625 Cast UNS N26625 Severe Corrosion and Heat Resistant Alloy, Cast UNS N26625; 1

### **Product Introduction: Alloy 625 Cast (UNS N26625 / CW-6MC) Severe Corrosion and Heat Resistant Alloy** **Overview** Cast Alloy 625, designated as UNS N26625 and commonly known by its cast grade **CW-6MC**, is a nickel-chromium-molybdenum-niobium alloy renowned for its exceptional combination of extreme corrosion resistance, high strength, and outstanding toughness over a wide temperature range. It is the cast equivalent of the widely used wrought alloy UNS N06625. The alloy's remarkable properties are derived from its unique strengthening mechanism, where niobium acts in concert with molybdenum to produce a tough, austenitic matrix that can be strengthened by a precipitation-hardening heat treatment, though it is most often used in the solution-annealed or as-cast condition for optimal corrosion resistance. --- #### **Chemical Composition (Typical % by Weight, per ASTM A494)** The composition of CW-6MC is precisely controlled to achieve its signature performance. | Element | Content (%) | Role & Benefit | | :--- | :--- | :--- | | **Nickel (Ni)** | Balance | Provides the fundamental austenitic matrix, offering inherent corrosion resistance and metallurgical stability. | | **Chromium (Cr)** | 20.0 - 23.0 | Imparts exceptional resistance to oxidizing media (e.g., nitric acid, nitrates) and high-temperature oxidation. | | **Molybdenum (Mo)** | 8.0 - 10.0 | Provides superior resistance to reducing acids (e.g., hydrochloric, sulfuric) and is critical for resisting pitting and crevice corrosion. | | **Niobium (Nb)** | 3.15 - 4.15 | The key strengthening element. It combines with carbon to form stable carbides and, more importantly, contributes to strength via solid solution hardening and the formation of gamma prime/carbide precipitates. | | **Iron (Fe)** | 5.0 max | Kept at a low level to optimize corrosion resistance. | | **Manganese (Mn)**| 0.50 max | Aids in castability. | | **Silicon (Si)** | 0.50 max | A deoxidizer in the casting process; kept low to maintain ductility. | | **Carbon (C)** | 0.06 max | Controlled to form strengthening carbides with niobium without compromising toughness. | | **Aluminum (Al)** | 0.40 max | A residual element. | | **Titanium (Ti)** | 0.40 max | A residual element that can also contribute to strengthening. | | **Phosphorus (P)**| 0.03 max | Kept low to ensure good ductility. | | **Sulfur (S)** | 0.03 max | A detrimental element kept to a minimum to prevent hot cracking. | *Note: "INCONEL" is a registered trademark of Special Metals Corporation.* --- #### **Physical & Mechanical Properties (Typical)** | Property | Value / Condition | | :--- | :--- | | **Density** | 8.44 g/cm³ (0.305 lb/in³) | | **Melting Range** | 1290 - 1350 °C (2350 - 2460 °F) | | **Specific Heat** | 410 J/kg·K (0.098 BTU/lb·°F) @ 20°C | | **Thermal Conductivity**| 9.8 W/m·K (68 BTU·in/hr·ft²·°F) @ 100°C | | **Thermal Expansion** | 12.8 μm/m·°C (7.1 μin/in·°F) @ 20-100°C | | **Tensile Strength** | 690 MPa (100 ksi) min | | **Yield Strength (0.2% Offset)** | 310 MPa (45 ksi) min | | **Elongation** | 20% min | --- #### **International Standards and Specifications** Cast Alloy 625 (CW-6MC) is recognized by all major international standards for high-performance castings. * **Cast Product Standards:** * **ASTM A494 / A494M:** Standard Specification for Castings, Nickel and Nickel Alloy. (Grade CW-6MC) * **UNS N26625:** Unified Numbering System designation for the cast alloy. * **AMS 5402:** Aerospace Material Specification for investment castings, ensuring high-integrity for critical components. * **ISO 15156-3 (MR0175):** Approved for use in sour service (H₂S-containing) environments in the oil and gas industry. * **Wrought Equivalent:** * **UNS N06625:** The standard wrought form of this alloy. * **ASTM B443 / B444 / B446:** Standards for wrought UNS N06625 plate, sheet, strip, bar, and wire. --- #### **Product Applications** CW-6MC cast components are deployed in the most aggressive environments across multiple industries. 1. **Aerospace & Defense:** * Engine components: static structures, cases, and mounts. * Gas turbine engine rings and assemblies. 2. **Marine & Offshore:** * Propeller and rudder blades, submarine components. * Pump impellers, valves, and fittings for seawater service. * Components in subsea systems. 3. **Chemical Process Industry (CPI):** * Agitators, mixing shafts, and heat exchanger tubesheets. * Pumps, valves, and fittings handling chlorides, acids, and alkalis. 4. **Pollution Control & Flue Gas Desulfurization (FGD):** * Scrubber internals, fan housings, and dampers resisting acidic chlorides. 5. **Oil & Gas:** * Downhole tool components, wellhead parts, and components for sour service. #### **Key Advantages** * **Exceptional Corrosion Resistance:** Outstanding resistance to a broad range of severe corrosive environments, including pitting, crevice corrosion, and erosion-corrosion. * **High Strength:** Offers excellent mechanical strength and toughness from cryogenic temperatures up to about 1000°C (1800°F). * **Excellent Fabricability & Weldability:** Can be readily welded and repaired with matching filler metals, with the weldment exhibiting corrosion resistance similar to the base metal. * **Resistance to Oxidation & Carburization:** Performs well in high-temperature oxidizing and carburizing atmospheres. **Conclusion** Cast Alloy 625 (UNS N26625 / CW-6MC) is a versatile, high-performance nickel-based alloy that sets the standard for severe-service applications. Its unique niobium-strengthened matrix provides an unparalleled balance of extreme corrosion resistance, high strength, and excellent fabricability. For critical components in aerospace, marine, chemical processing, and energy sectors, CW-6MC offers a proven and reliable solution, fully backed by international standards like ASTM A494 and AMS 5402.

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 3401 gallon liquid totes Special package is available on request.