Key influencing factors for the thermal shock resistance of La2Zr2O7 based multilayer TBCs

Abstract In this study, different multilayer thermal barrier coatings (TBCs) made from La2Zr2O7 (LZ), ZrO2-7 wt% Y2O3 (YSZ) and a freestanding LZ-YSZ coat were designed and produced by plasma spraying to determine the key influencing factors on the thermal shock resistance of LZ-based multilayer TBCs. The coatings were characterized in terms of their microstructure, phase composition and thermal expansion coefficient. The thermal shock behavior of the TBCs was evaluated using thermal cyclic tests at T = 1300 °C as well as at T = 1150 °C. The results show that the compressive stresses in the LZ top coat decreased with an increasing coating thickness of the YSZ interlayer. The LZ top coat failed in the interface areas to the YSZ interlayer for an YSZ interlayer that was not thick enough. Sintering ceramic coats significantly influenced the thermal shock resistance.