Welding torch with coaxial wire feed and rotating electrode for wire-arc directed energy deposition

In wire-arc directed energy deposition (DED), tungsten inert gas (TIG) welding/gas tungsten arc welding (GTAW), which offers high flexibility in deposition conditions and less spatter, are used as primary welding processes. However, in additive manufacturing of complex shapes with TIG welding, it is difficult to achieve uniform and stable fabrication because the wire is fed from a fixed lateral direction to the centered arc heat source. To overcome this problem, a novel rotary TIG torch was developed in this study. The wire was fed from the center of the torch, and the tilted electrode or arc heat source rotated around the wire during deposition, allowing the deposition process to be omnidirectional. In the experiment, the basic characteristics and process window of the rotary TIG were investigated, and single-layer and multilayer depositions were performed with changing torch travel directions to evaluate deposition accuracy and flexibility. In conventional TIG, particularly under the condition of low heat input per material input, the deposited bead position and shape were changed depending on the travel direction, and in multilayer deposition, up to 1 mm deviation of the deposition position was observed. In contrast, in the rotary TIG, beads were deposited uniformly regardless of the travel direction and deposition conditions, and in multilayer deposition, straight walls were obtained, and the deviation in the deposition position was small. The results suggest that the application of the rotary TIG torch to wire-arc DED can achieve highly accurate fabrication with higher flexibility in building conditions.