Mechanical analysis and modeling of porous thermal barrier coatings

Abstract Thermal barrier coatings (TBCs) are applied to gas turbines and aircraft engines as insulating materials. In this study, scanning electron microscopy was used to investigate the cross-sectional microstructures of TBCs. After calculating porosities and pore-size distributions, a two-dimensional finite element (FE) model with four different porosities (0, 1, 3, and 5%) was established, and a stochastic method was used to generate a randomly distributed porous structure. The overall stress within the ZrO2–8%Y2O3 coating increased during sintering; however, the locally concentrated stress was effectively eliminated by adding a 20-μm sealed layer. A relationship between the network micro-pore structure and the crack-initiation mechanism was proposed following FE analysis and nanoindentation testing. We found that radial cracks are affected by interactions between neighboring pores at high porosity (> 3%), and occur at the top/bond-coating interface where they remain in high energy states; these radial cracks continue to propagate after cooling. However, axial cracks are commonly generated on ZrO2–8%Y2O3 surfaces because the tensile stress resulting from a single micro-pore is up to three times higher than that of the surrounding area (porosity