Thermal cycling behavior of (Gd0.9Yb0.1)2Zr2O7/8YSZ gradient thermal barrier coatings deposited on Hf-doped NiAl bond coat by EB-PVD

Gradient thermal barrier coatings of (Gd0.9Yb0.1)2Zr2O7–yttria stabilized zirconia (8YSZ) were deposited on Hf-doped NiAl bond coat by EB-PVD. The effect of the structure at the interface between (Gd0.9Yb0.1)2Zr2O7 (GYbZ) and 8YSZ layers on the thermal cycling behavior has also been investigated by comparing the double-ceramic-layer (DCL) coatings with gradient thermal barrier coatings (GTBCs). The results of thermal cycling tests show that the GTBCs have a more extended lifetime than the DCL coatings. The failure of GYbZ-8YSZ DCL coating with clear interface between different ceramic layers occurred in the way of delamination cracking, which is mainly a result of crack initiation and propagation generated by stress concentration within the ceramic layers. On the other hand, the failure mechanism of GTBC is due to the thermal mismatch between the Hf-doped NiAl bond coat and TGO layer.