Evaluation of thermal barrier coating exposed to different oxygen partial pressure environments by impedance spectroscopy

In this investigation, the oxidation of two-layer thermal barrier coatings (TBCs) prepared by EB-PVD (electron beam physical vapor deposition) in different oxygen concentration environments at 1323 K was evaluated by impedance spectroscopy and microstructural observation (SEM). The higher partial pressure of oxygen accelerated the oxidation rate of bond coating and faster oxidation caused cracking at interface between the TGO and the bond coat. Impedance spectroscopy was used to evaluate the microstructural changes which occurred in the TBC system non-destructively. The relationship between the electrical conductivity of the YSZ layer and its microstructure including the parameters of microcracks was established.