PSI - Issue 68

Elena Fedorova et al. / Procedia Structural Integrity 68 (2025) 908–914 Elena Fedorova et al./ Structural Integrity Procedia 00 (2025) 000–000

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Fig. 1. Typical microstructure and schematic illustration of thickness of the TBC layers (a) on ZhS6U; (b) on ZhS32 turbine blade after cyclic oxidation tests.

According to SEM observation, the thickness of considered partially stabilized zirconia ZrO 2 -8wt%Y 2 O 3 top coat layer on ZhS6U varies from 45 to 95 µ m (Fig.1a). The TBC system on ZhS32 after thermal cycling at 1100 ° C consists of the following layers: the 30 μm thick NiCoCrAlY-bond coat, the 60 μm thick top coat, and α-Al 2 O 3 thermally grown oxide of an average 7 μm thickness (Fig.1b). 3. Experimental technique development To evaluate the interfacial adhesion of TBC on Ni-based single crystal superalloy under shear loading, the new designs of samples and test fixtures were proposed. The three different configurations were tested in order to facilitate and ensure the accuracy of experimental measurements of adhesion parameters. The schematic illustration of the developed loading fixture is shown in Fig. 2a. The loading fixture consists of two parts: a movable support and a punch. The punch was made of hardened steel and was attached directly to the load sensor of the testing machine. The cylinder-type specimen was mounted on the support using set screws. The disk-type specimen was mounted with a single screw in the center. The movable support was positioned relative to the punch using feeler gauges. Depending on the shape of the sample and the punch, the loading fixture allows three configurations which differ in contact area, see Fig. 2b. The tests were performed on the Tinius Olsen H25KT universal testing machine with a punch movement speed of 0.2 mm/min.

Fig. 2. Loading fixture for pullout testing (a); three types of loading configuration (b).

A typical force–displacement curve obtained during the test using cylinder-type specimen is shown in Fig. 3. The force increase nearly linearly. The diagram has a load drop points, which correspond to partial delamination of the coating.