STP942: Evaluation of Life Prediction Methods in High Temperature Fatigue

    L, Rémy
    Centre de Matériaux de l'Ecole des Mines de Paris, EVRY Cédex,

    F, Rezai-Aria
    Centre de Matériaux de l'Ecole des Mines de Paris, EVRY Cédex,

    R, Danzer
    Institut für Metallkunde und Werkstoffprüfung Institut für Physik, Leoben,

    W, Hoffelner
    BBC Brown Boveri, Baden,

    Pages: 18    Published: Jan 1988


    Abstract

    A collaborative study supported by the European Community COST 50 program has been conducted on life prediction methods under high-temperature low-cycle fatigue and thermal fatigue cycling in the case of MAR-M509, a cast cobalt-base superalloy. Low-cycle fatigue tests were carried out by the Ecole des Mines de Paris at 900°C in air under longitudinal strain control and included sawtooth triangular shape cycles at three strain rates (frequency range 10−3 to 20 Hz), tensile strain hold cycles, and compressive strain hold cycles. Life to initiation data deduced from a-c potential drop measurements were used to evaluate three types of predictive models: strainrange partitioning, studied by BBC-Baden; creep damage models, studied by the University of Leoben; and an oxidation-fatigue interaction model, studied by the Ecole des Mines de Paris. All the methods have been found to correlate experimental data within a factor of three. However, they range from simple correlating methods with adjustable parameters to be fitted to fully predictive methods with no fitting parameter. Thermal fatigue data on wedge-type specimens (i.e., components instead of laboratory specimens) have been used to check the prediction capability of the various methods and have shown the superiority of oxidation-fatigue interaction models for this material.

    Keywords:

    life prediction, high-temperature low-cycle fatigue, thermal fatigue, cobalt-base superalloy, crack initiation, oxidation


    Paper ID: STP24542S

    Committee/Subcommittee: E08.05

    DOI: 10.1520/STP24542S


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