Xiyuan Yao

Anti-oxidation properties of ZrB2 modified silicon-based multilayer coating for carbon/carbon composites at high temperatures

Abstract To improve the anti-oxidation ability of silicon-based coating for carbon/carbon (C/C) composites at high temperatures, a ZrB2 modified silicon-based multilayer oxidation protective coating was prepared by pack cementation. The phase composition, microstructure and oxidation resistance at 1773, 1873 and 1953 K in air were investigated. The prepared coating exhibits dense structure and good oxidation protective ability. Due to the formation of stable ZrSiO4–SiO2 compound, the coating can effectively protect C/C composites from oxidation at 1773 K for more than 550 h. The anti-oxidation performance decreases with the increase of oxidation temperature. The mass loss of coated sample is 2.44% after oxidation at 1953 K for 50 h, which is attributed to the decomposition of ZrSiO4 and the volatilization of SiO2 protection layer.

OXIDATION RESISTANT (Mo,W)Si2 COATING FOR SiC-COATED CARBON/CARBON COMPOSITES BY IN SITU FORMATION METHOD

In order to protect carbon/carbon (C/C) composites against oxidation, a (Mo,W)Si2 coating was prepared on the surface of SiC-coated C/C composites by a simple in situ information method using Si, Mo and W as starting materials. The microstructures and oxidation protective ability of the as-received coating were investigated. The results show that the (Mo,W)Si2 outer layer coating containing free Si has a good bonding with SiC inner layer. The as-prepared SiC/(Mo,W)Si2 coating can protect C/C composites from oxidation in air at 1773 K for 252 h with a weight gain of 1.56 wt.%. The excellent oxidation resistant property of the double-layer coating is attributed to its dense microstructure and the formation of the stable glassy SiO2 film on the (Mo,W)Si2 coating surface during its exposure to air at high temperatures.