Eigenschaften einkristalliner Turbinenschaufelwerkstoffe

Wege, R.; Wortmann, J.

doi:10.1002/mawe.19890200614

Cited by 6 publications

(1 citation statement)

References 11 publications

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“…In Table III, we compare the results that we obtained in the present study with data that were published in the literature. [10,15,25,37,[47][48][49] It can be seen that apparent activation energies are often found close to 500 kJ/mole, independent of the type of test (tensile creep/shear creep), the crystallographic direction, or the specific Nibase superalloy. Experimental values for the apparent activation energies of creep of single-crystal superalloys are significantly higher than the values reported for the apparent activation energy of self-diffusion of Ni* in Ni (285 kJ/mole [50] ) and in Ni 3 Al (306 kJ/mole [51] ).…”

Section: A Miniature Creep Testing and Creep Parametersmentioning

confidence: 99%

Miniature Specimen Assessment of Creep of the Single-Crystal Superalloy LEK 94 in the 1000 °C Temperature Range

Mälzer

Hayes²,

Mack

et al. 2007

Metall Mater Trans A

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The creep behavior of the Ni-base superalloy LEK 94 in the 1000°C range has been investigated. Miniature tensile specimens were employed, which can be taken out of a thin walled blade or used when only limited amounts of material are available. We show that this miniature test technique yields reasonable creep data, including stress exponents n and apparent activation energies Q app . The n values are close to 5 and the Q app values are close to 500 kJ/mole, independent of the crystallographic direction. Creep rates are fastest for samples oriented in the [110] direction, followed by [001] samples. The lowest creep rates are observed for the [111] direction. This difference is related to a difference in resolved shear stresses and in the number of activated crystallographic slip systems. As a striking new result, it was observed that the onset of tertiary creep occurs earlier and rupture strains are significantly smaller in the case of [110] specimens as compared to [100] specimens, while the [111] specimens show an intermediate behavior. These effects are related to the alignment of cast porosity along the axis of primary dendrites. When cast micropores align perpendicular to the axis of the applied tensile stress, the onset of fast tertiary creep occurs early and small rupture strains are observed.

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Section: A Miniature Creep Testing and Creep Parametersmentioning

confidence: 99%

Miniature Specimen Assessment of Creep of the Single-Crystal Superalloy LEK 94 in the 1000 °C Temperature Range

Mälzer

Hayes²,

Mack

et al. 2007

Metall Mater Trans A

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Einkristalline Gasturbinenschaufeln aus Nickelbasis‐Legierungen. Teil I: Herstellung und Mikrogefüge

Goldschmidt

1994

Materialwissenschaft Werkst

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Der Beitrag gibt einen Überblick über die zur Herstellung hochbeanspruchter Gasturbinenschaufeln heute übliche Einkristalltechnologie. Nach einem kurzen Abriß der Anforderungen an Gasturbinenschaufeln mit dem sich daraus ergebenden Zwang zur Verbesserung der Nickelbasis‐Legierungen und nach einer kurzen Definition des “technischen” Einkristalls werden im vorliegenden Teil I das Verfahrensprinzip der gerichteten Erstarrung, die realisierbaren Erstarrungsfrontmorphologien und die Methoden der Kornselektion beschrieben. Am Beispiel der Legierung SRR99 wird der für industrielle Produktion sinnvolle Gießparameterbereich fixiert. Die für Einkristallbauteile aus Nickelbasis‐Legierungen wesentlichen Mikrostrukturmerkmale “Kristallorientierung, Mikroporosität, Morphologie der γ′‐Härtungsphase, dendritische Seigerung und Resteutektikum” werden vorgestellt. Nach dem Abguß befindet sich die Mikrostruktur in einer für die Gebrauchseigenschaften nicht optimierten Form. Daher ist eine Wärmebehandlung erforderlich. In Teil II wird beschrieben, wie durch die Wärmebehandlung Resteutektikum aufgelöst, Seigerungen ausgeglichen und die Morphologie der γ′‐Phase optimiert werden können. Abschließend wird das mechanische Verhalten behandelt. Bei den elastischen und plastischen Eigenschaften werden der dominante Einfluß der Anisotropie gezeigt und beim Kriechverhalten die Wechselwirkung mit der γ′‐Morphologie, bei der Schwingfestigkeit der Zusammenhang mit der Mikroporosität hervorgehoben.

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Shear Creep Deformation of the Super Alloy Single Crystal CMSX‐4 at High Temperatures and Low Stresses

Kamaraj

Serin

Kolbe³

et al. 2003

Materialwissenschaft Werkst

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In the present paper we investigate the shear creep behavior of the single crystal super alloy CMSX-4 at temperatures between 950 and 1100 C and shear stresses ranging from 80 to 155 MPa. A double shear creep test technique is used to study the shear creep behavior of four specific macroscopic crystallographic shear systems defined by a specific crystallographic shear plane and a specific crystallographic shear direction (systems investigated:The shear creep behavior is analyzed in terms of the shape of individual creep curves and in terms of the stress and the temperature dependence of the secondary shear creep rate. Individual creep curves are generally characterized by a pronounced primary creep range where creep rates decrease by up to three orders of magnitude. A sharp creep rate minimum is not observed. The secondary creep range starts at shear stresses of the order of 0.02 and is followed by a secondary creep range which extends over shear strain ranges of the order of 0.1. No pronounced increase of shear creep rate in the later stages of creep is observed. Norton plots yield power law stress exponents ranging from 5.5 to 9.7. The temperature dependence of the secondary creep rate is of an Arrhenius type and apparent activation energies between 549 and 690 kJ/mol were found. There is a clear influence of crystallography on shear creep rates, which vary between different macroscopic crystallographic shear systems; this effect decreases with increasing temperature. The shear creep results obtained in the present study are discussed in the light of results from uniaxial testing and in the light of underlying microscopic deformation processes.

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Eigenschaften einkristalliner Turbinenschaufelwerkstoffe

Cited by 6 publications

References 11 publications

Miniature Specimen Assessment of Creep of the Single-Crystal Superalloy LEK 94 in the 1000 °C Temperature Range

Miniature Specimen Assessment of Creep of the Single-Crystal Superalloy LEK 94 in the 1000 °C Temperature Range

Einkristalline Gasturbinenschaufeln aus Nickelbasis‐Legierungen. Teil I: Herstellung und Mikrogefüge

Shear Creep Deformation of the Super Alloy Single Crystal CMSX‐4 at High Temperatures and Low Stresses

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