STP467

    The Fatigue Strength of Nickel-Base Superalloys

    Published: Jan 1970


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    Abstract

    The service lives of nickel-base superalloy components in gas turbine engines are frequently limited by their fatigue properties. This paper reviews what is known about the fatigue behavior of nickel-base superalloys and suggests methods for improving their properties. Low-temperature crack initiation occurs preferentially at microstructural defects such as pores and brittle phases in cast materials and at defects such as brittle phases and annealing twin boundaries in wrought materials. The brittle phases may contain inherent cracks or be cracked during working operations or service exposures. Plastic deformation at low temperatures is concentrated in coarse planar bands, and as a result matrix cracking is predominantly transgranular and crystallographic. Techniques are discussed for increasing the low-temperature fatigue properties by minimizing the role of microstructural defects and achieving a more homogeneous distribution of deformation.

    At elevated temperatures, intergranular cracking predominates and methods are discussed for improving fatigue properties through grain size control, the use of columnar-grained and single-crystal materials, and the application of oxidation-resistant and fatigue-resistant coatings.

    Keywords:

    fatigue, fatigue strength, nickel alloys, nickel-base superalloys, Stage I fracture, Stage II fracture, crack initiation, crack propagation, microstructure, environment, coatings, temperature, frequency, grain size, single crystal


    Author Information:

    Gell, M
    Group leader, senior research associate, and assistant director, Advanced Materials Research and Development Laboratory, Pratt & Whitney Aircraft, Middletown, Conn.

    Leverant, GR
    Group leader, senior research associate, and assistant director, Advanced Materials Research and Development Laboratory, Pratt & Whitney Aircraft, Middletown, Conn.

    Wells, CH
    Group leader, senior research associate, and assistant director, Advanced Materials Research and Development Laboratory, Pratt & Whitney Aircraft, Middletown, Conn.


    Paper ID: STP26842S

    Committee/Subcommittee: E08.01

    DOI: 10.1520/STP26842S


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