Critical Analysis into Mechanical Properties and Microstructure of Dissimilar Welded Joint Between Stainless Steel-304 and Inconel-718

The present work analyses the mechanical properties and microstructural changes in similar and dissimilar joints between stainless steel (SS-304 grade) and Inconel (IN-718 grade) plates. The joints were made by metal inert gas welding. Both SS and IN include γ matrix surrounded by δ ferrite as a black boundary. Also, they possess metal carbide distribution through the metal matrix, providing hardness and resistance against machining. In this work, two mechanical properties such as tensile strength and hardness have been compared among similar and dissimilar joints. The SS–SS welded plate imparts twins, equiaxed γ-grains, and δ strings at the base metal zone. The appearance of ferrite has got thicker at the heat-affected zone (HAZ) and it is like a lathy appearance at welded zone (WZ). The appearance of ferrite at the HAZ of the Inconel plate is lathy whereas it is dendritic at WZ. In dissimilar joints, both combinations have been observed. The SS–IN welded joint has shown a good tensile strength and hardness combination. Its ultimate tensile strength is 14% higher and 13% lower than SS–SS and IN–IN joints respectively. The hardness of the SS–IN joint is comparable to the SS–SS plate but remarkably lower than the IN–IN joint.