Isothermal fatigue of an aluminide-coated single-crystal superalloy: Part I

T.C. Totemeier, J.E. King

    Research output: Contribution to journalArticle

    Abstract

    The isothermal fatigue behavior of a high-activity aluminide-coated single-crystal superalloy was studied in air at test temperatures of 600 °C, 800 °C, and 1000 °C. Tests were performed using cylindrical specimens under strain control at ∼0.25 Hz; total strain ranges from 0.5 to 1.6 pet were investigated. At 600 °C, crack initiation occurred at brittle coating cracks, which led to a significant reduction in fatigue life compared to the uncoated alloy. Fatigue cracks grew from the brittle coating cracks initially in a stage II manner with a subsequent transition to crystallographic stage I fatigue. At 800 °C and 1000 °C, the coating failed quickly by a fatigue process due to the drastic reduction in strength above 750 °C, the ductile-brittle transition temperature. These cracks were arrested or slowed by oxidation at the coating-substrate interface and only led to a detriment in life relative to the uncoated material for total strain ranges of 1.2 pet and above 800 °C. The presence of the coating was beneficial at 800 °C for total strain rangesless than 1.2 pet. No effect of the coating was observed at 1000 °C. Crack growth in the substrate at 800 °C was similar to 600 °C; at 1000 °C, greater plasticity and oxidationrwere observed and cracks grew exclusively in a stage II manner.

    Original languageEnglish
    Pages (from-to)353-361
    Number of pages9
    JournalMetallurgical and Materials Transactions A
    Volume27
    Issue number2
    DOIs
    Publication statusPublished - Feb 1996

    Keywords

    • aluminum alloys
    • brittle fracture
    • coated materials,biocompatible
    • crack initiation
    • crack propagation
    • fatigue of materials
    • fatigue testing
    • interfaces (materials)
    • intermetallics
    • oxidation
    • single crystals
    • strain control
    • aluminide coated single crystal superalloy
    • crystallographic stage I fatigue
    • isothermal fatigue
    • superalloys

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