Cold Spraying of Hard Martensitic Materials: Insights into Deposition Mechanism and Phase Transformations

Cold spraying of hard martensitic materials presents significant challenges due to the presence of hard phases that reduce deposition efficiency (DE). This study explores a hybrid approach involving heat treatment and particle size segregation to enhance the DE of nickel-aluminum bronze (NAB) in cold spray deposition. By eliminating martensite through heat treatment, the DE increased substantially from 20% for the as-received powder to nearly 100% for the heat-treated powder. Extensive mechanical and electrochemical corrosion analyses revealed that among the heat-treated powders, a specific particle size demonstrated superior performance. Interestingly, despite its lower DE, the as-received powder deposit exhibited better overall properties compared to the heat-treated deposits. Dynamic phase transformations during cold spraying effectively eliminated the martensitic phase in the as-received powder deposits, a phenomenon confirmed through detailed XPS analysis. This work provides valuable insights into the deposition mechanisms of hard martensitic materials in cold spray, offering a pathway to achieve high DE while maintaining improved material properties.