As cold spray additive manufacturing matures, significant efforts are being made to develop spray conditions for more challenging materials, thereby expanding the technology’s range of applications. One main challenge while using commercially available equipment is that, even under optimized conditions, deposition efficiency remains low for some materials. Powder particles that do not adhere are wasted, which can severely affect the process economics, especially in a mass production context and/or when expensive feedstocks are used. Powder recovery and reuse is a logical solution to mitigate this problem, yet few studies evaluate its feasibility and its impact on powder characteristics and ultimately coating performance. In this work, powder recovery was investigated for two cases: a Ni powder and a NdFeB-Al powder mix, used respectively for repair applications and for the fabrication of permanent magnets. A prototype recovery system was built, achieving a recovery efficiency of up to 75%. The powders were recovered after up to four spray runs, and their morphology and size distribution were characterized. The magnetic properties of both powders and coatings were evaluated using hysteresis measurements. Although the process affects the particle size distribution and their magnetic properties, powders remain suitable for re-deposition for both materials. In particular, it was shown that NdFeB-Al mix maintains 97% of its initial magnetic performance under industrial operating conditions.

Cold spray (CS) uses high-velocity gas to deposit solid particles without oxidation or phase change. To make the spraying process more economical, a wider-sized cut of feedstock particles needs to be deposited. The liquid cold spray (LCS) process, which uses water as a propellant, has been developed to achieve this goal. The use of water as a propellant may adversely affect particle deformation and adhesion. In this study, numerical methods are used to analyze particle and substrate oxide failure to determine the effects of wetting on particle adhesion to a substrate. The results indicate that water on the particle surface or on substrate would reduce the deformation of both. The area in which oxide layers fail and metallurgical bonding can occur would be reduced. A portion of the water may become entrapped between the particle and the substrate, adversely affecting the bonding area. Increasing particle velocity and decreasing water thickness can reduce the volume of trapped water and improve density by increasing particle deformation and decreasing pore size.