STP642: Corrosion-Fatigue Behavior of Coated 4340 Steel for Blade Retention Bolts of the AH-1 Helicopter

    Levy, M
    Corrosion research group leader and chemical engineer, Department of the Army, Army Materials and Mechanics Research Center, Watertown, Mass

    Morrossi, JL
    Corrosion research group leader and chemical engineer, Department of the Army, Army Materials and Mechanics Research Center, Watertown, Mass

    Pages: 13    Published: Jan 1978


    Abstract

    The main rotor blade bolt for the 540 helicopter rotor system of the AH-1G, UH-1C, and UH-1M helicopters is proposed to be improved by substituting a plasma-sprayed tungsten carbide coating on the outer shank of the 4340 steel bolt for the present cadmium or chromium plate. This study was undertaken to determine the effects of these coating systems on the fatigue behavior of 4340 steel in environments likely to be encountered in service. Both axial tension-tension and rotating bending fatigue testing of coated specimens were carried out in air and in 3.5 percent sodium chloride (NaCl) solution. The NaCl environment causes reductions in fatigue strength of bare and coated 4340 steel. The severity of the degradation depends on the coating applied and the type of fatigue test utilized.

    Keywords:

    corrosion fatigue, steels, protective coatings, tungsten carbides, environmental tests


    Paper ID: STP28727S

    Committee/Subcommittee: E08.05

    DOI: 10.1520/STP28727S


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