Features of the process of formation and dispersion of a liquid layer and formation of powder particles in plasma-arc atomization of current-conducting solid and flux-cored wires

The paper gives the results of mathematical modeling and experimental studies of the processes of formation and fragmentation of the liquid layer and formation of powder particles in plasma-arc atomization of current-conducting solid stainless steel AISI 316L wire and flux-cored Fe-Al wire.Mathematical modeling showed that initial fragments of size d 0 = 670-780 m form at plasma-arc atomization of the above-mentioned wires, where after their separation from the tip of the atomized wire their multiple disintegration in the plasma jet takes place, which ends at the distance of ~ 120 mm with formation of fine spherical fragments (powders) with the average diameter of 105-125 m.Experimental studies on determination of the initial size of the drops, forming at metal drop separation from the liquid layer, using high-speed filming, showed that their size is d 0 = 720-815 m, and size of atomization products (powder) determined using the sieve analysis method are equal to 119-142 m.Comparison of the obtained experimental and calculated data showed that that for atomization of both the solid stainless steel AISI 316L wire and flux-cored wire of Fe-Al system the main fraction of powder particles is 1-300 m, which makes up 96-99 wt.% in both the cases, the error between the theoretical and experimental data being not higher than 7-32 %, depending on powder fraction, allowing application of the mentioned mathematical complex model to determine the optimal modes of plasma-arc atomization process with a wide range of wire materials.The study of the shape parameters and structure of AISI 316L and Fe-Al powders showed that most of the particles have a regular spherical shape with a sphericity coefficient close to 0.8-0.9, the microstructure of which is characterized by the absence of pores and voids.