Material Family

Nickel-Iron-Chromium-Molybdenum-Copper Austenitic Alloy (Solid-Solution Strengthened)

Optimized chemistry for versatile aqueous corrosion resistance.

Common Designations

UNS N08825, Incoloy 825, W.Nr. 2.4858, NS 142

A globally recognized standard for severe corrosive service. "Incoloy" is a trademark of Special Metals Corporation.

Chemical Composition (Typical wt.%)

Ni: 38.0 - 46.0
Cr: 19.5 - 23.5
Fe: ≥ 22.0 (Balance)
Mo: 2.5 - 3.5
Cu: 1.5 - 3.0
Ti: 0.6 - 1.2
C: ≤ 0.05
Mn: ≤ 1.0
Si: ≤ 0.05

Molybdenum (Mo) resists pitting and reducing acids. Copper (Cu) enhances resistance to sulfuric acid. Titanium (Ti) stabilizes against sensitization.

Mechanical Properties (Annealed Plate, Room Temp)

Tensile Strength (Rm): 586 - 758 MPa
Yield Strength (Rp0.2): 241 - 345 MPa
Elongation (A): 30% min

Provides robust mechanical strength with good ductility for fabrication.

Physical Properties

Density: 8.14 g/cm³
Melting Range: 1370 - 1400 °C
Effective Service Temp: Up to 540°C (1000°F) for corrosion applications.

Primarily used in low to moderately high temperature corrosive services, not for extreme heat.

Key Corrosion Resistance Attributes

• Excellent resistance to sulfuric & phosphoric acids across a wide range of concentrations and temperatures.• Excellent resistance to chloride-ion stress corrosion cracking (SCC).• Good resistance to pitting and crevice corrosion in chloride solutions.• Good resistance to oxidizing acids (e.g., nitric) and alkali solutions.

Its versatility in mixed acid and chloride environments is its primary advantage.

Key Standards (Plate)

ASTM B424 / ASME SB-424 (Primary plate spec), DIN 2.4858

ASTM B424 is the main specification for plate, sheet, and strip.

Stabilization

The addition of Titanium (Ti) and the low carbon content stabilize the alloy against sensitization (chromium carbide precipitation) during welding, maintaining corrosion resistance in the as-welded condition.

This eliminates the need for post-weld heat treatment for most applications, a significant fabrication advantage.

Typical Applications

• Chemical Processing: Pickling tanks, heating coils, reactor vessels for sulfuric/phosphoric acid.
• Pollution Control: Flue gas desulfurization (FGD) scrubbers, ducting, stack liners.
• Oil & Gas: Sour service (H₂S-containing) tubing, casing, components.
• Marine: Seawater cooling pipes, propeller shafts, fasteners.
• Nuclear Fuel Reprocessing.

The go-to material for wet scrubber systems, acid handling, and sour service applications.