A Current T-T-T Diagram for Wrought Alloy 718

Oradei-Basile, A.; Radavich, J.F.

doi:10.7449/1991/superalloys_1991_325_335

Cited by 121 publications

(67 citation statements)

References 3 publications

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“…Since the pioneering work by Eisels tein, many investigators have produced TTT diagrams determined on alloys solution treated to be strain free. [2][3][4][5][6] All these latter studies differed from the former one by the fact that a brittle Laves phase was not found to precipitate at short holding time as reported by Eiselstein and another fact that the delta phase formed in shorter times than that reported by Eiselstein. Recently V. Beaubois et al [7] further studied short term precipitation kinetics of delta phase in strain free 718 alloy.…”

Section: Introductioncontrasting

confidence: 47%

TTT Diagram of a Newly Developed Nickel-Base Superalloy - Allvac 718Plus

Xie¹,

Xu²,

Wang³

et al. 2005

Superalloys 718, 625, 706 and Various Derivatives (2005)

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A new nickel-base superalloy designated as Allvac ® 718Plus ™ has been developed by ATI Allvac to be used at 700°C. For phase characterization, heat treatment selection and structure stability evaluation in high temperature range, the determination of TTT diagram for alloy 718Plus is not only a basic research issue but also an important matter for the alloy application at high temperatures. The conventional alloy 718 has been also studied for comparison. Both alloys were solution treated at 1040°C for full solution of precipitated phases except stable carbide MC. After solution treatment both alloy samples were heat treated at 649 to 954°C for the times from 3-6 minutes till 100 hrs. Phase identification was mainly by means of SEM, XRD and partially TEM and SAD. Hardness test was also conducted on the samples as the indication of γ" and γ' precipitation hardening. The experimentally determined T-T-T diagrams and discussion on the phase formation in alloys 718 and 718Plus are described in this paper.

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Section: Introductioncontrasting

confidence: 47%

TTT Diagram of a Newly Developed Nickel-Base Superalloy - Allvac 718Plus

Xie¹,

Xu²,

Wang³

et al. 2005

Superalloys 718, 625, 706 and Various Derivatives (2005)

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“…Laves phase is normally irregular in shape and forms as a result of Nb segregation with other alloying elements [18]. Thus, the absence of Laves phase in the current work might be due to the high cooling rate during SLM process [54] induced in the investigated area.…”

Section: Phase Evolution In Slm 3d Printed In718 Alloysmentioning

confidence: 81%

Structure, Texture and Phases in 3D Printed IN718 Alloy Subjected to Homogenization and HIP Treatments

Mostafa

Rubio

Braïlovski

et al. 2017

Metals

198

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3D printing results in anisotropy in the microstructure and mechanical properties. The focus of this study is to investigate the structure, texture and phase evolution of the as-printed and heat treated IN718 superalloy. Cylindrical specimens, printed by powder-bed additive manufacturing technique, were subjected to two post-treatments: homogenization (1100 • C, 1 h, furnace cooling) and hot isostatic pressing (HIP) (1160 • C, 100 MPa, 4 h, furnace cooling). The Selective laser melting (SLM) printed microstructure exhibited a columnar architecture, parallel to the building direction, due to the heat flow towards negative z-direction. Whereas, a unique structural morphology was observed in the x-y plane due to different cooling rates resulting from laser beam overlapping. Post-processing treatments reorganized the columnar structure of a strong {002} texture into fine columnar and/or equiaxed grains of random orientations. Equiaxed structure of about 150 µm average grain size, was achieved after homogenization and HIP treatments. Both δ-phase and MC-type brittle carbides, having rough morphologies, were formed at the grain boundaries. Delta-phase formed due to γ -phase dissolution in the γ matrix, while MC-type carbides nucleates grew by diffusion of solute atoms. The presence of (Nb 0.78 Ti 0.22 )C carbide phase, with an fcc structure having a lattice parameter a = 4.43 Å, was revealed using Energy dispersive spectrometer (EDS) and X-ray diffractometer (XRD) analysis. The solidification behavior of IN718 alloy was described to elucidate the evolution of different phases during selective laser melting and post-processing heat treatments of IN718.

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“…The hardness of the lowstrain-rate specimens reaches its maximum of 440 HV 10 after 8 hours, before the hardness decreases to 420 HV 10 after 50 hours at 718 • C. Relation (3) shows, that d c is independent of the volume fraction f of the precipitates. The increment ∆HV , however, depends of √ f , see (1) and (2). Hence, it is the volume fraction of γ that has to be taken into account also to understand the hardness vs. aging time curves in Figure 7.…”

Section: Resultsmentioning

confidence: 99%

“…Investigations dealing with these modifications are in progress. [2]. The dash-dot curves are the supposed modification for IN 718 forged at high strain rates.…”

Section: Discussionmentioning

confidence: 99%

“…The time-temperature-transformation-diagram of IN 718 [2] predicts no precipitation of the γ -phase during cooling from the forging temperature. Therefore, it seems that the common TTT-diagram for IN 718 as reported in [2] is not applicable to the material exposed to high strain rates as the precipitates develop much earlier than predicted. In this work investigations on the effects of high strain rate forging on the precipitation behavior of IN 718 are presented.…”

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confidence: 99%

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Analysis of Microstructural Properties of IN 718 After High Speed Forging

Renhof¹,

Krempaszky²,

Werner³

et al. 2005

Superalloys 718, 625, 706 and Various Derivatives (2005)

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The precipitation of the γ -Phase is the key to the excellent mechanical properties of IN 718. These can be improved by forging the material on a screw press (high strain rate forming) instead of a hydraulic press (low strain rate forming) [1]. The increase in hardness cannot be explained by grain size effects but is due to finely dispersed γ -particles found in the as-forged material. The time-temperature-transformation-diagram of IN 718 [2] predicts no precipitation of the γ -phase during cooling from the forging temperature. Therefore, it seems that the common TTT-diagram for IN 718 as reported in [2] is not applicable to the material exposed to high strain rates as the precipitates develop much earlier than predicted. In this work investigations on the effects of high strain rate forging on the precipitation behavior of IN 718 are presented. A modified TTT-diagram is suggested for IN 718 exposed to high strain rates.

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A Current T-T-T Diagram for Wrought Alloy 718

Abstract: A T-T-T study was carried out on the phase reactions in high quality wrought alloy 718 billet. Samples were exposed from 12OO'F to 17OO'F for times of 0

Cited by 121 publications

References 3 publications

TTT Diagram of a Newly Developed Nickel-Base Superalloy - Allvac 718Plus

TTT Diagram of a Newly Developed Nickel-Base Superalloy - Allvac 718Plus

Structure, Texture and Phases in 3D Printed IN718 Alloy Subjected to Homogenization and HIP Treatments

Analysis of Microstructural Properties of IN 718 After High Speed Forging

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