Experimental and numerical study of TGO-induced stresses of plasma-sprayed thermal barrier coating

Abstract

Experimental and numerical studies were conducted in order to investigate the stress changes of ZrO2-8 wt% Y2O3 (YSZ) thermal barrier coatings (TBC) under isothermal loading. After conducting the isothermal oxidation test at a temperature of 1070 °C, the Thermally Grown Oxide (TGO) growth process and the life of samples were evaluated using scanning electron microscopy (SEM). The X-ray diffraction (XRD) approach was selected for the measurement of surface residual stress and its change in terms of TGO growth. Furthermore, a finite element model based on a real TGO profile, extracted by SEM, was executed, where TGO-induced stress was measured at the TGO/Top Coat (TC) interface direction. Employing the finite element model, following the selection of the appropriate creep strength based on experimental results, the stress evolution and distribution were assessed during time exposure at maximum temperature. It was shown that the lifetime of samples was about 240 h under isothermal loading of 1070℃. By increasing the time exposure, stresses increased and resulted in the formation of a delamination line above peak regions.