Anisotropy effects during dwell-fatigue caused by δ-phase orientation in forged Inconel 718
Journal article, 2017

Inconel 718 is a commonly used superalloy for turbine discs in the gas turbine industry. Turbine discs are often subjected to dwell-fatigue as a result of long constant load cycles. The effect of anisotropy on dwell-fatigue cracking in forged turbine discs have not yet been thoroughly investigated. Crack propagation behaviour was characterised using compact tension (CT) samples cut in different orientations from a real turbine disc forging. Samples were also cut in two different thicknesses in order to investigate the influence of plane strain and plane stress condition on the crack propagation rates. The samples were subjected to dwell-fatigue tests at 550 °C with 90 s or 2160 s dwell-times at maximum load. Microstructure characterisation was done using scanning electron microscopy (SEM) techniques such as electron channelling contrast imaging (ECCI), electron backscatter diffraction (EBSD), and light optical microscopy (LOM). The forged alloy exhibits strong anisotropic behaviour caused by the non-random δ-phase orientation. When δ-phases were oriented perpendicular compared to parallel to the loading direction, the crack growth rates were approximately ten times faster. Crack growth occurred preferably in the interface between the γ-matrix and the δ-phase.


Nickel-based superalloys


Mechanical characterisation

Scanning electron microscopy


Jonas Saarimäki

Linköping University

Magnus Hörnqvist Colliander

Chalmers, Physics, Materials Microstructure

JJ Moverare

Linköping University

Materials Science & Engineering A: Structural Materials: Properties, Microstructure and Processing

0921-5093 (ISSN)

Vol. 692 174-181

Subject Categories

Materials Engineering

Other Engineering and Technologies

Other Materials Engineering

Metallurgy and Metallic Materials

Areas of Advance


Materials Science



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