NumericalStudybyFluid–StructureInteractionoftheSpreadingandSolidification ofaParticleonaSubstrateduringtheFormationofaCeramicorMetallicLamella

Abstract

Achieving high-performance coatings requires advanced surface treatment techniques capable of precisely controlling material properties and deposition behavior. Among these, thermal spray and cold spray processes. In this thesis, both techniques are investigated through numerical simulations to better understand the spreading, solidification, and bonding mechanisms that govern the formation of ceramic and metallic lamellae. In the thermal spray process, molten droplets at high temperature impact a solid substrate to produce a cohesive coating. While cold spray technology relies on the impact of high-velocity solid particles, where bonding occurs through plastic deformation without melting the material. A fluid– structure interaction (FSI) model was developed to simulate the spreading and solidification behavior of a molten or semi-molten particle impacting a solid substrate. The model accounts for the coupled fluid dynamics, solid response, and heat transfer between the droplet and the substrate, and investigates the influence of impact parameters such as multiple-droplet impacts, initial droplet velocity, the presence of a solid core, and substrate oxidation on the final lamella morphology. Subsequently, the solid-state particle deposition process in cold spray technology was simulated using a three-dimensional model based on the Coupled Eulerian–Lagrangian (CEL) approach. The effects of particle velocity, material properties, and thermal conditionson thedepositionand bondingmechanisms were thenanalyzed. Akey finding of this research is that the high kinetic energy of thermally sprayed droplets is closely associated with an increased spreading rate, which facilitates the formation of flat and uniform splats. Within the cold spray process, high kinetic energy primarily induces severe plastic deformation, thereby enhancing particle/substrate bonding strength. Additionally, the models used in the current study were corroborated through numerical and experimental analysesconductedunderthesameconditions