Recuperation and reuse of cold-sprayed Ni and NdFeB-Al powders

As cold spray additive manufacturing is maturing, significant efforts are invested to develop spray conditions for more challenging materials that can expand the range of applications of the technology. Unfortunately, optimized conditions, even using the best commercially available equipment, are seldom sufficient to deposit some materials at high deposition efficiency. Powder particles that do not adhere are wasted, which can severely affect the process economics, especially in a mass production context and/or if expensive feedstock is used. Powder recuperation and reuse is a logical solution to mitigate this problem. The effect of the spray process on the recuperated powder characteristics, for instance the powder size distribution and composition, has been the topic of a very limited number of studies. In this work, powder recuperation was investigated for the case of composite NdFeB-Al and Ni powders used respectively for the fabrication of permanent magnets and for repair applications. The powders were recuperated after multiple spray runs and their composition, morphology and size distribution were characterized. The powder and coating magnetic properties were evaluated using hysteresis measurements. Results indicate that, although the process slightly affects the particle size distribution, the magnetic properties are conserved, therefore the recuperated powder is suitable for re-deposition.