Process parameter optimization and characterization of cold spray pure and blended AA6061 powder depositions

Abstract

Cold spray is a solid-state deposition method belonging in the thermal spray group of technologies that creates coatings, mass restorations, and additively manufactured components by accelerating feedstock powders at supersonic speeds via a de Laval nozzle. Once accelerated particles collide with a substrate or existing layer build up, severe plastic deformation from impact creates mechanical and metallurgical bonding. Among the many materials compatible with cold spray, aluminum 6061 alloy is a widely used, a general-purpose metal commonly found in industries such as automotive and aerospace as a structural material. Typically, metallic powders are manufactured with gas atomization and available as pure AA6061, or as a blend with various ceramics to obtain desired deposition mechanical, material, and manufacturing requirements. Additionally, a solid-state powder manufacturing method using mechanical grinding has emerged providing cold spray users with AA6061 powders of different morphology and metallurgy more like AA6061 bulk material. This study investigates deposition properties for pure gas atomized and ground AA6061 powders, and gas atomized powders blended with Al₂O₃, SiO₂, and ZrO₂. Cold spray depositions are characterized by studying their deposition efficiency, thickness, density, and microhardness. Effects of powder size distribution, morphology, and blending are correlated with deposition characteristics. Observations made include higher deposition efficiency and thickness with blended powders, and general hardness and deposition efficiency tradeoff for gas atomized powders, and high deposition efficiency and hardness for ground powder. Response Surface Methodology is used to determine optimum temperature and pressure conditions for powders, with deposition efficiency, thickness, and microhardness explanatory variables.