Incoloy is a family of nickel-based alloys built primarily on nickel and chromium. More than ten grades carry the Incoloy name, but the two most widely used are Incoloy 825 and Incoloy 925.
Incoloy is produced under a trademark held by Special Metals Incorporated. Incoloy 825 reached the market in 1952, building on the earlier Incoloy 800 to better resist sulphuric acid, and for many years was the default choice for handling it. Incoloy 925 was developed later, in 1982, to increase the strength of Incoloy 825: its composition is very similar, but small additions of titanium and aluminium deliver precipitation-strengthening after an additional heat treatment, raising strength by a factor of 3-4.
Alloy 825 and Alloy 925 have similar compositions. The main additions and what they do:
- Nickel, up to 46% - gives resistance to stress corrosion cracking and a wider operating temperature range than many stainless steels.
- Chromium, up to 23.5% - improves general corrosion resistance, including resistance to acids such as nitric and sulphuric.
- Molybdenum, up to 3.5% - lifts overall pitting and corrosion resistance.
- Copper, up to 3% - improves resistance to acids, particularly sulphuric acid. The same effect is used in Ferralium® 255 super duplex stainless steel (2% copper) and the more highly alloyed Alloy 20 (3-4% copper).
- Titanium, up to 2.4% - protects these grades against intergranular corrosion.
What we stock
We stock Alloy 825 as round bars from 5/8"-10" diameter (15.87-254mm), with pipes and hollow bar also available. Alloy 925 is less readily available in the smallest diameters, so our stock typically starts at 4"-10" (101.6-254mm) diameter.