Failure mechanisms of (Gd0.9Yb0.1)2Zr2O7/Yb2SiO5/Si thermal/environmental barrier coatings during thermal exposure at 1300 °C/1400 °C

A novel tri-layer (Gd0.9Yb0.1)(2)Zr2O7/Yb2SiO5/Si (GYbZ/YbMS/Si) thermal and environmental barrier coatings (TEBCs) was first proposed for protecting SiC-based ceramic matrix composites (CMCs). Wherein, the GYbZ layer by plasma spray physical vapor deposition (PS-PVD) was quasi-columnar structured while the YbMS and the Si layers by atmospheric plasma spray (APS) were lamellar structured. The oxidation behavior and the failure mechanisms of the GYbZ/YbMS/Si TEBCs at 1300 degrees C/1400 degrees C are revealed. At 1300 degrees C, the mud-cracks pene-trated through the GYbZ/YbMS layer and transversely deflected in the Si layer are responsible for the oxidation at YbMS/Si interface. When the temperature increased to 1400 degrees C, the propagation of mud-cracks, cavities, and TGO channel cracks occurred due to the sintering of GYbZ and the fast growth of cristobalite. Eventually, these defects caused delaminating failure at interface. Moreover, another de-bonding failure of the coating was observed resulting from the significant thickening of oxide scale at the edge region.