Oxidation mechanism of HfC-TaC-B4C-SiC/ZrSiO4-glass coating with largely enhanced oxidation inhibition for C/C composites

Increasing the high-temperature anti-oxidation time of Carbon/carbon(C/C) composites faces significant challenges for conventional coatings. Herein, a unique bi-layer coating of HfC-TaC-B4C-SiC(HTBS)/ZrSiO4-glass(ZA) was proposed and prepared through slurry sintering method, and their oxidation behavior and mechanism were investigated. The results show that after oxidation at 1673 K in air for 750.5 h, the mass loss of the coated C/C was only 3.48% with about 720 h of weight gain oxidation, indicating that the anti-oxidation time has increased by two or three times compared to traditional coatings. The improved oxygen resistance performance was mainly attributed to the hinder layer of Si/Hf-Ta-Si-O during oxidation, which grew with the simultaneous carbothermal reduction reaction of SiO near matrix and oxidation reaction of HTBS. This is beneficial to lowering the thermal mismatch of coating system, reducing the connected thermal stress cracks as oxygen permeation channels. Our findings provide a new insight on improving the long-time thermal protection performance of C/C composites.