Metal-based Directed Energy Deposition (DED) is considered one of the variations of additive manufacturing with the highest potential, particularly for space industry and in-orbital manufacturing. The technology however still faces various challenges, many of which can be traced back to poor control and understanding of the powder delivery. Velocity distribution of powder particles at the DED nozzle outlet has a key influence on the results of any predictive model of powder stream and yet remains largely disputed. Certain numerical studies highlighted a possible influence of powder particle size on the velocity condition at the nozzle exit, yet no experimental studies confirmed this effect. The experimental campaign described in this paper quantifies this relation between powder particle size and velocity distribution at the nozzle outlet. A strong decrease of particle speed with particle size is indeed observed. Moreover, smaller particles are observed to travel at speeds higher than the mean carrier gas speed suggesting powder particle segregation within the nozzle as one of the mechanisms driving speed differences at the nozzle outlet. • Powder particle velocities near DED nozzle outlet are analysed against particle sizes. • A strong decrease in powder particle speed and increase is observed with increasing particle size. • Smaller powder particles move faster than the mean carrier gas speed due to their segregation within the nozzle.
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Mede et al. (2025) studied this question.
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