Arc behavior and droplet transfer characteristics in double-electrode arc-directed energy deposition

Achieving higher productivity while maintaining lower remelting of as-built layers is a key goal in arc-directed energy deposition (arc-DED). This study proposes a novel variant of arc-DED named double-electrode arc-DED, where a branch wire is sent into the arc to separate partial currents from the arc and establish a branch arc. This study aims to reveal arc and droplet transfer characteristics in double-electrode arc-DED. The novelty is how the branch wire feed speed (WFS) influences the arc and droplet transfer behaviors in three primary droplet transfer modes, i.e., short-circuit, globular, and spray. Moreover, the microstructure and hardness are compared with conventional GMA-DED by building thin walls. As the branch WFS increases, the branch arc burns more stably, both arcs’ current-voltage distributions are more concentrated when the branch arc is stable, the branch current increases as long as the branch wire tip does not contact the melt pool, the primary droplet's transfer frequency presents little change, and the branch droplet's transfer frequency increases. In globular and spray transfer modes, the primary droplet's transfer path points towards the melt pool tail due to the branch arc force's repulsive action. Forming quality and microstructure differ little in conventional GMA-DED and double-electrode arc-DED. This study provides valuable insights into the dynamic behaviors in double-electrode arc-DED, enhancing the understanding and engineering application of the novel technique.