Spheroidization of metal and ceramic powders in thermal plasma jet: Comparison between experimental results and theoretical estimation

For smooth and uniform feeding of powders into plasma jet, for thermal spray coating, the powder particles have to be spherical in shape since they have good flow quality. Spheroidization of micron sized metal and ceramic powders to produce flow quality powders using plasma processing is a modern concept. In the present work a theoretical estimation of the percentage of spheroidization of particles has been made from basic fluid dynamic equations. Particles of nickel and alumina of 50–60 μm were considered at different plasma gas flow rates and temperatures (input power). Particles with the same specifications were spheroidized using plasma processing. Optical micrographs showed spherical shape of processed powders. Percentage of spheroidization was measured by irregularity parameter (IP) and roundness (RN) and the same were compared with theoretical estimation. Experimentally a maximum of 87% spheroidization was obtained. Comparatively the maximum difference between theory and experiment is 7% that of the experimental value.