| Ceramic top layers of yttria stabilized zirconia (YSZ) have gained increasing importance as thermal barrier coatings (TBCs) of heat exposed components in advanced gas turbines. In air plasma sprayed (APS) coatings the low inherent thermal conductivity of YSZ is further enhanced by the numerous microstructural defects from the spraying process. However, these defects also influence severely the mechanical performance and integrity of the TBC. Based on results from an ongoing collaboration between the Research Centre Juelich, Germany, and the Central Glass and Ceramic Research Institute, Kolkata, India, the impact of the defects on the elastic behaviour is addressed in detail. Various characterization methods, e.g., bending and compression tests as well as depth sensitive indentation are presented. The experi-ments include global and local approaches with the TBC in tension or compression and after annealing. The obtained non- uniform stiffness results, which cover a range between 5 and 100 GPa, are discussed in terms of the lamellar microstructure and the crack-shaped inter- and intra-splat defects of an APS-TBC. |
