On microstructure and strength properties of microwave welded Inconel 718/ stainless steel (SS-316L)

Microstructure and mechanical properties of microwave welded Inconel 718/ austenitic stainless steel (SS-316L) were investigated in this work. Principles of microwave hybrid heating were effectively applied for joining of Inconel 718/SS-316L using Inconel 718 powder as an interfacing layer between the candidate surfaces. Experiments were carried out in a thermally insulating box placed inside an industrial microwave applicator for a duration of 600 s. The microwave-induced dissimilar welds were characterized using X-ray diffraction, field emission scanning electron microscope, microhardness tester, and universal testing machine. The X-ray diffraction study of the fusion zone showed the presence of various carbides and intermetallics. Microstructural study revealed metallurgical bonding between the two faying surfaces with no sign of interfacial cracking. The elemental analysis of the welded zone confirms dilution of Inconel 718 powder across the joint interface during microwave hybrid heating. The average microhardness on the joint interface was observed to be 230 +/- 5 HV; the average porosity was monitored to be 0.94%. The average ultimate tensile strength of the microwave welds was monitored as 517.5MPa with 18.18% elongation. The fractography study reveals a mixed mode of failure of the joints during tensile testing.