Welding between confinements as a new approach for high deposition rate additive manufacturing with laser-assisted double wire welding with nontransferred arc

Laser-assisted double wire welding with nontransferred arc uses an electric arc to melt two welding wires fed toward each other. The molten material drips onto the substrate, where it is joined to the substrate without undercuts by means of oscillated laser radiation. The process offers possibility of creating structures with high deposition rates (8.4 kg/h), but faces challenges in fulfilling the requirements for surface properties and geometric accuracy. One approach to meet the requirements is to confine the final seam geometry by applying the melt into a mold. Such a confinement can be a wall previously applied by a process with higher geometric accuracy. An investigation of this approach was carried out by studying the deposition of mild steel weld beads within two confining structures, in this case, a groove. A particular interest in the evaluation is connection of the weld bead to the base material in the corners, the bottom surface, and the side surface of the groove. In the first step, weld beads are deposited in 12 mm wide grooves in a mild steel substrate with variable laser beam oscillation amplitudes of 10–13 mm. In the second step, several layers are deposited with variable welding speeds. The oscillation amplitude that generates the best connection in the corners is 13 mm. Bonding on the bottom and side surfaces could be achieved with all parameter sets. When applying several layers, the best lateral connection in the groove was produced with a welding speed of 200 mm/min.