Alloy 825 (UNS N08825)

Alloy 825, often referred to as Incoloy 825 (where Incoloy is a trademark of Special Metals Corp), is a nickel-iron-chromium alloy with additions of molybdenum, copper and titanium (NiCr21Mo), supplied in the hot worked and annealed condition. It achieves good mechanical properties from cryogenic to medium-high temperatures (540⁰C) and can be significantly strengthened through cold working.

The high nickel content ensures resistance to stress corrosion cracking, combined with molybdenum and copper to strongly resist reducing environments such as sulphuric and phosphoric acids, chromium to resist oxidising environments such as nitric acid, titanium to inhibit intergranular corrosion, and overall resistance to pitting and crevice corrosion.

The Incoloy family of alloys are all based upon a nickel-iron-chromium base composition, but with a varying number of additional alloying elements. They were originally developed and produced by the Special Metals Corporation group of companies, which includes the former Wiggins business in Hereford, UK that pioneered new alloys for use in Sir Frank Whittle’s original jet engine. They are designed for excellent corrosion resistance as well as strength at high temperatures; with specific alloys created to resist attack by particular chemicals.

The Incoloy trademark, registered to Huntingdon Alloys Corporation (‘Special Metals Corporation’) has been in commercial use since the 1950’s, but many of the grades are now produced by other manufacturers. For instance, Sandvik manufacture a version of Incoloy 825 under their trademark Sanicro®41, whilst Bohler (Voest Alpine) manufacture L314.

Incoloy 825 was brought to the market in 1952, building upon Incoloy 800 in order to better resist sulphuric acid. Copper additions are well-known to improve resistance to reducing environments, such as sulphuric acid. This property is also exploited in Ferralium 255 (containing 2% copper additions) and the much more highly alloyed Alloy 20 (3-4% copper) to great effect. Although the nickel content is lower than the likes of Inconel 625 and Inconel 718, it is still sufficient to impart resistance to stress corrosion cracking (SCC) in chloride-containing environments. The increased chromium content ensures good resistance to oxidising environments such as nitric acid, whilst the molybdenum additions are well-known to improve pitting corrosion resistance.

The mechanical properties of Inconel 825 are relatively constant from very low temperatures (considered cryogenic i.e. -150degC) up to 540degC (100degF). Above this temperature there is the possibility of undesirable microstructural phase changes that significantly reduce impact toughness and elongation.

Langley Alloys carries a significant stock of Alloy 825 solid bar, from ¾” up to 10” in a large number of incremental sizes. In addition, we also carry some bespoke sizes of hollow bar or tube for specific customer applications, as well as using our in-house deep hole borer to offer one-offs and specific sizes of bored bar. Popular applications currently served by our customers includes valve components, thermowells and sensors, fasteners and also some downhole tooling which make use of its non-magnetic properties.

Incoloy and Inconel are trademarks of the Special Metals Corporation group of companies. Sanicro is a trademark of Sandvik Intellectual Property AB. Ferralium is a trademark of Langley Alloys Ltd.