Characterization of microstructure and mechanical properties of Super Ni 718 alloy and AISI 316L dissimilar weldments

The present investigation addressed the weldability of Super Ni 718 alloy and AISI 316L using gas tungsten arc (GTA) welding process using three different filler wires, such as ER2594, ERNiCrMo-4 and ERNiCrCoMo-1. Interface microstructures showed the formation of secondary phases at the heat-affected zone (HAZ) of Super Ni 718 alloy and delta ferrite colonies at the HAZ of AISI 316L. It was witnessed from the weld microstructures that the deleterious phases were suppressed or controlled while using these filler wires for joining the bimetals. Tensile results corroborated that the failure occurred at the parent metal of AISI 316L in all the cases. The presence of microvoids and dimples characterized for the ductile mode of fracture in these weldments. Charpy V-notch test results showed that the weldments using ERNiCrMo-4 filler exhibited higher impact energy. A detailed study has been made to investigate the structure-property relationships of these weldments using optical and scanning electron microscopic techniques.