Detailed investigations of thermally grown oxides (TGO) zone and areas adjoining to it were presented in this article. The thermal barrier coating (TBC) based on gadolinium zirconate (Gd2Zr2O7, GZ) and deposited by air plasma spraying (APS) on AMS 5599 superalloy with NiCrAlY type of bond-coat was the analysed material. Analyses were made on TBC system after spraying process and after time to 500 hours of oxidation at temperature 1100°C in atmosphere of laboratory air. Ultrahigh resolution scanning-transmission (S/TEM) electron microscope TITAN 80-300 was used to conduct the tests. Quanta 200i Dual Beam apparatus by FEI for precise and localized focused Ga+ ion beam (FIB) sample preparation was used as well.The basic aim of presented investigations was related with detailed characterization of interface zone between ceramic top-coat (TC) of Gd2Zr2O7 type and NiCrAlY bond-coat after spraying process and after 500 hours of deposition in oxidized atmosphere where the TGO zone was formed with the thickness ca. 5-10 µm. The special emphasis was placed on research of this zone and its morphology due to very strong influence of formed thermally grown oxides on overall life-time and destruction processes which took place on the interface between TGO and ceramic top-coat. Obtained data revealed that the most important factors influenced on destruction processes are related with the thickness of TGO zone (consisted mainly Al2O3, NiAl2O4 and eventually NiO) rather than formation of undesirable phases such as GdAlO3 complex oxide.

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