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Thermal barrier coatings allow increasing the operating temperature and efficiency of land-, sea-, or air-based turbines. As failure of the coating may result in serious damage of the turbine, reliable estimation of its lifetime is essential. To assess the lifetime, cyclic tests are conceived to combine thermal loading by heating the surface of the coating with laser irradiation and nondestructive methods for damage determination. Using laser irradiation allows a high reproducibility of the thermal load. The temperature of the sample surface during thermal loading is determined by an infrared-camera which also enables the possibility to detect damage in the coating via thermography. Additionally, four acoustic sensors, attached to the experimental setup, are used to detect damage in the sample and determine the source of acoustic events. Results of acoustic emission correlate well with thermographic images that visualize the formation and evolution of damage through delaminations in the samples.
Degradation of thermal barrier coatings (TBCs) in gas‐turbine engines due to calcium–magnesium–aluminosilicate (CMAS) glassy deposits from various sources has been a persistent issue since many years. In this study, state of the art electron microscopy was correlated with X‐ray refraction techniques to elucidate the intrusion of CMAS into the porous structure of atmospheric plasma sprayed (APS) TBCs and the formation and growth of cracks under thermal cycling in a burner rig. Results indicate that the sparse nature of the infiltration as well as kinetics in the burner rig are majorly influenced by the wetting behavior of the CMAS. Despite the obvious attack of CMAS on grain boundaries, the interaction of yttria‐stabilized zirconia (YSZ) with intruded CMAS has no immediate impact on structure and density of internal surfaces. At a later stage the formation of horizontal cracks is observed in a wider zone of the TBC layer.