayers, exfoliation occurred at the interface of two adjacent sublayers, leading to violent evaporation of exposed HfC-SiC sublayer. [ABSTRACT FROM AUTHOR]

Several multilayer architectures, based on ZrC-SiC system, were fabricated on SiC-coated carbon/carbon composites by plasma spraying and tested using an oxyacetylene torch. A remarkable variance in scale evolution was found in these multilayer coatings, referring to close correlation between multilayer architecture and ablation behavior. The multilayer coating made of consecutive sublayers of ZrC-10, 30, 10 and 70 vol% SiC survived three repeated ablation cycles with mass ablation rate of −0.467 mg/s and linear ablation rate of − 0.411 µm/s. Detailed phase analysis and morphology investigation attributed its preferable ablation performance to the formation of multifunctional scale and modest thermal stress. • Various ZrC-SiC multilayer coatings were prepared on SiC-coated C/C composites by plasma spraying. • The relationship between coating architecture and ablation behavior was studied using oxyacetylene torch. • Ablation mechanism was analyzed systematically as well as the roles of different sublayers. • Theoretical analysis was adopted to compare the stress level within these multilayer coatings. [ABSTRACT FROM AUTHOR]