This paper describes the development and verification of a thermal barrier coating (TBC) for use in class 1600 °C turbines. It explains how ceramic materials with different crystal structures were selected for the topcoat and how they were screened based on phase transformations. It discusses the method used determine a bond coat composition with high oxidation resistance and good ductility. It describes the TBC deposition process, the tuning of spray parameters, and the optimization of coating properties. It discusses the tests used to evaluate the topcoat, bond coat, and thermally grown oxide (TGO) layer and presents the results of 10,000 h of field testing in a power plant.

The thermal barrier coating (TBC) system is currently a standard technology of gas turbine hot gas path parts to achieve a highly reliable long life operation of engines for a power supply. Mitsubishi Heavy Industries, LTD. (MHI) has applied the TBC on the gas turbine blades, vanes and combustor parts. TBC system consists of MCrAlY as a bondcoat for oxidation protection at elevated temperature and YSZ (yttria stabilized zirconia) as a topcoat for efficient thermal barrier. The conditions where TBC has been in service are at the temperature up to 1500°C and with combustion gas environment. As far as the blades and the vanes are concerned, the MCrAlY bondcoat is coated by low pressure plasma spray (LPPS) or high velocity oxygen fuel (HVOF) system, and the YSZ topcoat is coated by atmospheric plasma spray (APS) system. In the case of the combustor parts, both the MCrAlY bondcoat and the YSZ topcoat are coated by APS. To increase the reliability and prolong the service life of the applied TBC in the gas turbine, it is very important to verify the coating properties, optimize the coating process parameters and control the coating process.