Oil & Gas
RAS Alloy provides NACE MR0175 compliant nickel alloys for sour service wellheads, downhole completion tools, subsea manifolds and offshore platform piping. All sour-service grades are supplied with full PMI, hardness testing and HIC/SSC certification.
Typical Alloy Grades
625 / 825 / K-500 / C-276 / 718
Subsea wellhead connectors and Christmas trees
Inconel 718, Inconel 625
Downhole completion tools and packer components
Incoloy 925, Inconel 718
Sour gas production tubing hangers
Hastelloy C-276, Inconel 625
High-pressure gate valve stems and seats
Incoloy 925, Monel K-500
Offshore platform seawater piping
Monel 400, Inconel 625
Applicable Standards
Downhole Tool Hydrogen Embrittlement — Monel K-500 Failure
A North Sea operator experienced catastrophic Monel K-500 completion tool failure after only 18 months in sour gas service (H2S partial pressure 0.5 psi, 120°C).
The material was supplied in the aged condition without post-machining stress relief. Residual tensile stress exceeding 400 MPa at the thread root, combined with hydrogen charging from H2S, caused intergranular cracking. Hardness was 38 HRC — above the NACE MR0175 limit of 35 HRC for K-500.
RAS Alloy now supplies K-500 in solution-treated condition (max 35 HRC) with post-machining stress relief at 530°C for 4 hours. Slow-strain-rate tensile testing (ASTM G129) confirms >15% elongation after processing.