20. Finite Element Modelling and Experimental Verification of Dissimilar Joining Between Inconel 718 and SS 316L by Micro-plasma Arc Welding

In the present research work, an attempt is made to successfully weld Inconel 718, a nickel-based superalloy with SS 316L, an austenitic stainless steel in autogenous mode by using constant current micro-plasma welding process. A finite element method (FEM)-based, three-dimensional (3D) thermal model is developed for butt welding configuration between the selected bimetallic combinations by using a double-ellipsoidal volumetric heat source model. A good consistency is found between the numerically obtained and experimentally obtained weld bead measurements. The numerical model is further used to extract peak temperatures, time–temperature profiles along with average cooling rates of the welding processes. Obtained cooling rates are correlated with the weld micro-structures and mechanical properties. Micro-structural study by SEM analysis has shown coarse columnar dendritic structure in the weld interior for the higher heat input welding case, whereas lower heat input during welding leads to fine weld micro-structure due to high cooling rate. An improvement in the tensile strength and hardness value is observed with increase in weld cooling rate and low heat input during the joining process.