Abstract

In light of the in progress revision process of API 6A718 and API 5CRA specifications, a new precipitation hardenable Ni-base alloy has been developed for applications in H2S and hydrogen charging environments. The new alloy has received the UNS assignment of UNS N09955. It is patent pending and is being submitted for inclusion in NACE MR0175/ISO 15156. The UNS N09955 alloy is produced at strength levels of 827 MPa (120 ksi) of minimum yield strength (MYS) and 965 MPa (140 ksi) MYS with very good toughness and with microstructure characterized by uniform and equiaxed grain size distribution, minimized secondary phase precipitation and free of continuous grain boundary precipitates. It shows corrosion resistance similar to or better than that of UNS N07716 and UNS N07718 and exhibits a low susceptibility to hydrogen embrittlement, similar to that of UNS N07718 and much lower than UNS N07716. Details of the manufacturing process and characterization of UNS N09955 alloy in terms of mechanical properties, microstructure, corrosion resistance and hydrogen embrittlement susceptibility are presented and discussed in this paper.

Keywords:
corrosion inhibition, oilfield chemistry, pipeline corrosion, subsurface corrosion, well integrity, materials and corrosion, riser corrosion, flowline corrosion, production chemistry, h2s management
Subjects:
Production Chemistry, Metallurgy and Biology, Pipelines, Flowlines and Risers, Materials and corrosion, Well Integrity, Subsurface corrosion (tubing, casing, completion equipment, conductor), Corrosion inhibition and management (including H2S and CO2)
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2015. NACE International
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