Durable aluminate toughened zirconate composite thermal barrier coating ( TBC ) materials for high temperature operation

Research on advanced thermal barrier coating ( TBC ) materials capable of operating beyond 1200°C has primarily focused on the rare earth zirconate pyrochlores, particularly gadolinium zirconate (Gd 2 Zr 2 O 7 – GZO ). The drawback of this material is a significant reduction in durability due to a low fracture toughness. This study investigates utilization of a thermodynamically compatible gadolinia alumina perovskite (GdAlO 3 – GAP ) toughening phase to improve the durability of GZO . Dense pellets were fabricated to assess the material properties with minimal microstructural influence. Thermal stability, elastic modulus, hardness, indentation fracture resistance and erosion durability were evaluated for GZO , GAP , and composite pellets containing 10, 30, and 50 wt.% GAP . It was demonstrated that GAP and GZO are thermodynamically compatible through 1600°C and thus capable of operating well beyond the limits of traditional 7 wt.% yttria stabilized zirconia ( YSZ ). Grain sizes are maintained due to a lack of diffusion, and thus microstructural stability is enhanced. The GAP fracture toughness was shown to be over 2X that of GZO while exhibiting a lower elastic modulus and similar hardness. The 50:50 GZO ‐ GAP composite exhibited a 63% reduction in the absolute erosion rate, demonstrating the immense toughening capabilities of this system. The implications for composite TBC s utilizing this system are discussed, along with future work.