Control of Grain Size Via Forging Strain Rate Limits for R�88DT

Huron, Eric S.; Srivatsa, Shesh; Raymond, E. L.

doi:10.7449/2000/superalloys_2000_49_58

Cited by 25 publications

(17 citation statements)

References 6 publications

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“…The temperature of this treatment -T sol -is adjusted regarding to the solvus temperature and depends on the alloy itself. However, some unwanted exaggerated grain growth may occur during this solution treatment, as already reported in various Nickel-based superalloys [10][11][12][13][14][15][16][17][18]. This selective growth of some grains leads to heterogeneous microstructures, consisting of fine grains and overgrown grains which size can be up to 10 times greater than the average.…”

Section: Introductionmentioning

confidence: 78%

“…Such microstructures do not match the requirements [1,19,20] on mechanical properties and have to be avoided. This phenomenon has been reported under different terminologies as "Abnormal Grain Growth" (AGG), "Critical Grain Growth" (CGG) [18], "Inhomogeneous Grain Growth" (IGG) [21] in the literature. Numerous studies have been carried on, aiming at determining the influence of the deformation and/or treatment conditions in a given alloy.…”

Section: Introductionmentioning

confidence: 99%

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Overgrown grains appearing during sub-solvus heat treatment in a polycrystalline γ-γ’ Nickel-based superalloy

2018

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Highlights 1) Grain overgrowth during annealing after deformation is a case of critical recrystallization involving a limited number of nuclei. 2) The difference in stored energy between the overgrown grains and the matrix is the key microstructural driving force. 3) The self-impingement of the overgrown grains is the main size-limiting phenomenon, before Zener-pinning by second-phase particles. 4) The relative magnitudes of the driving forces at the deformed state enable to predict the occurrence of this phenomenon.

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Section: Introductionmentioning

confidence: 78%

Section: Introductionmentioning

confidence: 99%

Overgrown grains appearing during sub-solvus heat treatment in a polycrystalline γ-γ’ Nickel-based superalloy

2018

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“…Varied disk forging conditions have been found to significantly influence grain size response in powder metallurgy disk superalloys during subsequent heat treatments [20]. Therefore, varied forging conditions could be used to help tailor grain size and fatigue properties in the transition zone and rim.…”

Section: Effects Of Dwells On Fatigue Failures In the Transition Zonementioning

confidence: 99%

Fatigue Failure Modes of the Grain Size Transition Zone in a Dual Microstructure Disk

Gabb¹,

Kantzos²,

Palsa³

et al. 2012

Superalloys 2012 (Twelfth International Symposium)

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Mechanical property requirements vary with location in nickelbased superalloy disks. In order to maximize the associated mechanical properties, heat treatment methods have been developed for producing tailored grain microstructures. In this study, fatigue failure modes of a grain size transition zone in a dual microstructure disk were evaluated. A specialized heat treatment method was applied to produce varying grain microstructure in the bore to rim portions of a powder metallurgy processed nickel-based superalloy disk. The transition in grain size was concentrated in a zone of the disk web, between the bore and rim. Specimens were extracted parallel and transversely across this transition zone, and multiple fatigue tests were performed at 427 °C and 704 °C. Grain size distributions were characterized in the specimens, and related to operative failure initiation modes. Mean fatigue life decreased with increasing maximum grain size, going out through the transition zone. The scatter in limited tests of replicates was comparable for failures of uniform gage specimens in all transition zone locations examined.

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“…All of these factors are known to affect grain growth [3] , and the specific deformation processing conditions can affect all of these parameters [4][5][6][7][8]. For example, forging is usually performed at temperatures below the γ solvus to take advantage of superplastic and near-superplastic behavior [9,10].…”

Section: Introductionmentioning

confidence: 99%

“…The strain rate of deformation is a critical parameter affecting supersolvus heat treated grain size in disk superalloys [6,8,28]. The effects of strain rate on grain size in René 104 are shown for two example conditions in Figure 5.…”

Section: Strain Rate Effectsmentioning

confidence: 99%

Integration of Simulations and Experiments for Modeling Superalloy Grain Growth

Payton¹,

Wang²,

Ma³

et al. 2008

Superalloys 2008 (Eleventh International Symposium)

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Grain size is an important parameter controlling the mechanical behavior and useful life of turbine disks. During heat treatment above the gamma prime (γ ) solvus the grain size increases dramatically as the γ particles dissolve. The grain size then stagnates as the volume fraction of the γ phase approaches zero. In general, the grain size at stagnation cannot be described by classic Zener pinning theory because of its strong dependence on the strain rate and thermal exposure during thermomechanical processing.The grain size distribution, twin boundary fraction, γ size distribution and volume fraction, carbide size distribution and volume fraction, γ dissolution rates, and carbide coarsening rates have been measured in two powder metallurgical disk superalloys. Stored energy and boundary properties after deformation have been assessed. The experimental results have been used as input parameters for a physics-based model of grain growth in a field of two populations of particles, one coarsening and one dissolving. Phase field models have been used to support and clarify interpretations of experimental results and to validate the appropriate functional forms for precipitate coarsening and dissolution. Comparison of experimental and modeling results have suggested avenues for further experimental investigations and vice versa. This established feedback loop between experimentation and simulation has enabled focused experimentation, increasing the accuracy and general applicability of the model.

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Control of Grain Size Via Forging Strain Rate Limits for R�88DT

Cited by 25 publications

References 6 publications

Overgrown grains appearing during sub-solvus heat treatment in a polycrystalline γ-γ’ Nickel-based superalloy

Overgrown grains appearing during sub-solvus heat treatment in a polycrystalline γ-γ’ Nickel-based superalloy

Fatigue Failure Modes of the Grain Size Transition Zone in a Dual Microstructure Disk

Integration of Simulations and Experiments for Modeling Superalloy Grain Growth

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