Fatigue strength of Inconel 718 at elevated temperatures

Kawagoishi,; Chen, Guihai; Nisitani,

doi:10.1046/j.1460-2695.2000.00263.x

Cited by 85 publications

(41 citation statements)

References 23 publications

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“…In the present study characterization by transmission electron microscope is under way to understand the deformation mechanisms operating at higher and lower strain range as a function of temperature. Kawagoishi et al [4] have also observed a similar behavior in their studies on rotating bending tests (stress controlled) containing partial notch in alloy 718. These authors attributed the main reason for the suppression of small crack growth is crack closure caused by the oxidation of crack faces, leading to higher life at elevated temperature at low stress levels.…”

Section: Notched Low Cycle Fatigue Propertiesmentioning

confidence: 48%

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Notched Low Cycle Fatigue of Alloy 718

Sridhar¹,

Kumar²,

Gogia³

2005

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

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Low Cycle Fatigue (LCF) damage is the life-limiting factor for rotating components in advanced gas turbines. LCF tests in laboratory are generally conducted in strain control using smooth cylindrical specimens. Smooth geometry may not represent actual component, as LCF life can be significantly influenced by notches present in components and the latter is not accounted by the data based on smooth specimens.Most of the data available in literature is generated using circumferential or single or double edge notch. Use of circumferential notch may not be entirely appropriate for comparison with smooth fatigue specimens, because of difference in their diameters, as there is a decrease in volume or surface area of the specimen as the diameter decreases, and this is of significance, since fatigue failures usually start at the surface.In the present study tangential slot notch was used to investigate the effect of slot notch on LCF behavior of Alloy 718 as it removes a very small percentage of the specimen cross-sectional area and does not cover entire circumference. So comparison can be made between the smooth and tangential notch specimens without much variation in their surface area or volume. The studies are conducted at ambient temperature and 650°C and a comparison is made with smooth specimen data. Results indicate that tangential slot notch also reduces significantly the fatigue life of alloy 718.

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Section: Notched Low Cycle Fatigue Propertiesmentioning

confidence: 48%

“…Effect of notches on LCF life of alloy 718 has been studied using double edge notch in stress control mode [2]. Studies have been performed to overcome the problem of time dependent notch sensitivity [3] and rotary bending fatigue in the presence of a partial notch [4].…”

Section: Introductionmentioning

confidence: 99%

Notched Low Cycle Fatigue of Alloy 718

Sridhar¹,

Kumar²,

Gogia³

2005

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

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“…Kawagoshi et al 30 used replica techniques in rotating bending of alloy 718 of 9 mm grain size in the range 300-600uC. Specimens were 8 mm diameter with 0?2 mm deep chordal notch (little effect was claimed on smooth specimen endurance).…”

Section: Superalloysmentioning

confidence: 99%

The treatment of very short crack growth in low cycle fatigue and creep fatigue

Skelton

2015

Materials at High Temperatures

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Given total endurances of low cycle fatigue specimens, several empirical formulae enable an estimate to be made of 'initiation' cycles to a specific crack depth in a zone ranging from 20 to 400 mm from the surface. For greater depths, the cyclic growth behaviour of cracks can be calculated directly from relations using established constants (including the effects of creep dwell) for a wide range of alloys. However, below a critical depth of 200 mm or thereabouts, these empirical growth laws, expressed in terms of total strain range, break down. Early crack growth can take place discontinuously, as the crack tip encounters grain boundaries or other obstacles. Such information arises from replica takings, or in situ microscopic observations of surfaces during continuous cycling and creep-fatigue tests. Striation spacings on the fracture surface and the first observed striation spacing provide valuable indications of early crack growth. In this region, the cyclic rate of growth depends on (i) crack shape which can change during advance; (ii) whether or not embryo cracks link up (coalescence); (iii) whether or not there is a small starter defect (deliberately introduced or otherwise); (iv) the degree of creep or oxidation damage; and (v) the repeat distance of obstacles or barriers. Creep effects can overtake these considerations by bulk damage accruing with consequent acceleration in growth. In this survey, crack growth characteristics in ferritic and austenitic steels up to 625uC and superalloys up to 1000uC are considered. Surface behaviour is connected to penetration into the depth. As part of a sensitivity analysis, various 'stop-start' models are examined and their related growth cycles calculated in the early region before the macroscopic growth law takes over. These are compared with an upper bound constant growth rate law. Alternatively, it is shown that crack growth can be described over the whole range by a single exponential function.

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“…In [57,58], the notched fatigue strength of the nickelbase superalloy Inconel 718 was investigated under rotating bending loading at room temperature and 500°C in air. The linear notch mechanics was employed to assess the fatigue strength at elevated temperature being for that material the small-scale yielding conditions satisfied also at elevated temperature.…”

Section: High Temperature Atigue Behaviour O Cr Steelsmentioning

confidence: 99%

Some recent results on the fatigue strength of notched specimens made of 40CrMoV13.9 steel at room and high temperature

Berto

2015

Phys Mesomech

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The work summarizes a large bulk of experimental data from specimens made of 40CrMoV13.9 steel. The first part of the paper deals with multiaxial fatigue strength of notched round bars tested under combined tension and torsion loading, both in-phase and out-of-phase. The results from multi-axial tests are discussed together with those obtained under pure tension and pure torsion loading from notched specimens with the same geometry. The second part of the paper summarizes data from uniaxial-tension stress-controlled fatigue tests on specimens made of the same steel. Tests are performed varying temperature, from room temperature up to 650°C. Altogether more than 180 new fatigue data are summarised in the present work, corresponding to more than two-years of testing programme. All fatigue data are presented first in terms of nominal stress amplitudes referred to the net area and then re-analysed in terms of the mean value of the strain energy density evaluated over a given, crescent shape volume embracing the stress concentration region. For the specific steel, the radius of the control volume is found to be independent of the loading mode

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Fatigue strength of Inconel 718 at elevated temperatures

Cited by 85 publications

References 23 publications

Notched Low Cycle Fatigue of Alloy 718

Notched Low Cycle Fatigue of Alloy 718

The treatment of very short crack growth in low cycle fatigue and creep fatigue

Some recent results on the fatigue strength of notched specimens made of 40CrMoV13.9 steel at room and high temperature

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