Plasma rotating electrode process is a method for manufacturing spherical powders with minimal internal pores. The method uses a plasma arc to melt the end surface of a disk-shaped electrode, which then produces the molten metal droplets that form the particles.
Unlike traditional gas atomization, the plasma rotating electrode process provides higher yield of fine powder particles. In addition, the process is suited for the production of titanium alloy powders. It has been developed in response to high gas consumption per unit weight of atomized powder. However, there is little research on granulation behavior of the powder in this process. This study aims to address this issue by investigating the effect of the morphology of the electrode end surface on the granulation mechanism of the molten droplets.
To investigate the granulation mechanism of the molten metal, numerical modeling of computational thermo-fluid dynamics (CtFD) was performed. The simulation results indicate that the shape of the electrode end surface can be a critical factor in the granulation process. Specifically, the shape of the electrode rim and its depth can change the fluid dynamic behavior during centrifugal granulation.
In order to investigate the effects of the morphology of the electrode end surfaces, simulations were carried out under different operating conditions. These include different gas flow rates and a gas blast around the electrode. Moreover, the impact of varying the plasma arc current on the granulation process was also examined.
When the plasma arc current was decreased, the mean powder size decreased. Furthermore, the diameter of the corresponding PSD was enlarged. Increasing the gas flow rate, the spatial density of the fluid strips increased.