On spallation of EB-PVD thermal barrier coatings on turbine blades

Room temperature blistering and spallation failures reduce the life time of thermal barrier coatings (TBC). Based on the theory of pockets of energy concentration, a mechanical model for the multilayer circular blister is presented, considering the variable material properties through the coating thickness. Con-ditions are revealed analytically for nucleation, propagation and the spallation of TBC blisters. The predictions from the mechanical model on radii for TBC blister unstable growth and spallation are in good agreement with experimental results. Furthermore, this model is beneficial to determine the interface fracture tough-ness and the residual stress in the coating system.