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<p>Double-pulse metal inert gas (DP-MIG) welding was successfully employed to join Inconel 718 superalloy. The wire feed rate (WFR), delta wire feed rate (DWFR), and thermal pulse frequency (TF) were maintained constant throughout the welding process, while the duty cycle (DC) was systematically varied. Microstructural characterization was performed using optical microscopy and high-resolution scanning electron microscopy (HR-SEM). Elemental distribution and the evolution of strengthening and deleterious phases were analyzed using energy-dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD). The results indicate that increasing the DC promotes the formation of secondary phases at the weld interface, accompanied by enhanced Nb segregation and increased Laves phase precipitation within the fusion zone. In comparison with the Inconel 718 base metal, the secondary dendrite arm spacing (SDAS) and Laves phase size increased by 97.3% and 69.5%, respectively, while the cooling rate decreased by 81.7%. Mechanical characterization revealed a reduction in ultimate tensile strength (UTS) relative to the base metal, primarily attributed to NbC and Laves phase formation. Among the investigated conditions, a DC range of 40–60% resulted in comparatively lower Nb segregation (2.58%) and a reduced Laves phase size (~ 3.2&#xa0;μm), leading to an improved UTS of 462&#xa0;MPa compared with other welded conditions. These findings demonstrate that optimization of duty cycle plays a critical role in controlling micro segregation, secondary phase evolution, and mechanical performance in DP-MIG welded Inconel 718.</p>

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Duty cycle-driven microsegregation control and mechanical performance optimization in double-pulse MIG welded Inconel 718 superalloy

  • 期刊论文

  • 发表日期：

    2026年7月19日

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  • M. Shantharaj,
  • Rajasekaran Thangaraju,
  • Chandan Pandey

摘要

Double-pulse metal inert gas (DP-MIG) welding was successfully employed to join Inconel 718 superalloy. The wire feed rate (WFR), delta wire feed rate (DWFR), and thermal pulse frequency (TF) were maintained constant throughout the welding process, while the duty cycle (DC) was systematically varied. Microstructural characterization was performed using optical microscopy and high-resolution scanning electron microscopy (HR-SEM). Elemental distribution and the evolution of strengthening and deleterious phases were analyzed using energy-dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD). The results indicate that increasing the DC promotes the formation of secondary phases at the weld interface, accompanied by enhanced Nb segregation and increased Laves phase precipitation within the fusion zone. In comparison with the Inconel 718 base metal, the secondary dendrite arm spacing (SDAS) and Laves phase size increased by 97.3% and 69.5%, respectively, while the cooling rate decreased by 81.7%. Mechanical characterization revealed a reduction in ultimate tensile strength (UTS) relative to the base metal, primarily attributed to NbC and Laves phase formation. Among the investigated conditions, a DC range of 40–60% resulted in comparatively lower Nb segregation (2.58%) and a reduced Laves phase size (~ 3.2 μm), leading to an improved UTS of 462 MPa compared with other welded conditions. These findings demonstrate that optimization of duty cycle plays a critical role in controlling micro segregation, secondary phase evolution, and mechanical performance in DP-MIG welded Inconel 718.