Surface damage and near-threshold fatigue crack growth in a Ni-base superalloy in vacuum

J.E. King*

*Corresponding author for this work

    Research output: Contribution to journalArticle

    Abstract

    Fatigue crack growth rate tests have been performed on Nimonic AP1, a powder formed Ni-base superalloy, in air and vacuum at room temperature. These show that threshold values are higher, and near-threshold (faceted) crack growth rates are lower, in vacuum than in air, although at high growth rates, in the “structure-insensitive” regime, R-ratio and a dilute environment have little effect. Changing the R-ratio from 0.1 to 0.5 in vacuum does not alter near-threshold crack growth rates very much, despite more extensive secondary cracking being noticeable at R= 0.5.
    In vacuum, rewelding occurs at contact points across the crack as ΔK falls. This leads to the production of extensive fracture surface damage and bulky fretting debris, and is thought to be a significant contributory factor to the observed increase in threshold values.
    Original languageEnglish
    Pages (from-to)177-188
    Number of pages12
    JournalFatigue of Engineering Materials and Structures
    Volume5
    Issue number2
    DOIs
    Publication statusPublished - Apr 1982

    Keywords

    • powder metallurgy
    • superalloys

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