Maximizing strength and corrosion resistance of InterPulsed TIG welded Superalloy 718 joints by RSM for aerospace applications

Abstract

Inconel 718 (IN-718) is a nickel-based alloy, mostly used in the aeroengine applications due to its good mechanical strength and resistance to corrosion. However, it is amenable to alloying segregation and Laves phase growth in fusion zone (FZ) which severely deteriorates the strength and corrosion resistance of IN-718 joints. To overcome this problem, InterPulsed TIG (IP-TIG) welding process, characterized by high frequency current pulsation and arc constriction, was attempted to join thin sheets of IN-718 alloy. The 3D graphs of response surfaces were built to establish the optimized welding parameters for maximizing the joint strength. The parametric mathematical equation was constructed to predict the strength of IN-718 joints. The mathematical equation was also built to predict the tensile strength from Laves phase. The potentiodynamic corrosion test was done in a 3.56 wt.% NaCl solution for the selected joints to determine the corrosion behavior of IN-718 joints. The IP-TIG welded IN-718 joints exhibited 99.20% of base metal strength and superior corrosion resistance at optimized condition of welding parameters. This refers to the refining of FZ dendritic structure which aids in minimizing the Laves phase. The IN-718 joints developed using optimized IP-TIG parameters exhibited 22–32% higher strength and superior corrosion resistance than TIG welded IN-718 joints and comparable to EBW and LBW IN-718 joints.