Oxidation pre-treatment to improve the mechanical property and oxidation resistance of Si–Mo–Cr coated C/C composites

• Pre-oxidation as a surface corrosion method was used to treat C/C composites.
• A porous surface layer was obtained on C/C composites by oxidation pre-treatment.
• A transition layer was obtained between oxidized C/C substrate and coating.
• Flexural strength of the coated samples was improved after oxidation pre-treatment.
• Pre-oxidation time has a big effect on oxidation resistance of the coated samples.

A transition layer with an interlocking structure was obtained at the interface between C/C composites and Si–Mo–Cr coating by oxidation pre-treatment and pack cementation process. The effects of pre-oxidation time on the microstructures, mechanical property and oxidation behavior of the coated C/C samples were investigated. After oxidation pre-treatment at 1173 K in air for 6 min, the flexural strength of the coated samples increases by 71.7% and the mass loss rate decreases by 77.4%. The improvements of the mechanical property and oxidation resistance are primarily attributed to the formation of the moderate transition layer between C/C and Si–Mo–Cr coating.