Numerical simulation on internal stress evolution based on formation of thermally grown oxide in thermal barrier coatings

Abstract

A finite element (FE) analysis method was developed to estimate internal stress in thermal barrier coatings (TBCs). The evolution equation of thermally grown oxide (TGO) based on oxygen diffusion in a bond coat (BC) was combined with the inelastic constitutive equation for a top coat (TC). Thermal cycling analysis to simulate start and stop of the gas turbine was performed using the developed analysis code. To investigate the influence of the TC/BC interfacial profile on thermal stress in the TBC, the profile of the analysis model was modeled with a sinusoidal waveform, with varying combinations of wavelength and amplitude. The results revealed that the growth of the TGO layer was a principal factor that increases thermal stress in the TC. The stress was therefore increased as it approached the TC/BC interface. Additionally, an investigation of the effect of the TC/BC interfacial profile on the stress revealed that stress increases with the increase in radius of curvature at the top of the sinusoidal waveform.