An oxidation protective Si-Mo-Cr coating for C/SiC coated carbon/carbon composites

A multilayer coating composed of C/SiC bonding layer and Si-Mo-Cr alloy exterior layer prepared by pack cementation and low-cost slurry method, which is expected to protect C/C composites at 1773 K in air for long-term application was studied. The microstructure and oxidation protective ability of the coating were investigated. Two kinds of specimens for the oxidation test and mechanical property test as substrates were cut from bulk two dimensional C/C composites with a density of 1.70 g/cm³. The specimens were cleaned ultrasonically with distilled water after being hand-polished with 400 and 800 grit SiC papers. The as-coated samples were heated at 1623-1873 K for 20-60 min in Ar atmosphere to perform metallurgical reaction after applying the slurry to the C/SiC coated C/C's surface and coating sintering. The cross-section SEM image of the coated specimens after oxidation at 1773 K for 342 h indicated a slight oxidation of C/C matrix under the penetration crack.