Preparation and water-oxygen corrosion behavior of (Yb_1-xSc_x)₂Si₂O₇ coatings on SiC-coated C/C composites

As an environmental barrier coating (EBC) for carbon/carbon (C/C) composites, rare earth silicates can effectively resist the erosion of water vapor and oxygen in high-temperature environments. The (Yb_1-xSc_x)₂Si₂O₇ (x = 0.25, 0.5 and 0.75) solid solution materials were prepared by solid sintering method. The influence laws of Sc doping ratio on microstructure, mechanical properties and resistance to water-oxygen corrosion were investigated. All prepared solid solutions are dominated by β-(Yb_1-xSc_x)₂Si₂O₇ matrix. Trace monosilicate impurity can only be observed in high-Sc (Yb_0.25Sc_0.75)₂Si₂O₇ sample. The (Yb_0.25Sc_0.75)₂Si₂O₇ presented the highest hardness and elastic modulus. Among all samples, the (Yb_0.75Sc_0.25)₂Si₂O₇ solid solution exhibited the most excellent water-oxygen corrosion resistance, making it an ideal material for environmental barrier coatings. The (Yb_0.75Sc_0.25)₂Si₂O₇ coating was prepared on SiC-coated C/C composites by slurry brushing method. However, the coating failed with a 3.853% weight loss after 120 h of water-oxygen corrosion at 1500 °C in 90% H₂O-10% O₂. The failure of (Yb_0.75Sc_0.25)₂Si₂O₇ coating is due to the water-oxygen environment causing the coating to become and porous.