Weld Strength and Microstructure Analysis on Resistance Spot Welding of Austenitic AISI 347 Stainless Steel and Duplex AISI 2205 Stainless Steel

In this research, the effect of welding current and heating cycle is studied against the weld strength. The AISI 347 and AISI 2205 of 2 mm thickness are taken for conducting the experiment. The squeezing time cycle, holding time cycle and electrode tip diameter are kept constant. The welded specimens are fractured using a tensile shear load testing facility and a macrograph examination is carried out. The specimen welded with the highest welding current of 8.5 kA and 14 heating cycles obtained the largest weld nugget and absorbed a maximum tensile shear load of 18.5 kN. All the samples except one failed under interfacial mode and sample 9 failed under pull-out failure mode. The scanning electron microscope (SEM) image of the failed nuggets shows a smooth transition from the austenitic to a mixture of austenitic-ferritic phase structures. The SEM-energy-dispersive spectroscopy analysis was carried out on the selected samples for their weld composition. The elemental spectrum shows a Cr-eq/Ni-eq ratio of 2.52 which confirms a ferritic phase formation upon solidification. The fractography results show the formation of dimples and torn bands on the lower and upper surfaces of the fractured nugget revealing the ductile failure of the weld. Maximizing the welding current and heating cycle maximizes the weld nugget area. The specimens which did not attain the minimum weld nugget size failed in the interfacial mode.