Search

Based on the investigation of ablation behavior and thermal stress of the monolayered ZrC-SiC coatings with different SiC amounts, an alternate coating consisting of 4 sublayers with 10 and 70 vol.% SiC was prepared on SiC-coated carbon/carbon (C/C) composites through plasma spraying technique. Ablation tests were carried out under oxyacetylene torch with a heat flux of 2.38 MW/m2. The alternate coating could offer 90 s ablation shield for C/C composites, providing superior ablation properties than all monolayered coatings. The improved ablation resistance is mostly induced by the fact that the outmost scale with abundant ZrO 2 particles was able to better endure the mechanical denudation from the torch. Moreover, due to the indirect contact with torch, the innermost sublayers were placed into relatively mild environment, thereby most of Si-based oxides could be retained and further hinder oxygen transport inward during ablation. [ABSTRACT FROM AUTHOR]

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]