Inconel 625

UNS N06625

625 is a nickel–chromium–molybdenum alloy strengthened by niobium and molybdenum in solid solution, so it holds high strength without heat treatment. That combination — corrosion resistance across oxidising and reducing media, plus strength that survives at temperature — is why it is used for subsea flanges, wellhead components and supercritical water piping.

It resists chloride stress-corrosion cracking, pitting and crevice attack in seawater, and is approved to NACE MR0175 for sour service. It is also readily weldable, which matters on large fabricated assemblies.

Properties

• Corrosion resistance in oxidising and reducing media, including mixed inorganic acids
• Excellent pitting and crevice resistance; no chloride SCC in practical service
• High strength without heat treatment, retained to about 600–650 °C
• NACE MR0175 approved for sour gas; good weldability

Applications

• Subsea and wellhead flanges, hubs and fittings
• Seawater piping and heat exchangers
• Flue-gas desulphurisation systems
• Supercritical water and high-temperature process lines
• Aerospace and marine hardware

Forms supplied

• Flanges (including special-alloy forgings for subsea)
• Fittings and pipe
• Bar, ring and shaped forgings

Standards

ASTM B564 (forgings), B443/B446 (sheet/plate), B444 (pipe), B446 (bar); NACE MR0175 / ISO 15156