Mo–Si–Al–C multiphase oxidation protective coating for carbon/carbon composites

A multiphase coating based on Mo–Si–Al–C was formed on the surface of carbon/carbon (C/C) composites by a two-step pack cementation technique in argon atmosphere. Microstructure of the multiphase coating was characterized by X-ray diffraction, scanning electron microscope and energy dispersive spectroscope. X-ray diffraction analysis showed that the multiphase coating was composed of SiC, Mo (Si, Al)2, MoSi2 and Al4Mo3Si2. The multiphase coating coated C/C composites exhibited a weight loss of only 0.409% after oxidation in air at 1773 K for 510 h and could endure thermal cycling between 1773 K and room temperature for 25 times. The weight loss of the coated C/C composites was primarily due to the reaction between C/C matrix and oxygen.