Characterization of Mechanical Behavior in Solution-Treated Micro Plasma Arc Welded Blanks of Inconel 625

Abstract

This investigation aims to comprehensively understand the mechanical properties and deformation response of Inconel 625 micro plasma arc welded blanks (MPAWB) of 0.5 mm sheets, with specific attention to their formability. The welded blanks are solution heat treated at 1100 ºC with holding time of 1 h for potential alterations in their forming behavior. The joint metallurgy of various zones, including the fusion zone (FZ), is assessed through advanced techniques such as FESEM, TEM and XRD analysis. A micro hardness, uniaxial tensile and limiting dome height tests (LDH) have been carried out to evaluate the mechanical properties of MPAWB and solution treated welded blank (STWB). The analysis reveals that the FZ of the MPAWB predominantly comprises of nickel γ-matrix along with diverse dendritic structures, alongside some secondary phases like Laves phase, NbC, and TiC. After the ST, the dendritic structures in the FZ of MPAWB melt and recrystallize, creating a more uniform microstructure. The dissolution of secondary phases in the STWB leads to a reduction in dislocation density compared to the MPAWB. Furthermore, the hardness of STWB decreases from 269 ± 9 HV to 252 ± 6.75 HV, and a notable increase in elongation by 12.4%, compared to the MPAWB. A significant improvement in the LDH is observed for STWB, with a value of 14.89 mm, compared to 13.7 mm for the MPAWB. The forming limit diagrams of IN 625, MPAWB and STWB exhibit similar strain and thickness distributions along the uniaxial-to-biaxial strain path. Notably, symmetric strain and thickness distribution are detected on both sides of the pole for all the cases.

Graphical Abstract