Effect of Cooling Rate on the Microstructure of Laser-Remelted INCONEL 718 Coating

Zhang, Yaocheng; Li, Zhuguo; Nie, Pulin; Wu, Yixiong

doi:10.1007/s11661-013-1903-8

Cited by 73 publications

(17 citation statements)

References 25 publications

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“…the center of the melt pool. However, it is suggested that the Laves phase spontaneously decomposes into an (Al, Ti, Nb)-rich phase [33]. This phase, upon remelting, appears to allow for increased Laves phase at the edges of the new melt pool, as seen in Figure 12 and supported by statistical analysis.…”

Section: Hardness Distributionmentioning

confidence: 77%

“…Transmission electron microscopy (TEM) results from similar samples in literature were examined closely to identify phases [27,28,32]. Laves phase and carbides have been well-documented in laser-deposited alloy 718 [27,30,33]. Figure 5a shows the δ phase, which is often plate-like but can appear in micrographs to be needle-shaped, appearing at stacking faults near the Laves phase [30,34].…”

Section: Elemental Analysis and Precipitate Identificationmentioning

confidence: 99%

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Variation of hardness, microstructure, and Laves phase distribution in direct laser deposited alloy 718 cuboids

et al. 2017

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Property anisotropy and its unpredictability in direct laser-deposited material is a drawback to this additive manufacturing method. In this study, direct laser deposition was used to build threedimensional cuboids of Ni-based superalloy 718, which were examined with microscopy, and analyzed for hardness trends with contour mapping. Secondary electron and backscatter electron contrast imaging were used in conjunction with electron backscatter diffraction to understand microstructure. It is found that hardness decreased with increasing height and linear energy used during deposition. Also, the hardness of the inner hatching was higher than the outer contour, in both planar and cross-sectional surfaces. After an examination of grain structure and phase distribution, it is proposed that the hardness trends are caused by a combination of detrimental Laves phase and strengthening γ″ phase distribution.

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Section: Hardness Distributionmentioning

confidence: 77%

Section: Elemental Analysis and Precipitate Identificationmentioning

confidence: 99%

Variation of hardness, microstructure, and Laves phase distribution in direct laser deposited alloy 718 cuboids

et al. 2017

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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%

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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“…Based on the relationship between experimentally derived cooling rate and PDAS in Eq. (1), a cooling rate of 1000-7000 K/s was estimated [7,[21][22][23][24].…”

Section: Microstructures Of the Ebm Samples In All Groupsmentioning

confidence: 99%

“…10c). It could be due to either the cooling condition of group F once the building job finished, was more favorable for precipitating gamma double prime than groups A and B, or grain boundary hardening by precipitation of inter-granular δ-phase at grain boundaries which avoid grain coarsening [23].…”

Section: Effect Of Height From Build Platementioning

confidence: 99%

Influence of build layout and orientation on microstructural characteristics of electron beam melted Alloy 718

Karimi

Sadeghimeresht

Deng

et al. 2018

Int J Adv Manuf Technol

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Effects of build layout and orientation consisting of (a) height from the build plate (Z-axis), (b) distance between samples, and (c) location in the build plate (X-Y plane) on porosity, NbC fraction, and hardness in electron beam melted (EBM) Alloy 718 were studied. The as-built samples predominantly showed columnar structure with strong ˂001˃ crystallographic orientation parallel to the build direction, as well as NbC and δ-phase in inter-dendrites and grain boundaries. These microstructural characteristics were correlated with the thermal history, specifically cooling rate, resulted from the build layout and orientation parameters. The hardness and NbC fraction of the samples increased around 6% and 116%, respectively, as the height increased from 2 to 45 mm. Moreover, by increasing the height, formation of δ-phase was also enhanced associated with lower cooling rate in the samples built with a greater distance from the build plate. However, the porosity fraction was unaffected. Increasing the sample gap from 2 to 10 mm did not change the NbC fraction and hardness; however, the porosity fraction increased by 94%. The sample location in the build chamber influenced the porosity fraction, particularly in interior and exterior areas of the build plate. The hardness and NbC fraction were not dependent on the sample location in the build chamber.

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Effect of Cooling Rate on the Microstructure of Laser-Remelted INCONEL 718 Coating

Cited by 73 publications

References 25 publications

Variation of hardness, microstructure, and Laves phase distribution in direct laser deposited alloy 718 cuboids

Variation of hardness, microstructure, and Laves phase distribution in direct laser deposited alloy 718 cuboids

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

Influence of build layout and orientation on microstructural characteristics of electron beam melted Alloy 718

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