Role of Y4Al2O9 in high temperature oxidation resistance of NiCoCrAlY-ZrO2•Y2O3 coatings

NiCoCrAlY-(ZrO2Y2O3)-Y-. coatings were deposited on the substrates by using a technology of combining electron, atom and ion beams (three beams). Isothermal oxidation for these samples was performed at 1100 degrees C for 100300 h. The results show that a thermally grown oxide (TGO) layer was formed between NiCoCrAlY layer and ZrO2.Y2O3 layers according to the cross-section morphologies of the samples after high temperature isothermal oxidation. The TGO contains alpha-Al2O3 and Y4Al2O9 etc. oxides. The intensity ratio of alpha-Al2O3/Y4Al2O9 was monotonously decreased with increasing oxidation time based on XRD (X-ray diffraction) analysis. The Y4Al2O9 phase plays the most important role in high temperature oxidation resistance at 1100 degrees C. The related mechanism was also discussed.