Preparation, characterization and application of high-temperature Al2O3 insulating film

NiCoCrAlY coatings were deposited on nickel-based superalloy by magnetron sputtering. The thermally grown oxide (TGO) layer of aluminum oxide (α - Al2O3) was formed on the surface of the NiCoCrAlY coating by heat treatment at 950 °C in an Ar atmosphere followed by subsequent thermal oxidation in air at 1100 °C. Another 2 μm thick Al2O3 film was deposited on the TGO layer by dual ion beam sputtering deposition (DIBSD) to further improve insulation resistance at high temperature. The effect of thermal oxide time on the morphology and microstructure of the TGO layers was investigated by SEM, XRD and XPS techniques. It's indicated that excessive thermal oxidation would produce NiO in the TGO layer, which was harmful to the high-temperature insulating property of TGO layer. The stoichiometric ratio Al/O for the sputtered Al2O3 film was close to 2:3. The electrical resistance of the insulating film was measured at 200 °C-800 °C. The result showed that the insulating Al2O3 film including TGO layer and sputtered Al2O3 layer had a good insulating property at high temperature. Finally, a thermal resistance temperature sensor was prepared on the surface of the Al2O3 film insulating film to verify its electrical insulating property.