Effect of hot wire feed rate on microstructural evolution and mechanical strength of pure nickel tubes joined using gas tungsten arc welding

Industries increasingly pay attention to hot wire assisted gas tungsten arc welding (HWGTAW) in the present decade for joining several materials. Limited works were reported on HWGTAW of nickel and its alloys. In this investigation, HWGTAW was applied to weld pure nickel tubes (Ni 200 grade) having a thickness of 4 mm and an outer diameter of 44 mm. Joints were fabricated by varying the wire feed rate (1100-2400 mm/min in the interval of 300 mm/min). The increment in the wire feed rate increased the quantity of deposited material causing the geometry of the fusion zone to enlarge. Increasing the feed rate of filler wire reduced the peak temperature and avoided further coarsening of grains. The joints were cracks free and no significant percentage of porosity was detected. Traces of dislocations were found inside the fusion zone. Microstructure variation across the joints was categorized into three distinct zones similar to conventional GTAW. The hardness of the fusion zone was recorded to be the lowest. The ductility of the joints was exceptionally high.