Failure lifetime prediction of single and dual-layer ZrO2-8Y2O3 / Gd2Zr2O7 new generation thermal barrier coatings undergoing thermal cycling

Prediction of the failure lifetime of thermal barrier coatings (TBCs) is usually considered as one of the important challenges in the hot section components of gas turbines. In this study, the effective stresses in determining the lifetime of new-generation single-layer Gd2Zr2O7 (GdZO) and dual-layer ZrO2-8Y2O3 (YSZ) / GdZO TBCs were investigated. For this purpose, singlelayer GdZO and dual-layer YSZ / GdZO TBCs were applied on IN738LC / CoNiCrAlY by atmospheric plasma spraying technique. Then, their cyclic oxidation behavior was studied at 1100°C with 4-h cycles. The morphologies of the TBCs (before and after oxidation) were investigated by field emission scanning electron microscopy. In addition, the mechanical behavior of the TBCs was examined by the Nanoindentation test. The variation in the energy release rate of the TBCs during oxidation cycles was calculated. The results showed that the changes in the energy release rate of dual-layer YSZ / GdZO TBC compared to single-layer GdZO TBC are less, and, therefore, have a better high-temperature performance. Applying an intermediate YSZ layer between the bond and top coats enhances the mechanical properties of new-generation TBCs and extends their lifetime by improving their resistance to high-temperature oxidation.