Failure Investigation of UNS N07718 (Inconel 718) Bolts under Cathodic Protection for Subsea Oil & Gas Operations




Abstract: Hydrogen embrittlement affects all alloy systems that are regularly used in the Oil & Gas industry for subsea operations; including carbon alloy steels, duplex stainless steels, and nickel alloys. Failures due to this phenomenon come from the interaction of susceptible materials with the employed cathodic protection system. Cathodic protection helps prevent subsea corrosion, however acts as the source of atomic hydrogen which can freely diffuse into the base metal during the operational life of the equipment. A failure investigation is presented of UNS N07718 (Inconel 718) bolts used for subsea production trees, which traces the interaction of the material variables, from processing to heat treatment, that resulted in their hydrogen embrittlement susceptibility and cracking.

Authors: Herman E. Amaya and Adam G. Dyer

Keywords: Failure Analysis, Inconel 718, Delta Phase, Fracture, Bolt, Microstructure, Heat Treatment, Microhardness, Cathodic Protection, Hydrogen Embrittlement, Subsea

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Page Count

10 pages


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