Effect of Aluminum Oxide Diffusion Barrier Layer on the Oxidation Behavior of Detonation Gun-Sprayed Thermal Barrier Coating at 1,200°C

Zirconium oxide or zirconia (ZrO₂)-based thermal barrier coatings (TBC) and aluminum oxide (Al₂O₃) layers were fabricated by detonation gun (D-gun) spraying. Al₂O₃ layers with thicknesses of 50 μm, 150 μm, or 250 μm were applied to a duplex TBC system as an intermediate layer or a surface layer, and their effects on the oxidation behavior of the TBC coatings were investigated at 1,200°C. Oxidation kinetics showed that the suitable application of Al₂O₃ layers suppressed the oxidation of the Ni-Cr-Al-Y bond coat, and the oxidized rates were partially dependent on the thickness of the Al₂O₃ layers. In the case of an Al₂O₃ layer applied onto the surface, the durability and integrity of the TBC coatings were improved remarkably and the oxidation resistance was enhanced. However, a deteriorating spallation occurred for the specimens with an Al₂O₃ intermediate layer thicker than 50 μm. The main failure modes were identified based on microstructural analyses.