Microstructure and oxidation protective ability of MoSi₂-SiC-Si coating toughened with SiC whiskers for carbon/carbon composites

To prevent carbon/carbon (C/C) composites from oxidation at high temperatures, a SiC whisker (SiCw) toughened MoSi₂-SiC-Si coating was prepared on the C/C surface by a two step technique of slurry and pack cementation. Scanning electron microscopy (SEM) analysis shows that, with the content of SiCw increasing, the dimensions and frequency of cracks in the coating decrease obviously. At the same time, the thickness and compact degree of the coating reduce with the increase of the SiCw content. Oxidation tests show that, as the content of SiCw is 10 wt-%, the coating possesses a better anti-oxidation property, and the weight loss of the coated sample is only 0-8% after oxidation at 1773 K for 200 h. The weight loss of the as-coated C/C composites is primarily due to the reaction of the C/C matrix and oxygen diffusing through the penetration cracks and holes in the coating.