Effect of MoSi2-Si3N4/SiC Multi-Layer Coating on the Oxidation Resistance of Carbon/Carbon Composites above 1770 K

摘要

To improve the oxidation resistance of carbon/carbon composites at high temperatures (>1770 K), they were coated with MoSi_(2)-Si_(3)N_(4)/SiC. The slurry and pack cementation methods were adopted to deposit the inner SiC layer and outer MoSi_(2)-Si_(3)N_(4) layer. The phase composition, microstructure, and elemental distributions in the coating were analyzed using SEM, XRD, EDS, and Raman spectroscopy. Oxidation tests show that the deposited multi-layer coating can protect the carbon/carbon matrix from oxidation at high temperatures (>1770 K) for 150h and that the coating can withstand 40 thermal cycles between 1773 and 300 K. It is observed that Si_(3)N_(4) assists in the formation of a dense SiO_(2) layer at a high temperature, which plays a vital role in increasing the thermal cyclic and oxidation resistance of the coating itself. The weight loss of coated carbon/carbon composite is attributed to the formation of micro-cracks and diffusion of SiO_(2), MoO_(3), and N_(2) out of the material at high temperatures.