Process Stability and Material Properties of TC4 Alloy Welded by Bypass Current Hot Wire Plasma Arc Welding (BC-PAW)

To improve welding efficiency, bypass current hot wire plasma arc welding (BC-PAW) was employed to weld Ti-6Al-4V alloy. The influence of process variables on metal transfer behaviour was explored using high-speed camera, and the material properties were investigated by means of different microscopes and mechanical test. The result shows that the weld seam has a good surface finish without welding defects. The main current, bypass current, and wire feeding speed have a significant influence on the metal transfer behaviour, which further influence the grains’ formation in the weld zone. The microstructure of the weld mainly comprises α martensite and the average tensile strength (UTS) of the as-received joint is 986 MPa, which is larger than that obtained using the conventional PAW method. The fracture occurs in the heat-affected zone (HAZ), which shows a typical ductile fracture surface.