Numerical Investigation of the Impact of a Hollow Ceramic Droplet on Metallic Substrate

The objective of this study is to numerically investigate the spreading and solidification of a hollow ceramic droplet impacting a metallic substrate, with a particular focus on the melting of the substrate. The numerical model employs the PISO (Pressure-Implicit with Splitting of Operators) algorithm to solve the equations governing transient fluid dynamics, utilizing the pressure-based finite volume method in a ۲D axisymmetric domain. The volume of fluid (VOF) method is employed to ensure the tracking of the droplet/air interface during spreading and solidification. The enthalpy porosity method is utilized for the monitoring of the liquid/solid interface throughout the processes of droplet solidification and substrate melting. The interaction between the spreading droplet and the substrate is represented by a thermal contact resistance. To validate the hollow droplet impact model, a comparison with published experimental results was performed. Simulations were conducted under plasma spray conditions for varying initial droplet temperatures and contact thermal resistances to assess their influences on droplet spreading and solidification, as well as substrate melting. It was observed that the initial droplet temperature significantly affects the splat morphology and substrate melting. However, thermal contact resistance exerts a greater influence on substrate melting than on the final splat shape. Thus, it was found that the droplets, whose initial temperature is high, impacting the substrates with low thermal contact resistance, improve the adhesion of the coatings.

Keywords:

Hollow droplet , Spreading , Solidification , Substrate melting , Computational fluid dynamics