Fatigue crack growth mechanisms in superalloys: an overview
Fatigue crack growth mechanisms in superalloys: an overview
Fatigue studies on disc and blade nickel based superalloys by the author and co-workers are reviewed. Crack initiation in single crystal turbine blade alloys is dominated by interdendritic porosity with oxidation processes affecting initiation position. Lifetime trends can be modelled using a multipart Paris type lifing approach. Orientation, loading state, temperature and environment determine stage I/II crack growth mechanisms and the resulting crack path and should be considered in lifing. Mechanistic insights on how complex stress states, subsurface failures and different temperatures/environments affect fatigue processes can thus improve turbine blade lifing, and direct alloy development programmes. In polycrystalline disc alloys
cracks at high temperature may initiate at oxidised subsurface carbides or porosity. Grain size controls cycle and time dependent crack growth: the benefits of increased grain size in resisting
grain boundary attack mechanisms predominate over those of gamma' distribution variation. Optimising grain boundary character and gamma' distribution should yield the best alloy design strategy for high
temperature fatigue performance in turbine discs.
Single crystal, Fatigue, Ni based superalloys, Initiation, Grain size, Loading state, Environment, Fatigue crack growth rate
258-270
Reed, P.A.S.
8b79d87f-3288-4167-bcfc-c1de4b93ce17
February 2009
Reed, P.A.S.
8b79d87f-3288-4167-bcfc-c1de4b93ce17
Reed, P.A.S.
(2009)
Fatigue crack growth mechanisms in superalloys: an overview.
Materials Science and Technology, 25 (2), .
(doi:10.1179/174328408X361463).
Abstract
Fatigue studies on disc and blade nickel based superalloys by the author and co-workers are reviewed. Crack initiation in single crystal turbine blade alloys is dominated by interdendritic porosity with oxidation processes affecting initiation position. Lifetime trends can be modelled using a multipart Paris type lifing approach. Orientation, loading state, temperature and environment determine stage I/II crack growth mechanisms and the resulting crack path and should be considered in lifing. Mechanistic insights on how complex stress states, subsurface failures and different temperatures/environments affect fatigue processes can thus improve turbine blade lifing, and direct alloy development programmes. In polycrystalline disc alloys
cracks at high temperature may initiate at oxidised subsurface carbides or porosity. Grain size controls cycle and time dependent crack growth: the benefits of increased grain size in resisting
grain boundary attack mechanisms predominate over those of gamma' distribution variation. Optimising grain boundary character and gamma' distribution should yield the best alloy design strategy for high
temperature fatigue performance in turbine discs.
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Published date: February 2009
Keywords:
Single crystal, Fatigue, Ni based superalloys, Initiation, Grain size, Loading state, Environment, Fatigue crack growth rate
Organisations:
Engineering Mats & Surface Engineerg Gp
Identifiers
Local EPrints ID: 65062
URI: http://eprints.soton.ac.uk/id/eprint/65062
ISSN: 0267-0836
PURE UUID: 3089dbfb-3242-4b2f-a5b0-f2da9a96082b
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Date deposited: 29 Jan 2009
Last modified: 16 Mar 2024 02:44
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