In situ Mechanical Investigation of Splat Sliding in Cold Sprayed 6061Al Coatings

Cold Spray is a solid-state consolidation process that utilizes powder feed stock that is accelerated through a spray gun using a heated high-pressure gas such that the particles exit at supersonic velocities and form a coating or a near-net shaped part upon impacting a suitable surface. The consolidated material has an anisotropic structure, comprising of splats formed by impact and flattening of powder particles, which are the building blocks of the deposit. The splats are susceptible to sliding along the splat boundaries in case of poor inter-splat adhesion, resulting in inferior mechanical properties such as hardness, modulus, and strength compared to their bulk counterparts. This study examines the phenomenon of ‘splat sliding’ in cold-sprayed 6061Al coatings by in situ mechanical investigations. The coatings are subjected to cyclic bending loads, and the deformation is observed in real time inside a scanning electron microscope chamber. Digital image correlation approach is used to map strain evolution in the coatings during deformation, to develop insight into splat mechanics. Influence of processing parameters, splat structure and mechanical deformation conditions on splat sliding is investigated. The study seeks to establish correlation between processing, microstructure and splat mechanics, to be able to develop coatings with predictable properties.