Actual microstructure-based FEM simulation of crack interaction in thick thermal barrier coating using cohesive zone models

• Application of actual TTBC microstructure as RVE in FEM simulation of delamination • Numerical simulation of spallation induced by monotonic mechanical loading • Examination of the effect of TC characteristics on fracture using micromechanical simulation Thick Thermal barrier coatings (TTBC) are overlaid on the superalloy components used in gas turbine parts for enhancing the thermal insulation and oxidation performance. The interaction of segmentation and delamination cracking in thick thermal barrier coatings was studied by cohesive zone (CZM) micromechanics-based finite element model (FEM). Actual microstructural features of the TTBC, obtained via electron microscopy, were employed to construct a representative volume element (RVE) for FEM simulations. The study revealed that segmentation crack density significantly governs the progression of interlayer delamination. The influence of top coat (TC) thickness and interfacial adhesion parameters on surface cracking and delamination was systematically analyzed. Furthermore, mechanical stress localization under tensile loading was identified as the dominant failure mechanism in the RVE domain. The findings demonstrate that coatings with increased segmentation crack density and higher interlayer adhesion energy exhibited reduced susceptibility to delamination. These results can be integrated into a cohesive zone traction-separation model to predict crack propagation under monotonic mechanical loading. A comparative assessment between the simulated data and experimental results showed strong agreement, validating the model's predictive accuracy.