Improved oxidation resistance of CVD-SiC coating at 1300 ℃ by Ti addition

Abstract

To broaden the protective temperature range of SiC coatings, Ti was incorporated into SiC coatings by molten salts-mediated pack cementation method. During the coating preparation, molten salts accelerated the reactions between Ti and SiC, especially the generation of intermediate products, TiCl_x and SiCl_x, for gas-solid reactions. The growth rate of the reaction layer conforms to the parabolic diffusion law. After multiple heat treatments and molten salt exposition, the mechanical properties of Ti-Si-C-C/C composites are not damaged, which is still at the same level as SiC-C/C composites and higher than that of C/C composites. Furthermore, the mass losses of Ti-Si-C-C/C composites, after oxidation at 1300 ℃ for 508 h and 30 thermal cycles between 1300 ℃ to room temperature, are only 0.77 % and 0.79 %, respectively. Such improved oxidation resistances can be attributed to the timely healing of surface cracks by the Ti-Si-O glass.