Residual stress in thermal spray coating and its impact on interfacial adhesion

Thermal spray coatings are commonly used as protective coatings for several technological applications such as hard coatings on cutting tools, decorative coatings, and protective coatings for advanced power engineering applications to improve performance. Residual stresses in such coatings play an important role in the performance and lifetime of the coated component. The mechanical integrity of these coatings is strongly influenced by these residual stresses, which derive from sources including growth stress, geometric constraints, thermal gradients and service stress. Therefore, stress-induced cracking in the coating itself or interfacial decohesion will affect the thermo-mechanical integrity of the coated component. In the proposed project, a computational methodology will be developed to predict the residual stress field developed during thermal spray deposition process and subsequent cooling as a function of material and process parameters. Moreover, the effect of the bonding properties on the structural and thermal behaviour of the structure will be studied and analysed. In addition to the FE simulations of the adhesion between the coating and the substrate, FE simulations will also be performed to study the effect of the coating process parameters on the residual stresses developed in the system. Various deposition process parameters including deposition of splats, geometry, time delay and interaction of splats; and cooling of splats will be included in the investigation. The developed computational model will be validated with experimentally developed coatings in collaboration with the Centre for Advanced Coating Technologies at University of Toronto. As a major outcome of the proposed project, a guideline to design thermal spray coating with enhanced service life would be established.