Thermal cycling behavior of (Gd_(0.9)Yb_(0.1))_2Zr_2O_7/8YSZ gradient thermal barrier coatings deposited on Hf-doped NiAl bond coat by EB-PVD

摘要

Gradient thermal barrier coatings of (Gd_(0.9)Yb_(0.1))_2Zr_2O_7–yttria stabilized zirconia (8YSZ) were deposited on Hf-doped NiAl bond coat by EB-PVD. The effect of the structure at the interface between (Gd_(0.9)Yb_(0.1))_2Zr_2O_7 (GYbZ) and 8YSZ layers on the thermal cycling behavior has also been investigated by comparing the double-ceramic-layer (DCL) coatingswith 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 ismainly a result of crack initiation and propagation generated by stress concentrationwithin the ceramic layers. On the other hand, the failure mechanismof GTBC is due to the thermal mismatch between the Hf-doped NiAl bond coat and TGO layer.