Investigation on spheroidization of refractory tungsten powders by laminar DC plasma torch

Abstract The spherical tungsten powders were prepared by a low-power DC laminar plasma torch. At discharge current of 50 A, the powder fed downstream cannot be spheroidized using Ar discharge, while small number particles can observed with upstream feeding. When N 2 is added to working gas, input power increased maintain same current, which leads increase jet length, thereby expanding effective high temperature region. Optical emission spectroscopy measurements show that electron excitation -Ar mixed higher than argon discharge. In addition, compared plasma, gas has larger thermal conductivity due molecular dissociation. Therefore, heat more efficiently transferred from particles. improvement and transfer characteristics introducing nitrogen into contributes spheroidization rate. EDS analysis shows oxygen content in decreases after spheroidization, caused evaporation oxide during treatment.