Physical properties of thermal spray coatings, such as porosity, are sensitive to a large number of process parameters (e.g.: droplet size distribution, velocity, temperature and degree of solidification; substrate material and temperature) which are optimized by trial and error [1]. Better control of the process requires a fundamental understanding of the fluid flow and heat transfer that occurs during the impact, spreading, and solidification of molten droplets. In a previous study [2], we developed a 2D/axisymmetric model to simulate the impact of molten tin droplets on a steel plate; the predictions of the model were compared with photographs of impacting droplets. Modeling the impact of several droplets or the impact on a previously solidified splat, however, requires a 3D model. The objectives of this study are: to develop a 3D numerical model of free-surface flows and heat transfer\" including phase cpange, and to demonstrate that the model oan simulate a complex phenomenon of theE impact of a droplet on a previously solidified splat.

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