Short crack initiation and growth at 600°C in notched specimens of Inconel718

Connolley, Thomas; Reed, P.A.S.; Starink, M.J.

doi:10.1016/s0921-5093(02)00169-7

Cited by 116 publications

(87 citation statements)

References 33 publications

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“…Previous work by the authors on Batch A specimens [25] demonstrated that primary carbides at or close to the surface of IN718 oxidised at elevated temperatures, and there was a substantial volume expansion associated with oxidation. This was observed in unstressed specimens and U-notch fatigue specimens exposed at 550 o C and 600 o C in air.…”

Section: Discussionmentioning

confidence: 95%

“…Volume expansion of oxidising primary carbides was identified as a mechanism of environmentally assisted crack propagation in notch-rupture tests on IN718 [21] . The role of oxidised primary carbides in fatigue crack initiation has also been studied [22,23,24,25] .…”

Section: Introductionmentioning

confidence: 99%

“…The natural initiation and growth of short cracks in U-notch IN718 specimens has been studied at 600 o C in air and reported in detail elsewhere by the authors [25] . Fatigue tests were conducted under load control using a 1-1-1-1 trapezoidal waveform, on specimens with as-broached and polished U-notches.…”

Section: Introductionmentioning

confidence: 99%

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Effect of broaching on high-temperature fatigue behavior in notched specimens of INCONEL 718

Connolley

Starink

Reed

2004

Metall Mater Trans A

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Notches were machined in specimens of Inconel 718 by a broaching process, where differing broaching runs led to differing extents of sub-surface deformation and surface roughness.Fatigue tests were carried out at 600˚C with a trapezoidal loading waveform at 0.25Hz. The broaching process that led to the more severe sub-surface deformation (but lower surface roughness) showed the worst fatigue performance. Analysis of total strain amplitude in the notch root with the aid of an elasto-plastic finite element model, showed that the workhardening related to the subsurface deformation caused by the different broaching can account for the difference in fatigue lives. Differences in initiation and growth behaviour were seen for the two broached finishes as well as for broached and subsequently polished samples.These differences are discussed in terms of a change in crack growth initiation and growth mechanisms due to the presence of the work hardened layer.

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Section: Discussionmentioning

confidence: 95%

Section: Introductionmentioning

confidence: 99%

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Effect of broaching on high-temperature fatigue behavior in notched specimens of INCONEL 718

Connolley

Starink

Reed

2004

Metall Mater Trans A

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“…It has been reported that the oxidation behavior at intermediate temperature of IN718 alloy was controlled by the oxidation of NbC carbide and the formation of Cr 2 O 3 and Fe 2 O 3. [7,8] The Cr 2 O 3 would preferentially form at grain boundaries, which inhibits the progression of oxygen along grain boundaries. However, the Cr contents were not high enough to form continuous protective oxide layer at the initial oxidation stage, therefore other elements can be oxidized within the grain.…”

Section: Hot Corrosionmentioning

confidence: 99%

Effect of Phosphorus on Microstructure and Mechanical Properties of IN718 Alloy after Hot Corrosion and Oxidation

Hu¹,

Yu²,

Wang³

et al. 2010

7th International Symposium on Superalloy 718 and Derivatives (2010)

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In this paper, the IN718 alloys added with various phosphorus concentration underwent hot corrosion in the mixed salts of 75%Na 2 SO 4 and 25%NaCl at 650 ℃ and oxidation in air at 650 ℃, and then the microstructure and properties of the alloys were characterized. No difference was found of the tensile properties of IN718 alloy after soaking at 100 h in air and in mixed salt. However, phosphorus exhibits an effect to inhibit the ingression of sulfur along the grain boundaries. The thermal exposure in air at 650 ℃ makes no differences on the tensile properties, but reduces the total term of the primary and secondary creep stages of IN718 alloy, while the alloy added with 0.019% phosphorus exhibits the same creep curves with and without thermal exposure. The interaction mechanism between phosphorus and hot corrosion and oxidation is discussed briefly in the paper. IntroductionIN718 alloy, as one of the most important nickel-based superalloys, is widely used for high temperature parts of aircraft turbines and steam turbines. With various compositions, IN718 alloy is mainly strengthened by the precipitation of γ″-Ni 3 Nb (DO 22 structure) and γ′-Ni 3 (Al, Ti)(L1 2 structure) phases. Recently, it has been found that phosphorus greatly improved the stress rupture and creep properties of IN718 alloy [1][2][3]. The researches related to the mechanism of this phenomenon were mainly focused on the influence of phosphorus on the grain boundaries because it has a strong tendency to be highly concentrated there. It has also been proposed that when phosphorus segregates to the grain boundaries, it can inhibit the diffusion of oxygen atoms along the grain boundaries [4].

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“…[1,3,[8][9][10]). The effect of grain size reduction ,assumed to be beneficial on fatigue lives, was more particularly studied for conventional and DA 718 alloys (see e.g.…”

Section: Fatigue Crack Initiation Sitesmentioning

confidence: 99%

Probabilistic Life of DA718 for Aircraft Engine Disks

Deyber¹,

Alexandre²,

Vaissaud³

et al. 2005

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

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The micro-mechanisms of crack initiation and propagation identified for DA 718, as well as the competition between initiation site types and locations, cannot be accurately accounted for by current certified methods used to establish aircraft engine disks life,essentially phenomenological.Once identified, these micro-mechanisms have been modelized by mesoscopic models using very few parameters and depending strongly on material mechanical behavior. LCF data scatter was mainly attributed to probabilistic nature of particle presence in a given volume, and probability of fracture at the first LCF cycle.In order to describe these effects and develop a model able to account for LCF scatter by the only means of physical mechanisms description, a global macroscopic and probabilistic model has been proposed. This model can be used as a post-processing routine of a finite element analysis.Confrontation of the global probabilistic model to experimental data gathered on notched samples gives good results, and the proposed method shows more realistic than the standard one on the cases exposed. Contrary to the standard method, it allows in addition to determine the predominant initiation site as a function of loading, material behavior and microstructure inherited from forging process, giving way to possible material and forging route optimisation at the design stage, to fulfill given structural life objectives.

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Short crack initiation and growth at 600°C in notched specimens of Inconel718

Cited by 116 publications

References 33 publications

Effect of broaching on high-temperature fatigue behavior in notched specimens of INCONEL 718

Effect of broaching on high-temperature fatigue behavior in notched specimens of INCONEL 718

Effect of Phosphorus on Microstructure and Mechanical Properties of IN718 Alloy after Hot Corrosion and Oxidation

Probabilistic Life of DA718 for Aircraft Engine Disks

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