The influence of axial loading on the interface stresses of thermal barrier coatings

In this paper, a thermal barrier coating system is studied numerically using finite elements. If the system is isothermally compressed, large stresses at the coating interface may develop due to the differences in Young’s modulus. Since the coefficient of thermal expansion of the substrate differs from those of the coating materials, axial loading of the coating system is also relevant upon cooling. By artificially changing the coefficient of thermal expansion of the coating materials, the effect of axial loading and of stresses due to thermal differential strains in radial direction can be evaluated. Consequences for mechanical loading are discussed, showing that out-of-phase loading of a TBC system unloads critical regions of the TBC on the microscale.