Research Article
Paul D. Eason
Abstract
Cold gas dynamic spray processing (cold spray) is a solid-state material deposition process used for coating and repair processes in many alloy systems. Cold spray has long been proposed as a potential method for freeform fabrication. The cold spray process imparts great deformation to the impacting particles, affecting the final properties of the deposit through work hardening, grain refinement and inter-particle bonding. For the purpose of demonstrating the feasibility of cold spray as a viable freeform fabrication method, the microstructure and hardness of bulk cold sprayed samples were characterized in as received and annealed condition, then compared to cold rolled material, which was previously vacuum hot pressed from the same powder stock used in spraying. Microstructure was analyzed via scanning electron microscopy and electron channeling contrast imaging to assess grain refinement and thermal annealing response in the cold sprayed and cold rolled materials. Vickers micro hardness was measured to assess the effects of cold spray impact on the properties of bulk, as-sprayed copper relative to cold rolled copper. In postannealed materials, greater hardness is achieved with the cold spray process through the suspected mechanism of grain refinement unachievable in the rolling process.