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Low cycle fatigue behaviour and fatigue crack initiation in MAR-M247 at 700 °c

  1. 1.
    0505861 - ÚFM 2020 RIV CZ eng C - Konferenční příspěvek (zahraniční konf.)
    Šulák, Ivo - Obrtlík, Karel - Hrbáček, K.
    Low cycle fatigue behaviour and fatigue crack initiation in MAR-M247 at 700 °c.
    METAL 2017. 26th International Conference on Metallurgy and Materials. Conference Proceedings. Ostrava: TANGER, 2017, s. 1580-1586. ISBN 978-80-87294-79-6.
    [METAL 2017: International Conference on Metallurgy and Materials /26./. Brno (CZ), 24.05.2017-26.05.2017]
    Grant CEP: GA TA ČR(CZ) TA04011525; GA ČR(CZ) GA15-20991S
    Institucionální podpora: RVO:68081723
    Klíčová slova: Cyclic stress-strain curve * Fatigue crack initiation * Fatigue life
    Kód oboru RIV: JL - Únava materiálu a lomová mechanika
    Obor OECD: Audio engineering, reliability analysis

    The second generation nickel-based superalloy MAR-M247 offersa satisfying combination of fatigue and creep properties and oxidation and corrosion resistance that arerequired for application at elevated temperatures in hostile environments. The microstructure consists mainly oftheface centred cubic γ matrix and ordered γ ́ strengthening precipitates (L12crystal structure). The present work focuses on low cycle fatigue (LCF) behaviour of polycrystalline nickel-based superalloy MAR-M247 at high temperature. LCF tests were conducted on cylindrical specimens in symmetrical push-pull cycle under strain control with constant total strain amplitude and strain rate at 700 °C in ambientair. Cyclic stress-strain curvesand fatigue life curves in the representation ofplastic strain amplitude vs. stress amplitude andstress amplitude vs. the number of cycles to failure, respectively,were plotted and compared with data obtained on Inconel 713LC. Special attention waspaid to the investigation of crack initiation in MAR-M247 during low cycle fatigue. Crack initiation sites were studied by means of scanning electron microscopy (SEM) in dual beam microscope TESCAN LYRA 3 XMU FESEM equipped with focus ion beam (FIB). Specimens’ surface observations revealed the formation of pronounced surface relief indicating localisation of plastic deformation.Observations in transmission electron microscope (TEM)confirmed localisation of cyclic plastic deformation in persistent slip bands along {111} slip planes. Fractographic analysis revealed fatigue crack initiation sites. Fatigue crack propagation in stage I was typical of smooth facets up to 500 μm long.
    Trvalý link: http://hdl.handle.net/11104/0301451
     
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