Review of the physical metallurgy of Alloy 718

Keiser, Dennis D.; Brown, H. L.

doi:10.2172/4016087

Cited by 27 publications

(26 citation statements)

References 4 publications

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“…They also observed the precipitation of δ phase around the partially dissolved Laves particles. Solution treatment at 1080°C was found to lead to complete dissolution of Laves phase [32]. This has also been demonstrated in the post weld heat-treated IN718 electron beam welds [9].…”

Section: Needles In the Laves Phasementioning

confidence: 76%

“…Extensive research has been carried out on the phase transformation under both continuous cooling and isothermal conditions [30][31][32], that indicates the precipitation temperature of δ phase is lower than that of Laves phase. Fig.…”

Section: Needles In the Laves Phasementioning

confidence: 99%

“…Continuous-cooling-transformation diagram of IN718 homogenised at 1180°C for 24 h (a)[30]; time-temperature-transformation diagram of IN718 solution-annealed at 1149°C for 1 h and water-quenched (b)[32].…”

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confidence: 99%

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Electron microscopy study of direct laser deposited IN718

Ding

Huang

et al. 2015

Materials Characterization

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a b s t r a c tThe microstructure of direct laser deposited (DLD) IN718 has been investigated in detail using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results confirm that the dendrite core microstructure can be linked to the cooling rate experienced during the deposition. A~100 μm wide δ partially dissolved region in the IN718 substrate was observed close to the substrate/deposit boundary. In the deposited IN718, γ/Laves eutectic constituent is the predominant minor microconstituent. Irregular and regular (small) (Nb,Ti)C carbides and a mixture of the carbides and Laves were observed. Most M 3 B 2 borides were nucleated around a (Nb,Ti)C carbide. Needles of δ phase precipitated from the Laves phase were also observed. A complex constituent (of Laves, δ, α-Cr, γ″, and γ matrix) is reported in IN718 for the first time. The formation of α-Cr particles could be related to Cr rejection during the formation and growth of Cr-depleted δ phase.

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Section: Needles In the Laves Phasementioning

confidence: 76%

Section: Needles In the Laves Phasementioning

confidence: 99%

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Electron microscopy study of direct laser deposited IN718

Ding

Huang

et al. 2015

Materials Characterization

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“…Tensile tests were conducted in the temperature range 650-900°C, at which the effect of precipitates is the strongest [28,29], to determine the impact of aging time and temperature on the mechanical properties of the investigated alloy. The reference sample had the highest elongation to fracture, and one of the lowest material strengths (Fig.…”

Section: Resultsmentioning

confidence: 99%

The Precipitation Processes and Mechanical Properties of Aged Inconel 718 Alloy After Annealing

Maj

Adamczyk‐Cieślak

Slesik

et al. 2017

Archives of Metallurgy and Materials

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Inconel 718 is a precipitation hardenable nickel-iron based superalloy. It has exceptionally high strength and ductility compared to other metallic materials. This is due to intense precipitation of the γ' and γ" strengthening phases in the temperature range 650-850°C. The main purpose of the authors was to analyze the aging process in Inconel 718 obtained in accordance with AMS 5596, and its effect on the mechanical properties. Tensile and hardness tests were used to evaluate the mechanical properties, in the initial aging process and after reheating, as a function of temperature and time respectively in the ranges 650°-900°C and 5-480 min. In addition, to link the mechanical properties with the microstructure transmission microscopy observations were carried out in selected specimens. As a result, factors influencing the microstructure changes at various stages of strengthening were observed. The authors found that the γ'' phase nucleates mostly homogenously in the temperature range 650-750°C, causing the greatest increase in strength. On the other hand, the γ' and δ phases are formed heterogeneously at 850°C or after longer annealing in 800°C, which may weaken the material.

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“…Past reports (1,2) have claimed the presence of secondary carbides (M7C3 or M2C -type), which could play a part in pinning grain boundaries during heat treatment and also in some strengthening mechanisms, but their presence has not been subsequently substantiated. M6C has also been reported (3) in samples which have undergone longterm heat treatment, forming in small amounts at grain boundaries. Carbon is almost insoluble in the primary gamma phase of 718 and segregates strongly during solidification (4).…”

Section: Introductionmentioning

confidence: 85%

Primary Carbides in Alloy 718

Mitchell¹

2010

7th International Symposium on Superalloy 718 and Derivatives (2010)

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This study presents the effects of long term homogenisation at 1200C on the as-cast structure of alloy 718 in terms of the size distribution of the primary carbides. We find that the size distribution changes slightly over the first 20h of treatment, following a solution of some of the carbide, but that it does not change significantly over the next 180h, indicating a rapid process of following the solution equilibrium at temperature. The effect is also reported in relation to the melting of an electrode of the same structure during the VAR process. It is found that the as-cast structure of the electrode used in VAR does not influence the structure of the VAR ingot in respect of primary carbide size distribution.

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Review of the physical metallurgy of Alloy 718

Cited by 27 publications

References 4 publications

Electron microscopy study of direct laser deposited IN718

Electron microscopy study of direct laser deposited IN718

The Precipitation Processes and Mechanical Properties of Aged Inconel 718 Alloy After Annealing

Primary Carbides in Alloy 718

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