Oxygen-induced intergranular cracking of a Ni-base alloy at elevated temperatures—an example of dynamic embrittlement

Pfaendtner, J.A.; McMahon, C.J.

doi:10.1016/s1359-6454(01)00005-2

Cited by 156 publications

(137 citation statements)

References 27 publications

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“…It has been confirmed that there was deleterious effect of oxygen on the high temperature strength of IN718, especially under creep loading [16,17]. However, further investigation is needed to make clear this point.…”

Section: Discussionmentioning

confidence: 95%

Creep-Fatigue and Thermo-Mechanical Fatigue of Friction-Welded IN 718/MarM247 Dissimilar Joint

Okazaki¹,

Sakaguchi²,

Tran³

et al. 2008

Superalloys 2008 (Eleventh International Symposium)

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The high temperature strength of the friction welded superalloy joint between cast polycrystalline Mar-M247 and the forged IN718 alloys has been investigated under low cycle and thermomechanical fatigue loadings, in comparison with those of the base materials. The experiments showed that the lives of the dissimilar joints were significantly influenced by the test conditions and loading modes. Not only the lives themselves but also the failure positions and mechanisms were sensitive to the loading mode. Especially under the loading conditions in which the creep-fatigue interaction was pronounced, some specific failure phenomena appeared in the DFW joint. The fracture behavior dependences on the loading modes and test conditions were discussed, based on analyses of the macroscopic elastic follow-up mechanism, the stress state by finite element method, and the inhomogeneous microstructure in the joint.

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Section: Discussionmentioning

confidence: 95%

Creep-Fatigue and Thermo-Mechanical Fatigue of Friction-Welded IN 718/MarM247 Dissimilar Joint

Okazaki¹,

Sakaguchi²,

Tran³

et al. 2008

Superalloys 2008 (Eleventh International Symposium)

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“…The diffusion process is facilitated by high tensile stresses near the crack tip [12,22], especially for superimposed dwell periods at the maximum load where the crack tip is fully open and experiences sustained high tensile stresses. Oxygen-diffusion-assisted crack growth in nickel superalloys, also termed as dynamic embrittlement [23,24], has been supported, though indirectly, by experimental observation in Inconel 718 [19,21]. Firstly, the individual grain boundary facets were found to be smooth on the submicrometer level, and oxides were only observed on the fracture surfaces where the crack front had passed.…”

Section: Introductionmentioning

confidence: 98%

“…Recently, it has been acknowledged [19][20][21] that oxidation-assisted crack propagation in nickel alloys is a result of oxygen diffusion into a local area with increasing tensile stress, such as crack tips. The oxygen element attacks the grain boundaries by lowering boundary cohesion and prompts accelerated intergranular cracking [19][20][21].…”

Section: Introductionmentioning

confidence: 99%

“…The oxygen element attacks the grain boundaries by lowering boundary cohesion and prompts accelerated intergranular cracking [19][20][21]. The diffusion process is facilitated by high tensile stresses near the crack tip [12,22], especially for superimposed dwell periods at the maximum load where the crack tip is fully open and experiences sustained high tensile stresses.…”

Section: Introductionmentioning

confidence: 99%

“…Oxidation kinetics for nickel alloys at 650°C is extremely slow [25,26], and oxidation reaction does not have sufficient time to occur within the order of seconds. Dynamic embrittlement was introduced to define a time-dependent intergranular brittle cracking process in which the supply of embrittling elements is due to grain boundary diffusion into an area of increasing tensile stress ahead of a crack tip [19][20][21][22][23][24]. Here, stress may be regarded as a driving force to accelerate the diffusion of embrittling elements into the crack tip and promote crack propagation by weakening grain boundary cohesion, i.e., a dynamic process of embrittlement.…”

Section: Introductionmentioning

confidence: 99%

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Prediction of crack growth in a nickel-based superalloy under fatigue-oxidation conditions

Tong

Hardy

2010

Engineering Fracture Mechanics

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• This is the author's version of a work that was accepted for publication in the journal Engineering Fracture Mechanics. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication.A definitive version was subsequently pub- AbstractPrediction of oxidation-assisted crack growth has been carried out for a nickel-based superalloy at elevated temperature based on finite element analyses of oxygen diffusion, coupled with viscoplastic deformation, near a fatigue crack tip. The material constitutive behaviour, implemented in the finite element code ABAQUS via a user-defined material subroutine (UMAT), was described by a unified viscoplastic model with non-linear kinematic and isotropic hardening rules. Diffusion of oxygen was assumed to be controlled by two parameters, the oxygen diffusivity and deformation-assisted oxygen mobility. Low frequencies and superimposed hold periods at peak loads significantly enhanced oxygen concentration near the crack tip. Evaluations of near-tip deformation and oxygen concentration were performed, which led to the construction of a failure envelop for crack growth based on the consideration of both oxygen concentration and accumulated inelastic strain near the crack tip. The failure envelop was then utilised to predict crack growth rates in a compact tension (CT) specimen under fatigue-oxidation conditions for selected loading ranges, frequencies and dwell periods. The predictions from the fatigue-oxidation failure envelop compared well with the experimental results for triangular and dwell loading waveforms, with marked improvements 2 achieved over those predicted from the viscoplastic model alone. The fatigue-oxidation predictions also agree well with the experimental results for slow-fast loading waveforms, but not for fast-slow waveforms where the effect of oxidation is much reduced.

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Grain Boundary Engineering Alloy 706 for Improved High Temperature Performance

Detor¹,

Deal²,

Hanlon³

2012

Superalloys 2012

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Grain boundary engineering aims to improve material performance by optimizing the structure of interfaces in polycrystalline metals. In the present work we grain boundary engineer the Ni-Fe-based superalloy 706 and measure the effect of this process on high temperature crack growth rate. The microstructure of traditionally processed material is compared to that after grain boundary engineering using electron backscatter diffraction to identify grain boundary character according to the coincidence site lattice model. The incorporation of so called special boundaries is examined in detail through grain size and triple junction distributions. It is shown that the grain boundary engineering process can effectively disrupt the connectivity of general, crack-prone grain boundaries in the microstructure. To test a proposed structure-property relationship, crack growth rate is measured for baseline and grain boundary engineered 706 under high temperature static load -conditions which typically result in an intergranular crack path. We find an order-of-magnitude improvement in crack growth rate at low stress intensities following the grain boundary engineering process. To understand the role of grain boundary engineering in more detail we analyze secondary crack paths to determine which boundary types are truly special (i.e. arrest cracks) for this test condition. We treat the problem in a continuum way, exploring the idea that grain boundaries may become "more special" as their coincident site lattice index decreases. This approach is in contrast to the majority of the literature where a binary classification is typically assumed. The work presented here highlights the potential benefit of grain boundary engineering for improved performance of superalloys and metals in general.

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Oxygen-induced intergranular cracking of a Ni-base alloy at elevated temperatures—an example of dynamic embrittlement

Cited by 156 publications

References 27 publications

Creep-Fatigue and Thermo-Mechanical Fatigue of Friction-Welded IN 718/MarM247 Dissimilar Joint

Creep-Fatigue and Thermo-Mechanical Fatigue of Friction-Welded IN 718/MarM247 Dissimilar Joint

Prediction of crack growth in a nickel-based superalloy under fatigue-oxidation conditions

Grain Boundary Engineering Alloy 706 for Improved High Temperature Performance

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