The proposed project is an investigation of the mechanisms in bonding and failure of thermal spray coatings. The objectives for this project are as follows: establish an understanding of the mechanisms responsible for bonding, including metallurgical bonding and mechanical interlocking, and understand the mechanisms that dominate during coating failure. Understanding of bonding mechanisms will allow for optimization of the coating process to increase the strength of coatings as well as production of new combinations of coatings and substrates. Understanding the failure mechanisms of coatings allows one to tailor microstructures and optimize pre and post treatments to optimize coating performance. This investigation will be conducted through several steps. First is characterizing coating/substrate systems' stress state and dislocation densities using nanoindentation, electron backscatter and diffraction. Second is by inducing coating failure by several methods: surface indentation, interface indentation, and tensile testing. Characterizing the failed states and then comparing with initial states will provide insight into the aforementioned mechanisms. Finally, a cohesive zone finite element model will be utilized to model these behaviors and predict failure under different starting states. This project holds great significance to NASA because of the large requirements for specially engineered materials. Though the investigation is not explicitly creating a new kind of coating, it holds significance to the application of all coatings, including established and as yet undeveloped coatings.