Influence of the initial cooling rate from γ′ supersolvus temperatures on microstructure and phase compositions in a nickel superalloy
Author(s)
Li, Muzi
Coakley, James
Isheim, Dieter
Tian, Gaofeng
Shollock, Barbara
Type
Journal Article
Abstract
Different cooling paths from a supersolvus temperature have been applied to FGH96, a polycrystalline nickel base superalloy for turbine disc applications, in order to simulate the different microstructures that exist through the thickness of a disc following an industrial heat treatment. Secondary and tertiary γ′ precipitate size distributions and morphology have been analysed and compared for the different heat treatments using SEM and atom probe tomography (APT). Detailed compositional data for both γ′ precipitate and γ matrix are presented, and compared to equilibrium compositions calculated by Thermo-Calc. For the heat-treatments studied, the secondary γ′ composition indicates a shell of differing composition to that towards the precipitate core. From sequential equilibria compositional calculations, it is suggested that the ‘shell’ forms at a lower temperature than the precipitate core. The fine tertiary precipitates do not show the core-shell compositional differences on continuous cooling. W peaks are noted at the γ/γ′ interfacial region, which is of significance for retarding coarsening. A γ′ depletion zone surrounds the secondary precipitates, within which the γ matrix composition differs significantly to the γ far-field values, Finally, a precipitate nucleation and growth mechanistic model is suggested based on the experimental data and Thermo-Calc calculations.
Date Issued
2018-01
Date Acceptance
2017-10-28
Citation
Journal of Alloys and Compounds, 2018, 732, pp.765-776
ISSN
0925-8388
Publisher
Elsevier
Start Page
765
End Page
776
Journal / Book Title
Journal of Alloys and Compounds
Volume
732
Copyright Statement
© 2017 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND
license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
Subjects
0912 Materials Engineering
0914 Resources Engineering And Extractive Metallurgy
0204 Condensed Matter Physics
Materials
Notes
publisher: Elsevier articletitle: Influence of the initial cooling rate from γ′ supersolvus temperatures on microstructure and phase compositions in a nickel superalloy journaltitle: Journal of Alloys and Compounds articlelink: http://dx.doi.org/10.1016/j.jallcom.2017.10.263 content_type: article copyright: © 2017 Published by Elsevier B.V.
Publication Status
Published