Environmental enhancement of creep crack growth in inconel 718 by oxygen and water vapor

Valerio, Paul F.; Gao, Ming; Wei, Robert P.

doi:10.1016/0956-716x(94)90257-7

Cited by 53 publications

(39 citation statements)

References 4 publications

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“…The results showed that sustained load crack growth rates in oxygen at 973 K were increased, for example, by more than 104x over those in highpurity argon for Inconel 718 [1,12]. It was suggested that the enhancement in crack growth was caused by the formation and rupture of a non-protective and brittle NbzOs-type oxide film at the grain boundaries; the films being formed through the oxidation and decomposition of niobiumrich carbides and, perhaps, oxidation of 1/' (Ni3Nb) precipitates at the grain boundaries at a much higher concentration (-10:1, Ni3Nb:NbC).…”

Section: Introductionmentioning

confidence: 84%

Mechanistic Considerations of Oxygen Enhanced Crack Growth in INCONEL 718

Wei¹,

Huang²,

Miller³

et al. 2001

Superalloys 718, 625, 706 and Various Derivatives (2001)

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A coordinated, multidisciplinary study was conducted to elucidate the mechanism for oxygen enhanced crack growth in Inconel 718 at high temperatures. Sustained-load tests were conducted in high-purity argon and oxygen, at 873 to 973 K, to characterize the kinetics of crack growth. The reactivity of the alloy, Nb, NbC and Ni3Nb with oxygen was determined by x-ray photoelectron spectroscopy (XPS). Crack growth experiments, in oxygen at 973 K, were interrupted and the specimens were charged with hydrogen and fractured in UHV to determine the state of oxidation of various elements, particularly ahead of the crack tip. The existence of a damage zone ahead of the crack tip had been demonstrated previously by reloading interrupted specimens of comparable alloys in argon at lower temperatures and stress intensity levels. A mechanism for oxygen enhanced crack growth in Inconel 718, based on the formation of a brittle niobium oxide film ahead of the crack tip from the oxidation of grain boundary Ni3Nb and Nb-rich carbides, is proposed and discussed.

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Section: Introductionmentioning

confidence: 84%

Mechanistic Considerations of Oxygen Enhanced Crack Growth in INCONEL 718

Wei¹,

Huang²,

Miller³

et al. 2001

Superalloys 718, 625, 706 and Various Derivatives (2001)

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“…Valerio et al [11] found that the crack propagation rate is increased by two orders of magnitude in a mixture of water vapour and argon (without any O 2 ) compared to dry argon. They identified both oxygen and hydrogen as embrittling species and found a higher concentration of niobium at the grain boundaries.…”

Section: Introductionmentioning

confidence: 99%

Effect of SO2 and water vapour on the low-cycle fatigue properties of nickel-base superalloys at elevated temperature

Moverare

Leijon

Brodin

et al. 2013

Materials Science and Engineering: A

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Abstract:In this study the effect of SO 2 + water vapour on strain controlled low cycle fatigue resistance of three different nickel based superalloys has been studied at 450°C and 550°C. A negative effect was found on both the crack initiation and crack propagation process. The effect increases with increasing temperature and is likely to be influenced by both the chemical composition and the grain size of the material. In general the negative effect decreases with decreasing strain range even if this means that the total exposure time increases. This is explained by the importance of the protective oxide scale on the specimen surface, which is more likely to crack when the strain range increases. When the oxide scale cracks, preferably at the grain boundaries, oxidation can proceed into the material, causing preferable crack initiation sites and reduced fatigue resistance.

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“…Alloy 718 is, as many other nickel based alloys such as alloy 600 or X750 are, sensitive to an oxidation assisted crack growth mechanism. Indeed, many studies have emphasized the detrimental effect of oxygen and more generally of environment on the mechanical behavior of alloy 718 at high temperatures [1][2][3][4][5][6][7][8][9]. The present paper is aimed at studying the effect of two oxidation conditions close to those encountered industrially: -1000°C in air: similar to hot rolling conditions.…”

Section: Introductionmentioning

confidence: 99%

“…-650°C in air: similar to "in service" conditions of turbomachine disks. Under such conditions, the material is known to be sensitive to oxidation assisted crack propagation [3][4][5][6][7][8][9][10][11][12][13]. The core of the present study is to assess the harmfulness of intergranular oxides penetrations (IOP) on the mechanical properties of alloy 718.…”

Section: Introductionmentioning

confidence: 99%

High Temperature Intergranular Oxidation of Alloy 718

Garat¹,

Deleume²,

Cloue³

et al. 2005

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

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Alloy 718 samples were oxidized in air under experimental conditions close to those experienced during high-temperature heat treatments (shaping: about 1000°C) or in service (turbomachine disks: 650°C). The main objective of the study was to evaluate the impact of these treatments on oxygen penetration into the grain boundaries and, hence, to assess the harmfulness of these penetrations in terms of defect initiation and propagation. The method relies mainly on the SIMS-based imaging technique. This technique, which supplements those applied in previous studies, uses a series of basic maps to locate within the volume the oxygen in free or combined state, in relation with the microstructural features (grain boundaries, grains, delta phase, etc). The results point out to intergranular oxidation for both exposure conditions without clearly demonstrating the existence of atomic oxygen penetrations ahead of the intergranular oxidation front. The affected depths seem sufficient both to form preferential initiation sites (oxidation at 1000°C) and to assist intergranular propagation of defects and/or cracks (oxidation at 650°C).

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Environmental enhancement of creep crack growth in inconel 718 by oxygen and water vapor

Cited by 53 publications

References 4 publications

Mechanistic Considerations of Oxygen Enhanced Crack Growth in INCONEL 718

Mechanistic Considerations of Oxygen Enhanced Crack Growth in INCONEL 718

Effect of SO2 and water vapour on the low-cycle fatigue properties of nickel-base superalloys at elevated temperature

High Temperature Intergranular Oxidation of Alloy 718

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