Microstructural and oxidation effects on fatigue crack initiation mechanisms in a turbine disc alloy

Effects of microstructure and oxidation on fatigue crack initiation and early propagation processes were investigated in RR1000 turbine disc alloy with different γ′ distributions and carbide distributions on the grain boundary. Fatigue tests were carried out under three-point bending and trapezoidal...

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Bibliographic Details
Published in:Journal of materials science 2023, Vol.58 (4), p.1869-1885
Main Authors: Kim, D., Jiang, R., Reed, P. A. S.
Format: Article
Language:English
Subjects:
Alloying effects
Alloys
Bending fatigue
Carbides
Characterization and Evaluation of Materials
Chemistry and Materials Science
Classical Mechanics
Corrosion
Crack initiation
Crack propagation
Crystallography and Scattering Methods
Failure modes
Fatigue cracks
Fatigue failure
Fatigue tests
Fracture mechanics
Grain boundaries
Grain size
Materials fatigue
Materials Science
Metal fatigue
Metals & Corrosion
Microstructure
Oxidation effects
Polymer Sciences
Powder metallurgy
Propagation
Solid Mechanics
Superalloys
Turbine disks
Turbines
Waveforms
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Summary:Effects of microstructure and oxidation on fatigue crack initiation and early propagation processes were investigated in RR1000 turbine disc alloy with different γ′ distributions and carbide distributions on the grain boundary. Fatigue tests were carried out under three-point bending and trapezoidal waveform loading (with a 90 s dwell) at 650 °C in air. The failure mode in both γ′ variants is clearly characterised by intergranular features. A number of fatigue cracks are seen to initiate at grain boundaries with bulged Co-rich oxides at the surface and/or interfaces between carbides and grain boundaries, resulting from oxidation damage assisted by applied loading. Reduced lifetime is closely linked to significant intergranular crack initiation and frequent consequent crack coalescence events, which results in enhanced fatigue crack growth (FCG) rates. The extent of intergranular features and enhanced FCG are more marked where more continuous carbides exist at the grain boundary.
ISSN:0022-2461
1573-4803
DOI:10.1007/s10853-022-08120-9