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 Yb2Si2O7/SiC EBC was prepared on the surface of C-f/SiC composites by chemical vapor deposition and sol-gel combined with air spraying method. Results show that bi-layer Yb2Si2O7/SiC coating showed better oxidation resistance for C-f/SiC samples in the first 20 thermal cycles (300 min), which can efficiently prevent the oxidation of C-f/SiC samples in a gas scour environment at 1773 K for 300 min with a weight loss of 5.93 x 10(-3) g center dot cm(-2). After 20 thermal cycles (>= 300 min), the weight loss of the coated sample was 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 Yb2Si2O7 outer coating, and 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.

Automated summary

The study shows that the bi-layer Yb2Si2O7/SiC coating can significantly improve the oxidation resistance of C-f/SiC samples in high-temperature gas flow environment, delaying the oxidation process. However, after more than 20 thermal cycles, the performance of the coating starts to decrease due to the formation of penetrating cracks.