Fabrication of Y2Si2O7 coating and its oxidation protection for C/SiC composites
(National Key Laboratory of Advanced Ceramic Fibers and Composites, National University of Defense Technology, Changsha 410073, China)
Abstract: Yttrium silicate (Y2Si2O7) coating was fabricated on C/SiC composites through dip-coating with silicone resin + Y2O3 powder slurry as raw materials. The synthesis, microstructure and oxidation resistance and the anti-oxidation mechanism of Y2Si2O7 coating were investigated. Y2Si2O7 can be synthesized by the pyrolysis of Y2O3 powder filled silicone resin at mass ratio of 54.2:45.8 and 800 °C in air and then heat treated at 1400 °C under Ar. The as-fabricated coating shows high density and favorable bonding to C/SiC composites. After oxidation in air at 1400, 1500 and 1600 °C for 30 min, the coating-containing composites possess 130%-140% of original flexural strength. The desirable thermal stability and the further densification of coating during oxidation are responsible for the excellent oxidation resistance. In addition, the formation of eutectic Y-Si-Al-O glassy phase between Y2Si2O7 and Al2O3 sample bracket at 1500 °C is discovered.
Key words: C/SiC composites; yttrium silicate; coating; oxidation resistance