Structure-processing-property relationships in bulk copper produced by cold gas dynamic spray processing

Cold gas dynamic spray (cold spray) processing has been demonstrated as an effective process for coating and repair utilizing many alloy systems. Free-form fabrication of bulk materials by cold spray remains on the periphery of potential applications. While particle deformation and inter-particle bonding mechanisms in the sprayed deposit have been modeled, the atomistic mechanisms involved in these processes have yet to be fully characterized. In this study, helium and nitrogen were employed, separately, as the main process gas in production of thick copper deposits to demonstrate the feasibility of creating bulk deposits by the cold spray process. The differences in microstructure, microhardness and annealing response between the two materials were characterized using a variety of methods including optical, scanning electron and transmission electron microscopy. The results will be presented to shed light on the fundamental limitations of the cold spray process for coating and bulk deposits.