Influence of preparation technology on the microstructure and anti-oxidation property of SiC–Al2O3–mullite multi-coatings for carbon/carbon composites

Oxidation protective SiC–Al2O3–mullite multi-coatings for carbon/carbon (C/C) composites were prepared with a two-step pack cementation process. The influence of preparation temperature and SiO2/Al2O3 ratio of the pack powder on the phase, microstructure and oxidation resistance of the multi-coatings were investigated. It showed that the multi-coatings that contained mullite could be produced at 1700–1800 8C. A denser coating surface was acquired with the decrease of SiO2/Al2O3 ratio in the pack chemistries while a little damnification to the interface of the coating and C/C substrate. The as-prepared coating could effectively protect C/C composites from oxidation at 1600 8C for 81 h.