STP1428: Thermomechanical Fatigue Behavior of an Aluminide-Coated Monocrystalline Ni-Base Superalloy

    Grube, F
    Research Associate and Professor, University of Erlangen-Nürnberg, Institut für Werkstoffwissenschaften, Erlangen,

    Affeldt, EE
    MTU Aero Engines, Munich,

    Mughrabi, H
    Research Associate and Professor, University of Erlangen-Nürnberg, Institut für Werkstoffwissenschaften, Erlangen,

    Pages: 16    Published: Jan 2003


    Abstract

    This study is part of a project concerned with the effect of diffusional aluminide coatings on the stress response and life of a coated monocrystalline nickel-base superalloy (CMSX-6) during thermomechanical fatigue (TMF) testing.

    In this project, the effects of different platinum-modified aluminide coatings are studied. To separate the effects induced by the coatings from other effects with respect to the TMF life, uncoated specimens are investigated as reference specimens.

    In this paper, TMF studies on specimens coated with a two-phase platinum-modified aluminide coating are reported. The TMF tests were performed with a particular type of asymmetric counterclockwise diamond cycle (lower and upper temperatures: 400 °C and 1100 °C, respectively) representing typical loads experienced by turbine blades under conditions of service during start-up and shut-down operation. The life of the specimen is determined by crack initiation and propagation. Crack initiation is observed to occur early during TMF life at the surface of the coating as a consequence of its brittleness at low temperatures. Thus, the coating shortens the life of the substrate-coating system. In this context, the characteristics of the two-phase platinum-aluminide coating studied here and its influence on the mechanisms of crack initiation and propagation during TMF are of special interest.

    Keywords:

    thermomechanical fatigue, coating, platinum-aluminide, nickel-base superalloy, single crystal, crack initiation


    Paper ID: STP11433S

    Committee/Subcommittee: E08.04

    DOI: 10.1520/STP11433S


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