STP1263

    Thermomechanical Fatigue Behaviour of Coated and Bare Nickel-Based Superalloy Single Crystals

    Published: Jan 1996


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    Abstract

    The thermal-mechanical fatigue behaviour of chromium-aluminium coated [001] single crystals of AM1, a nickel-base superalloy for turbine blades, is studied using a “diamond” shape cycle from 600‡ to 1100‡C. Comparison with bare specimens does not show any significant difference in thermal-mechanical fatigue nor in isothermal low cycle fatigue at high temperature. Metallographic observations on fracture surfaces and longitudinal sections of specimens tested to fatigue life or to a definite fraction of expected life have shown that the major crack tends to initiate from casting micropores in the sub-surface area very early in bare and coated specimens, under low cycle fatigue or thermal-mechanical fatigue. But the interaction between oxidation and fatigue cracking seems to play a major role. A simple model proposed by Reuchet and Rémy has been identified for this single crystal superalloy. Its application to the life prediction under low cycle fatigue and thermal-mechanical fatigue for bare and coated single crystals with different orientations is shown.

    Keywords:

    thermomechanical fatigue, nickel-based superalloy, single crystals, coatings, lifetime prediction


    Author Information:

    Chataigner, E

    Remy, L
    Centre des Matériaux P.M. FOURT E.N.S.M.P., EVRY,


    Paper ID: STP16443S

    Committee/Subcommittee: E08.06

    DOI: 10.1520/STP16443S


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