Laser directed energy deposition of nickel-based superalloy: A numerical investigation of melt pool morphology and thermal evolution

A three-dimensional powder scale multi-physics model was developed to investigate melt pool morphology and thermal field evolution during laser directed energy deposition (LDED) of GH4163 nickel-based superalloy. The model couples heat transfer and melt pool flow, tracks free surface evolution using the volume of fluid method, and introduces powder mass, momentum and energy through source terms based on Lagrangian particle data. Because suitable quantitative experimental data for LDED of GH4163 were unavailable, the model framework was evaluated against published IN718 single-track experimental data. The relative errors in track height, width and melt depth were 0.4%, 7.6% and 3.8%, respectively. The model was then applied to examine the effects of laser power, scanning speed, powder feed rate and pulse frequency on GH4163 deposition. Under continuous-wave irradiation, increasing laser power enlarges the molten region and promotes lateral spreading and substrate penetration. Increasing scanning speed reduces the energy and powder supplied per unit length, resulting in smaller deposition dimensions. A higher powder feed rate promotes vertical buildup but decreases the energy available per unit mass of supplied powder, thereby limiting powder melting, lateral spreading and substrate fusion. After removal of the heat source, the cooling process comprises rapid liquid cooling (RLC), solidification plateau (SP) and solid-state cooling (SSC). Under pulsed irradiation, increasing the pulse frequency reduces the pulse energy and weakens transient Marangoni convection, producing a narrower and taller track. These results reveal how heat input, powder supply and pulse modulation jointly govern track formation and thermal evolution in LDED of GH4163.