Microstructure and oxidation protection of a MoSi2/SiO2-B2O3-Al2O3 coating for SiC-coated carbon/carbon composites

A MoSi2/SiO2-B2O3-Al2O3 double layer coating was prepared on the surface of SiC-coated carbon/carbon (C/C) composites by pulse arc discharge deposition (PADD). The phase compositions and morphology were analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The oxidation resistance and thermal cycling property of the multi-layer coating were investigated. Results indicate that the multi-layer coating exhibit excellent anti-oxidation property. The MoSi2/SiO2-B2O3-Al2O3 coating can effectively protect C/C composites from oxidation in air at 1073 K for 200 h with negligible weight loss and 1773 K for 200 h with a weight loss of 0.7%. Meanwhile, the coating can endure the thermal cycling for 50 cycles between 1773 K and room temperature (298 K). The formation of B2O3 glass phase at low temperature and borosilicate glass at high temperature are the main reasons for the good oxidation resistance of the coating.