SiC/(SiC+glass)/glass coating for carbon-bonded carbon fibre composites

An oxidation resistant coating for highly porous carbon-bonded carbon fibre composites (CBCFs) was prepared by slurry method. The compositionally and structurally gradient coating consists of a carbon fibre reinforced SiC inner layer, a SiC with CaO-MgO-Al₂O₃-SiO₂ (CMAS) glass inter layer, and a dense CMAS glass outer layer. The effectiveness of the S-SG-G coating in protecting the CBCFs from degradation at 1000 °C in air has been evaluated. The results indicated that the coating could protect CBCFs from oxidation for 100 min with the weight loss of 20.7%. In contrast, the uncoated CBCFs were completely combusted after 50 min. Good oxidation resistance of the coating is mainly attributed to high temperature stability of SiC, CMAS glass sealant, and good adhesion within the coating layers and with the substrate.