Incoloy 825 is a nickel-iron-chromium alloy widely used in oil and gas and chemical process applications. It offers good corrosion resistance and works at higher temperatures than most stainless steels. We supply it as solid bar, and as pipe, flanges and fittings through our supply partners.
What Incoloy 825 is
Incoloy is a Special Metals Corporation family of nickel-iron-chromium alloys. Nickel-based alloys are sometimes called corrosion-resistant alloys (CRA), high-performance alloys (HPA) or super alloys, though the last term is better reserved for alloys made up almost entirely of nickel, cobalt or more exotic metals. This family, developed from the 1990s onwards, includes Alloy 825 (UNS N08825, 2.4858), Alloy 925 (UNS N09925) and Alloy 800. Higher-performance Inconel alloys were originally created for the first jet engines, while Incoloy alloys offered a more cost-effective option by lowering the expensive nickel content.
Why it resists corrosion
Alloy 825 contains more than 40% nickel, which gives resistance to stress corrosion cracking. A controlled titanium addition inhibits the intergranular corrosion that could otherwise occur at elevated temperatures, and additions of molybdenum and copper let it resist reducing environments such as sulphuric and phosphoric acids - hence its wide use in the chemical process industry.
Applications
Because it combines good corrosion resistance with a useful temperature range, Alloy 825 is used in oil and gas wellheads, risers, piping, casing and tubing. Our supply partnerships mean we can offer pipe, flanges and fittings alongside our solid bar stock. Solid bar is available ex-stock from 3/4" up to 10" diameter.
In the chemical process industry, applications include thermowells and sensors, pump and valve components, and hydrogen and ethylene furnaces, as well as components for fertiliser and ammonia plants. Typical items are vessels for handling seawater, ammonium sulphate, pickling acids, and sulphuric and phosphoric acids.
Alloy 825 is also approved for pressure vessel operating temperatures up to 525degC (AS1210, AS4041) and 538degC (ASME Boiler & Pressure Vessel Code, Sections I, III, VIII, IX, Cases 1936, N-188). Brittle phases can form above about 540degC, so it is not normally used at those temperatures, where creep-rupture properties would become design factors.
| Standard | Max approved operating temperature |
|---|---|
| AS1210 / AS4041 | 525°C |
| ASME Boiler & Pressure Vessel Code (Sections I, III, VIII, IX) | 538°C |