(407d) Adapting Cold Spray Technology to Polymer Powders

Cold spray processing has proven to be an effective method of applying coatings, repairing structures, and high-rate additive manufacturing.^{1, 2} In the cold spray process, micron-sized powders in the solid state are accelerated with a supersonic stream of gas and impacted on a substrate. At ideal material-specific processing conditions, powders will deposit onto a substrate and form a coating due to extensive plastic deformation between the particle and substrate. This process has been shown to produce hard, dense, and efficient coatings from metal powder feedstocks over the past several decades.¹ Recently, interest in applying the technology to polymer powders has been expressed in the literature. ^3-7 Although a promising technology, polymer powders have proven to be challenging to spray with reports generally struggling to achieve efficient sprays and high deposition quality. The macromolecular structure of polymers and their thermophysical properties require re-thinking the cold spray process from concepts that were developed from metal particle sprays. Our work investigates how these fundamental polymer properties affect cold sprayed polymers through a combined approach including multiphysics modeling, highly controlled single-particle impact experiments, and the analysis of cold sprayed polymer powders. We highlight some of the critical changes that arise in the process (heat transfer characteristics, polymer chain length, and thermophysical properties) and how the process must be adapted to achieve efficient and quality polymer deposits. Ultimately, a foundational understanding of the process will enable a versatile method of rapidly repairing, building, and coating a range of materials with polymers.

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