Effect of aluminum oxide diffusion barrier layer on the oxidation behavior of detonation gun-sprayed thermal barrier coating at 1,200 degrees C

Abstract

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 mu m, 150 mu m, or 250 mu m 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 degrees 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 mu m The main failure modes were identified based on microstructural analyses.