Modeling and analysis of the plasma primary atomization for controllable preparation of high-quality spherical metal powders

Plasma primary atomization (PPA) is a unique and critical process in the plasma atomization (PA), which is a highly recognized materials processing technology for producing high-quality spherical powder, but there lacks of in-depth understanding and models on how the metal wire is converted into high-quality spherical metal powders. Therefore, experimental observations and theoretical analysis on the PPA process were carried out to reveal the behavior of molten metal for controllable preparation of the metal powders. Firstly, the typical stages in the PPA were firstly revealed by experimental observations. Secondly, heat and mass transfer models on PPA were established to reveal how the molten metal is generated and transferred on the wire surface. Thirdly, the behavior of the molten metal in PPA was phenomenologically modeled and quantitatively analyzed based on the experimental observations and the proposed models. As such behavior determines the average size and yield of the produced powders, two key influencing parameters were identified to quantitatively reflect the melting and transfer behavior of the molten metal respectively. Then, calculation equations for them were established based on the proposed models of PPA and then verified. With the proposed models of PPA and the established calculation equations of the key influencing parameters, the quality of the produced powders may be quantitatively controlled by optimal design of the plasma torch and selection of the processing parameters of PA.