Insights into cold-spray deposition of Nickel-Aluminum Bronze (NAB) on a soft substrate (Al alloy): emphasizing substrate influence on inter-splat bonding

Nickel-Aluminum Bronze (NAB) alloys are widely used in marine and aerospace industries due to their excellent corrosion resistance, cavitation resistance, and moderate wear properties. While cold spraying of NAB has been extensively studied for repair applications on NAB or similar substrates, their deposition on softer substrates for coating application remains unexplored. This study investigates the cold spray deposition of as-received and heat-treated NAB feedstock powder on a soft aluminum alloy substrate. Contrary to expectations of mechanical interlocking in the as-received powder, negligible deposition efficiency (DE) was observed due to erosion of the deposited layers. In contrast, under identical process parameters, nearly 100 % DE was achieved with heat-treated powder, attributed to the reduced martensite content. Hardness and corrosion resistance were evaluated to assess the inter-splat bonding quality. A comparative study involving deposition on an NAB substrate further elucidated the influence of substrate on inter-splat bonding and overall coating properties. Finite element modeling (FEM) was employed to analyze the impact of substrate deformation on inter-splat boundary temperatures. Results indicate that the surface oxide layer and the energy expended in substrate deformation significantly affect inter-splat boundary temperatures, thereby influencing inter-splat dependent functional properties.