Morphological change occurring near a surface groove on an alumina-forming alloy subjected to thermal and mechanical cycling

Thermal barrier coatings (TBCs) provide protection against high temperature corrosion of superalloy substrates in gas turbines. However, the lateral growth of the thermally-grown oxide (TGO) and the thermal expansion misfit between TGO and the underlying bond coat (BC) induce internal stresses which can be sufficient to activate plastic deformation or buckling in the TGO. The displacement instability of TBCs is affected by the TGO deformation. In this work, the deformation occurring near a groove on a heat-resistant alloy subjected to thermal or thermo-mechanical cycling was investigated. Experiments were performed with two different maximum temperatures and three mechanical load levels. The experiments showed that the deformation of the groove increased with maximum temperature. In addition, effects of load level, groove orientation, and the yttrium content in the substrate alloy on the deformation were determined.