Alloy 28,Incoloy 028,UNS N08028,E FORU

Alloy 28, commercially known as **Incoloy 028** (UNS N08028), is a nickel-iron-chromium super-austenitic stainless steel alloyed with significant amounts of molybdenum and copper. It was specifically developed to offer exceptional resistance to sulfuric acid corrosion and to combat stress corrosion cracking (SCC) in demanding environments, particularly those containing chlorides. This alloy occupies a performance level between standard austenitic stainless steels like 316L and more expensive nickel-based alloys like Alloy C-276. Its high chromium and molybdenum content provides superior resistance to pitting and crevice corrosion, making it a cost-effective and reliable solution for the most aggressive process conditions in the chemical processing industry. --- #### **1. Chemical Composition** The chemical composition (in weight %) is precisely balanced to deliver its signature corrosion resistance. | Element | Content (%) | Role & Benefit | | :--- | :--- | :--- | | **Nickel (Ni)** | 29.5 - 32.5 | Stabilizes the austenitic phase, providing inherent toughness and basic corrosion resistance. | | **Chromium (Cr)** | 26.0 - 28.0 | Confers excellent resistance to oxidizing environments (e.g., nitric acid, hot oxidizing gases). | | **Iron (Fe)** | Balance | The base element of the alloy. | | **Molybdenum (Mo)** | 3.0 - 4.0 | Significantly enhances resistance to pitting and crevice corrosion in chloride-containing solutions. | | **Copper (Cu)** | 0.6 - 1.4 | Provides improved resistance to sulfuric acid and other reducing acids. | | **Manganese (Mn)** | ≤ 2.5 | Aids in deoxidation during the steelmaking process. | | **Silicon (Si)** | ≤ 0.7 | Enhances resistance to oxidation and hot workability. | | **Carbon (C)** | ≤ 0.03 | Very low level ("L-grade") to minimize carbide precipitation during welding and service, enhancing resistance to intergranular corrosion. | | **Phosphorus (P)** | ≤ 0.030 | Impurity element, controlled to a low level to prevent embrittlement. | | **Sulfur (S)** | ≤ 0.030 | Impurity element, controlled to improve hot workability and corrosion resistance. | | **Nitrogen (N)** | ≤ 0.030 | Added to enhance mechanical strength and improve pitting resistance. | *Note: "Incoloy" is a registered trademark of Special Metals Corporation (now part of Haynes International). "Incoloy 028" is their specific brand of UNS N08028.* --- #### **2. Physical Properties** These properties are essential for engineering design and fabrication. | Property | Typical Value | | :--- | :--- | | **Density** | 8.0 g/cm³ (0.289 lb/in³) | | **Melting Range** | 1370 - 1400 °C (2500 - 2550 °F) | | **Specific Heat (20°C)** | 450 J/kg·K | | **Electrical Resistivity** | 0.90 μΩ·m | | **Thermal Conductivity** | 12.0 W/m·K (at 100°C) | | **Mean Coefficient of Thermal Expansion (20-100°C)** | 14.0 μm/m·°C | | **Modulus of Elasticity (Tensile)** | 200 GPa (29 x 10⁶ psi) | | **Magnetic Permeability (Annealed)** | Typically < 1.05 (Essentially non-magnetic) | --- #### **3. Mechanical Properties (Typical for Annealed Condition)** Alloy 28 offers a strong combination of strength and ductility. | Property | Room Temperature Value | | :--- | :--- | | **Tensile Strength** | 600 - 800 MPa (87 - 116 ksi) | | **Yield Strength (0.2% Offset)** | 280 MPa (41 ksi) min. | | **Elongation (in 2 inches / 50mm)** | 35% min. | | **Hardness (Rockwell B)** | ≤ 95 HRB | --- #### **4. Product Applications** Incoloy 028 is widely used in industries where resistance to hot, concentrated sulfuric acid and chlorides is paramount. * **Chemical Processing Industry (CPI):** * Production, storage, and transportation of **sulfuric acid** (across a wide range of concentrations and temperatures). * Phosphoric acid production equipment (evaporators, heat exchangers). * Piping, reactors, and columns in plants handling halogens and acid chlorides. * **Oil and Gas Industry:** * Downhole tubing and casing in sour gas wells (resisting H₂S and chlorides). * Components in gas treatment plants handling aggressive condensed fluids. * **Pollution Control & FGD Systems:** Scrubbers, ducting, and mist eliminators in flue gas desulfurization units. * **Pulp and Paper Industry:** Digesters and bleach plant equipment where chloride-induced stress corrosion cracking is a concern. * **Nuclear Fuel Processing:** Equipment for handling sulfuric and nitric acid mixtures. --- #### **5. International Standards** Incoloy 028 (UNS N08028) is covered by various international standards for different product forms. | Product Form | Standard Specification | | :--- | :--- | | **Plate, Sheet, and Strip** | ASTM B710 / ASME SB710 | | **Seamless Pipe and Tube** | ASTM B668 / ASME SB668 | | **Welded Pipe and Tube** | ASTM B676 / ASME SB676 | | **Pipe Fittings (Butt-weld)** | ASTM B366 / ASME SB366 | | **Forgings** | ASTM B462 / ASME SB462 (Grade N08028) | | **Bar, Rod, and Wire** | ASTM B473 / ASME SB473 | | **European Material Designation** | **EN 1.4563** (X1NiCrMoCu31-27-4) | --- **Summary** **Incoloy 028 (Alloy 28 / UNS N08028)** is a super-austenitic stainless steel specifically designed to bridge the gap between standard stainless steels and high-end nickel alloys. Its high chromium and molybdenum content, combined with a low carbon level and added copper, provides an outstanding defense against sulfuric acid attack, chloride pitting, and stress corrosion cracking. Governed by a well-defined set of international standards like ASTM and ASME, it remains a preferred and cost-effective material for critical equipment in the chemical processing, oil and gas, and pollution control industries.

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 1704 gallon liquid totes Special package is available on request.