Fracture behaviour of an aluminide coating on a single crystal nickel base superalloy

T.C. Totemeier, W.F. Gale, J.E. King

    Research output: Contribution to journalArticle

    Abstract

    Measurement of the coating fracture strain of an aluminide coating on a single crystal nickel base superalloy has been performed both in three-point bending and using variable wall thickness testpieces. As-aged specimens, 28 to 33 μm in thickness, were tested at room temperature, 600, 700 and 750 °C; specimens pre-exposed for 140 h at 850 and 1100 °C in air and vacuum were tested at room temperature. Fracture strains varied from 0.52 to 0.70% for as-aged specimens tested at temperatures up to 700 °C and specimens exposed at 850 °C and tested at room temperature. The crack path for these conditions was intergranular or transgranular in the main coating, along carbide-matrix interfaces in the coating transition zone, and at an angle of 30-45° to the original crack path in the substrate. The as-aged coating tested at 750 °C was ductile; a ductile-brittle transition occurs between 700 and 750 °C for the strain rate used (1 × 10-5 s-1). Following 1100 °C pre-exposure, specimens were ductile at room temperature with fractures strains of several percent. In this condition the crack morphology changed to one of subsurface nucleation in β grains and at β-γ′ interfaces. © 1993.

    Original languageEnglish
    Pages (from-to)19-26
    Number of pages8
    JournalMaterials Science and Engineering A
    Volume169
    Issue number1-2
    DOIs
    Publication statusPublished - 15 Sep 1993

    Keywords

    • aging of materials
    • bending deformation
    • coatings
    • cracks
    • ductility
    • fracture
    • materials interfaces
    • morphology
    • nickel alloys
    • strain
    • superalloys
    • thermal effects
    • aluminide coating
    • carbide matrix interfaces
    • coating transition zone
    • crack morphology
    • crack path
    • ductile brittle transition
    • single crystal nickel base superalloy
    • aluminum compounds

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