High Strength Fasteners for Seawater Immersion Service

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					Number:      97

Title:       High Strength Fasteners for Seawater Immersion Service
Authors:     D.M. Aylor, C.A. Bowles and R.L. Tregoning
Citation:    Tri-Service Corrosion Conference, 1997
Keywords:    Alloys, Galvanic Corrosion, Environmentally Assisted Cracking and Sustained
             load Cracking.

Abstract:    Alloy K-500 is the currently used high strength alloy for Navy fastener
             applications in immersion service. Alloy K-500 has performed well as a fastener
             material in seawater but is susceptible to hydrogen cracking in areas of intense
             cathodic polarization and is galvanically incompatible with titanium and alloy 625
             components. Due to these inadequacies, it is necessary to identify alternate
             fastener materials that can suitably replace Alloy K-500. Numerous alloys that
             meet the minimum yield strength requirements of Alloy K-500 (90 ksi) have been
             considered. These include titanium-base, nickel base and stainless steel alloys.
             Data and guidelines on corrosion behavior, mechanical properties, fatigue
             behavior and other relevant material properties are currently being assembled in
             to a high strength fastener handbook for 14 alloys. The technical information in
             the handbook will include data generated from in house Navy programs as well as
             data reported in the literature by government and industry sources. Information
             included in the fastener handbook will be presented here, with particular emphasis
             on the applicability of specific alloys based on seawater corrosion behavior.

Pros/Cons:   In this paper a detailed assessment was made for localized, galvanic and
             environmentally assisted cracking susceptibilities of 14 fastener alloys for
             seawater service. Some of them are found to be the most promising candidates for
             high strength fastener applications. In this work mechanical and physical
             properties are not taken in to account when selecting the alloy for fastener

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