Application of mechanical grinding and refractory ultrafine powders for thermal sprayed thermal barrier coatings

The elucidation of the degradation mechanisms of thermal barrier coatings (TBC) for high temperature parts used in jet planes or gas turbines for power generation, and the development of lifetime improvement technologies for TBC have been performed. We succeeded in ascertaining that one reason for the delamination of TBC near its interface is due to the decrease in bond strength and the formation of stress concentration sites caused by the formation of pores in the thermally grown oxide (TGO) at the interface. In order to increase the bond strength by improving TGO formation, Ce and Si were added to the bond coating material, and a laser remelting technique for the bond coating was developed. As a result, the improved TBC had superior bond strength compared with a conventional TBC. It is likely that the reason for the superior bond strength is due to the notable difference in oxidation behavior. As a next step, a new coating is suggested to further improve coating properties, such as oxidation, hot corrosion or delamination resistance. This coating applies a combination of two factors, i.e. the use of active ultrafine particles and generation of high mechanochemical energy by high energy ball milling.