Hydrogen Transport Conditions and Effects in Cathodically Polarized AF1410 Steel
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STEELS are important structural materials used extensively in a host of industries (e.g., for containments in manufacturing industries) and areas such as in aircraft applications. Given the vast variety of steels, specific or unique applications abound to take advantage of their diverse properties. For instance, stainless steel is used in differing applications where corrosion resistance is an important consideration, whereas carbon steels and high-strength steels are used for their combined higher strength and toughness properties. In austenitic steels, hydrogen diffusion is usually low while their hydrogen solubility in comparison to the ferriticor martensitic-based steels is comparatively higher.[1,2] The ultra-high-strength steels such as the AF1410 and others, based on their improved Ni-Co ratio and low carbon contents, have an improved combination of strength, damage tolerance, and stress corrosion cracking resistance. As a consequence, they are employed in SAMUEL M. CHARCA, Graduate Student, Department of Mechanical Engineering, and OSWALD N.C. UWAKWEH, Professor, are with the Department of Engineering Science and Materials, College of Engineering, University of Puerto Rico–Mayagu¨ez, P.O. Box 9044, Mayagu¨ez, Puerto Rico 00681-9044. Contact e-mails: uwakweh@ece. uprm.edu; [email protected] VINOD S. AGARWALA, Navair Esteemed Fellow Associate Director, is with Materials Science & Engineering, U.S. Office of Naval Research Global–London Edison House, London NW1 5TH, United Kingdom. Manuscript submitted October 27, 2005. Article published online September 13, 2007. METALLURGICAL AND MATERIALS TRANSACTIONS A
severe conditions, such as in naval aircraft environments, and are used specifically in such applications as landing gear on carrier-based aircrafts, attached fittings, horizontal stabilizer spindles, arresting hooks, catapult hooks, etc.[3] Despite improvement in comparison to the 300M types, they are prone to general corrosion attack, including hydrogen embrittlement. Hydrogen embrittlement can lead to loss of aircraft when combined with other damaging conditions based on numerous studies. To this effect, there is a need to study the effects of hydrogen interaction with steels with the aim to determine means of designing improved materials, preserving the life of existing ones, and predicting the life expectations of components in service.[4–8] The problem of hydrogen interaction with steels is a multifaceted phenomenon that is affected by many factors such as the rate of hydrogen ingress and its subsequent transport behaviors following dissolution. The factors that are of considerable importance include the crystal structures of the steel, phases present, grain size distribution, whether the steel is under the coldworked or annealed state, etc. While these are important factors to be considered, the extent of their individual contributions toward property changes as a result of hydrogen exposure depends on the nature or type of steel under consideration. Further, the presence of hydrogen even in small amoun
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