Final reportĭOE Office of Scientific and Technical Information (OSTI.GOV)Įnvironmental effects can significantly reduce the fatigue life of metals. The fatigue data are fitted by regression equations to allow determination of fatigue strength for a given number of cycles to failure.Ĭorrosion fatigue of high strength fastener materials in seawater. The AISI 4140, PH 13-8Mo stainless steel, alloy 718 and alloy MP-35N were tested in axial fatigue at a frequency of 20 Hz in dry air and natural seawater. The reduction of fatigue strength of AISI 41L4O in marine environments and to obtain similar corrosion fatigue data for candidate replacement materials was studied. The corrosion fatigue failure of an AISI 41L4O high strength steel blade to hub attachment bolt at the MOD-OA 200 kW wind turbine generator was investigated. Corrosion fatigue is a major concern in the engineering application of high strength fasteners in marine environments. This article is part of the themed issue 'The challenges of hydrogen and metals'.Ĭorrosion fatigue of high strength fastener materials in seawaterĮnvironmental effects which significantly reduce the fatigue life of metals are discussed.
Below 1200 MPa, non-conforming quality is often the root cause of real-life failures. Additionally, non-homogeneity of the metallurgical structure resulting from poorly controlled heat treatment, impurities and non-metallic inclusions can increase HE susceptibility of steel in ways that are measurable but unpredictable. For a given concentration of hydrogen and at equal strength, the critical strength above which the ductile-brittle transition begins can vary due to second-order effects of chemistry, tempering temperature and sub-microstructure. Material strength has a first-order effect on HE susceptibility, which increases significantly above 1200 MPa and is characterized by a ductile-brittle transition. HE susceptibility is a function of the material condition, which is comprehensively described by the metallurgical and mechanical properties. Additionally, inconsistencies and even contradictions in fastener industry standards have led to much confusion and many preventable or misdiagnosed fastener failures. Research is typically conducted under idealized conditions that cannot be translated into know-how prescribed in fastener industry standards and practices. Preventing hydrogen embrittlement (HE) failure is a fundamental concern implicating the entire fastener supply chain. High-strength steel fasteners characterized by tensile strengths above 1100 MPa are often used in critical applications where a failure can have catastrophic consequences. Alloy and composition dependence of hydrogen embrittlement susceptibility in high-strength steel fasteners
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