STP942

    Grain Boundary Oxidation and an Analysis of the Effects of Oxidation on Fatigue Crack Nucleation Life

    Published: Jan 1988


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    Abstract

    A study on the effects of pre-oxidation on subsequent fatigue life was conducted. The surface oxidation and grain boundary oxidation of a nickel-base superalloy (TAZ-8A) were studied at 600 to 1000°C for 10 to 1000 h in air. The surface oxides were identified and the kinetics of surface oxidation was discussed.

    The grain boundary oxide penetration and morphology were studied. The pancake-type grain boundary oxide penetrates deeper and its size is larger, therefore, it is more detrimental to fatigue life than the cone-type grain boundary oxide. The oxide penetration depth, am, is related to oxidation temperature, T, and exposure time, t, by an empirical relation of the Arrhenius type. The effects of T and t on the statistical variation of am were analyzed according to the Weibull distribution function. Once the oxide is cracked, it serves as a fatigue crack nucleus. The statistical variation of the remaining fatigue life, after the formation of an oxide crack of a critical length, could be related directly to the statistical variation of grain boundary oxide penetration depth.

    Keywords:

    oxidation, grain boundary oxidation, oxidation kinetics, oxide morphology, oxide crack, fatigue life, elevated temperatures, Weibull distribution function


    Author Information:

    Y, Oshida
    Research Assistant Professor and Professor of Mechanical Engineering, Syracuse University, Syracuse, NY

    HW, Liu
    Research Assistant Professor and Professor of Mechanical Engineering, Syracuse University, Syracuse, NY


    Paper ID: STP24547S

    Committee/Subcommittee: E08.05

    DOI: 10.1520/STP24547S


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