Thermal gradient of in-flight polymer particles during cold spraying

[Display omitted] •Discontinuous nozzle induces the flow to choke at the discontinuity location.•At the nozzle exit, the particle velocity reaches 190 m.s−1 for 60 μm diameter.•During cold-spray, polymeric particles are submitted to important thermal gradient. The manufacture of polymer coatings via the cold-spray process remains challenging owing to the viscoelastic-viscoplastic behavior exhibited by polymers. One crucial step to improve cold-spray polymer coating is to determine the particles’ thermal history during their flight from inside the nozzle to their impact on the substrate. In this study, we propose estimating the velocity and temperature of an isolated polymer particle traveling through a nozzle with a sharp change in its cross-section. The preliminary results show that the geometric discontinuity constricts the flow, thereby increasing the particle velocity. Moreover, a significant thermal gradient is expected inside the particle, which in turn leads to a gradient of mechanical properties of the polymeric particle during impact.