C 825 Nickel-Iron-Chromium Alloy,UNS N08825,E FORU

### **Alloy 825 (UNS N08825) - Nickel-Iron-Chromium Alloy** #### **Overview** Alloy 825, also known by its UNS designation N08825, is a nickel-iron-chromium austenitic alloy with additions of molybdenum and copper. It is specifically designed for exceptional resistance to a wide variety of corrosive environments. The high nickel content provides immunity to chloride-ion stress-corrosion cracking, while the chromium confers resistance to oxidizing media. The molybdenum and copper additions enhance its resistance to reducing acids, such as sulfuric and phosphoric acid. Furthermore, the alloy is stabilized with titanium, which prevents sensitization and subsequent intergranular corrosion when exposed in the carbide precipitation range. This combination of properties makes Alloy 825 a versatile and highly reliable material for demanding applications in chemical processing, pollution control, oil and gas recovery, and acid production. --- #### **Chemical Composition (Weight % - Typical)** The typical chemical composition of UNS N08825 is as follows: | Element | Content (%) | | :--- | :--- | | Nickel (Ni) | 38.0 - 46.0 | | Chromium (Cr) | 19.5 - 23.5 | | Iron (Fe) | ≥ 22.0 | | Molybdenum (Mo) | 2.5 - 3.5 | | Copper (Cu) | 1.5 - 3.0 | | Titanium (Ti) | 0.6 - 1.2 | | Carbon (C) | ≤ 0.05 | | Manganese (Mn) | ≤ 1.0 | | Silicon (Si) | ≤ 0.5 | | Sulfur (S) | ≤ 0.03 | | **Aluminum (Al)** | **0.1 - 0.5** | *Note: Aluminum (Al) is a key component and is always present within the specified range.* --- #### **Physical Properties** The following table outlines the key physical properties of Alloy 825. | Property | Value | | :--- | :--- | | Density | 8.14 g/cm³ (0.294 lb/in³) | | Melting Range | 1370 - 1400 °C (2500 - 2550 °F) | | Specific Heat (20°C) | 440 J/kg·K | | Electrical Resistivity | 1.12 μΩ·m | | Thermal Conductivity (20°C) | 10.8 W/m·K | | Mean Coefficient of Thermal Expansion (20-100°C) | 14.0 μm/m·°C | | Modulus of Elasticity (Elastic Modulus) | 196 GPa (28.4 x 10⁶ psi) | --- #### **Mechanical Properties (Typical at Room Temperature)** Mechanical properties can vary with product form and heat treatment. The following are typical minimum values for annealed condition. **Sheet/Plate** * **Tensile Strength:** 655 MPa (95 ksi) min * **Yield Strength (0.2% Offset):** 275 MPa (40 ksi) min * **Elongation (in 2 inches / 50 mm):** 30% min **Tube** * **Tensile Strength:** 620 MPa (90 ksi) min * **Yield Strength (0.2% Offset):** 240 MPa (35 ksi) min * **Elongation:** 30% min --- #### **Key Characteristics & Applications** **Key Characteristics:** 1. **Excellent General Corrosion Resistance:** Performs well in both oxidizing and reducing environments. 2. **Resistance to Stress-Corrosion Cracking (SCC):** Immune to chloride-induced stress-corrosion cracking due to its high nickel content. 3. **Resistance to Localized Attack:** Good resistance to pitting and crevice corrosion. 4. **Resistance to Acids:** Excellent resistance to sulfuric and phosphoric acids, and good resistance to nitric acid. 5. **Stabilized against Sensitization:** The titanium addition ties up carbon, preventing the formation of chromium carbides at grain boundaries during welding or high-temperature service. **Typical Applications:** * **Chemical Processing:** Pickling tanks, heating coils, reaction vessels, and transfer piping for acids. * **Oil and Gas Industry:** Scrubbers, piping systems, downhole tubing, and seals in sour service (H₂S-containing environments). * **Pollution Control:** Flue gas desulfurization systems (scrubbers, dampers, stack gas reheaters). * **Acid Production:** Equipment for the production and handling of sulfuric and phosphoric acid. * **Nuclear Fuel Reprocessing:** Component handling in radioactive and corrosive solutions. * **Seawater Applications:** Heat exchangers, piping, and pumps where resistance to chloride attack is critical. --- #### **International Standards** Alloy 825 is covered by numerous international standards for various product forms. | Product Form | ASTM (USA) | ASME (USA) | EN (European) | UNS | | :--- | :--- | :--- | :--- | :--- | | **Plate, Sheet, Strip** | ASTM B424 | SB-424 | EN 2.4858 / NiCr21Mo | N08825 | | **Seamless Pipe & Tube** | ASTM B423 / B163 | SB-423 / SB-163 | EN 2.4858 / NiCr21Mo | N08825 | | **Welded Tube** | ASTM B704 / B705 | SB-704 / SB-705 | EN 2.4858 / NiCr21Mo | N08825 | | **Bar, Rod, Wire** | ASTM B425 / B164 | SB-425 / SB-164 | EN 2.4858 / NiCr21Mo | N08825 | | **Forgings** | ASTM B564 | SB-564 | EN 2.4858 / NiCr21Mo | N08825 | | **Fittings** | ASTM B366 | - | EN 2.4858 / NiCr21Mo | N08825 | **Note:** The European standard **EN 2.4858** (Material Number: 2.4858) is the direct equivalent to UNS N08825. The old DIN designation was **NiCr21Mo**. --- #### **Summary** In summary, **Alloy 825 (UNS N08825)** is a robust, versatile, and widely used nickel-based alloy that offers an optimal balance of corrosion resistance, mechanical strength, and fabricability. Its standardization across major international codes (ASTM, ASME, EN) makes it a trusted and readily available material for engineers designing equipment to withstand some of the most aggressive industrial environments.

Packing of Standard Packing: Typical bulk packaging includes palletized plastic 5 gallon/25 kg. pails, fiber and steel drums to 1 ton super sacks in full container (FCL) or truck load (T/L) quantities. Research and sample quantities and hygroscopic, oxidizing or other air sensitive materials may be packaged under argon or vacuum. Solutions are packaged in polypropylene, plastic or glass jars up to palletized 3194 gallon liquid totes Special package is available on request.