CW-2M Cast UNS N26455 Severe Corrosion and Heat Resistant Alloy, Cast UNS N26455; 1

### **Product Introduction: CW-2M (Cast UNS N26455) Severe Corrosion and Heat Resistant Alloy** **Overview** CW-2M, designated as UNS N26455 in the cast form, is a nickel-molybdenum-chromium alloy specifically engineered for exceptional resistance to a wide range of severe corrosive environments. It is the cast equivalent of the wrought alloy UNS N06455 (Hastelloy® C-4). This low-carbon, precipitation-stabilized alloy was developed to offer superior thermal stability and outstanding resistance to stress-corrosion cracking, pitting, and crevice corrosion. Its key advantage lies in its ability to resist the formation of grain boundary precipitates in the weld heat-affected zone, making it ideal for applications in the chemical processing industry and other fields involving aggressive media at elevated temperatures. --- #### **Chemical Composition (Typical % by Weight, per ASTM A494)** The carefully controlled composition of CW-2M is fundamental to its performance and thermal stability. | Element | Content (%) | Role & Benefit | | :--- | :--- | :--- | | **Nickel (Ni)** | Balance | Provides the fundamental austenitic matrix, offering excellent metallurgical stability and ductility. | | **Molybdenum (Mo)** | 14.0 - 17.0 | Imparts superior resistance to reducing acids like hydrochloric (HCl) and sulfuric (H₂SO₄), and protects against pitting and crevice corrosion. | | **Chromium (Cr)** | 14.0 - 18.0 | Provides resistance to oxidizing media such as nitric acid (HNO₃), ferric salts, and chlorinated environments. | | **Iron (Fe)** | 3.0 max | Kept at a low level to optimize corrosion resistance and minimize detrimental phase formation. | | **Titanium (Ti)** | 0.70 max | Acts as a stabilizer. It combines with carbon to form stable carbides, preventing chromium depletion at grain boundaries and enhancing resistance to sensitization. | | **Cobalt (Co)** | 2.0 max | A residual element controlled to ensure consistent properties. | | **Manganese (Mn)**| 1.00 max | Aids in castability and controls sulfur. | | **Silicon (Si)** | 0.08 max | Kept very low to improve ductility and corrosion resistance. | | **Carbon (C)** | 0.015 max | Very low carbon content is crucial for minimizing carbide precipitation and ensuring excellent intergranular corrosion resistance in the as-welded condition. | | **Sulfur (S)** | 0.03 max | A detrimental element kept to a minimum to prevent hot cracking and maintain ductility. | | **Tungsten (W)** | - | Notably absent. This differentiates it from alloys like C-276, contributing to its superior thermal stability. | *Note: "Hastelloy®" is a registered trademark of Haynes International Inc.* --- #### **Physical & Mechanical Properties (Typical)** | Property | Value / Condition | | :--- | :--- | | **Density** | 8.64 g/cm³ (0.312 lb/in³) | | **Melting Range** | 1350 - 1400 °C (2460 - 2550 °F) | | **Specific Heat** | 427 J/kg·K (0.102 BTU/lb·°F) @ 20°C | | **Thermal Conductivity**| 10.9 W/m·K (75 BTU·in/hr·ft²·°F) @ 100°C | | **Thermal Expansion** | 11.3 μm/m·°C (6.3 μin/in·°F) @ 20-100°C | | **Tensile Strength** | 586 MPa (85 ksi) min | | **Yield Strength (0.2% Offset)** | 241 MPa (35 ksi) min | | **Elongation** | 4.5% min | --- #### **International Standards and Specifications** CW-2M is specified by several key international standards for cast components. * **Cast Product Standards:** * **ASTM A494 / A494M:** Standard Specification for Castings, Nickel and Nickel Alloy. (Grade CW-2M) * **UNS N26455:** Unified Numbering System designation for the cast alloy. * **AMS 5408:** Aerospace Material Specification for investment cast or centrifugally cast components, ensuring high-quality for critical applications. * **Wrought Equivalent:** * **UNS N06455:** The standard wrought form of this alloy (e.g., plate, sheet, bar). * **ASTM B574 / B575:** Standards for low-carbon nickel-molybdenum-chromium alloy rod, bar, plate, sheet, and strip. * **DIN 2.4610:** The corresponding material number in the German standard. --- #### **Product Applications** CW-2M cast components are selected for their reliability in the most aggressive environments, particularly where thermal stability is paramount. 1. **Chemical Processing Industry (CPI):** * Reactors and vessels for acetic acid and anhydride production. * Pumps, valves, and agitators handling hydrochloric acid and chlorinated hydrocarbons. * Ducting and fans for corrosive fumes. 2. **Pollution Control & Flue Gas Desulfurization (FGD):** * Scrubber towers, outlet ducts, and fan housings that resist acid condensation containing chlorides and fluorides. 3. **Pharmaceutical and Fine Chemical Industries:** * Process equipment requiring high purity and resistance to aggressive cleaning agents and process streams at elevated temperatures. 4. **Oil & Gas Production:** * Components in downhole and surface equipment exposed to sour gas (H₂S) and chlorides. #### **Key Advantages** * **Excellent Thermal Stability:** The low carbon content and titanium stabilization provide outstanding resistance to sensitization and intergranular attack after exposure to high temperatures (650°C - 1040°C). * **Versatile Corrosion Resistance:** Effectively handles both oxidizing and reducing chemicals, including chlorides. * **Resistance to Localized Attack:** High molybdenum content provides superior resistance to pitting and crevice corrosion. * **Fabrication Friendliness:** Can be welded and fabricated with a low risk of intergranular corrosion in the heat-affected zones (HAZ). **Conclusion** CW-2M (UNS N26455) is a premium corrosion-resistant casting alloy renowned for its thermal stability and versatility. It is the material of choice for critical components in chemical processing, pollution control, and other demanding industries where exposure to high temperatures and aggressive corrosives would degrade the performance of standard alloys. Its compliance with international standards like ASTM A494 and AMS 5408 guarantees consistent quality and performance for engineered cast solutions.

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 3393 gallon liquid totes Special package is available on request.