Original title: Low cycle fatigue behaviour and fatigue crack initiation in MAR-M247 at 700 °c
Authors: Šulák, Ivo ; Obrtlík, Karel ; Hrbáček, K.
Document type: Papers
Conference/Event: METAL 2017: International Conference on Metallurgy and Materials /26./, Brno (CZ), 20170524
Year: 2017
Language: eng
Abstract: 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.
Keywords: Cyclic stress-strain curve; Fatigue crack initiation; Fatigue life
Project no.: TA04011525 (CEP), GA15-20991S (CEP)
Funding provider: GA TA ČR, GA ČR
Host item entry: METAL 2017. 26th International Conference on Metallurgy and Materials. Conference Proceedings, ISBN 978-80-87294-79-6

Institution: Institute of Physics of Materials AS ČR (web)
Document availability information: Fulltext is available at the institute of the Academy of Sciences.
Original record: http://hdl.handle.net/11104/0301451

Permalink: http://www.nusl.cz/ntk/nusl-407859


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