What is Incoloy Alloy 825?
Incoloy Alloy 825 is a corrosive resistant and powerful nickel-iron-chromium alloy. It contains a lot of nickel which prevents cracking, which is brought about by chloride ions. Molybdenum and copper enhance resistance to strong acids and reducing environments. Chromium also prevents the alloy from oxidising in environments such as nitric acid and other corrosive agents.
This is also a titanium-stabilised alloy that prevents pitting and intergranular corrosion following such processes as welding or exposure to heat.
Due to such a balanced chemistry composition, Incoloy 825 is a reliable and economical material to deal with sulphuric and phosphoric acids so it finds extensive use in chemical, petrochemical and marine service.
ASTM specifications of Incoloy Alloy 825
Key ASTM standards and specifications for Incoloy Alloy 825 are listed below.
| 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 | 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 |
Chemical Composition of Incoloy Alloy 825
Incoloy Alloy 825 comes with a different chemical composition, and the detailed information about this is given below.
| Element | % | Element | % |
|---|---|---|---|
| Nickel | 38.0 – 46.0 | Carbon | 0.05 max |
| Chromium | 19.5 – 23.5 | Manganese | 1.0 max |
| Molybdenum | 2.5 – 3.5 | Sulfur | 0.03 max |
| Copper | 1.5 – 3.0 | Silicon | 0.5 max |
| Titanium | 0.6 – 1.2 | Aluminium | 0.2 max |
| Iron | 22.0 min (~33%) |
Tensile Properties of Incoloy Alloy 825
Incoloy Alloy 825 offers reliable tensile strength and flexibility. The important mechanical details are provided below.
| Form | Condition | 0.2% Proof Stress MPa | Tensile Strength MPa | Elong % |
|---|---|---|---|---|
| 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 |
Thermal Properties of Incoloy Alloy 825
Temperature-dependent thermal characteristics of Incoloy Alloy 825 are summarised below.
| Temperature | Thermal Conductivity (Btu-in/ft²·h·°F) | Thermal Conductivity (W/m·°C) | Coefficient of Expansion (in/in·°F) | Coefficient of Expansion (µm/m·°C) |
|---|---|---|---|---|
| -250°F | 55 | – | – | – |
| -200°F | 59 | – | – | – |
| -100°F | 66 | – | – | – |
| 0°F | 72.6 | – | – | – |
| 78°F | 76.8 | – | – | – |
| 100°F | 78.4 | – | – | – |
| 200°F | 85.0 | – | – | – |
| 400°F | 97.5 | – | – | – |
| 600°F | 109.6 | – | – | – |
| 800°F | 119.7 | – | – | – |
| 1000°F | 130.9 | – | – | – |
| 1200°F | 141.8 | – | – | – |
| 1400°F | 154.9 | – | – | – |
| 1600°F | 171.8 | – | – | – |
| 1800°F | 192.0 | – | – | – |
| 2000°F | – | – | – | – |
| -150°C | – | 7.9 | – | – |
| -100°C | – | 8.9 | – | – |
| 0°C | – | 10.7 | – | – |
| 25°C | – | 11.1 | – | – |
| 100°C | – | 12.3 | – | 14.1 |
| 200°C | – | 13.8 | – | 14.8 |
| 300°C | – | 15.4 | – | 15.3 |
| 400°C | – | 16.9 | – | 15.6 |
| 500°C | – | 18.2 | – | 15.8 |
| 600°C | – | 19.6 | – | 16.0 |
| 700°C | – | 21.2 | – | 16.7 |
| 800°C | – | 23.1 | – | 17.3 |
| 900°C | – | 25.5 | – | – |
| 1000°C | – | – | – | – |
Electrical Properties of Incoloy Alloy 825
The electrical resistivity of Incoloy Alloy 825 at various temperatures is shown below.
| Temperature | Electrical Resistivity (ohm-cir mil/ft²) | Electrical Resistivity (µΩ·m) |
|---|---|---|
| – | – | – |
| 200°F | 7.8 | – |
| 400°F | 8.3 | – |
| 600°F | 8.5 | – |
| 800°F | 8.7 | – |
| 1000°F | 8.8 | – |
| 1200°F | 9.1 | – |
| 1400°F | 9.5 | – |
| 1600°F | 9.7 | – |
| -150°C | – | – |
| 25°C | – | 1.13 |
| 100°C | – | 1.14 |
| 200°C | – | 1.18 |
| 300°C | – | 1.21 |
| 400°C | – | 1.24 |
| 500°C | – | 1.26 |
| 600°C | – | 1.27 |
| 700°C | – | 1.27 |
| 800°C | – | 1.28 |
| 900°C | – | 1.29 |
| 1000°C | – | 1.30 |
Equivalent Grades of Incoloy Alloy 825
Similar global and regional grades that are equivalent to Incoloy Alloy 825 are presented below.
| Country | Body | Designation |
|---|---|---|
| USA | UNS | N08825 |
| France | AFNOR | NC 21 FeDU |
| GB | BS | NA 16 |
| Germany | DIN | NiCr21Mo |
| Germany | Werkstoff | Nr 2.4858 |
Applications of Incoloy 825
- Sulphuric acid piping and vessels: Perfect in handling and storage of sulphuric acid since it is highly resilient to corrosion by strong acids.
- Phosphoric acid evaporators: phosphoric acid evaporators are used in evaporators where the phosphoric acid is concentrated, and so it is not susceptible to acid or high temperatures.
- Pickling tank heaters: Cover equipment engaging in a metal surface treatment with corrosive pickling acids.
- Equipment of a chemical process: Equipment is so used in reactors, heat exchangers and tanks which contain aggressive chemicals.
- Propeller shafts: These are appropriate in the marine use as they can withstand corrosion in the sea water.
- Hot food, water, and seawater: These vessels are used to transport hot fluids so that it is safe and lasts longer even in hostile environments.
- Ammonium sulphate vessels: This steel also works with strong chemical vessels such as ammonium sulphate.
- Expansion bellows: Used in Flexible materials which resist thermal expansion and corrosion.
- Marine exhaust system: Many industries use this steel for coating exhaust systems against salt water and heat corrosion.
- Power station: These are anti-erosion and anti-corrosion hoppers used in power plants due to the abrasive ash and flue gases.
Final Words:
Incoloy Alloy 825 is a very versatile and corrosive-resistant nickel-chromium-iron alloy, which is very resistant to acids, cracking by chlorides, and high temperatures. Its special mixture of nickel, molybdenum, copper and titanium is applicable in a large variety of applications, both chemical and petrochemical equipment and marine and power industry. Incoloy 825 is long lasting, safe, and durable with good mechanical, thermal, as well as electrical properties. Supported by international ASTM specifications and by equivalent grades, this alloy is still one of the favorite materials in industries that demand strength, corrosion resistance, and cost effective solutions and the value of this alloy is undeniable in the contemporary engineering practices.