Development of Cold-Sprayed Nickel Aluminum Bronze Coatings on Magnesium for Enhanced Corrosion Resistance

Nickel aluminum bronze (NAB) is renowned for its exceptional corrosion and cavitation erosion resistance, making it ideal for marine applications like shipbuilding. However, traditional thermal spray processes used to apply NAB coatings can induce phase changes, necessitating long heat treatments. In this study, cold spray, a solid-state deposition method, was employed to develop NAB coating on a magnesium alloy substrate. Despite the expectation that cold spray would facilitate the deposition of a hard material on a soft substrate, initial results showed nearly 0% deposition efficiency (DE). This was attributed to the martensitic structure of the NAB, which resists deformation during cold spraying. To overcome this, the NAB powder was heat-treated to reduce its martensitic content, significantly improving DE to nearly 100%. Characterizations such as hardness, scratch, and electrochemical corrosion tests were conducted to evaluate the inter-splat bonding of the generated coating. Furthermore, the tamping effect, inherent to cold spray, was leveraged to enhance bonding in the top layers. This was achieved through laser remelting as a post-processing technique by integrating scan speed, beam diameter, and laser power into the optimization analysis.