Abstract
Recently, metal temperature of combustor and blade in a land-based gas turbine is increasing with inlet gas temperature, in order to improve the thermal efficiency. Thus, thermal barrier coating (TBC) technology is applied to the surface of these hot parts for reducing the metal temperature. Advanced TBC materials and its processing technology such as functionally graded TBC and electron beam deposited TBC had been developed for these demands. But, application of these developed TBCs to the actual turbine blade was found to be difficult, because of a high cost of the processing machine and so on. In this study, advanced TBC with vertical crack in the top coating layer (vertical-crack induced TBC) was tried to fabricate by using a combination of conventional thermal spray technology and the special heat treatment. And, the bonding strength between the top coating and bond coating was examined by four-point bending test. As results obtained, the bonding strength of the vertical-crack induced TBC is very higher than one of the conventional TBC. It was found from interfactial crack path observed by optical microscope that the exsistence of the vertical crack is available for relaxation of the coating stress and reduction of interfacial stress.
