STP942: Grain Boundary Oxidation and an Analysis of the Effects of Oxidation on Fatigue Crack Nucleation Life

    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

    Pages: 19    Published: Jan 1988


    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


    Paper ID: STP24547S

    Committee/Subcommittee: E08.05

    DOI: 10.1520/STP24547S


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