STP1049

    Cyclic Tension Corrosion Fatigue of High-Strength Steels in Seawater

    Published: Jan 1990


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    Abstract

    Four low-alloy steels with nickel contents varying from 0.2 to 4.0% (BS 970:722M24, 817M40, 976M33, and 835M30) quench hardened and tempered to give yield or 0.2% proof strengths of approximately 800 MPa were tested in cyclic tensile loading (R = 0.05) at a frequency of 0.167 Hz in plain and notched (SCF = 2) forms in air, freely corroding in ASTM synthetic seawater (temperature 8°C and pH 8.2) and with cathodic protection of - 850 mV and - 1050 mV to establish S-N data for offshore platform design.

    The steels suffered considerable reductions in fatigue performance in the freely corroding condition. Cathodic protection at — 850 mV improved the performance of all four steels and in one case (817M40) restored it to that in air. Notched specimens were not improved to the same degree as plain specimens.

    Cathodic protection at - 1050 mV fully restored the fatigue performance of plain and notched steel 817M40 but the others showed a reduction in performance due to intergranular cracking in initiation and early crack propagation life in place of the otherwise ductile transgranular fracture; this was attributed to hydrogen absorption.

    Keywords:

    low-alloy steels, quenched and tempered high-strength steels, cyclic tension, corrosion fatigue, seawater corrosion, marine corrosion, cathodic protection, fatigue (materials), cracking, environmental effects


    Author Information:

    Jones, WJD
    Reader in Engineering Metallurgy and research assistant, University College London, London,

    Blackie, AP
    Reader in Engineering Metallurgy and research assistant, University College London, London,


    Paper ID: STP24080S

    Committee/Subcommittee: G01.06

    DOI: 10.1520/STP24080S


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