Correlation of mechanical properties and electrochemical impedance spectroscopy analysis of thermal barrier coatings

Electrochemical impedance spectroscopy (EIS) has been explored as a non destructive evaluation method to monitor thermal barrier coating (TBC) degradation. ZrO2(Y2O3) top coat and NiCrAlY bond coating were air plasma sprayed onto an Inconel 600 Ni base alloy. The TBCs were isothermally oxidized in air at 950 °C and 1050 °C for 72, 144 and 336 h. EIS measurements were carried out and the TBC impedance response was simulated using an alternate current equivalent circuit. The electrical parameters of this circuit were correlated with the microstructural and mechanical degradation of the TBC during isothermal oxidation.