Incoloy 825 (2.4858)

Q: What are the Mechanical Properties of Incoloy 825?

Typical values: tensile strength approx 690 MPa; yield strength approx 310 MPa; elongation approx 30 percent; hardness approx 170 HB (Brinell); modulus of elasticity approx 195 GPa. These support reliable performance in pressure bearing and load bearing systems.

Q: What are the Physical Properties of Incoloy 825?

Typical values: density 8.14 g/cm3; melting point 1370-1400 C; thermal conductivity approx 11 W/m K; thermal expansion approx 14.5 x 10^-6 per K; electrical resistivity approx 1.15 micro-ohm m. Suitable for long term use under thermal, chemical and mechanical cycling.

Q: Are there Variants or Equivalent Grades of Incoloy 825?

Common alternatives include: Incoloy 800H/800HT for higher creep strength and thermal stability at very high temperature; Inconel 625 for improved oxidation resistance and mechanical strength; Alloy 20 as a cost optimised Ni Fe Cr alloy for sulfuric acid in less extreme environments. Selection depends on media, temperature, fabrication needs and lifecycle targets.

Q: What is the Chemical Composition of Incoloy 825?

Typical composition in percent: Nickel 38.0-46.0; Iron 22.0-25.5; Chromium 19.5-23.5; Molybdenum 2.5-3.5; Copper 1.5-3.0; Titanium 0.6-1.2; Manganese 1.0 max; Silicon 0.5 max; Carbon 0.05 max; Sulfur 0.03 max. The balance provides resistance to chloride stress corrosion, pitting and intergranular attack.

Q: Where is Incoloy 825 USed?

Common applications: heat exchangers and acid recovery units; marine exhaust and seawater systems; flue gas desulfurisation equipment; nuclear fuel reprocessing components; chemical processing vessels and tanks; pollution control and waste treatment plants. Chosen for durability in aggressive environments and long service life.

Exceptional resistance to corrosion, pitting, and stress cracking in aggressive chemical, marine, and high-pressure environments.

Incoloy 825

Incoloy 825 is a highly corrosion-resistant nickel-iron-chromium alloy built for severe-service environments involving aggressive acids, chlorides, and high mechanical stress. Known by its designation UNS N08825 or 2.4858, this material offers dependable stability in both oxidising and reducing conditions, making it a trusted choice in chemical processing, marine systems, pollution control, and nuclear applications.

Its balanced chemistry includes molybdenum for pitting resistance, copper to strengthen acid performance, and titanium for structural stability. The result is a material capable of withstanding sulphuric, nitric, and phosphoric acid exposure, along with high-pressure steam, saltwater, and contaminated process media.

Incoloy 825 is widely used in pressure vessels, marine piping, reactors, scrubbers, and acid handling systems, wherever equipment failure could pose safety or operational risks. Its long service life and resistance to metal fatigue make it an asset in infrastructure that cannot afford corrosion-related downtime.

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AVAILABLE FORMS

Intamet offers Incoloy 825 in a wide range of forms, including:

Incoloy 825 maintains structural strength and ductility even in chemically aggressive or high-temperature environments. Its resilience supports reliable operation in pressure-bearing and load-bearing systems.

Typical Mechanical Properties:

Tensile Strength: ~690 MPa - Enables robust performance in chemical processing vessels, tanks, and exhaust systems.

Yield Strength: ~310 MPa - Supports pressure resistance and mechanical stability in pipework and containment.

Elongation: ~30% - Provides flexibility during fabrication, bending, and welding.

Hardness (Brinell): ~170 HB - Offers moderate wear resistance with good machinability.

Modulus of Elasticity: ~195 GPa - Delivers stiffness and reliability under mechanical and thermal stress.

These properties make Incoloy 825 a strong candidate for demanding process systems and industrial infrastructure.

What are the Physical Properties of Incoloy 825?

Incoloy 825 exhibits consistent physical behaviour under thermal, chemical, and mechanical cycling, ideal for long-term use in variable conditions.

Typical Physical Properties:

Density: 8.14 g/cm³
Maintains high mechanical strength with a balanced weight-to-performance ratio.

Melting Point: 1370–1400 °C
Supports elevated temperature use in thermal and chemical systems.

Thermal Conductivity: ~11 W/m·K
Ensures effective heat transfer in piping, ducts, and reactor walls.

Thermal Expansion Coefficient: ~14.5 × 10⁻⁶/K
Allows dimensional consistency under temperature fluctuation.

Electrical Resistivity: ~1.15 µΩ·m
Provides stable performance in electrochemical or heat-exposed systems.

These characteristics make 825 a practical choice in heat exchangers, flue systems, and pressure vessels exposed to heat and corrosion.

Are there Variants or Equivalent Grades of Incoloy 825?

While Incoloy 825 is a popular specification in corrosive-service design, alternative alloys may be selected for higher temperature strength or cost optimisation.

Incoloy 800H/800HT: Engineered for higher creep strength and thermal stability, better suited to extreme heat applications.

Inconel 625: Offers improved oxidation and mechanical strength for harsher or more demanding high-temperature conditions.

Alloy 20: A lower-cost nickel-iron-chromium alloy, widely used for sulphuric acid resistance in less extreme environments.

Each alloy presents a different performance envelope. Material selection depends on media type, operating temperature, fabrication requirements, and expected lifespan.

What is the Chemical Composition of Incoloy 825?

The alloy’s chemistry balances corrosion resistance, thermal stability, and mechanical strength, especially where chloride stress corrosion, pitting, and intergranular attack are concerns.

Nickel (Ni): 38.0–46.0
Delivers resistance to both oxidising and reducing chemicals.

Iron (Fe): 22.0–25.5
Provides core strength and structural integrity.

Chromium (Cr): 19.5–23.5
Enhances resistance to scaling, oxidation, and stress corrosion cracking.

Molybdenum (Mo): 2.5–3.5
Improves protection against pitting and crevice corrosion.

Copper (Cu): 1.5–3.0
Boosts performance in sulphuric and phosphoric acid environments.

Titanium (Ti): 0.6–1.2
Stabilises the alloy during welding and heat exposure.

Manganese (Mn): ≤ 1.0

Silicon (Si): ≤ 0.5

Carbon (C): ≤ 0.05

Sulfur (S): ≤ 0.03

This chemistry is carefully tuned to prevent embrittlement and ensure long-term corrosion resistance in hostile service conditions.

Where is Incoloy 825 Used?

Incoloy 825 is trusted across industries where failure due to chemical corrosion or thermal stress can compromise safety, output, or equipment lifespan.

Heat Exchangers & Acid Recovery Units: Resists corrosion from process acids and contaminated heat transfer fluids.

Marine Exhaust & Seawater Systems: Withstands salt spray, chlorides, and biofouling in offshore environments.

Flue Gas Desulfurisation Equipment: Delivers long-term performance in acidic and high-temperature emissions control.

Nuclear Fuel Reprocessing Components: Offers radiation stability and acid resistance in high-value infrastructure.

Chemical Processing Vessels & Tanks: Maintains integrity in sulphuric and phosphoric acid service.

Pollution Control & Waste Treatment Plants: Resists chemical attack in scrubbers, filters, and industrial fluid systems.

Its proven track record in aggressive environments makes Incoloy 825 a preferred choice for applications that demand both safety and performance over time.

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Incoloy 825 (2.4858)