Abstract
ABSTRACT Inconel 718 possesses issues like microsegregation of Nb, Mo leads to the formation of Laves phase which degrades the mechanical properties of the welded joints. This study aims to investigate the mechanical properties and microstructural characteristics of Inconel 718 welded joints using the double pulse metal inert gas (DP-MIG) process by the combined effect of filler wires, such as ERNiFeCr-2, ERNiCrCoMo-1, and 9Cr-1Mo. All the weldments were found to have columnar dendrites with coarser grain morphology. Liquated grain boundaries, secondary phases, unmixed zones at the heat affected zone (HAZ) and segregation of Nb (21.3%) and Mo (10.4%) at the weld zone were identified for ERNiFeCr-2 and ERNiCrCoMo-1 fillers. From EBSD findings, the formation of peninsula and island at the HAZ and segregation of Fe (68%) in the weld zone of 9Cr-1Mo filler weldment was noticed. Even though the ultimate tensile strength (UTS) of all the weldments was found to be inferior to that of base metal (788.9MPa), the 9Cr-1Mo filler weldment shows better tensile strength of 403.5MPa with a joint efficiency of (51.14%). From the fractography results, the void formation due to secondary phases along with dimple networks ensures the ductility mode of fracture for all the weldments.
Published Version
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