STP1186: Thermomechanical Fatigue of Turbo-Engine Blade Superalloys

    Guedou, JY
    Material structure, and mechanics manager and head, Snecma, Evry,

    Honnorat, Y
    Material structure, and mechanics manager and head, Snecma, Evry,

    Pages: 19    Published: Jan 1993


    Abstract

    A thermomechanical fatigue (TMF) facility has been developed in the Snecma Materials Laboratory to characterize the mechanical behavior and the damaging processes of blade superalloys under realistic loading conditions. Three nickel-base superalloys have been investigated using a reference TMF cycle representative of blade leading edge. Stabilized stress-strain loops exhibit greater plastic strains and higher stress amplitudes for an equiaxed alloy IN-100, mainly due to elastic anisotropy of the directionally solidifed DS-200 and AM1 single crystal alloys. The application of a viscoplastic constitutive model shows a good correlation between calculation and experiment for DS-200 and AM1 but indicates that the IN-100 model coefficients need improvement.

    The TMF lives are much more important for the two oriented alloys (that is, AM1 and DS-200) as compared with the equiaxed IN-100, as in isothermal LCF conditions, but a correlation between TMF and LCF lives cannot be easily proposed and depends upon the material considered. The damaging mechanisms have been investigated on single crystal failed specimens, and compressive loads at high temperature play an important role in the damaging process. A continuous damage model delivered good predictions for TMF lives on equiaxed alloy specimens. Nevertheless, the application of such a model to structure calculations must take into account possible effects of crystallographic anisotropy in the case of directionally solidified (DS) and single crystal alloys.

    Keywords:

    cast superalloys, equiaxed, directionally solidified (DS), single crystal, constitutive law, damage


    Paper ID: STP24255S

    Committee/Subcommittee: E08.05

    DOI: 10.1520/STP24255S


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