STP1337

    Effect of Intergranular Surface Attack on the Fatigue and Corrosion Properties of AM-355 CRT Material

    Published: Jan 1998


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    Abstract

    A dynamic part, consisting of a stack of laminates, failed in the field after an unexpectedly short life. Failure analysis showed that a multitude of fatigue cracks originated from a combination of corrosion and fretting. Recent changes in the production process of the laminates resulted in the presence of an intergranular (IG) morphology on the surface. Due to the criticality of this part's application, a better understanding of the influence of varying degrees of IG attack on fatigue properties was pursued. Coupon specimens were machined from actual components with different surface IG conditions and were subjected to fatigue testing. Results showed a direct relationship between the number of cycles to failure and the severity of surface IG attack. Potentiodynamic polarization measurements indicated that a sample with IG attack had a lower breakdown potential and an unstable passivation behavior as compared to that without an IG attack. The detrimental effects of surface IG attack on the crack initiation process, endurance limit and corrosion resistance is discussed in terms of the stress concentration and breakdown of the passivation layer.

    Keywords:

    AM-355, fatigue, fretting, corrosion, corrosion potential, passivation


    Author Information:

    Bhansali, KJ
    U. S. Army Aviation Troop Command, St. Louis, Missouri

    Liu, G
    Westar Corporation, St. Louis, Missouri

    Grendahl, SM
    U.S. Army Research Laboratory, Maryland

    Champagne, VK
    U.S. Army Research Laboratory, Maryland

    Pepi, MS
    U.S. Army Research Laboratory, Maryland


    Paper ID: STP12340S

    Committee/Subcommittee: E08.05

    DOI: 10.1520/STP12340S


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