A SiC–Si–ZrB2 multiphase oxidation protective ceramic coating for SiC-coated carbon/carbon composites

In order to improve the oxidation protective ability of SiC-coated carbon/carbon (C/C) composites, a SiC–Si–ZrB2 multiphase ceramic coating was prepared on the surface of SiC-coated C/C composite by the process of pack cementation. The microstructures of the coating were characterized using X-ray diffraction and scanning electron microscopy. The coating was found to be composed of SiC, Si and ZrB2. The oxidation resistance of the coated specimens was investigated at 1773 K. The results show that the SiC–Si–ZrB2 can protect C/C against oxidation at 1773 K for more than 386 h. The excellent oxidation protective performance is attributed to the integrity and stability of SiO2 glass improved by the formation of ZrSiO4 phase during oxidation. The coated specimens were given thermal shocks between 1773 K and room temperature for 20 times. After thermal shocks, the residual flexural strength of the coated C/C composites was decreased by 16.3%.