Cold spray deposition of 316L stainless steel coatings on aluminium surface with following laser post-treatment

Cold spray deposition of 1-3 mm thick 316L coatings on aluminium substrate using nitrogen as a carrier gas is considered. Dependence of coating properties on particle size distribution and spraying strategy is studied. It was obtained that the absolute value of coating porosity depends on particle size distribution and could be varied from 3% (fine powders) to 8% (coarse powders). The pores are mostly concentrated along the boundaries between deposited layers and the shape of the boundaries is strongly influenced by spraying strategy. It was found that coating deposited using coarse powder has higher microhardness than the one deposited using fine powder, whereas adhesion does not depend on powder granulometry. Eventual decrease of coating porosity is analyzed. In particular, it is shown that laser post re-melting of the deposited coatings can decrease the porosity in the near-surface layers down to <1% with limited heat input to aluminium substrate. Evaluation of anodic polarization behavior showed that corrosion resistance of the laser-treated coating is close to the bulk material whereas performance of as-sprayed coatings is significantly lower.