Existence of Laves Phase in Nb-Hardened Superalloys

Chang, Keh‐Minn; Lai, Hsuan-Han; Hwang, Jihoon

doi:10.7449/1994/superalloys_1994_683_694

Cited by 13 publications

(10 citation statements)

References 11 publications

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“…The formation of Laves phase is a result of Nb, Si and Mo segregation during solidification, where these alloying elements are rejected from the dendrites into the interdendrites [29,30]. Chang et al [31] suggested that the relatively high contents of Cr and Fe in IN718 are the necessary condition for Laves phase, aside from the segregation of Nb. The chemical composition of Laves might differ with solidification condition, but is generally referred as (Ni,Fe,Cr) 2 (Nb,Mo,Ti).…”

Section: Lavesmentioning

confidence: 99%

Additively Manufactured Inconel 718 : Microstructures and Mechanical Properties

Deng

2018

Linköping Studies in Science and Technology. Licentiate Thesis

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Linköping 2018Cover image: A fracture surface of EBM IN718 after tensile test at room temperature.During the course of research underlying this thesis, Dunyong Deng was enrolled in Agora Materiae, a multidiciplinary doctoral program at Linköping University, Sweden. Printed by LiU-Tryck 2018 © Dunyong Deng AbstractAdditive manufacturing (AM), also known as 3D printing, has gained significant interest in aerospace, energy, automotive and medical industries due to its capabilities of manufacturing components that are either prohibitively costly or impossible to manufacture by conventional processes. Among the various additive manufacturing processes for metallic components, electron beam melting (EBM) and selective laser melting (SLM) are two of the most widely used powder bed based processes, and have shown great potential for manufacturing high-end critical components, such as turbine blades and customized medical implants. The futures of the EBM and SLM are doubtlessly promising, but to fully realize their potentials there are still many challenges to overcome.Inconel 718 (IN718) is a nickel-base superalloy and has impressive combination of good mechanical properties and low cost. Though IN718 is being mostly used as a turbine disk material now, the initial introduction of IN718 was to overcome the poor weldability of superalloys in 1960s, since sluggish precipitation of strengthening phases γ ′ /γ ′′ enables good resistance to strain-age cracking during welding or post weld heat treatment. Given the similarity between AM and welding processes, IN718 has been widely applied to the metallic AM field to facilitate the understandings of process-microstructure-property relationships.The work presented in this licentiate thesis aims to better understand microstructures and mechanical properties EBM and SLM IN718, which have not been systematically investigated. Microstructures of EBM and SLM IN718 have been characterized with scanning electron microscopy (SEM), transmission electron microscopy (TEM) and correlated with the process conditions. Monotonic mechanical properties (e.g., Vickers microhardness and tensile properties) have also been measured and rationalized with regards to the microstructure evolutions before and after heat treatments.For EBM IN718, the results show the microstructure is not homogeneous but dependant on the location in the components, and the anisotropic mechanical properties are probably attributed to alignment of porosities rather than texture.iii Post heat treatment can slightly increase the mechanical strength compared to the as-manufactured condition but does not alter the anisotropy. SLM IN718 shows significantly different microstructure and mechanical properties to EBM IN718. The as-manufactured SLM IN718 has very fine dendritic microstructure and Laves phases in the interdendrites, and is "work-hardened" by the residual strains and dislocations present in the material. Mechanical properties are different between horizontally and vertically built samples, and heat treatment can m...

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Section: Lavesmentioning

confidence: 99%

Additively Manufactured Inconel 718 : Microstructures and Mechanical Properties

Deng

2018

Linköping Studies in Science and Technology. Licentiate Thesis

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“…This constitutes a fact evidencing the difference in the relative intensity of different crystalline peaks for the same phase (e.g., 2θ = 75 • in BM and 2θ = 91 • in WM for austenite phase). The texture observed in the WM region is due to the columnar grains and the orientation of the intermetallic particles that change the reflection angle of the XRD pattern for each phase [21,[31][32][33]. distribution in the BM are different when compared to the WM.…”

Section: Microstructural Characterizationmentioning

confidence: 99%

“…Additionally, X-ray diffraction (XRD) analyses using a Bruker diffractometer model D8 Advance ECO operated with Cu Kα at 40 kV and 25 mA and the sweep angle range (2θ) from 30 • to 120 • with a scanning speed of 2 • /min were used to analyze the phases and intermetallics present in the material. The crystalline peaks of the XRD spectra were identified based on powder diffraction files (PDF) 330945, 893890 and 653574, and a literature survey [31][32][33][34]. The percentages of intermetallics in each one of the welding regions were quantified based on the ASTM E1245.…”

Section: Microstructure Characterizationmentioning

confidence: 99%

Corrosion Behavior of CW6MC Nickel Cast Alloy (Inconel 625) Welded by Shielded Metal Arc Welding

Vacchi

Silva

Kugelmeier

et al. 2021

Metals

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The aim of this study concerns the effect of multi-pass shielded metal arc welding (SMAW) on the corrosion behavior of CW6MC cast nickel alloy. Using optical and SEM techniques the welded joint is analyzed. Vickers microhardness mapping and potentiodynamic polarization in NaCl and H2SO4 solutions are also evaluated. Both the Laves phase and NbC-type carbides are identified in the base metal (BM) and weld metal (WM) regions. The main microstructural difference observed between these regions is the morphology aspect and fineness of the dendritic arrays. The welding process promotes the finer columnar grains formation with refined intermetallic particles in the WM than equiaxed grains of the BM, which in turn results in higher microhardness values in the former region. However, no substantial changes were observed in the corrosion behavior between the BM and WM regions, considering both acid and saline media. Nevertheless, during the multi-pass SMAW process, some non-metallic micrometric inclusions (Mo and S-rich regions) can be constituted to occur in the WM region. This is associated with a significant drop in the corrosion performance of this region when the electrochemical tests are evaluated.

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“…The formation of Laves phase is a result of Nb, Si and Mo segregation during solidification, where these alloying elements are rejected from the dendrites into the interdendrites [22,27]. Chang et al [28] suggested that the relatively high contents of Cr and Fe in IN718 are necessary for forming Laves phase, aside from the segregation of Nb. The chemical composition of Laves might differ with solidification condition, but is generally referred as (Ni,Fe,Cr) 2 (Nb,Mo,Ti).…”

Section: Lavesmentioning

confidence: 99%

On the Microstructures and Anisotropic Mechanical Behaviours of Additively Manufactured IN718

Deng

2019

Linköping Studies in Science and Technology. Dissertations

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Additive manufacturing (AM), also known as 3D printing, offers great design flexibility for manufacturing components with complex geometries, and has attracted significant interest in the aero and energy industries in the past decades. Among the commercial AM processes, selective laser melting (SLM) and electron beam melting (EBM) are the two most widely used ones for metallic materials. Inconel 718 (IN718) is a nickel-base superalloy and has impressive combination of good mechanical properties, weldability and low cost. Due to its excellent weldability, IN718 has been intensively applied in the AM filed, to gain more understanding of the AM processes and fully realize AM's potentials. The study objects in the present thesis include both EBM and SLM IN718. The solidification conditions in EBM and SLM are very different and are different to that of conventional cast, leading to unique microstructures mechanical properties. Therefore, this thesis aims to gain better understanding of the microstructures and anisotropic mechanical behaviours of both EBM and SLM IN718, by detailed characterizations and by comparisons with the forged counterpart. The as-built microstructure of EBM IN718 is spatially dependent: the periphery (contour) region has a mixture of equiaxed and columnar grains, while the bulk (hatch) region has columnar grains elongated along the building direction; the last solidified region close to the top sample surface shows segregation and Laves phases, otherwise the rest of the whole sample is well homogenized. Differently, the as-built microstructure of SLM IN718 is spatially homogeneous: the grains is rather equiaxed and with subgrain cell structures. These microstructures also respond differently to the standard heat treatment routines for the conventional counterparts. Anisotropic mechanical properties are evident in the room temperature tensile tests and high temperature dwell-fatigue tests. The anisotropic tensile properties of EBM IN718 at room temperature are more likely due to the directional alignment of porosities along the building direction rather than the strong crys-In these papers I have been the main contributor, performing all the experimental work, characterization, analysis and manuscript writing, under the supervision of Johan Moverare and Ru Lin Peng.

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Existence of Laves Phase in Nb-Hardened Superalloys

Cited by 13 publications

References 11 publications

Additively Manufactured Inconel 718 : Microstructures and Mechanical Properties

Additively Manufactured Inconel 718 : Microstructures and Mechanical Properties

Corrosion Behavior of CW6MC Nickel Cast Alloy (Inconel 625) Welded by Shielded Metal Arc Welding

On the Microstructures and Anisotropic Mechanical Behaviours of Additively Manufactured IN718

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