Abstract
An initial stage of the current work including a preliminary comparative numerical analysis of molten polymer and metal droplets upon impact on a cold steel substrate was presented. A commercially available Volume-of-Fluid [VoF] code was used to model particle deformation and cooling of molten nylon-11 and zinc droplets on impact with a steel substrate. Comparison between polymer and metal splatting was chosen in order to better understand how large fundamental differences between the materials affected their spreading behavior under similar thermal spray conditions. It was found that the inertia is more strongly balanced by the viscous flow resistance in molten polymers while high surface tension of molten metals may lead to particle breakup onto rivulets and satellite during later stage of particle deformation. Spreading ratios of nylon-11 and zinc droplets were 0.53 and 0.34, respectively, owing to the zinc droplets being almost twice the size of the nylon. Zinc splats less than 5 ìm in thickness spread fully and solidified in less than 1.5 µs. Over the same time interval, 17 µm thick nylon-11 splats were also fully developed, however, only a thin boundary layer [<2 µm] was solidified owing to a significantly lower thermal conductivity.
