Cold spraying of martensite NAB deposits: a strategy for improved inter-splat bonding

Cold spray is a solid-state deposition technique that can be used for both coating and repair applications. Aluminum bronzes are renowned for their excellent corrosion and cavitation resistance in marine environment. Deposition of gas-atomized aluminum bronzes using cold spray is challenging due to the presence of hard martensite. In the present work, gas-atomized nickel aluminum bronze (NAB) powder was heat-treated and segregated according to particle size and subsequently deposited using cold spray. This strategy was successful in enhancing the deposition efficiency (DE) to nearly 100% for the segregated powders from 20% for the as-received powders. Deposition efficiency, hardness, and scratch resistance were used as the parameters to evaluate the inter-splat bonding of the deposits. The bonding state was found to be dependent upon the powder size, as comparatively better properties were achieved for the deposits fabricated with the heat-treated coarser powder.