Incoloy 825 (UNS N08825 / W.Nr. 2.4858) is a nickel-iron-chromium alloy with additions of molybdenum, copper and titanium. It was developed to resist sulphuric acid and to withstand chloride-induced stress corrosion cracking.
The Incoloy family of alloys share a nickel-iron-chromium base with varying additional elements. They were originally developed by the Special Metals Corporation group of companies, which includes the former Wiggins business in Hereford, UK, that pioneered new alloys for Sir Frank Whittle's original jet engine. They are designed for corrosion resistance and 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 1950s, but many grades are now produced by other manufacturers. Alleima makes a version of Incoloy 825 under its Sanicro 41 trademark, while Bohler (Voest Alpine) makes L314.
The first Incoloy alloy on the market was Incoloy 800, launched in 1949. Nickel was in relatively short supply at the time, so this lower-nickel alloy met the need for a cost-competitive material that could retain strength and resist oxidation and high-temperature corrosion, suiting it to furnace components, petrochemical items and protective sheathing for electrical heating elements.
Incoloy 825 came to market in 1952, building on Incoloy 800 to better resist sulphuric acid. Copper additions are well known to improve resistance to reducing environments such as sulphuric acid, a property also exploited in Ferralium® 255 (with 2% copper) and in the much more highly alloyed Alloy 20 (3-4% copper). Although its nickel content is lower than Inconel 625 or Inconel 718, it is still enough to give resistance to stress corrosion cracking in chloride-containing environments. The increased chromium ensures good resistance to oxidising environments such as nitric acid, while molybdenum improves pitting resistance.
The mechanical properties of Alloy 825 are relatively constant from cryogenic temperatures (around -150degC) up to 540degC (100degF). Above this, undesirable microstructural phase changes can significantly reduce impact toughness and elongation.
We carry a significant stock of Alloy 825 solid bar, from ¾" up to 10" in a large number of incremental sizes. We also hold some bespoke sizes of hollow bar or tube for specific applications, and use our in-house deep hole borer to offer one-offs and specific sizes of bored bar. Popular applications include valve components, thermowells and sensors, fasteners, and downhole tooling that makes use of the alloy's non-magnetic properties.