Si–Mo–SiO2 oxidation protective coatings prepared by slurry painting for C/C–SiC composites

Three types of Si–Mo–SiO2 coatings: two single-layered ones by different slurry paintings and a final sintering, and three-layered one by triple paintings followed by sintering each time, have been fabricated on the surface of C/C–SiC composites. The coatings were composed of SiC, MoSi2, Si and SiO2. The two single coatings had a microstructure with many pinholes and deep microcracks and had no obvious protection for C/C–SiC composites in air in the range of 1273–1673 K. While the triple Si–Mo–SiO2 coating had a microstructure with much less defects and could provide more than 100 h protection at 1473–1673 K in air and kept intact in the course of 50 cycles of thermal shock test between 1673 K and 373 K. The excellent anti-oxidation ability and thermal shock resistance of the triple Si–Mo–SiO2 coating can be attributed to its relatively integral microstructure and the self-sealing of microcracks during oxidation.