C/SiC/Si-Mo-B/glass multilayer oxidation protective coating for carbon/carbon composites

To prevent carbon/carbon (C/C) composites from oxidation, a self-sealing multilayer oxidation resistant coating including a C/SiC gradient inner layer, a Si-Mo-B middle layer and a glass exterior layer was prepared by pack cementation and slurry method. Scanning electron microscopy and X-ray diffraction were used to analyze the microstructure and phase composition of the as-prepared coating. The isothermal and thermal shock oxidation resistance of the coating was also investigated. The results showed that the multilayer coating exhibited excellent oxidation resistance from room temperature to 1873 K. It could effectively protect C/C composites for 100 h at 1173 K and 150 h at 1873 K, and endure 40 thermal cycles between 1873 K and room temperature. The excellent oxidation and thermal shock resistance could be attributed to the gradient structure and the self-sealing property of the multilayer coating.