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

Zirconium oxide or zirconia (ZrO2)-based thermal barrier coatings (TBC) and aluminum oxide Al2O3 layers were fabricated by detonation gun (D-gun) spra ying. 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 inves tigated at 1,200 degrees C. Oxidation kinetics showed that the suitable app lication of Al2O3 layers suppressed the oxidation of the Ni-Cr-AL-Y bond co at, 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 t he oxidation resistance was enhanced However, a deteriorating spallation oc curred for the specimens with an Al2O3 intermediate layer thicker than 50 m u m The main failure modes were identified based on microstructural analyse s.