Optimization of GMAW process parameters for weld overlay of Inconel 686 superalloy on low-carbon steel

Abstract

Weld overlays of Ni-based superalloys provide high-temperature corrosion, oxidation, and wear resistance for industrial applications. The objective of this study was to evaluate the microstructure of Ni–Cr-Mo superalloy Inconel 686 overlays fabricated using automatic gas metal arc welding (GMAW) with three different levels of voltage, travel speed, and wire feed speed. The variation of these parameters and their effects on the weld quality, dilution, and microsegregation were analyzed. The weld surface quality was assessed by visual examination. The weld dilution was measured by both geometric and chemical composition definitions. The maximum dilution was measured at 13.63%, induced by the highest weld heat input (5.97 kJ cm⁻¹) and lowest wire feed speed (6 m min⁻¹). The overlay dilution and the heat-affected zone (HAZ) size decreased by increasing the wire feed speed. However, increasing the wire feed speed and the heat input reduced the weld quality and even resulted in noncomplete joints. Microsegregation of elements was evaluated using energy-dispersive X-ray spectroscopy (EDS) analysis and it was found that microsegregation of Mo and Cr and the volume fraction of secondary phases in the interdendritic areas increased with increasing the weld heat input. According to the visual examination results and macro- and microscopic evaluation, the weld overlay parameters were found to be optimized for the mid-level heat inputs (4–5 kJ cm⁻¹) and wire feed speeds between 6 and 8 m min⁻¹.