Analyzing the Influence of Microstructure on the Mechanical Properties of Mig Welded Similar and Dissimilar Joints Between AISI-304 and Inconel 718 Plates

In this work, the microstructure and mechanical properties were analyzed in the similar and dissimilar welded joints of SS-304 (SS) and Inconel 718 (IN) plates. The welded joints between SS-SS, IN-IN, and SS-IN were made through metal inert gas welding by using identical values of current and voltage. The welded plates were tested for tensile strength, toughness, and hardness. Also, the microstructural changes from base metal (BM) to welded zone (WZ) were analyzed by using light optical microscopy. The fracture behavior of broken samples from the tensile test and toughness test was analyzed through a field emission scanning electron microscope (FESEM). The welded zone in all three joints possesses the austenitic (γ) phase with solidified boundaries. The orientation of δ-ferrite was cellular and dendritic in appearance. The HAZ has mainly a large accumulation of ferrite which is responsible for its higher hardness than BM. The yield strength and elongation of the SS-IN welded joint were found 35 and 49%, respectively, higher than the same of the SS-SS joint. In comparison with the IN-IN joint, the strength of the dissimilar joint was found 4% less than the IN-IN joint with a significant improvement of elongation before failure. Under the toughness test, the SS-SS joint showed high ductility. It has been completely deformed but not fractured. IN-IN joint had failed through the welded joint, whereas SS-IN joint was weak at HAZ. The fractured part of dissimilar joint exhibited dimples with a small number of facets as proof of some brittleness. The hardness pattern in each plate was: hardness at BM < hardness at HAZ < hardness at WZ. The hardness at WZ of the SS-IN plate was found lower than that of SS-SS and IN-IN joints.