Numerical investigation of splat morphology in thermal spray with non-flat surfaces using SPH

Thermal spray processes are incresingly recognized in additive manufacturing as versatile techniques for surface functionality and component life extension.The dynamics of molten droplet impact and spreading critically influence the resulting splat morphology and in turn coating performance.In this study, we employ a three dimensional Smoothed Particle Hydrodynamics (SPH) framework to numerically investigate the impact of the single molten droplets impact on engineered aluminum substrates featuring cubic extensions and machine-line textures.The cubic extensions have 2 different surface configurations.

The SPH predictions are validated against experimental high-speed imaging of alumina droplet impacts, confirming the models ability to resolve spreading kinematics, molten material flow guided by surface grooves, pore entrapment, and rapid solidification. Beyond alumina, simulations with yittria-stabilized zirconia (YSZ) droplets reveal the distinctive influence of thermophysical properties particularly YSZ's lower thermal conductivity and high melting point on splat evolution. Compared to alumina YSZ droplets exhibit extended molten life time , enhanced penetration into substrate valleys, and more complex lateral flow paths that promote interfacial porosity under denser substrate features.

This comparitive analysis highlights the coupled role of surface topography and material thermal behavior in governing droplet spreading and solidification.These findings provide critical insight for tailoring substrate design and material selection to optimize splat morphology, thereby enabling more reiable and application specific thermal spray additive manufacturing strategies.