Plasma spheroidization process of refractory metal powders

摘要

Because of the need to use spherical powders in many powder metallurgy technologies an investigation was carried out into spheroidization process of the powders of tungsten, molybdenum and rhenium obtained by plasma spraying technique. An effect of electrical parameters of the plasma arc (current, voltage), powder morphology, grain size and feeding rate, as well as of plasma stream temperature on powder spheroidization process was investigated. In the paper results of morphology examination and of the analysis of powder particles size distribution for the studied metals have been presented in dependence on starting powder characteristics and on atomization process parameters. Optimal process parameters ensuring maximum yield of spherical powder fraction were chosen for each studied metal. Taking tungsten as an example it was demonstrated that the plasma spraying technique leads to the increase in metal's chemical purity.