Brittle intergranular fracture of a Ni-base superalloy at high temperatures by dynamic embrittlement

Krupp, Ulrich; Kane, William M.; Laird, C.; McMahon, C.J.

doi:10.1016/j.msea.2004.05.053

Cited by 78 publications

(52 citation statements)

References 21 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Dynamic embrittlement for nickel superalloys has been supported by experimental observations in Inconel 718 four-point bending tests [19][20][21]. Firstly, the individual grain boundary facets were found to be smooth on the sub-micrometer level, and oxidation of NbC precipitates was only observed on the fractured surface where the crack front had passed.…”

Section: Discussionmentioning

confidence: 86%

“…In fact, the constitutive law (4) for the mass diffusion is an enhanced form of Fick's law, which has been modified to include the pressure (equivalent to dilatational strain) gradient effects. The equation (4) was derived from a thermodynamics point of view, in terms of chemical potential of diffusive species [32], which has been generally used to consider the influence of mechanical stress on mass transport [e.g., 20,22,[33][34]. The gradient of hydrostatic stress (or pressure) is considered to be the driving force for stressassisted diffusion process.…”

Section: Deformation-assisted Oxygen Diffusionmentioning

confidence: 99%

“…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%

See 4 more Smart Citations

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

Tong

Hardy

2010

Engineering Fracture Mechanics

View full text Add to dashboard Cite

• 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.

show abstract

Section: Discussionmentioning

confidence: 86%

Section: Deformation-assisted Oxygen Diffusionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

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

Tong

Hardy

2010

Engineering Fracture Mechanics

View full text Add to dashboard Cite

show abstract

Effects of Oxidation on Fatigue Crack Initiation and Propagation in an Advanced Disk Alloy

et al. 2016

View full text Add to dashboard Cite

Environmentally assisted crack growth rate of an austenitic steel TP347HFG in high‐temperature medium

Khan

Zhang

Yue

et al. 2017

Materials & Corrosion

View full text Add to dashboard Cite

The crack growth rate (CGR) tests of austenitic steel TP347HFG were conducted under <10‐8000 ppb dissolved oxygen (DO) in steam, the alternating environment of air and steam and supercritical water (SCW) at 600–650 °C. A constant stress intensity factor (K) method and direct current potential drop technique were used in the tests to evaluate its environmentally assisted cracking (EAC) properties as superheater and reheater boiler tubes in ultra‐supercritical power plants. CGR increases monotonically with temperature and DO content. CGR in SCW is greater than that in the high‐temperature steam which indicates that exposure pressure has an obvious effect on crack propagation. The varying CGR in different experimental environments show that exposure medium participates in the cracking process. Fracture surface and cross‐sectional surface of compact tension specimen were analyzed by scanning electron microscope. The mechanism of crack propagation in different exposure environment is further discussed.

show abstract

Brittle intergranular fracture of a Ni-base superalloy at high temperatures by dynamic embrittlement

Cited by 78 publications

References 21 publications

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

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

Effects of Oxidation on Fatigue Crack Initiation and Propagation in an Advanced Disk Alloy

Environmentally assisted crack growth rate of an austenitic steel TP347HFG in high‐temperature medium

Contact Info

Product

Resources

About