Investigation of mechanical and metallurgical properties of super alloy 59 welded with continuous current and pulsed current gas tungsten arc welding

Abstract

The current research examines the mechanical, metallurgical and newlinecorrosion behaviour of nickel-based Super Alloy 59, a key candidate in newlinepollution control applications. Continuous current and pulsed current Gas newlineTungsten Arc Welding (GTAW) with autogenous mode (without filler wire) newlineand nickel-based filler wires (ERNiCrMo-13 and ERNiCrMO-14) was used to newlineweld Alloy 59 plates. The macrostructure investigation was performed to newlineidentify weld flaws and the weld aspect ratio of the weldments. The newlinemicrostructure of the weldments was analysed with a Scanning Electron newlineMicroscope (SEM) and Optical Microscope (OM). The results exhibited newlinecellular and columnar structures in continuous current GTA weld joints and newlinerefined equiaxed structures in pulse current GTA weld joints. Pulsed current newlineGTA weldments showed a narrow weld bead, a reduced heat-affected zone, newlineand a refined grain structure compared to continuous current GTA weldments. newlineEnergy Dispersive X-ray Spectroscopy (EDS) was used to analyse the newlineelemental segregation of alloying elements at the weld interface (WI) and newlineweld centre (WC). The metallurgical analysis revealed that pulse current GTA newlineweld joints have less elemental segregation at the inter-dendritic zone than newlinecontinuous current GTA weld joints. When transitioning from CCGTA to newlinePCGTA welding, X-Ray Diffraction (XRD) analysis shows an increase in newlinegrain refinement in the autogenous mode and with filler wires (ERNiCrMo-13 newlineand ERNiCrMo-14). Tensile, microhardness and Charpy impact tests were newlineperformed to determine the mechanical properties of the weld joints. PCGTA newlinewelding offers higher tensile strength, toughness, and hardness than CCGTA newlinewelding. Regardless of the type of welding used in the current research, the newlinecorrosion test proved that the weldment of Alloy 59 has good corrosion newlineresistance in the marine environment newline