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Fatigue crack initiation and growth in 43Fe-25Ni-22.5Cr austenitic steel at a temperature of 700 °C

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    0492025 - ÚFM 2019 RIV GB eng J - Journal Article
    Mazánová, Veronika - Heczko, Milan - Polák, Jaroslav
    Fatigue crack initiation and growth in 43Fe-25Ni-22.5Cr austenitic steel at a temperature of 700 °C.
    International Journal of Fatigue. Roč. 114, SEP (2018), s. 11-21. ISSN 0142-1123
    R&D Projects: GA MŠk LM2015069; GA MŠk(CZ) LQ1601; GA ČR(CZ) GA13-23652S; GA ČR GA15-08826S; GA MŠk(CZ) EF16_027/0008056
    Institutional support: RVO:68081723
    Keywords : High temperature fatigue * oxidation * crack initiation * crack growth * Sanicro 25
    Subject RIV: JL - Materials Fatigue, Friction Mechanics
    OBOR OECD: Audio engineering, reliability analysis
    Impact factor: 3.673, year: 2018

    Crack initiation and short crack growth in highly-alloyed austenitic steel Sanicro 25 cyclically strained at atemperature of 700 °C has been studied. Specimens cycled to 10% of the fatigue life and to the fracture wereinspected using scanning electron microscopy and electron backscatter diffraction. On the surface, thin lamellaewere extracted site-specifically by focused ion beam and then they were further characterized by high spatialresolution scanning transmission electron microscopy and energy dispersive X-ray spectroscopy. The preferentialoxidation of grain boundaries was found to play a principal role in the initiation of multiple cracks. The oxidescale was analysed to show the distribution of individual elements during crack initiation and growth. Two typesof crack paths were observed: intergranular due to the oxidation and transgranular accompanied by a cyclicplastic zone. Cracks preferentially initiated at the grain boundaries perpendicular to the stress axis and propa-gated in the bulk of the material. The role of the oxidation in high temperature fatigue crack initiation isdiscussed as well as the mechanisms of the crack initiation and growth.
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