Multi-scale numerical modeling of inductively coupled plasma spheroidization of refractory tungsten powders for additive manufacturing

Abstract

This study presents a multi-step, multi-scale modeling framework to address the complexities of particle spheroidization in inductively coupled plasma (ICP) processing of refractory tungsten powders, a precursor for refractory additive manufacturing. The framework integrates 2D axisymmetric and 3D non-transient multiphysics models to resolve plasma dynamics and turbulent flow fields within the ICP system. Additionally, a transient 3D Discrete Phase Model (DPM) was employed to predict particle flow behavior, heating, vaporization, and mass loss, while a 2D multiphase thermo-fluidic model at the particle scale simulated morphology evolution, including melting, vaporization, and sphericity transformations. The particle morphology evolution was governed by the interplay of surface tension, vaporization-induced recoil pressure, and non-uniform temperature distributions. Surface tension dominated the early melting phase, rapidly stabilizing smaller particles, while larger particles exhibited prolonged oscillations due to significant thermal gradients. Vaporization-induced recoil pressure dominated later stages, inducing localized deformation and altering droplet trajectories, with particles larger than 100 µm showing resistance to vaporization effects. The numerical results matched well with experimental observations, including the bimodal particle size distribution and post-spheroidization particle morphologies. The multi-scale multiphysics framework successfully predicted thermal flow, and morphological transformations providing a physics informed spheroidization pathways offering a robust platform for optimizing ICP-based spheroidization of refractory materials.