Anisotropy effects during dwell-fatigue caused by δ-phase orientation in forged Inconel 718

MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING

卷:692

Article

Saarimaki, Jonas¹  Colliander, Magnus Hornqvist^2,3  Moverare, Johan J.¹ 

[1] Linkoping Univ, Dept Management & Engn, Div Engn Mat, SE-58183 Linkoping, Sweden

[2] Chalmers, Dept Appl Phys, SE-41296 Gothenburg, Sweden

[3] GKN Aerosp Engine Syst, R&T Ctr, SE-46181 Trollhattan, Sweden

关键词: Anisotropy;    Nickel-based superalloys;    Fatigue;    Mechanical characterisation;    Scanning electron microscopy;   

DOI  :  10.1016/j.msea.2017.03.063

来源: Elsevier

【 摘 要 】

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 degrees C with 90 5 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 delta-phase orientation. When delta-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 gamma-matrix and the delta-phase.

【 授权许可】

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