Microstructural study of keyhole TIG welded nickel-based superalloy G27

Ariaseta, Achmad; Khan, Abdul Khaliq; Andersson, Joel; Ojo, O.A.

doi:10.1016/j.matchar.2023.113178

Cited by 5 publications

(1 citation statement)

References 29 publications

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“…The carbides remain stable, and there are δ-Ni3Nb precipitates at the Laves eutectic and grain boundaries after 750 °C heat exposure, and some of the δ phases "passed" the Laves eutectic, and the eutectic microstructure size decreases due to the dissolution of the C14 Laves phases inside the eutectic. Numerous studies have shown that the Laves eutectic has a high thermal stability [34][35][36]. The Laves eutectic remains at 950 and 1050 °C heat exposure, with significant a coarsening of grains at these two temperatures, as well as carbide dissolution.…”

Section: Microstructure Variations Of Welded Joints After Heat Exposuresmentioning

confidence: 99%

Different Heat-Exposure Temperatures on the Microstructure and Properties of Dissimilar GH4169/IC10 Superalloy Vacuum Electron Beam Welded Joint

Cai,

Ma,

Zhang

et al. 2024

Metals

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Vacuum electron-beam welding (EBW) was used to join the precipitation-strengthened GH4169 superalloy and a new nickel-based superalloy IC10 to fabricate the turbine blade discs. In this study, a solid solution (1050 °C/2 h for GH4169 and 1150 °C/2 h for IC10) and different heat-exposure temperatures (650 °C, 750 °C, 950 °C and 1050 °C/200 h, respectively) were used to study the high-temperature tensile properties and microstructure evolution of welded joints; meanwhile, the formation and evolution of the second phases of the joints were analyzed. After EBW, the welded joint exhibited a typical nail morphology, and the fusion zone (FZ) consisted of columnar and cellular structures. During the solidification process of the molten pool, Mo elements are enriched in the dendrites and inter-dendrites, and that of Nb and Ti elements was enriched in the dendrites, which lead to forming a non-uniform distribution of Laves eutectic and MC carbides in the FZ. The microhardness of the FZ gradually increased during thermal exposure at 650 °C and reached 300–320 HV, and the γ′ and γ″ phases were gradually precipitated with size of about 50 nm. Meanwhile, the microhardness of the FZ decreased to 260–280 HV at 750 °C, and the higher temperature resulted in the coarsening of the γ″ phase (with a final size of about 100 nm) and the formation of the acicular δ-phase. At 950 °C and 1050 °C, the microhardness of FZ decreased sharply, reaching up to 170~190 HV and 160~180 HV, respectively. Moreover, the Laves eutectic and MC carbides are dissolved to a greater extent without the formation of γ″ and δ phases; as a result, the absent of γ″ and δ phases are attributed to the significant improvement of segregation at higher temperatures.

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Section: Microstructure Variations Of Welded Joints After Heat Exposuresmentioning

confidence: 99%

Different Heat-Exposure Temperatures on the Microstructure and Properties of Dissimilar GH4169/IC10 Superalloy Vacuum Electron Beam Welded Joint

Cai,

Ma,

Zhang

et al. 2024

Metals

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Microstructural Analysis of K-TIG-Welded New Ni-Based Superalloy VDM Alloy 780

Ariaseta,

Khan,

Andersson

et al. 2024

Metall Mater Trans A

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The fusion zone microstructures in K-TIG-welded and post-weld solution heat-treated new superalloy VDM Alloy 780 were examined. In addition, the kinetics of the base metal grain growth during solution heat treatments were analyzed. (S)TEM analyses show that major interdendritic microconstituents formed in the fusion zone due to elemental microsegregation are MC carbides and coarse irregularly shaped Laves phase. Additionally, minor secondary interdendritic phases are found to include γ′, γ″, and tiny plate-like Laves particles. To prevent any potential deterioration of mechanical properties caused by the irregular Laves phase, post-weld solution heat treatments (PWSHTs) at 954 °C to 1060 °C/1 hours were performed to remove the Laves phase. PWSHT at 954 °C only partially eliminates the Laves particles while forming an abundance of interdendritic δ/η phase. Laves phase is dissolved entirely without forming δ/η platelets after PWSHT at 1060 °C. It is proven that Laves eutectics in VDM Alloy 780’s fusion zone can be eliminated through PWSHT without significantly coarsening the base metal’s grain size in comparison to Alloy 718 as a result of substantial grain growth inhibition likely caused by solute segregation at grain boundaries.

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