Alloy 925 (UNS N09925)

Alloy 925, often referred to as Incoloy 925 (where Incoloy is a trademark of Special Metals Corp), is a precipitation-hardenable Nickel-Iron-Chromium Alloys with additions of Molybdenum, Copper, Titanium and Aluminium, supplied in the solution annealed condition and an aged condition.

The Titanium and Aluminium are specifically added to give a strengthening of the alloy during ageing, as Ni₃(Al, Ti) gamma (‘ϒ’) prime precipitates form throughout the alloy matrix and greatly increases the hardness and strength in a similar way to Alloy K500, 718 and 725.

Alloy 925 has excellent corrosion resistance consistent with Alloy 825. High levels of nickel ensure protection against stress corrosion cracking, whilst the additional molybdenum and copper resist reducing environments, in the same way that Chromium resists oxidising environments. Molybdenum enhances resistance to pitting and crevice corrosion, lifting the Pitting Resistance Equivalent number (PREN) to above 26. With such a balanced composition, Alloy 925 is particularly suited to down-hole applications in sour gas wells , but can also be used in less aggressive applications as it resists general, pitting, crevice and stress corrosion cracking in most aqueous environments where chloride or sulphide ions may be present.