Investigation on stability of weld morphology, microstructure of processed zones, and weld quality assessment for hot wire gas tungsten arc welding of electrolytic tough pitch copper

In the present investigation, stability of weld morphology was investigated in case of electrolytic tough pitch copper (12 mm thickness) processed by Hot Wire Gas Tungsten Arc Welding (HW GTAW) using CuNi filler wire with variations of processing conditions, using different combination of hot wire's parameters such as feed rate and current. The assessment of weld bead geometry was performed using visual examination (during and after welding), and macrographic dimensional measurements of weld bead geometry such as depth of penetration and depth to width ratio. In addition to the stability of weld bead geometries, microstructural variations and weld quality assessments were studied using optical microscopy, scanning electron microscopy, energy dispersive x-ray spectroscopy, and micro-hardness measurements in case of processed sample observed with most uniform weld bead geometry. The results revealed that minimum dimensional variations of weld bead geometry throughout the processed length was obtained with 5.42 mm bead width, 1.2 mm bead height, 1.8 mm penetration, and 0.36 depth to width ratio when hot wire's parameters were 0.6 m/min wire feed rate and 90 amps hot wire current. The bridging mode of metal transfer helps to receive more stable weld bead geometry with minimum dimensional variations. Ni filler wire of HW GTAW improves the hardness in the Heat affected zone (70 HV0.3) and weld zone (80 HV0.3), which were 33% and 17% higher of base material. The weld zone was consisting of mixed mode of grains such as dendrites just above the fusion line and cellular grains further above dendrites in case of processed sample of minimum dimensional variations of weld bead geometry throughout the processed length.