A SiC/Mo(Six, Al1−x)2 oxidation-resistant coating for carbon/carbon composites

SiC/Mo(Six, Al1−x)2 multilayer coatings were prepared on carbon/carbon (C/C) composites using a multi-phase reaction technique to improve their high temperature oxidation resistance. The microstructure and phase compositions of the multilayer coatings were investigated by SEM, XRD and EDS. The coating exhibits a binary-layer microstructure, i.e. an outer Mo(Six, Al1−x)2 layer and an inner SiC layer with a small amount of Mo4.8Si3C0.6. The oxidation behavior of the coated C/C composites was evaluated in a supersonic flow of about 1 500 m·s−1 at 1 800 K in a wind tunnel. No destruction of the coated C/C composites was found after 4 s oxidation after 24 exposures and thermal cycling between room temperature and 2 550 K for 24 times in air. The excellent oxidation resistance and thermal shock resistance are attributed to a high cohesion between the layers and the C/C composite, and the formation of a continuous and stable glassy film consisting of SiO2 and Al2O3 on the coated layers during oxidation.