Experimental Evaluation of Metallic Coating on Polymer by Cold Spray

Cold spray (CS) is an emerging coating technology that makes use of a converging/diverging nozzle, a high pressure and a heated gas source to create a high‐velocity gas flow. Coating deposition occurs at relatively low temperatures compared to other spray technologies, therefore the sprayed particles remaining in the solid-state. The process can produce dense coatings when the process parameters are optimized. Despite the incredible advantages of CS and the established knowledge of CS considering metal substrates, some questions like the bonding mechanism and the adhesion/cohesion strength of the coating with polymeric substrates remain an open research topic. In this paper, a metal coating (AlSi10Mg) was deposited on a plate in polypropylene by cold spray in order to increase the properties of the surface. Metallic particles, in the range of 20-40 µm, were injected into gas flow and propelled to supersonic velocities. Polymers require a deposition technique in which the substrate remains at relatively low temperatures during the whole process in order to avoid plastic deformation or degradation. Determination of the mechanical properties of thin films on substrates by indentation has always been difficult because of the influence of the substrate on the measured properties. In order to evaluate the local properties of the deposited coating, microindentation tests and DMA were carried out. In particular hardness values by microindentation tests and values of elastic modulus by DMA were calculated.