Fracture modeling and experimental study on interfacial adhesion in a thermal barrier coating system on Ni-based superalloys

This work aims to analyse the existing approaches to quantify the interfacial adhesion for multi-layered structurally heterogeneous coating systems on Ni-based superalloys as well to evaluate the ability of a proposed experimental technique. New designs of samples and test fixtures to measure the adhesion parameters are presented. The microstructural analysis is employed to study TBC layers thickness, its uniformity and geometry of the interfaces in pristine samples as well as to control the occurrence and spread of spallation during testing. Numerical study is carried out using a finite element model based on representation of the contact between coating components as a cohesive interaction. The main attention is paid to evaluate the effect of morphology and interfacial strength parameters on the stress state and cracking behavior of the coating during cooling stage.