Incoloy 925

Development

Incoloy 925 was launched in 1982 by Special Metals Corporation as a development of Incoloy 825, which was itself introduced in 1952 for higher-temperature applications with superior acid resistance. Alloy 825 proved cost-effective thanks to its lower nickel content, but its modest mechanical properties limited its applications.

To increase the strength of the Incoloy 825 base alloy, controlled additions of titanium and aluminium are made. These form very fine Ni3(Al, Ti) precipitates (gamma prime) throughout the matrix during final heat treatment. This age-hardening greatly increases the hardness and strength of Incoloy 925, in a similar way to Monel^® K-500, Inconel^® 718 and Inconel 725.

Corrosion resistance and applications

As a nickel-based alloy, Incoloy 925 resists stress corrosion cracking and sulphide stress cracking well in sour, H2S environments for oil and gas, and is included by NACE MR0175. Common applications include down-hole and well-head components, hangers, joints and packers.

Its chromium content gives good general corrosion resistance in oxidising environments, and additional molybdenum enhances pitting resistance, giving a Pitting Resistance Equivalent number (PREN) of 26. Its copper content is recognised to improve resistance to sulphuric acid, mirrored in Ferralium^® 255 and its 2% copper. This balance of resistance across several aggressive environments is exploited in valve components, pump shafts, fasteners and marine applications.

The combination of corrosion resistance and strength makes Incoloy 925 a potential alternative to the more highly alloyed and more expensive Inconel 718, and it is increasingly specified by oil companies and OEMs to reduce project costs.

We carry an extensive stock of nickel alloys, including Alloy 925 in sizes from 3" (76.2mm) to 9" (228.6mm) diameter.