Enhanced model for axisymmetric stability analysis of propagating circular defect-driven coating delamination under combined compressive and diffusion-induced stresses

This paper examines the delamination of palladium (Pd) coatings bonded to a steel substrate under equi-biaxial compression coupled with diffusion-induced stress. The study focuses on circular delaminations. Large delaminations cause the coating to debond, forming blisters, which generate a driving force on the edge crack tip. A two-part theoretical model is developed: axisymmetric blister propagation in a stable circular pattern and non-axisymmetric perturbation of the blister leading to branching. Detailed experimental studies validate the theoretical predictions. The experiments show that non-axisymmetric crack tip instabilities during propagation result in worm-like patterns.