Abstract

A numerical model has been developed to study the rapid solidification of an alumina splat in thermal spray deposition. The model focuses on the melt undercooling, the selection of the various phases of Al2O3, and the subsequent non-equilibrium rapid solidification process. A thin molten layer is assumed to be brought into contact with the substrate at time t = 0. One-dimensional heat transfer is considered through splat and substrate along with a thermal contact resistance between them. The classical theory of nucleation kinetics is used to determine the nucleation temperature, assuming that nucleation takes place heterogeneously on the substrate surface. The most likely nucleated crystalline phase is investigated, based on the nucleation kinetics of various phases. Once the particular phase is identified and the nucleation temperature is calculated, the solidification starts assuming a planar interface between the solid and the liquid. Non-equilibrium kinetics of the chosen phase is applied at the moving interface to calculate the interface velocity from the interface melt undercooling. In this paper, the effect of splat variables on the solidification and cooling process of the splat are analyzed. Special attention is paid to the value of the wetting angle between the growing nucleus and the substrate, which affects greatly the nucleation temperature.

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