MECHANICAL BEHAVIOR OF COLD SPRAYED CU-NI COATING

Abstract

Cold spray is a developing additive-manufacturing technology well suited as a preventive and corrective measure for metallic materials. The key challenge lies in formulating the optimal multifaceted spray parameters to achieve a functional coating on a substrate. Copper-nickel (Cu-Ni) alloy is particularly suited for study, due to its feasibility as both coating and repair material to be deposited onto a substrate through cold spray technology and its well-established characteristics for corrosion protection and mechanical strength. This thesis studied the change in mechanical behavior due to annealing of cold-sprayed Cu-Ni coating. In order to do so, the subject Cu-Ni powder's behavior and coating quality were characterized through the variation of certain spray parameters and examined by the mechanical behavior of multiple passes of Cu-Ni coatings through tensile testing, adhesion testing and nanoindentation testing. The as-sprayed coating exhibited brittleness and had weak mechanical interlocking adhesion with the substrate. Annealing mitigates and delays the mechanical deficiencies associated with porosity in the coating, which showed signs of the stronger metallurgical bonding with the substrate. Annealed cold spray coating itself can bear significant load and strengthen the substrate. Thus, cold spray coating with appropriate post-processing treatment can potentially reinforce and even repair the component to achieve robust mechanical behavior.