Effect of Cr content on the microstructure and thermal properties of ZrSi₂–CrSi₂–SiC multiphase coating for the SiC coated C/C composites

A series of ZrSi₂-CrSi₂-SiC multiphase coatings with different Cr content in the pack powders were prepared on the surface of the SiC coated carbon/carbon (C/C) composites by pack cementation in argon. The phase composition, microstructure and spot elements of the multiphase coatings were analyzed by X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy. The effect of Cr content on the microstructure, oxidation and thermal shock resistance of the multiphase coating was investigated. The results indicated that with the increase of Cr content, the content of CrSi₂ phase and the number and sizes of cracks in the coating increase. The ZrSi₂-CrSi₂-SiC multiphase coating prepared with Cr content of 10 wt% demonstrated the best oxidation and thermal shock resistance. The weight loss of the specimen was 0.84% after oxidation at 1500 °C for 115 h, and the weight gain was 0.66% after 50 thermal cycles between 1500 °C and room temperature.