Effect of Delta Current Frequency (DCF) on Microstructure and Tensile properties of Gas Tungsten Constricted Arc (GTCA) welded Inconel 718 Alloy Joints

Inconel 718 is a nickel-based superalloy mostly used in high temperature applications in aerospace sector due to its extensive mechanical properties and weldability . Gas T ungsten Arc Welding (GT AW) process is widely used for joining of Inconel 718 alloy for cleaner , precise and high-quality welds. However , due to the high heat input and wider arc associated with this process, it is having certain metallurgical problems in welding, such as coarse dendritic structure and segregation of alloying elements in weld metal region which significantly reduces the mechanical properties of the joints. T o overcome these limitations, a newly developed Gas T ungsten Constricted Arc Welding (GTCAW) process is employed to join Inconel 718 alloy . It is the advanced configuration of GTAW process, based on magnetic arc constriction induced by high frequency pulsing of the current known as Delta Current. The main objective of this investigation is to study the effect of Delta Current Frequency (DCF) on the weldability of Inconel 718 alloy for its viability in aerospace applications. The joints welded at 4 kHz showed superior tensile properties due to the refinement of grains in fusion zone. Increase in DCF results in decrease in tensile properties of the joints due to the coarsening of dendritic fusion zone microstructure. It is attributed to the stacking of heat input during welding.