HIGH-SPEED VIDEO IMAGE ANALYSIS OF LIQUID METAL ATOMIZATION PROCESS

Gas-assisted atomization is used to produce metal powders for additive manufacturing. In these systems the primary atomization governs the powder size distribution, but it is experimentally challenging to investigate. In this study, the primary atomization of a molten metal spray was monitored with a calibrated high-speed camera and digital image processing. The technique enabled the generation of spatio-temporal maps at different distances from the nozzle. Among the characteristics of the spray, mean values and standard deviation of the spray width along the spraying direction, and the frequency of the oscillation of the spray boundaries are presented. Statistically relevant spray asymmetries were identified, which can be caused by faulty spray operation in form of a localized metal solidification at the pouring nozzle. By systematically varying the gas temperature and the gas atomization pressure, it is shown that heating of the gas up to 573 K stabilizes the spraying process and enhances the liquid dispersion in the recirculation zone.