High Temperature Performance of TiAlON Thin Films

In this paper, the thermal oxidation behavior, adhesion and tribological properties of TiAlON films coated on hastelloyX substrate, typically used for fuel nozzle in gas turbine engine application, have been studied. The uncoated and coated samples were heated to different temperatures, i.e. 950, 1050 and 1150 °C in the controlled atmosphere. The surface appearance, microstructure, chemical composition and adhesion of films were investigated. The thermal oxidations were observed in all testing conditions showing thicker oxide film at higher temperature. However, spalling of oxide scales was found in hastelloyX and TiAlON coated at 1150°C suggesting the maximum working temperature of < 1150 °C. The critical loads corresponding to the full delamination of the thermal oxidation coated specimens were found to be higher than the non-thermal oxidation specimens. The effect of thermal oxidation on damage patterns during scratch tests, i.e. less chipping and cracking for thermal oxidation specimen, were also observed. The tribological properties were also investigated under different load under room temperature and 600 and 1000°C. The results suggested significant improvement in wear resistance of coated sample especially at low load at all temperatures.