Nickel Alloys Incoloy Alloy 825 N08825
Austral Wright Speciality Metals

 Product Data Sheet  Nickel Alloys

Incoloy® Alloy 825™  UNS N08825

Incoloy® Alloy 825™ is a nickel iron chromium alloy with additions of molybdenum, copper and titanium, with exceptional resistance to many aggressive corrosion environments.

Chemical Composition

ASTM B163 – Heat Exchanger Tube

Element %
Nickel
38.0-46.0
Chromium
19.5-23.5
Molybdenum
2.5-3.5
Copper
1.5-3.0
Titanium
0.6-1.2
Iron
22.0 min (~33%)
Carbon
0.05 max
Manganese
1.0 max
Sulphur
0.03 max
Silicon
0.5 max
Aluminium
0.2 max

Typical Room Temperature Tensile Properties

NOT FOR DESIGN. Consult the relevant material or product specification for design values.

Form Condition 0.2% Proof Stress
Tensile Strength
Elongation
MPa
MPa
%
Tube Annealed 440 770 35
Tube Cold Drawn 880 1000 15
Bar Annealed 325 690 45
Plate Annealed 340 660 45
Sheet Annealed 420 760 39

Typical Applications

Sulphuric acid piping and vessels, phosphoric acid evaporators, pickling tank heaters, pickling tanks and equipment, chemical process equipment, propellor shafts, tank trucks, calorifiers, electrostatic precipitator electrodes, hot vessels for food, water and seawater, ammonium sulphate vessels, expansion bellows, marine exhaust systems, power station ash hoppers.

Description

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.

Availability

Austral Wright Metals can supply this alloy as plate, sheet, strip, bar, rod, wire, tube, pipe, fittings, fasteners.

Pressure Vessels

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.

Corrosion Resistance

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.

Nickel Alloys Incoloy Alloy 825 N08825 Nickel Alloys Incoloy Alloy 825 N08825
High temperature tensile properties of annealed bar Isocorrosion chart in laboratory pure sulphuric acid

Fabrication

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.

Machinability

Incoloy 825 is classed as a ‘C’ alloy, and is reasonably easy to machine.

Weldability

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.

Welding Consumables

Normal Service Higher Strength Best Corrosion Resistance
Welding Electrode Inconel WE 112 Inconel WE 112 Inconel WE 112
Filler Metal Inconel FM 625 Inconel FM 625 Inconel FM 625
Flux Cored Wire Inco Cored 625DH Inco Cored 625DH Inco Cored 625DH

Heat Treatment

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. Please consult Austral Wright Metals for specific advice on your application.

Equivalent Specifications

Country Body Grade
USA UNS N08825
France AFNOR NC 21 FeDU
GB BS NA16
Germany DIN 2.4858
Germany Werkstoff Nr NiCr21Mo

Physical Properties

Property
Metric Units
Density
8,140 kg/m³ @ 20°C
Melting Point
1370-1400°C
Electrical Resistivity
1.13 micro-ohm . m @ 25°C
Specific Heat
440 J/kg . °C @ 20°C
Mean Coefficient of Expansion
14.1 x 10-6 / °C @ 20-100°C
15.3 x 10-6 / °C @ 20-300°C
15.8 x 10-6 / °C @ 20-500°C
Thermal Conductivity
11.1 W / m . °C @ 25°C
Curie Temperature
< -196°C
Modulus of Elasticity
Tension
206 GPa @ 23°C
Torsion
72.5 GPa @ 23°C
Poisson’s Ratio
0.42 @ 23°C
Relative Permeability
1.005 @ 200 Oe

ASTM Product Specifications

Specification Title
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
Nickel Iron Chromium Molybdenum Copper Alloy (UNS N08825 and N08221) Plate, Sheet and Strip
B425
Nickel Iron Chromium Molybdenum Copper 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
The technical advice and recommendations made in this Product Data Sheet should not be relied or acted upon without conducting your own further investigations, including corrosion exposure tests where needed. Please consult current editions of standards for design properties. Austral Wright Metals assumes no liability in connection with the information in this Product Data Sheet. Austral Wright Metals supplies a comprehensive range of stainless steels, copper alloys, nickel alloys and other high performance metals for challenging service conditions. Our engineers and metallurgists will be pleased to provide further data and applications advice.

 

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