Assessment of Microstructure and Tensile Behavior of Hot Wire Gas Tungsten Arc Welded Pure Nickel Tubes

The interest in hot wire gas tungsten arc welding (HWGTAW) process is increasing in industrial sector in the current decade. Pure nickel (Ni 200) tubes having 4-mm-thickness and 44-mm-outer diameter were effectively joined by HWGTAW. The heating current of the filler wire was varied from 80 amps to 120 amps in steps of 10 amps. The joint microstructure was recorded using conventional optical microscope and advanced transmission electron microscope. Electron backscatter diffraction was applied to visualize the grain structure and orientation. The increase in heating current enlarged the fusion zone geometry and caused coarsening of grains. There were no cracks or pores present in the joints. Three kinds of microstructure zones were observed across the joints. Few dislocations were formed in the fusion zone which recorded the lowest hardness. All joints demonstrated excellent ductility. The joint fabricated using a heating current of 100 amps showed highest tensile strength.