High-Cycle Fatigue Properties at Cryogenic Temperatures in INCONEL 718 Nickel-based Superalloy

Yuri, Tetsumi; Sumiyoshi, Hideshi; Takeuchi, Etsuo; Matsuoka, Saburo; Ogata, Tetsuya

doi:10.2320/matertrans.45.342

Cited by 48 publications

(21 citation statements)

References 9 publications

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“…At lower stresses (<550 MPa), NT specimens have longer fatigue lifetimes, but the preyielded C sample shows the same fatigue behavior as the NT samples. Both NT and C samples exhibited a fatigue limit of approximately 445 MPa, which agrees with the findings of Ono et al [26] when a correction is made to their results to account for their fatigue testing condition of R = 0.01 versus R = -1, used here.…”

Section: G Uniaxial Tensile and High Cycle Fatigue Testingsupporting

confidence: 89%

Low-Temperature Carburization of the Ni-base Superalloy IN718: Improvements in Surface Hardness and Crevice Corrosion Resistance

Sharghi-Moshtaghin

Kahn

et al. 2010

Metall Mater Trans A

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Case-hardening'' of the Ni-base superalloy IN718 has been achieved by low-temperature gas-phase carburization. After carburization under optimum conditions, the hardened surface layer (the ''case'') has about twice the hardness of the core (HV of %800) and contains %12 at pct carbon in interstitial solid solution. This causes a lattice parameter expansion of %1 pct perpendicular to the surface and, because of the mechanical constraint provided by the noncarburized core below, develops a large biaxial surface compressive residual stress (%1.9 GPa) parallel to the surface. Microstructural studies and X-ray diffractometry reveal no carbide precipitates in the case. In agreement with this observation, low-temperature carburization does not compromise the ductility and actually improves the crevice corrosion resistance of the alloy.

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Section: G Uniaxial Tensile and High Cycle Fatigue Testingsupporting

confidence: 89%

Low-Temperature Carburization of the Ni-base Superalloy IN718: Improvements in Surface Hardness and Crevice Corrosion Resistance

Sharghi-Moshtaghin

Kahn

et al. 2010

Metall Mater Trans A

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“…From the perspective of the fatigue source area as the fracture mode, the ST state had an obvious plastic fracture mode (Figures 5b and 7a), and the small facet of the cleavage for the fatigue fracture area of the ST + A state (Figure 6b,c) illustrated a cleavage fracture mode. Chen et al [10] showed that the fracture mode of the fatigue source area for an aged state Inconel 718 alloy changed from a transgranular ductile fracture to a cleavage fracture mode as the stress intensity factor k increased at the tip of the fatigue fracture. Accordingly, the k of the fatigue source area of the ST state was inferred to be smaller than that of the ST + A state.…”

Section: Analysis Of the High Cycle Fatigue Fracture Of The Inconel 7mentioning

confidence: 99%

“…Therefore, the research on fatigue performance of the Inconel 718 alloy has been widely concerned. According to the specific service environment temperature and load of the parts, it can be roughly divided into several aspects: high temperature [2]/medium temperature [3]/room temperature [4,5] low cycle fatigue, high temperature [6,7]/room temperature [8]/low temperature [9,10] high cycle fatigue, and ultra-high cycle fatigue [11,12] performance. Fournier et al [13] found that the Inconel 718 alloy in the solution treated and aged (ST + A) state had cyclic softening while in the direct aged (DA) state [14] had cyclic hardening under high temperature.…”

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confidence: 99%

High Cycle Fatigue Performance of Inconel 718 Alloys with Different Strengths at Room Temperature

Liqiong

Liang

et al. 2018

Metals

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In this paper, the high cycle fatigue performance of solid solution state and aged Inconel 718 superalloys was studied at room temperature. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to analyze the original structural features and fatigue deformation features of two kinds of alloys. SEM, laser scanning confocal microscopy, and electron backscatter diffraction (EBSD) were used to analyze the secondary fracture features of the fatigue fracture morphology and fatigue fracture profile. The results showed that the aging treatment significantly affected the strength and plasticity of the alloy, which in turn affected the fatigue performance of the alloy. After the aging treatment, the yield strength σ s and the tensile strength σ b of the Inconel 718 alloy increased by 152% and 65.9%, respectively, compared with those of the solid solution state, but the rate of elongation δ and rate of contraction in the cross-section area ϕ decreased by 63.7% and 52.3%, respectively. The fatigue limit of the aged state was lower than that of the solid solution state by 6.3%. The quadratic function relationship between the high cycle fatigue limit σ −1 and the tensile strength σ b of the Inconel 718 superalloy at room temperature was σ −1 = σ b · (0.869−3.67 × 10 −4 · σ b ). An analysis of the fatigue fracture mechanism showed that the fatigue fractures before and after aging were all initiated in the grains oriented relatively unfavorably on the surface of the sample, with a mixture of intergranular and transgranular propagation after the transgranular propagation of several grains. The higher plasticity of the solid solution state Inconel 718 alloy resulted in a large number of slip deformation zones under high cycle fatigue loads, and the plastic deformation was relatively uniform. The lengths of the secondary fractures were as high as 120 µm, which formed the single-source plastic fatigue fracture that promoted an increase in the fatigue limit. After aging treatment, the higher strength of the Inconel 718 alloy made dislocation slip difficult under high cycle fatigue loads, and the plasticity compatible deformation capability was poor. When local dislocations slipped to the intragranular γ" phase, γ' phase, or interfaces with nonmetallic compounds (NMCs), plugging occurred. The degree of stress concentration increased, causing the initiation of fatigue fracture; the secondary fracture was approximately 20 µm. Brittle cleavage due to multiple sources significantly reduced the fatigue limit.

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“…It is desirable that the fatigue critical disks are produced with a fine grained microstructure in the range of 5-20 μm to maximize fatigue benefits. However, prior studies have shown that crack initiation at carbides is promoted at high stress amplitude [5] and also, at lower test temperatures [6], and therefore, the carbides might limit the benefits from grain refinement under certain conditions. Further, the carbides at the surface of the part are sensitive to damage from surface machining [7,8] or surface treatment processing, and in such cases, cracks may initiate early from carbides [9,10].…”

Section: Introductionmentioning

confidence: 99%

Surface Effects on Low Cycle Fatigue Behavior in IN718 Alloy

Bhowal¹,

Stolz²,

Wusatowska-Sarnek³

et al. 2008

Superalloys 2008 (Eleventh International Symposium)

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Superalloys used in gas turbine engine rotating components require superior low cycle fatigue (LCF) properties, but often, the intrinsic LCF capability of the rotor, as determined by laboratory specimen tests, is limited by presence of fine particles such as carbides, borides and ceramic inclusions, as well as, pores, voids, and large grains in the alloy. Further, manufacturing processes such as turning, milling, and broaching can limit LCF life if they introduce surface damage and/or tensile residual stress. In IN718, prior studies have shown that fatigue initiation from MC carbides is promoted at lower test temperature and high stress, and the LCF life is significantly reduced. The present study investigates the effect of machining that can introduce carbide damage on LCF life, and a few post-machine processing methods for LCF recovery. The IN718 material used in this study came from a gas turbine disk forging that was directly aged without the conventional solution heat-treatment. The microstructure was fine-grained with an average grain size of 11 μm. Smooth and notched LCF properties were evaluated with machined and polished surfaces at test temperature and stress that promoted carbide initiation of fatigue cracks.Majority of the tests were performed at temperature of 560 K and at stresses of 1102 and 1240 MPa for smooth, and nominal stresses of 595 and 650 MPa for notched specimens. The min to max stress ratio (R) was 0.05. The cycles to failure were analyzed in terms of machining effect on surface carbides, and the fatigue initiation sites were studied by scanning electron microscopy (SEM). Smooth LCF specimens included asmachined (lathe-turned) and polished (600 grit SiC) surfaces and the notched LCF specimens included single-point bored (SPB) and media-polished notch surfaces. Lathe-turning and SPB cracked or damaged surface and subsurface carbides, considerably impacting the LCF life by factors of 3-15X (depending on test conditions). For a smooth lathe-turned surface, shot peening was effective in recovering LCF life by 5-10X at minimum over the as-machined surface. Some conventional post-machine processes for holes, such as mechanical honing, extrude hone and jig grinding and their influence on LCF life were studied as well.

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High-Cycle Fatigue Properties at Cryogenic Temperatures in INCONEL 718 Nickel-based Superalloy

Cited by 48 publications

References 9 publications

Low-Temperature Carburization of the Ni-base Superalloy IN718: Improvements in Surface Hardness and Crevice Corrosion Resistance

Low-Temperature Carburization of the Ni-base Superalloy IN718: Improvements in Surface Hardness and Crevice Corrosion Resistance

High Cycle Fatigue Performance of Inconel 718 Alloys with Different Strengths at Room Temperature

Surface Effects on Low Cycle Fatigue Behavior in IN718 Alloy

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