Numerical Modeling of Impact and Solidification of a Molten Alloy Droplet on a Substrate

Most of the studies reported for droplet impact and spreading on a substrate in a thermal spray coating process assume that droplet material solidifies as a pure substance, i.e., phase change occurs at a fixed temperature. The alloy-type behavior of the droplet impact where it solidifies within liquidus and solidus temperature is not well reported. The role of formation of mushy zone and species composition variation during the coating layer formation while using a multi-constituent alloy material is not established. This work investigates the spreading and solidification characteristics of an alloy droplet impacting on a substrate. Two-dimensional axisymmetric model has been used to simulate the transient flow and alloy solidification dynamics during the droplet impingement process. Volume of fluid (VOF) surface tracking method coupled with the alloy solidification model within a one-domain continuum formulation is developed to describe the transport phenomena during the droplet impact, spreading, and solidification of an alloy droplet on a flat substrate. Using the model, the characteristics of alloy solidification in coating formation are highlighted.