Influence of welding current on the microstructure, mechanical properties, residual stresses, and nano-mechanical behavior of tungsten inert gas-welded dissimilar joints of Inconel 625 and Incoloy 800

Abstract

In the present work, Inconel 625 and Incoloy 800 thin sheets were TIG-welded without using fillers and at three different welding currents (40 A, 50 A, and 60 A). The influence of variation in welding currents on various characteristics of the weldments was investigated using various characterization techniques. Weldments obtained at 60 A showed the highest tensile strength and plastic deformation due to the formation of cellular dendritic microstructure in the fusion zone. Observation of the fractured surfaces revealed ductile nature for all the weldments. In addition, impact tests were performed at 25°C, 150°C, and 250°C, and the results indicated that with the rise in temperature, impact toughness decreased due to coarsening of carbides at grain boundaries in all the weldments. Furthermore, impact properties and hardness of weldments were also affected owing to the differences in interdendritic spacing and grain size. Weldments obtained at 40 A depicted higher nanohardness, whereas 50 A weldment showed relatively greater pileup height as compared to other weldments. Moreover, 60 A weldments showed highest longitudinal and transverse residual stresses due to relatively higher volumetric changes.