Alloy 28，Incoloy 028 Other/Similar Specs，UNS N08028,E FORU

British Specs:，American Specs:，German Specs:WS 1.4563

### **Introduction to Alloy 28 (UNS N08028)** **Alloy 28**, also known by its trade name **Incoloy 028** and the unified numbering system code **UNS N08028**, is a nickel-iron-chromium superalloy with significant additions of molybdenum and copper. It is specifically designed to offer outstanding resistance to sulfuric acid and other highly corrosive environments. This austenitic alloy is part of the "super-austenitic" stainless steel family, characterized by its high Molybdenum content (>3%), which provides superior pitting and crevice corrosion resistance. Alloy 28 is an evolution of alloys like Alloy 20, with enhanced performance, particularly in acidic chloride media and aggressive process streams found in the chemical process industry. --- ### **Chemical Composition (Weight %)** The typical chemical composition of Alloy 28 is a key factor in its corrosion resistance: | Element | Content (%) | Role in the Alloy | | :--- | :--- | :--- | | **Nickel (Ni)** | 29.0 - 32.0 | Austenite stabilizer, provides base corrosion resistance. | | **Chromium (Cr)** | 26.0 - 28.0 | Confers resistance to oxidizing environments and scaling. | | **Iron (Fe)** | Balance | Base element. | | **Molybdenum (Mo)** | 3.0 - 4.0 | Enhances resistance to pitting and crevice corrosion in chloride ions. | | **Copper (Cu)** | 0.6 - 1.4 | Provides specific resistance to sulfuric acid. | | **Manganese (Mn)** | ≤ 2.0 | Aids in deoxidation during melting. | | **Silicon (Si)** | ≤ 1.0 | Improves resistance to oxidizing acids. | | **Carbon (C)** | ≤ 0.030 | Kept low to prevent sensitization and intergranular corrosion. | | **Sulfur (S)** | ≤ 0.030 | Impurity, controlled for mechanical properties. | | **Nitrogen (N)** | - | - | **Key Feature:** The balanced combination of Ni, Cr, Mo, and Cu gives Alloy 28 a high **Pitting Resistance Equivalent Number (PREN)**. PREN = %Cr + 3.3(%Mo) + 16(%N), typically placing it in a robust category for chloride-containing environments. --- ### **Physical Properties** | Property | Value | | :--- | :--- | | **Density** | 8.0 g/cm³ (0.289 lb/in³) | | **Melting Point** | 1370 - 1400 °C (2500 - 2550 °F) | | **Specific Heat** | 450 J/kg·K (0.11 Btu/lb·°F) at 20°C | | **Thermal Conductivity** | 12.0 W/m·K (83.0 Btu·in/hr·ft²·°F) at 100°C | | **Thermal Expansion** | 14.2 μm/m·°C (7.9 μin/in·°F) from 20-100°C | | **Electrical Resistivity** | 0.95 μΩ·m | | **Modulus of Elasticity** | 200 GPa (29 x 10⁶ psi) | --- ### **Mechanical Properties (Typical for Annealed Condition)** The mechanical properties can vary with product form and size, but typical room temperature properties are: | Property | Plate / Sheet | Bar | | :--- | :--- | :--- | | **Tensile Strength** | 620 - 830 MPa (90 - 120 ksi) | 586 MPa (85 ksi) min | | **Yield Strength (0.2% Offset)** | 270 MPa (39 ksi) min | 241 MPa (35 ksi) min | | **Elongation (% in 2 inches)** | 35% min | 30% min | | **Hardness (Rockwell B)** | ≤ 95 HRB | ≤ 100 HRB | --- ### **International Standards** Alloy 28 is covered by numerous international standards for different product forms: | Product Form | ASTM / ASME | EN / DIN | UNS | | :--- | :--- | :--- | :--- | | **Plate, Sheet, Strip** | ASTM B709 / ASME SB-709 | EN 10095 | **N08028** | | **Seamless Pipe & Tube** | ASTM B829 / ASME SB-829 | - | **N08028** | | **Welded Pipe** | ASTM B775 / ASME SB-775 | - | **N08028** | | **Fittings (Forged)** | ASTM B564 / ASME SB-564 | - | **N08028** | | **Bar, Wire, Billet** | ASTM B581 / ASME SB-581 | - | **N08028** | | **Flanges & Forged Fittings**| ASTM B462 / ASME SB-462 | - | **N08028** | *Note: "SB" designates the ASME Boiler and Pressure Vessel Code version of the ASTM standard.* --- ### **Product Applications** Alloy 28 is predominantly used in industries where resistance to sulfuric acid and chloride-induced corrosion is paramount. Key applications include: * **Chemical Process Industry (CPI):** * Sulfuric acid pickling plants, heat exchangers, and reaction vessels. * Equipment for handling phosphoric acid. * Components in acid production and recovery systems. * **Oil & Gas (Downstream):** * Tubing and piping in refineries for handling sour crude (containing H₂S and chlorides). * Heat exchangers in crude distillation units. * **Pollution Control:** * Flue gas desulfurization (FGD) systems in power plants. * **Pharmaceutical Industry:** * Reactors and vessels where high purity and corrosion resistance are required. * **Pulp & Paper Industry:** * Digesters and bleaching equipment handling corrosive chemicals. --- ### **Other / Similar Specifications and Alloys** Alloy 28 is part of a family of nickel-based alloys designed for sulfuric acid service. Key similar alloys include: * **Alloy 20 (UNS N08020 / CN7M):** The predecessor to Alloy 28, with slightly lower Ni and Cr. Excellent in sulfuric acid, but less resistant to chlorides than Alloy 28. * **Incoloy 825 (UNS N08825):** Very similar to Alloy 28 but with the addition of Titanium for stabilization. Offers excellent resistance to both reducing and oxidizing environments. * **Hastelloy B-3 (UNS N10675):** High Molybdenum and Nickel, excellent for hydrochloric acid and other non-oxidizing environments, but not for oxidizing conditions. * **Super Austenitic Stainless Steels (e.g., 904L, 6Mo alloys):** Alloys like UNS N08904, N08367, and S31254 offer high PREN and are often compared for chloride resistance, but Alloy 28's specific Ni-Cr-Mo-Cu balance makes it superior for hot sulfuric acid. **Conclusion:** Alloy 28 (UNS N08028) is a versatile, high-performance nickel-iron-chromium alloy engineered to withstand some of the most aggressive industrial environments, particularly those involving sulfuric acid and chlorides. Its robust combination of chemical composition, mechanical strength, and widespread international standardization makes it a critical material for safety and reliability in demanding chemical processing, oil refining, and pollution control applications.

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 2700 gallon liquid totes Special package is available on request.