Observations of directional gamma prime coarsening during engine operation

Draper, Susan L.; Hull, David R.; Dreshfield, R. L.

doi:10.1007/bf02667585

Cited by 51 publications

(21 citation statements)

References 5 publications

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“…As far as we know, this phenomenon, often denoted "y' raftening", has been observed in the presence of two asymmetry causes. The first one is a large-scale chemical gradient, resulting either from segregation due to the solidification process [22] or from long range diffusion [23,24]. In this case, the plates align perpendicular to the main chemical gradient [14].…”

Section: Morphological Evolution During Isothermal Thermo-mechanical mentioning

confidence: 99%

Internal Mismatch Stresses in Nickel-Based Superalloys : A Finite Element Approach

1996

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Abstract. A three-dimensional finite element (F.E.) model is used to estimate the mismatch stresses at a microscopic scale in y -y ' single-crystal nickel-based snpedloys. F.E. calculations point out the specificity of stress/strain distributions in these alloys, in particular the fact that internal stresses concentrate in the connected y matrix. The analysis of stress/strain fields and elastic energy evolution as a function of precipitate morphology and volume fraction allows to explain some atypical precipitate shape changes such as "splitting" during precipitation treatments or "raftening" during high temperature creep tests.

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Section: Morphological Evolution During Isothermal Thermo-mechanical mentioning

confidence: 99%

Internal Mismatch Stresses in Nickel-Based Superalloys : A Finite Element Approach

1996

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“…in that region of a blade in which the combined action of thermal and mechanical loads is most severe (stress above ca. 150 MPa, temperature ≤ 950 C, compare [18]), the development of the raft structure leads to a deterioration of the mechanical properties of the alloy [9,19]. In this respect, it is interesting to investigate the effects of different alloying elements on the development of the γ/γ microstructure.…”

Section: Introductionmentioning

confidence: 99%

The Effects of Different Alloying Elements on the Thermal Expansion Coefficients, Lattice Constants and Misfit of Nickel-Based Superalloys Investigated by X-Ray Diffraction

Pyczak¹,

Devirent²,

Mughrabi³

2004

Superalloys 2004 (Tenth International Symposium)

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The influence of variations of the chemical composition, especially by adding refractory elements, on the lattice parameter and thermal expansion coefficients of nickel-based superalloys was investigated. To analyse these effects in a systematic way, measurements in a series of experimental and commercial alloys with different alloy compositions were performed. The lattice constants of the γ and γ phases were measured by X-ray diffraction at temperatures between 25• C and 1100• C. The main focus was on the effects of rhenium additions, but alloy compositions containing ruthenium and iridium were also included. It was possible to interpret the changes of the lattice parameters of γ and γ as effects of certain alloying elements by analysing the local chemical composition of the γ and γ phases and the partitioning behaviour of the alloying elements between the γ and γ phases.

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“…70 %) of the ordered y'-phase (Ll;?-structure), which is coherently embedded in the fee y-matrix, are widely used as turbine blade material in aircrafts. In these hightemperature materials, so-called rafting (directional coarsening) has emerged as an important phenomenon both in laboratory tests [1,2,3] and in hot sections of turbine blades subjected to service conditions [4]. Furthermore, rafting has been observed after thermomechanical fatigue (TMF) [S].…”

Section: Introductionmentioning

confidence: 99%

“…Since rafting was also detected in turbine blades subjected to service conditions [4,8], it was of considerable interest to study the effect of this modified microstructure on the fatigue and creep strengths. Therefore, Ott et al [9,10] studied systematically the effect of pre-rafting on the isothermal fatigue behaviour of the alloys CMSX-6 and CMSX-4.…”

Section: Introductionmentioning

confidence: 99%

Enhancement of the High-Temperature Tensile Creep Strength of Monocrystalline Nickel-Base Superalloys by Pre-rafting in Compression

Tetzlaff¹,

Mughrabi²

2000

Superalloys 2000 (Ninth International Symposium)

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In recent years, the development of Y.-hardened monocrystalline nickel-base superalloys focused on different aspects of alloy composition and microstructural refinement. In particular, the formation of so-called y/y'-raft structures, lying typically, in the case of a negative y/y'-lattice misfit 6, perpendicular to the stress axis during high-temperature tensile creep had attracted much attention. Unfortunately, this microstructural transformation leads in most cases to deteriorated creep properties. Earlier attempts to prevent rafting by suitable prior annealing treatments had been in so far unsuccessful, that while the applied annealing treatment retarded raft formation, it inevitably lead to microstructural coarsening accompanied by creep acceleration. The goal of the present extensive study is to show that suitable pre-rafting in compression, leading to a y/y'-raft structure parallel to the stress axis in the case of a negative lattice misfit, enhances not only the isothermal hightemperature fatigue strength, as shown earlier, but also the hightemperature creep properties. The observed macroscopic creep behaviour will be discussed with reference of microstructural observations.

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Observations of directional gamma prime coarsening during engine operation

Cited by 51 publications

References 5 publications

Internal Mismatch Stresses in Nickel-Based Superalloys : A Finite Element Approach

Internal Mismatch Stresses in Nickel-Based Superalloys : A Finite Element Approach

The Effects of Different Alloying Elements on the Thermal Expansion Coefficients, Lattice Constants and Misfit of Nickel-Based Superalloys Investigated by X-Ray Diffraction

Enhancement of the High-Temperature Tensile Creep Strength of Monocrystalline Nickel-Base Superalloys by Pre-rafting in Compression

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