Ablation mechanism and properties of SiO₂ modified ZrB₂-SiC coatings fabricated on C/C composites via plasma spraying technology

To improve the ablation resistance performance of carbon/carbon (C/C) composites at high temperature, SiO₂ modified ZrB₂-SiC (ZSS) coating with 4 different SiO₂ contents was prepared on SiC-Al₂O₃-coated C/C composites by plasma spraying technology. And the ablation behaviors of ZSS protective coatings was investigated at 1400 °C, 1700 °C and 1800 °C using oxyacetylene torch. The results show that the adding 30 vol% SiO₂ could visibly improve the densification of ZrB₂-SiC coatings. However, the ZSS coating with 10 vol% SiO₂ can effectively protect C/C composites for 600 s at 1800 °C with the ablation mass rate of 3.4 × 10^{− 4} g/s. The ZSS coating with 30 vol% SiO₂ cracked at the center of ablation region after the same ablation condition because of breakthrough of gaseous by-products inside coating. It is revealed that SiO₂ could successfully prevent the active oxidation of SiC by breaking the interconnected SiC network and reducing its chances of contact with oxygen, and a discontinuous SiC consumption layer formed after ablation at 1700 °C.