Thermal Gradient in Polymeric Particles During the Cold Spray Process

Understanding the particle history during the cold spray process is primordial to better apprehend the particle's mechanical behavior during the impact. If the particle velocity can easily be measured using a high-speed camera, measuring the particle temperature remains a challenge. A solution is to perform numerical simulations of the process using computational fluid dynamics (CFD) simulations. However, most CFD simulation results only give an idea of the particle average temperature. Although it would be valid for metallic particles which exhibit a small temperature difference between the particle core and surface with high thermal stability, it is not the case for polymeric material, because of their low thermal conductivity. In this paper, the thermal gradient of a polymer particle is investigated. While small particles exhibit a uniform temperature distribution, a large temperature gradient is observed for particle diameter larger than 30 µm. In addition, assuming that the particle is spherical without rotation during the flight, the particle exhibits melting at the front. Such a phenomenon can have considerable consequences on the particle behavior during the impact. Furthermore, the influence of the feeding rate on the particle temperature distribution is investigated. If the particles are well diluted inside the nozzle (low feeding rate), the difference in the average temperature of two successive particles is limited to 5 K.