Surface enrichment and grain boundary segregation of niobium in inconel 718 single- and poly-crystals

Pang, Xinkuan; Dwyer, Daniel J.; Gao, Ming; Valerio, Paul F.; Wei, Robert P.

doi:10.1016/0956-716x(94)90294-1

Cited by 48 publications

(18 citation statements)

References 9 publications

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“…OAIC is characterized, not only by the fractographic observations, but also by the decrease in ductility. Pang et al [1] showed that the niobium concentration in these regions increased substantially after heat treatments above 300°C and a binding energy shift in Nb XPS data was observed, according to the authors, this may indicate niobium reaction with trace amounts of oxygen on the surface or trapped in the bulk to form niobium oxide. Gao formation of c 0 and c 00 instead of niobium oxide.…”

Section: Discussionmentioning

confidence: 91%

“…However, brittle intergranular cracking is observed when the alloy is deformed at elevated temperatures [1][2][3][4][5][6][7]. This embrittlement effect is related to grain boundary penetration by oxygen (Oxygen Assisted Intergranular Cracking -OAIC).…”

Section: Introductionmentioning

confidence: 96%

“…Although literature indicates that OAIC is responsible for this environmental effect in Inconel 718, its interaction with DSA precipitation and are still under discussion. Pang et al [1] investigated the kinetics and mechanisms of oxygen reaction in Inconel 718. They have reported that niobium may segregate to the surface and grain boundaries during heat treatment bringing susceptibility to oxidation.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Oxidation assisted intergranular cracking under loading at dynamic strain aging temperatures in Inconel 718 superalloy

Rezende

Araújo

Gabriel

et al. 2015

Journal of Alloys and Compounds

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Section: Discussionmentioning

confidence: 91%

Section: Introductionmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Oxidation assisted intergranular cracking under loading at dynamic strain aging temperatures in Inconel 718 superalloy

Rezende

Araújo

Gabriel

et al. 2015

Journal of Alloys and Compounds

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“…Studies of polished surfaces of Inconel 718 single crystals and polycrystals, and of grain boundary surfaces exposed by in situ fracture of hydrogen charged samples were carried out by x-ray photoelectron spectroscopy (XPS) [ 1,17,18]. Strong enrichment of Nb was observed on the alloy surfaces after heating to 973 K for 1 h in ultrahigh vacuum (UHV).…”

Section: Reactivity Of Inconel 7 18 Surfaces and Grain Boundary Enricmentioning

confidence: 99%

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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“…Substitutional alloying elements have a strong influence on these properties of the material: they are involved in solid solution hardening of the matrix, in the formation of strengthening phases and confer to the alloy its resistance to oxidation and corrosion [1][2][3][4][5][6]. Nevertheless, alloy 718 remains sensitive to intergranular stress corrosion cracking for various in service conditions for different types of applications.…”

Section: Introductionmentioning

confidence: 99%

Studying the influence of substitutional elements on mechanical behavior of Alloy 718

Max

Juán

Nó

et al. 2014

MATEC Web of Conferences

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Abstract. In nickel-based superalloys, substitutional solute species have a strong impact on in service mechanical properties as well as on oxidation and corrosion resistances. In alloy 718, recent studies carried out by tensile tests highlighted the fact that refractory solute species are able to interact strongly with mobile dislocations during plastic deformation, generating dynamic strain ageing, and, in wide ranges of tests temperatures and strain rates, Portevin-Le Chatelier effect. The precise nature of the substitutional element responsible for such a dynamic interaction is still subject to debate. We addressed this question by means of mechanical spectroscopy studies of alloy 718 and various related alloys corresponding to monitored changes in the chemical composition. Only a single internal friction relaxation peak has been observed for all the studied alloys. By analyzing the damping behavior of these alloys at different imposed solicitation frequencies by sweeping a large temperatures range, the activation energies of the relaxation process and the type of mechanism involved have been determined. The process is a "Zener relaxation" in the alloys, i.e. a substitutional atoms dipole reorientation under applied stress. The results tend to prove that Niobium is not involved in the relaxation process whereas Molybdenum content seems to play an important role in the relaxation intensity.

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Surface enrichment and grain boundary segregation of niobium in inconel 718 single- and poly-crystals

Cited by 48 publications

References 9 publications

Oxidation assisted intergranular cracking under loading at dynamic strain aging temperatures in Inconel 718 superalloy

Oxidation assisted intergranular cracking under loading at dynamic strain aging temperatures in Inconel 718 superalloy

Mechanistic Considerations of Oxygen Enhanced Crack Growth in INCONEL 718

Studying the influence of substitutional elements on mechanical behavior of Alloy 718

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