After a number of failures in the Oil and Gas industry research works on hydrogen embrittlement (HE) of nickel-based alloys has been quite significant. Much work had been done previously in other industries, nuclear and aeronautic in particular. Despite this work, a lot remains to be understood. Among them, precipitation-hardened (PH) nickel alloys UNS N07718 has been significantly studied and its HE resistance is now better assessed based on its microstructure. Less work has been performed on some of the other PH nickel alloys, although, their HE resistance is better appreciated from recent literature data. The results published at NACE Corrosion 2019 from a large JIP study indicated that PH nickel alloys could be split in three families with less susceptible alloys, like UNS N07718, UNS N09925 and UNS N09935, more susceptible alloys like UNS N07725 and UNS N07716, while alloy UNS N09945 had variable susceptibility. Besides PH nickel alloys, other solution-annealed or cold worked alloys are used in environments where hydrogen can be present. As PH alloys they are also susceptible to HE, but published studies are scarce. This paper is a review of internal and published work setting the base of our current understanding on the HE resistance of various PH, solution annealed and cold worked nickel-based alloys. Consequences on the use of these alloys are discussed for Oil and Gas applications.
A literature survey and results of internal studies have been used to summarize our knowledge concerning hydrogen embrittlement (HE), also called HSC (hydrogen stress cracking) or HISC (hydrogen-induced stress cracking) of nickel-based alloys, specifically alloys in use in the upstream Oil and Gas industry. Since the first major failure reported in an HPHT well in early 2000's a number of studies have completed previous work primarily on UNS(1) N07718 in the nuclear and aeronautics and space industries. Other alloys have since been developed specifically for the upstream Oil and Gas production, while others were already in use. The objective of these alloys is to be resistant to internal corrosion in severe sour conditions, where carbon and low alloy steels cannot be used, and be also resistant to HSC in case hydrogen charging occurs in wells and subsea components. This means these alloys must be listed in NACE(2) MR0175/ISO 15156 Standard with high sour limits and they should have the highest possible resistance to HSC. This paper only deals with HSC and attempts to give an update on the current knowledge on the resistance of nickel-based alloys to HSC and how they can be used in the field to avoid failures.
