Investigation of thermal and fluid dynamics behaviors of melt pool during laser direct metal deposition on inclined substrates

The laser direct metal deposition (DMD) technique offers an efficient solution for repairing and manufacturing structures with variable curvatures, such as impeller blades. However, how the non-vertical laser irradiation on curved surfaces impacts the thermal and fluid dynamics of the melt pool still remains unclear. In the current research, a high-fidelity multi-physics numerical model is developed to explore the mechanisms of melt pool development and the effects of inclined angle and laser spot diameter on morphological evolution of deposition layers during DMD under non-vertical irradiation on inclined substrates. Results indicate that as the inclination angle increases, deposited track fluctuations become evident, with a critical angle from 40 degrees to 42.5 degrees identified for hump formation. A smaller laser spot diameter increases the likelihood of humps and irregularities, while a larger spot diameter expands the deposition layer and enhances melt pool wettability. This study is expected to provide significant theoretical guidance for selecting and applying process parameters for the fabrication of curved structures by DMD.