1 What is thermal barrier coating? Definition and components of TBC Thermal Barrier Coating (TBC) thermal insulator of substrate Why TBC? Thermal barrier coatings (TBCs) perform the important function of insulating components, such as industrial gas turbine and aero-derivative engine parts, operating at elevated temperature. Turbine efficiency can be increased by allowing the TBC to increase its operating temperature. Construction of TBC Substrate : Ni- or Co-based Superalloy Bond Coat : Oxidation resistance metallic layer, MCrAlY, Thermally grown oxide(TGO) : Oxide layer between top and bond layer Top coat : Thermal insulative ceramic layer Materials for TBC Limitation of the conventional YSZ-TBC material Candidated new TBC composition & structures CrystalStructure Compositions Tetragonal (6-8 wt% YSZ; 12 wt% YbSZ; YbGd-YSZ; YbGdTiTa-YSZ; YbSm Stabilized Zirconia; ZrO2-HfO2-YbO1.5-TiO2-TaO2.5; YTaO4- ZrO2) Cubic yttria, gadolinia, ytterbia stabilized ZrO2; d2O3/ZrO2 Pryrochlores (e.g. La2Zr2O7, Gd2Zr2O7, Nd2Zr2O7, Sm2Zr2O7, Gd2Hf2O7) Perovskite structure e.g. SrZrO3, CaZrO3, LaAlO3 BNT{ BaNd2Ti3O10 }; BaCeO3 or SrCeO3) Rhombohedral e.g. SrZrO3, CaZrO3, LaAlO3 BNT{ BaNd2Ti3O10 }; BaCeO3 or SrCeO3) Hexagonal e.g Yb3Zr2O12,Lu3Zr2O12 or Er3Zr2O12, Yb3Hf2O12 Spinels (BaY2O4 or SrY2O4) Process for TBC Microstructural improvement Multi-layered structures Evaluation of TBC Thermal durability & Chemical stability Test Thermal fatigue fest Thermal shock test Flame thermal fatigue test Hot corrosion test Establishment an advanced evaluation system [Advanced evaluation systems: JETS test] [Thermally graded mechanical fatigue, TGMF test]
