New technique for characterization of microstructural degradation under creep: Application to the nickel-base superalloy CMSX-4

Epishin, Alexander; Link, Thomas; Klingelhöffer, Hellmuth; Fedelich, Bernard; Brückner, U.; Portella, Pedro Dolabella

doi:10.1016/j.msea.2008.04.135

Cited by 45 publications

(26 citation statements)

References 7 publications

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“…the applied procedure allowed to perform up to 5 successive degradation experiments accompanied by metallographic analysis of the evolving microstructure. Experimental details of this technique are presented in [8]. The FW specimens of CMSX-4 were annealed under constant load at different temperatures in the range of 850-1050°C.…”

Section: Methodsmentioning

confidence: 99%

Microstructural Degradation of CMSX-4: Kinetics and Effect on Mechanical Properties

Epishin¹,

Link²,

Nazmy³

et al. 2008

Superalloys 2008 (Eleventh International Symposium)

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The γ/γ'-microstructure of nickel-base superalloys gradually degrades during high temperature loading which deteriorates the mechanical properties. In the work presented the kinetics of microstructural degradation of the superalloy CMSX-4 was investigated metallographically in a wide parameter field (T, σ, t).The effect of microstructural degradation on mechanical properties was determined by mechanical testing of specimens pre-annealed under load. The laboratory results were compared with the microstructure of ex-service blades of CMSX-4.

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Section: Methodsmentioning

confidence: 99%

Microstructural Degradation of CMSX-4: Kinetics and Effect on Mechanical Properties

Epishin¹,

Link²,

Nazmy³

et al. 2008

Superalloys 2008 (Eleventh International Symposium)

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“…1b). The stress (σ), temperature (T) and time (t) dependence of the raft formation is presented in [1]. Representative TEM images of the dislocation structure in the γ'-phase are given in Fig.…”

Section: Resultsmentioning

confidence: 99%

“…Laboratory investigations however are mostly performed in the several hundreds hour range, which is about a factor of 10 below realistic conditions. It is well known, that the microstructure of superalloys is not stable during high temperature creep: the cubical γ'-precipitates coalesce and grow [1], dislocations relax coherency stresses and generate internal stresses on their part [2]. A central question is, how plastic deformation continues, when dislocation movement, starting in the matrix channels, is blocked by back stresses, built up by preceding dislocations.…”

Section: Introductionmentioning

confidence: 99%

Dislocation Structures in the Gamma Prime-Phase of CMSX-4 and TMS75 after Degradation under Service Conditions

Link

Epishin

Nawrath

et al. 2011

AMR

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Abstract. The single crystal superalloys CMSX-4 and TMS75 were tested for very long times at high temperatures in laboratory creep tests and in service. The microstructure was investigated in TEM and SEM. It was found, that the γ'-phase is cut at stresses much below the threshold given in literature. Cutting takes place by <110> screw dislocations. These mobile dislocations can be locked locally by a Giamei-lock. Thus a stacking fault dipole forms between the locked segment and the preceding ones. The dipole consists of two supershockley dislocations with 30° character, which are also stabilized by Giamei locks. The dipole formation is analyzed and discussed in detail.

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“…Because of the wedge shape of the specimens, the stress changes linearly along the specimen axis, thus allowing investigating several (6) stress levels with a single specimen. Experimental details of the technique have been published in [5]. Moreover, at every test temperature specimens have been annealed without load.…”

Section: Experimental Conditionsmentioning

confidence: 99%

Rafting during High Temperature Deformation in a Single Crystal Superalloy: Experiments and Modeling

Fedelich¹,

Epishin²,

Link³

et al. 2012

Superalloys 2012 (Twelfth International Symposium)

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To characterize the kinetics of rafting, mechanical tests and microstructural investigations have been performed for the single crystal superalloy CMSX-4. The kinetics of microstructural degradation under constant load have been investigated in the temperature range 850-1100°C and for a large range of stress levels. An analytical model of the rafting kinetics has been proposed to represent the influence of temperature, stress and time on the microstructure degradation. To predict the degradation effect of rafting on the mechanical behavior of single crystal superalloys and its kinetics during complex loadings, a specific viscoplastic constitutive model has been developed. The degree of rafting is incorporated in the model via the γ-channels width, which determines the Orowan stress. The rafting kinetics are assumed to be driven by the reduction of internal stresses represented by the macroscopic back-stress. The model has been calibrated for the temperatures 950°C and 1050°C. Several validation tests have been simulated.

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New technique for characterization of microstructural degradation under creep: Application to the nickel-base superalloy CMSX-4

Cited by 45 publications

References 7 publications

Microstructural Degradation of CMSX-4: Kinetics and Effect on Mechanical Properties

Microstructural Degradation of CMSX-4: Kinetics and Effect on Mechanical Properties

Dislocation Structures in the Gamma Prime-Phase of CMSX-4 and TMS75 after Degradation under Service Conditions

Rafting during High Temperature Deformation in a Single Crystal Superalloy: Experiments and Modeling

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