Numerical Analysis of Droplet Impact on Non-flat Surfaces Using SPH for Thermal Spray Applications

Abstract In surface treatment methods, thermal spray is one of the promising technologies to enhance material functionality and life. This study presents a numerical investigation of molten droplet impact on engineered substrates using the smoothed particle hydrodynamics (SPH) method on splat morphology. Aluminum substrates incorporating two cubic extensions and machine lines were examined. Experimental observations of alumina droplet impact were used to validate the SPH model, demonstrating the model’s capability to reproduce spreading, flow of molten material along or across the grooves, pore formation, and solidification. Simulations were extended to yttria-stabilized zirconia (YSZ) droplets to assess the role of thermophysical properties, including low thermal conductivity and high melting point, on the splat morphology. Results from the simulations show that YSZ droplets exhibit longer molten lifetime, deeper penetration into the valleys, and a complex lateral flow pattern that induces interfacial pores, particularly in denser configurations. Comparative analysis between alumina and YSZ highlights the coupled effects of surface patterns and material thermal behavior on spreading dynamics. These findings provide new insights into tailoring the substrate design and material selection to control splat morphology in additive manufacturing technologies based on different application conditions.