Thermal Cycling Behavior of Bi-layer Yb2Si2O7/SiC EBC Coated Cf/SiC Composites in Burner Rig Tests

To improve the oxidation resistance of carbon fiber reinforced SiC ceramic matrix composites (C f /SiC) at high-temperature and high-speed gas scour environment in burner rig tests, a novel bi-layer Yb 2 Si 2 O 7 /SiC EBC was prepared on the surface of C f /SiC composites by chemical vapor deposition (CVD) and sol-gel method united with air spraying. Results show that bi-layer Yb 2 Si 2 O 7 /SiC coating showed better oxidation resistance for C f /SiC specimens before 20 thermal cycles (300 min), which can efficiently prevent the oxidation of C f /SiC specimens in a gas scour environment at 1773 K for 300 min with a weight loss of 5.93 × 10 -3 g·cm -2 . After 20 thermal cycles (≥300 min), the weight loss of the coated specimen is rapidly increased due to the formation of penetrating cracks. After the corrosion of 36 thermal cycles (540 min), some obvious annular corrosion pit area were found on the surface of Yb 2 Si 2 O 7 outer coating, the center of the corrosion pit was easier to be the origin area of the cracks due to the greater impact force of the gas.