Influence of Post-Sprayed Heat Treatment Conditions on High-Temperature Oxidation Property for Plasma Sprayed Thermal Barrier Coating Systems

Abstract

In order to improve the high temperature durability of the plasma sprayed thermal barrier coating (TBC) systems, high temperature oxidation test was conducted under the isothermal condition at 1100°C for 100 h for several kinds of TBC systems in connection with their coating characteristics such as the coating microstructures and interfacial natures depending on the coating process conditions. Specimens with different coating characteristics were prepared by controlling the coating parameters such as the top coat spraying conditions and the reheat treatment (RHT) conditions after spraying. Especially, the RHT was applied to the TBC specimen with different temperature, heating rate, holding time at maximum temperature and so on in inert argon (Ar) gas atmosphere.High temperature oxidation behavior was found to differ depending strongly on the RHT conditions. The RHT at lower temperature could not inhibit the heterogeneous development of thermally grown oxides (TGO) layer and the wart like oxides at the top coat/bond coat interface. On the contrary, the RHT with either the slow rate heating or the long time holding at the maximum temperature was found to be effective for an improvement of the oxidation resistance, since such a RHT process is able to develop dominantly the continuous a Al 2 O 3 layer at the interface so as to reduce sufficiently the growth rate of TGO to maintain the suitable environmental barrier function during high temperature oxidation.The influence of the RHT conditions on the high temperature oxidation property was discussed in connection with both the morphology of bond coat powders and the surface morphology of bond coat sprayed.