Low thermal conductivity coatings for gas turbine applications

Plasma spraying of thermal barrier coatings (TBCs) on gas turbine parts is widely used today either to enable higher-turbine inlet temperatures with consequent improvement of combustion efficiency or to reduce the requirements for the cooling system and increase component life-time. Development of low conductivity TBCs, which allows us to further increase gas turbine efficiency and availability, is an ongoing challenge. In order to get low thermal conductivity values an experimental program was conducted. Yttria partially stabilized zirconia (YPSZ) and dysprosia partially stabilized zirconia (DyPSZ) were used to study the influence of power input in the plasma torch and powder feed rate on coating properties. Microstructure evaluations were performed to evaluate the influence of the spraying parameters on the coating morphology and porosity level. Laser Flash (LF) and Transient Plane Source (TPS) methods were utilized to evaluate the coatings thermal conductivity and a comparison between the two methods conducted as well as a correlation study between coating microstructure/composition and thermal conductivity (TC).