Thermal cycling behavior of La2Zr2O7/Yb2Si2O7/SiC coated PIP Cf/SiC composites under burner rig tests

Ytterbium disilicate (Yb2Si2O7) and lanthanum zirconate (La2Zr2O7) powders were synthesized by solvent gel (sol-gel) method. To improve the oxidation resistance of C-f/SiC composites at high-temperature and high-speed gas scour environment, a tri-layer La2Zr2O7/Yb2Si2O7/SiC EBCs was prepared on the surface of C-f/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 C-f/SiC samples than bi-layer Yb2Si2O7/SiC coating, which can efficiently prevent the oxidation of C-f/SiC samples in gas scour environment at 1773 K for 24 thermal cycles (360 min) with a weight loss of 7.06 x 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.

Automated summary

Ytterbium disilicate and lanthanum zirconate powders were synthesized by solvent gel method. A tri-layer La2Zr2O7/Yb2Si2O7/SiC EBCs was prepared on the surface of C-f/SiC composites, showing better oxidation resistance compared to a bi-layer Yb2Si2O7/SiC coating. The crack deflection phenomenon in the tri-layer coating can largely avoid the formation of penetrating cracks and improve the oxidation resistance of the coating, resulting in only a small amount of coating falling off after corrosion in high-speed and high-temperature gas.