Si–Mo–Cr coating for C/SiC coated carbon/carbon composites against oxidation

Si–Mo–Cr oxidation protective coating has been prepared on the surface of C/SiC coated carbon/carbon (C/C) composites by pack cementation technique. The phase composition and microstructure of the as prepared coatings were characterised by X-ray diffraction, scanning electron microscopy (SEM) and energy dispersion spectrum (EDS) analyses. The oxidation behaviour of the coated C/C specimens was also investigated at 1500°C in air. The results show that the as prepared coating is mainly composed of SiC, MoSi₂, CrSi₂ and Si. The coating characterised by excellent oxidation resistance and thermal shock resistance can effectively protect C/C composites from oxidation for 186 h at 1500°C in air and endure the thermal cycle between 1500°C and room temperature for nine times, while the corresponding weight loss is only 0·33%. The excellent oxidation protection ability of the coating is primarily attributed to the formation of a compound glass layer, including SiO₂ and Cr₂O₃.