New design of conduit plasma atomization for fabricating spherical metal powder and its optimization using design of experiments method

Abstract

This research presents a new design of plasma atomization conducted using a graphite plasma conduit to assure prolonged interaction between molten metal and hot plasma jets. The conduit plasma atomization technique implies using a heat-collecting duct to minimize the transfer of heat energy from the plasma arc into the surrounding environment. The interaction between the molten metal and plasma arc jet is more extended. Therefore, the surface tension force of molten metal may be sufficient to form completely spherical particles, thereby eliminating satellites. The scanning electron microscopy (SEM) shows powder particles without satellites after conduit plasma atomization. This research has a strategic role in getting fundamental data for improving the efficiency of the conduit plasma atomization. A statistically designed experimental approach was followed to study the current and pressure parameter variations during newly designed conduit plasma atomization for determining median particle size distribution (D₁₀, D₅₀, and D₉₀). Spherical Ti-based alloy metal powder without satellites was successfully fabricated by conduit plasma atomization with an electric current of 40 and 45 A and at gas pressures of 1.5 and 2.5 bar, using a constant feed of 2 mm³/sec. The results showed that optimization is the best parameter for the minimum particle size distribution in metal powders. After optimization, the minimum values resulting from particle size distribution D₁₀, D₅₀, and D₉₀ are 71, 325, and 534 µm. The required value can be achieved by combining the current and pressure parameters of 45 A and 2.5 bar, accordingly. The regression equation can be used as a reference for operating conduit plasma atomization to obtain the required particle size distribution.