Oxidation Protective C/SiC/Si-SiC Multilayer Coating for Carbon/Carbon Composites Applying at 1873 K

A C/SiC/Si-SiC multilayer coating for protecting carbon/carbon (C/C) composites against oxidation was prepared by slurry and pack cementation. X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS) analysis showed that the inner coating obtained from the slurry and pack cementation was a C/SiC gradient layer acting as bonding layer, and the exterior coating formed in the second pack cementation was a Si-SiC double phase coating. Oxidation tests at 1873 K in air showed that the coating exhibited excellent oxidation protective ability and thermal shock resistance. The coating could effectively protect C/C composites from oxidation at 1873 K in air for 170 h and undergo the thermal cycling between 1873 K and room temperature for 8 cycles. The weight loss of the coated C/C composites is due to the formation of cracks and holes in the coating and the volatilization of SiO₂ glass at high temperature.