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 degrees C, 1700 degrees C and 1800 degrees 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 sat 1800 degrees C with the ablation mass rate of 3.4 x 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 degrees C.