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Abstract Cold spray (CS) is a solid-state deposition process that accelerates particles in a gas to create parts or coatings. Deformation is central to the mechanical and metallurgical bonds that facilitate particle cohesion and deposit formation. Most research works focus on high-pressure inert gas CS (HPCS), neglecting the potential of air-based CS which is often overlooked because of its poorer deposit qualities. Despite this, air-based CS presents advantages in terms of cost and energy savings and has recently gained attention as a promising new CS additive manufacturing method. This review contrasts HPCS and air-based CS, identifying key differences and bonding modes. Then, state-of-the-art air-based CS research is captured and reviewed revealing a diverse range of application areas including functional coatings, medical, machine tool manufacture, and metal-to-ceramic interfacing. Additionally, research efforts to improve air-based CS quality and bonding, which mainly centre around feed-stock morphology optimisation, print pathing, and post-treatment techniques, are captured. Literature is grouped into three main research categories: metal feed-stocks, metal matrix composites and powder mixes, and novel applications. Accompanying tabulated summaries are presented, detailing CS system parameters, such as gas pressures and temperatures, feed-stock and substrate materials, and application area. Future research directions in air-based CS are also discussed in the context of technology promotion, key strengths and applications, and methods for enhancing CS systems and deposit qualities.
Tregenza et al. (Sat,) studied this question.