The Physical Metallurgy of Cast and Wrought Alloy 718

Radavich, J.F.

doi:10.7449/1989/superalloys_1989_229_240

Cited by 98 publications

(118 citation statements)

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“…This process has been tried in many wrought Ni-base superalloys, including alloys 718 [1][2][3][4], 625 [5,6], X751 [7], IN783 [8] and others [9,10]. Different degrees of success have been achieved.…”

Section: Introductionmentioning

confidence: 99%

Application of Direct Aging to Allvac 718Plus Alloy for Improved Performance

Cao¹,

Kennedy²

2005

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

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Direct aging can result in significant improvement in mechanical properties of many wrought Nibase superalloys. Its effectiveness is closely related to hot working and aging conditions and is also alloy-dependent. This process is most often used with γ" rather than γ' strengthening alloys.Allvac ® 718Plus™ alloy is predominantly a γ' strengthening alloy which shows excellent mechanical properties and high thermal stability up to 704°C in the solution treated and aged condition. It was uncertain if direct aging could be effective in this alloy. A test program was initiated to explore if direct aging could improve the alloy's performance and to determine the optimum process conditions. The variables evaluated included forging temperature, forging reduction, forging heating time and post-forging cooling rate. Mechanical tests and microstructural study after different direct aging treatments demonstrated that direct aging is feasible at a production scale for alloy 718Plus and a significant improvement in performance can be achieved under well-controlled conditions. The mechanism responsible for such improvement is briefly discussed.

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Section: Introductionmentioning

confidence: 99%

Application of Direct Aging to Allvac 718Plus Alloy for Improved Performance

Cao¹,

Kennedy²

2005

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

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“…mogenization temperature can surely accelerate the homogenization proecess, but attention must be paid to incipient melting at grain boundaries caused by the rapid heating over the Laves solvus temperature [29]. Note that the grain boundary δ is dissolved during the homogenization treatment, which would cause unfavourable notch brittleness.…”

Section: Inconel 718mentioning

confidence: 99%

“…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.…”

Section: Lavesmentioning

confidence: 99%

“…This segregation can cause composition differences between the dendrites and interdendrites. For instance, the dendritic Nb content can be as low as 2 wt.%, while Nb level in the interdendritic regions can range as high as 12 wt.% [29]. Driven by the particular interest in Nb and the Laves and NbC features, a solidification diagram based on the Nb evolution was constructed under a cooling rate somewhat less than 500 • C/s by Knorovsky et al [35], as shown in Fig.…”

Section: Solidification Metallurgymentioning

confidence: 99%

“…Severe interdendritic segregation and presence of Laves phases, with/without cast porosity, make the cast microstructure considerably different from that of wrought form. Cast porosity can be closed by applying a HIP cycle; minimizing segregation can be achieved partly by the HIP cycle or by a separate homogenization heat treatment [5,29,39]. The homogenization temperature and duration are largely dependent on size of Laves phase: the bigger Laves phases, the higher homogenization temperature and longer homogenization duration [40].…”

Section: Cast In718mentioning

confidence: 99%

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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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Effect of Nickel Content on Delta Solvus Temperature and Mechanical Properties of Alloy 718

Frank¹,

Roberts²,

Zhang³

2010

Superalloy 718 and Derivatives

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Knowledge and control of the delta phase (Ni 3 Nb) solvus temperature is critical to optimize processing and heat treatment of alloy 718 for best mechanical properties. This is the case in aerospace applications where delta phase is used to produce fine grain structures during forging, and in oil-field applications where the delta phase is dissolved during solution treatment. Delta phase solvus is primarily controlled by niobium content. The effect of nickel content on delta phase solvus is not well understood as thermodynamic models and previous experiments have produced conflicting results. The purpose of this study was to confirm the effect of nickel content on delta solvus temperature using experimental heats and to document mechanical properties vs. nickel content. In addition, solvus results were compared with modeling predictions and an improved database was developed to more accurately predict delta phase solvus temperature in alloy 718.

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The Physical Metallurgy of Cast and Wrought Alloy 718

Cited by 98 publications

References 0 publications

Application of Direct Aging to Allvac 718Plus Alloy for Improved Performance

Application of Direct Aging to Allvac 718Plus Alloy for Improved Performance

Additively Manufactured Inconel 718 : Microstructures and Mechanical Properties

Effect of Nickel Content on Delta Solvus Temperature and Mechanical Properties of Alloy 718

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