Effect of heat input on the mechanical and metallurgical aspects of double-pulse MIG welded IN 617

In this article, an attempt is made to analyze the influence of heat input in double-pulse metal inert gas (DP MIG) welding of Inconel 617 (IN 617). IN 617 plates were joined in the butt joint configuration with 1.2 mm diameter IN 617 filler wire. Three welding trials were conducted at different heat input, viz. 31.3, 37.1, and 41.5 J/mm. Weld quality was assessed using bead geometry, tensile strength, toughness, and hardness. The changes in mechanical properties were discussed using the optical microscope, scanning electron microscope with energy dispersion spectroscopy, and backscattered energy diffraction. Substantial changes were observed in the weld tensile strength for a small variation in heat input. Molybdenum segregation was observed in all the weld samples. At lower heat input, the tensile test was reduced by 31.62% compared with base metal. Similarly, for the medium and high heat input, the tensile strength was reduced by 25.13% and 49.59%, respectively. Weld had lower toughness compared with the base metal and no significant variation was observed in toughness to changes in heat input. Hardness of the weld at all three heat inputs was almost similar to base metal. Liquation cracks were seen in the partially melted zone. At higher heat input, the lack of sidewall fusion was observed along with liquation crack.