On the formation of microstructural gradients in a nickel-base superalloy during electron beam melting

Deng, Dewei; Peng, Ru Lin; Söderberg, Hans; Moverare, Johan

doi:10.1016/j.matdes.2018.09.006

Cited by 54 publications

(31 citation statements)

References 32 publications

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“…In L-DED, EB-PBF, and LB-PBF, the build direction is from bottom to top. Source: Sources: cast [12] , welding [27] , L-DED [15] , EB-PBF [14] and LB-BPF [28] .…”

Section: Effect Of Solidification Conditions On Non-equilibrium Solidmentioning

confidence: 99%

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Toward a Better Understanding of Phase Transformations in Additive Manufacturing of Alloy 718

et al. 2020

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This paper presents a discussion on the phase-transformation aspects of additively manufactured Alloy 718 during the additive manufacturing (AM) process and subsequent commonly used post-heat treatments. To this end, fundamental theoretical principles, thermodynamic and kinetics modeling, and existing literature data are employed. Two different AM processes, namely, laser-directed energy deposition and electron-beam powder-bed fusion are considered. The general aspects of phase formation during solidification and solid state in Alloy 718 are first examined, followed by a detailed discussion on phase transformations during the two processes and subsequent standard post heat-treatments. The effect of cooling rates, thermal gradients, and thermal cycling on the phase transformation in Alloy 718 during the AM processes are considered. Special attention is given to illustrate how the segregated composition during the solidification could affect the phase transformations in the Alloy 718. The information provided in this study will contribute to a better understanding of the overall process-structure-property relationship in the AM of Alloy 718 718.

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“…In L-DED, EB-PBF, and LB-PBF, the build direction is from bottom to top. Source: Sources: cast [12] , welding [27] , L-DED [15] , EB-PBF [14] and LB-BPF [28] .…”

Section: Effect Of Solidification Conditions On Non-equilibrium Solidmentioning

confidence: 99%

“…D. Deng et al [14] and Kumara et al [24] investigated the effect of the elevated build temperature on the as-solidified microstructure through experiments and modeling. The thermocouple data from the bottom of the build plate from these studies are shown in Fig.…”

Section: Phase Transformation During the Eb-pbf Processing Of Alloy 718mentioning

confidence: 99%

Toward a Better Understanding of Phase Transformations in Additive Manufacturing of Alloy 718

et al. 2020

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“…The areas close to the center line of one strut are virtually free of Laves phase. The common array-like segregations pattern of the Laves phase, as shown for example by Deng et al [41], are not visible. Instead, the Laves phase only formed along grain boundaries (Figure 2b) or is dispersedly distributed within a grain (Figure 2c).…”

Section: Microstructurementioning

confidence: 82%

Damage Tolerance Evaluation of E-PBF-Manufactured Inconel 718 Strut Geometries by Advanced Characterization Techniques

et al. 2020

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By means of electron beam powder bed fusion (E-PBF), highly complex lightweight structures can be manufactured within short process times. Due to the increasing complexity of producible components and the entangled interplay of damage mechanisms, common bulk material properties such as ultimate tensile or fatigue strength are not sufficient to guarantee safe and reliable use in demanding applications. Within this work, the damage tolerance of E-PBF-manufactured Ni-based alloy Inconel 718 (IN 718) strut geometries under uniaxial cyclic loading was investigated supported by several advanced measurement techniques. Based on thermal and electrical measurements, the failure of single struts could reliably be detected, revealing that continuous monitoring is applicable for such complex geometries. Process-induced surface roughness was found to be the main reason for early failure during cyclic loading. Thus, adequate post-processing steps have to be established for complex geometries to significantly improve damage tolerance and, eventually, in-service properties.

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“…That means, the as-built microstructure is spatially dependent, since the early solidified part of a build inevitably experiences longer in-situ 'heat-treatment' than the subsequently solidified part. Therefore, a microstructure gradient is observed in the as-built EBM IN718 component [94,[99][100][101][102]. However, such a segregation or Laves/δ-phases gradient [94,95,101] might be unfavourable for the mechanical properties, and it is also largely dependent on the process parameters.…”

Section: Ebm In718mentioning

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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On the formation of microstructural gradients in a nickel-base superalloy during electron beam melting

Cited by 54 publications

References 32 publications

Toward a Better Understanding of Phase Transformations in Additive Manufacturing of Alloy 718

Toward a Better Understanding of Phase Transformations in Additive Manufacturing of Alloy 718

Damage Tolerance Evaluation of E-PBF-Manufactured Inconel 718 Strut Geometries by Advanced Characterization Techniques

On the Microstructures and Anisotropic Mechanical Behaviours of Additively Manufactured IN718

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