Effect of Viscosity on Air Entrapment and Spreading of Molten Droplet in Thermal Spray Coating Deposition

When high-velocity molten liquid droplet impacts over a solid substrate, air present in between the droplet and substrate gets trapped inside the droplet and leads to the formation of a pore inside the splat after solidification in thermal spray coating deposition, earlier many researchers have done works in the fields of droplet impact, spreading, and solidification. Despite various experimental and numerical studies, less attention has been focused on the effect of droplet viscosity on the behavior of drop spreading and air entrapment. The current study focused on a numerical study of spreading and entrapped air behavior at low to high viscosity of droplets in the thermal spray coating deposition process. Numerical analysis is carried out by considering heat distribution, solidification, and fluid flow. The result shows that splashing of the droplet in case of high viscosity is more compared to low-viscosity droplet. It has also been observed that at high viscosity, more air entrapment occurs. Splat thickness at the periphery is more in case of high-viscosity droplets.