Microstructural characterization of interfaces between cold sprayed copper and electrodeposited copper corrosion barrier coatings for used nuclear fuel containers

Copper coatings on steel, manufactured by a novel combination of two different manufacturing technologies, electrodeposition and cold spraying, are employed as a corrosion barrier in the current design of used fuel containers (UFCs) for the long-term storage of Canada's used nuclear fuel. This study examines such copper coatings on a prototype container section, with a particular focus on the interface region where copper materials fabricated by the two processes converge. Distinct microstructures for the electrodeposited and cold sprayed copper layers were observed. An unexpected recrystallized layer on top of electrodeposited copper was identified for the first time. Local annealing at 350 C-degrees and 600 C-degrees for one hour resulted in more homogeneous microstructures and Vickers hardness profiles among the copper layers, which is favorable for this application by reducing processing related heterogeneity in the interface region. More homogenized structures with high fractions of special grain boundaries in this region are expected to provide enhanced mechanical and corrosion properties.