Applications for Incoloy 825

29th August 2019

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Incoloy 825 is a nickel-iron-chrome alloy that is widely used in Oil & Gas and Chemical Process Industry applications. It has good corrosion resistance and an ability to operate at higher temperatures than most stainless steels.

Incoloy is a trademark of Special Metals Corporation that is applied to a family of nickel-iron-chrome alloys. Nickel-based alloys are sometimes also referred to as corrosion resistant alloys (CRA), high performance alloys (HPA) and even super alloys, although this caption should really be retained for those alloys that consist almost entirely of nickel, cobalt or other more exotic metals. They were developed from the 1990’s onwards and include Alloy 825 (UNS N08825, 2.4858), Alloy 925 (UNS N09925) and Alloy 800. Higher-performance Inconel alloys were originally created to support the development of the first jet engines, whilst Incoloy alloys were developed to provide a more cost-effective offering – achieved by lowering the (expensive) nickel content.

Alloy 825 contains >40% Ni which ensures resistance to stress corrosion cracking. A controlled addition of titanium inhibits the intergranular corrosion that might otherwise occur at elevated temperatures. Additions of molybdenum and copper allow it to resist reducing environments such as sulphuric and phosphoric acids, hence its widespread use in various chemical process industry end uses.

Due to the combination of good corrosion resistance and working temperature range, it is used in Oil and Gas wellheads, risers, piping, casing and tubing. Langley Alloys supply chain partnerships means that we are able to offer pipes, flanges and fittings in addition to our solid bar stock. Solid bar is available ex-stock in sizes from 3/4″ up to 10″ diameter.

Applications in the Chemical Process Industry include thermowells and sensors, pump and valve components, hydrogen and ethylene furnaces as well as components for fertilizer and ammonia plants. Typical components comprise vessels for the handling of seawater, ammonium sulphate, pickling acids, sulphuric and phosphoric acids.

Alloy 825 is also approved for pressure vessel operating temperatures up to 525°C (AS1210, AS4041), 538°C (ASME Boiler & Pressure Vessel Code, Sections I, III, VIII, IX, Cases 1936, N-188). Brittle phases may form in Alloy 825 at temperatures above ~ 540°C, so it is not normally used at these temperatures, where creep-rupture properties would be design factors.