3D predictions of thermally sprayed polymer splats: Modeling particle acceleration, heating and deformation on impact with a flat substrate

During thermal spray deposition, jets of high temperature and high velocity gases are used to melt and accelerate materials injected into the jet and propel them toward the surface to be coated. Upon impact at the surface, multiple hot particles deform, cool and consolidate to form a coating. Mathematical models have been developed to predict the particle transport and splatting on impact with a flat substrate during the High Velocity Oxy-Fuel (HVOF) combustion spraying of polymeric materials. The predicted shapes of deformed particles exhibited good qualitative agreement with experimentally observed splats including a characteristic “fried-egg” shape with large, nearly-hemispherical, core in the center of a thin disk. These shapes were formed by polymer particles having a low temperature, high viscosity core and a high temperature, low viscosity surface.