Surface recrystallization in a single crystal nickel-based superalloy

Bond, Stephen; Martin, J.W.

doi:10.1007/bf00980749

Cited by 64 publications

(36 citation statements)

References 2 publications

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“…In order to Conditions ofReheat Treatments. procedure on Ni-based superalloys before coating, which is often conducted to improve the adhesion between the film/substrate, is also a straining process [2]. More recently, Walston et al [S] have studied microstructural instability in the second and third generation single crystal superalloys including higher levels of refractory elements, or the precipitation of Topologically Close Packed (TCP) phases.…”

Section: Resultsmentioning

confidence: 99%

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Effect of Local Cellular Transformation on Fatigue Small Crack Growth in CMSX-4 and CMSX-2 at High Temperature

Okazaki¹,

Hiura²,

Suzuki³

2000

Superalloys 2000 (Ninth International Symposium)

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In order to get fundamental understanding to establish a refurbishment technology for advanced gas turbine components, the cellular formation associated with a y/y microstructure coarsened in lamellar or equiaxed arrays in single crystal Ni-base superalloys, CMSX-2 and CMSX-4, have been studied, supposing the case in which they were previously subjected to a damage associated with local plastic deformation, followed by a re-heat treatment. During this study special attention was paid to understand the nucleation and the growth of the transformation from viewpoints of crystallo-plasticity and therm0 dynamics. The experimental evidence indicated that the transformation originated and developed with high anisotropy, being influenced by the following factors: the strain field produced by local plastic deformation, the crystallographic orientation, the re-heat treatment temperature and time, and the microsegregation in the material. It was shown that the transformation was reproduced in material previously subjected to fatigue and thermo-mechanical fatigue damage, in which the shearing of y precipitates resulting from the activation of { 11 l}4fO> slip systems was significant. It was shown that diffusion was controlling the growth rate of the transformation, accompanied with an activation energy of 36 kcal/mol. Furthermore, the effect of the local cellular transformation on the high temperature small fatigue crack propagation was quantified experimentally. supeml10ys 2oc0 Edited byT

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Section: Resultsmentioning

confidence: 99%

“…The former and the latter are planned to simulate the process of damage during servicing, and that of recovery as usual in high temperature components, respectively. From another point of view the former can be reproduced by shot-blasting process before the coating [2]. The Vickers indentations with a pyramidal angle of 136 deg.…”

Section: Resultsmentioning

confidence: 99%

Effect of Local Cellular Transformation on Fatigue Small Crack Growth in CMSX-4 and CMSX-2 at High Temperature

Okazaki¹,

Hiura²,

Suzuki³

2000

Superalloys 2000 (Ninth International Symposium)

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“…• The recrystallisation nuclei have misorientations of [20][21][22][23][24][25][26][27][28][29][30] • with the deformed region, similar to the lattice rotations induced after indentation. The grains twin 2-3 times to form mobile higher angle grain boundaries.…”

Section: Discussionmentioning

confidence: 99%

“…9 to reveal a bimodal distribution. Distribution A is sharper and consists mainly of grains misorientated [20][21][22][23][24][25][26][27][28][29][30] • from the deformed matrix; distribution B shows a greater spread comprising of grains misorientated by 40-55…”

Section: Nucleationmentioning

confidence: 99%

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A study on the effect of composition, and the mechanisms of recrystallisation in single crystal Ni-based superalloys

Mathur

Jones

Rae

2014

MATEC Web of Conferences

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Abstract. The effect of composition on recrystallisation of single crystal Ni-based superalloys was studied in a series of alloys that vary systematically in composition. Following room temperature macro-indentation and subsequent annealing, alloys containing higher Co concentration showed greater susceptibility to recrystallisation, and this has been attributed to the effect on the γ solvus temperature and the stacking fault energy of the γ phase. Mo, W and Ru did not appear to influence the recrystallisation behaviour systematically, although high concentration of all these elements led to the highest recrystallisation. Moreover, with grain orientation mapping, it was found that the nucleating recrystallisation grains form in orientations similar to the deformed regions, and subsequently twin to form higher angle boundaries and proliferate further within the deformed microstructure. The effects of the interaction between grain boundaries and secondary phases, such as the γ and topologically close packed phases, were also studied.

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Prediction of Plastic Strain for Recrystallisation during Investment Casting of Single Crystal Superalloys

Panwisawas¹,

Mathur²,

Gebelin³

et al. 2012

Superalloys 2012

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Castings for single crystal aerofoils can be prone to recrystallisation during solution heat treatment; however quantitative information concerning the factors causing this phenomenon is lacking. In this paper, mathematical modelling and targeted experimentation are used to deduce the levels of localised plastic strain needed for recrystallisation to occur. The influences of differential thermal contraction against the shell, specimen geometry and stress concentration factor are quantified. The model predicts that the induced strain in the metal increased with the ceramic shell thickness, and in some geometries, with the solidification height. Negligible plastic strains were predicted in a solid casting with no stress concentration features. However, as the geometry became more complex by reducing the casting cross-section, by the insertion of a core and introduction of stress concentration features, the induced plastic strains increased significantly. The predicted plastic strain for recrystallisation in a cored casting was in good agreement with experimental critical strain data. The model provides the foundation for a systems-based approach which enables recrystallisation to be predicted and thus avoided, prior to its occurrence in the foundry.

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Surface recrystallization in a single crystal nickel-based superalloy

Cited by 64 publications

References 2 publications

Effect of Local Cellular Transformation on Fatigue Small Crack Growth in CMSX-4 and CMSX-2 at High Temperature

Effect of Local Cellular Transformation on Fatigue Small Crack Growth in CMSX-4 and CMSX-2 at High Temperature

A study on the effect of composition, and the mechanisms of recrystallisation in single crystal Ni-based superalloys

Prediction of Plastic Strain for Recrystallisation during Investment Casting of Single Crystal Superalloys

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