Effect of electroplated interlayers on properties of cold-sprayed copper coatings on SS316L steel

Cold-sprayed copper (Cu) coatings have been recommended for the passivation of plasma-facing components in the vacuum vessel of Tokamaks. Therefore, research is under progress to develop such coatings with desired properties, which is still a challenging task. In the present work, the effect of nickel (Ni) and Cu electroplated interlayers on several properties of cold-spray copper coated SS316L steel was investigated. Further, the effect of heat-treatment on the developed coatings was also analyzed. The developed coatings were characterized by scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS), X-ray diffraction (XRD), microhard-ness, nanoindentation, macro-tensile, and lap-shear test/adhesion testing, and porosity, density and, electrical and thermal conductivity measurements. The novelty of the article includes the in-situ micro-tensile investigations performed under SEM to reveal the fracture phenomenon for the coatings. It was observed that the heat-treatment, in general, improves the coating properties. Additionally, gamma (gamma)-ray and heavy nuclei irradiation and thermal cyclic tests were performed to elucidate the actual environmental performance of the coatings. Based on the overall results of the study, the heat-treated Cu-coating developed on Ni-electroplated steel substrate was found to be the most suitable material for protecting the plasma-facing components.