Microstructure and oxidation resistant property of C/C composites modified by SiC-MoSi₂-CrSi₂ coating

To prevent carbon/carbon (C/C) composites from oxidation, a dense and multiphase inlaid SiC-MoSi₂-CrSi₂ coating was prepared by pack cementation. The coatings were characterised by scanning electron microscopy, energy dispersive spectroscopy and X-ray diffraction. The effect of pack composition on the oxidation properties was studied on low density C/C composite, and then optimum composition was finalised. The optimum composition was the one containing 5 wt-%Cr and oxidation behaviour of high and low density C/C composites coatings with this composition was studied. Oxidation test shows that, when the Cr content was 5 wt-%, the SiC-MoSi₂-CrSi₂ coating possessed excellent oxidation resistant ability. After application of the SiC-MoSi₂-CrSi₂ multiphase coating, the low density C/C composite showed a mass loss of only 1·36% after oxidation at 1873 K for 43 h, while the mass loss of the coated high density sample was up to 7·45% after oxidation at 1873 K for 8 h.