Thermal cycling behavior of tri-layer La2Zr2O7/Yb2Si2O7/SiC EBCs coated Cf/SiC composites in burner rig tests

Abstract Ytterbium disilicate (Yb2Si2O7) and lanthanum zirconate (La2Zr2O7) powders were synthesized by solvent gel (sol-gel) method. To improve the oxidation resistance of Cf/SiC composites at high-temperature and high-speed gas scour environment, a novel tri-layer La2Zr2O7/Yb2Si2O7/SiC EBCs was prepared on the surface of Cf/SiC composites by chemical vapor deposition (CVD) and sol-gel method combined with air spraying. Results show that tri-layer La2Zr2O7/Yb2Si2O7/SiC coating showed better oxidation resistance for Cf/SiC samples than bi-layer Yb2Si2O7/SiC coating, which can efficiently prevent the oxidation of Cf/SiC samples in gas scour environment at 1773 K for 24 thermal cycles (360 min) with a weight loss of 7.06 × 10-3 g·cm-2. Microstructure characterization revealed that crack deflection phenomenon in tri-layer coating can largely avoid the formation of penetrating cracks and even improve the oxidation resistance of the coating. After the corrosion of tri-layer coating in high-speed and high-temperature gas, a small amount of coating fell off and eventually formed coating corrosion pit area and coating fracture area.