Incoloy — material overview
Looking for a valve in this exotic alloy? Find it in the following configurations: Ball, Butterfly, Cast, Check, Control, Cryogenic, Custom made, Foot, Forged, Gate, Globe, Needle, Plug, and Safety relief, as well as Strainers.
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Incoloy alloy 825 is a nickel iron chromium alloy with additions of molybdenum, copper and titanium, with exceptional resistance to many aggressive corrosion environments.
Incoloy 825 is highly resistant to corrosion. It has a high nickel content, sufficient to resist chloride ion stress corrosion cracking, and a very stable austenite structure. The levels of molybdenum and copper enable the alloy to resist reducing agents and acids. Chromium gives resistance to oxidising conditions, such as nitric acid solutions, nitrates and oxidising salts. The alloy is titanium stabilised to resist pitting and intergranular attack after fabrication, particularly welding, which includes heating in the critical sensitisation temperature range ( 650°C – 760°C ).
Alloy 825 offers exceptional resistance to corrosion by sulphuric and phosphoric acids and is often the most cost effective alloy in sulphuric acid service.
Incoloy 825 is 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.
Applications of Incoloy 825
Typical Applications of Incoloy Alloy 825 include:
. Sulphuric acid piping and vessels
. Phosphoric acid evaporators
. Pickling tank heaters, pickling tanks and equipment
. Chemical process equipment
. Propellor shafts
. Tank trucks
. Electrostatic precipitator electrodes
. Hot vessels for food, water and seawater,
. ammonium sulphate vessels
. Expansion bellows
. Marine exhaust systems
. Power station ash hoppers
The outstanding property of Incoloy 825 is its corrosion resistance. In reducing & oxidising conditions, Incoloy 825 resists general corrosion, pitting & crevice corrosion, intergranular corrosion and stress corrosion cracking. It is particularly useful in sulphuric & phosphoric acids, sulphur containing flue gases, sour gas and oil wells and sea water.
Incoloy 825 can be readily hot or cold worked. Hot working should be in the range 870 – 1180°C , finishing at 870 – 980°C . For maximum corrosion resistance hot worked parts should be stabilise annealed before use. The alloy is easier to cold form than stainless steels.
Incoloy 825 is classed as a ‘C’ alloy, and is reasonably easy to machine.
The alloy is readily weldable by the normal processes (GMAW (MIG), GTAW (TIG), SMAW (manual), SAW). The joint must be clean to avoid contamination of the weld pool.
Incoloy 825 is stabilise annealed at 940°C . The softest structure is obtained at 980°C . Sections heavier than sheet, strip and wire should be quenched to avoid sensitisation.
ASTM Product Specifications
B163 Seamless Nickel and Nickel Alloy Condenser and Heat-Exchanger Tubes
B423 Nickel-Iron-Chromium-Molybdenum-Copper Alloy (UNS N08825 and N08221)* Seamless Pipe and Tube
B424 Ni-Fe-Cr-Mo-Cu Alloy (UNS N08825 and UNS N08221)* Plate, Sheet, and Strip
B425 Ni-Fe-Cr-Mo-Cu Alloy (UNS N08825)
B704 Welded UNS N06625 and UNS N08825 Alloy Tubes
B705 Nickel-Alloy (UNS N06625 and N08825) Welded Pipe
B751 General Requirements for Nickel and Nickel Alloy Welded Tube
Equivalent Grade Designations
Other international grades that are equivalent to Incoloy Alloy 825.
USA UNS N08825
France AFNOR NC 21 FeDU
GB BS NA 16
Germany DIN NiCr21Mo
Germany Werkstoff Nr 2.4858