Optimization of fatigue property of ceramic coating for next-generation gas turbine

点击翻译按钮获取中文摘要

Thermal shock and thermal fatigue tests of a PSZ/NiCrAlY plasma-spray coating were carried out, and with fracture mechanical analysis thermal fatigue fracture mechanisms were estimated. On the basis of this estimation an optimum processing conditions for the plasma spraying of the heat insulation coating were determined with reference to the composition profiles and microstructure of the coated film. The optimized coatings were subjected to the cyclic burner heating test, and a detailed observation on the fracture during testing. Along with the fracture mechanical consideration and optimum process conditions and microstructure morphology were worked out, as presented as follows : (1) Different AE signals were observed for heating and cooling period of the thermal shock testing, which indicated the crack initiation and their propagation. (2) Graded structure was found to be effective to prolong the thermal fatigue life. (3) Under a smaller thermal lord small crack was observed to form in the graded layer, which was found to be effective to prolong the thermal fatigue life. (4) Insertion of alumina layer between ceramic overcoat and NiCrAlY bond coat effectively suppressed the oxidation of the bond coat, and this will avoid the oxidation damage which is often observed in the actual working circumstance of the gas turbine, and will bring about high performance of the ceramic coatings. The obtained results will be presented at the 5th International Symposium on Functionally Graded Materials at Colorado, USA.