P/M N690 Corrosion Resistant Alloy,UNS N06690,E FORU

### **P/M Alloy 690 (UNS N06690) - Nickel-Chromium Corrosion Resistant Alloy** #### **Overview** **P/M Alloy 690 (UNS N06690)** is the powder metallurgy (P/M) form of a nickel-chromium alloy specifically engineered for exceptional resistance to corrosion, particularly in high-temperature aqueous environments. With a significantly higher chromium content (~30%) than alloys like Alloy 600 (UNS N06600), it exhibits superior performance against oxidizing media, stress corrosion cracking (SCC), and caustic corrosion. The P/M manufacturing process, typically involving gas atomization and consolidation via **Hot Isostatic Pressing (HIP)**, produces a material with a fine, homogeneous, and isotropic microstructure. This eliminates the chemical segregation and banding that can sometimes occur in wrought products, leading to highly consistent and predictable corrosion resistance and mechanical properties in all directions. This makes it an ideal choice for critical, high-integrity components. --- #### **Chemical Composition (Weight % - Typical)** The high chromium content is the defining feature of this alloy's composition. | Element | Content (%) | | :--- | :--- | | **Nickel (Ni)** | **≥ 58.0** | | **Chromium (Cr)** | **28.0 - 31.0** | | **Iron (Fe)** | **7.0 - 11.0** | | **Carbon (C)** | **≤ 0.05** | | **Manganese (Mn)** | **≤ 0.50** | | **Silicon (Si)** | **≤ 0.50** | | **Copper (Cu)** | **≤ 0.50** | | **Aluminum (Al)** | **≤ 0.50** | | **Titanium (Ti)** | **≤ 0.50** | | **Sulfur (S)** | **≤ 0.015** | * **Nickel (Ni):** Provides a stable austenitic matrix and inherent resistance to chloride stress corrosion cracking and reducing environments. * **Chromium (Cr):** The key alloying element. The high chromium content is responsible for its outstanding resistance to oxidizing corrosives (e.g., nitric acid, hot oxidizing chlorides) and for forming a highly protective chromium oxide film. This is crucial for resisting stress corrosion cracking in environments containing chlorides and caustics. * **Iron (Fe):** Added for solid solution strengthening and cost-effectiveness. --- #### **Physical & Mechanical Properties** The following table outlines the key properties of P/M Alloy 690 in the solution annealed condition. | Property | Value / Description | | :--- | :--- | | **Density** | 8.19 g/cm³ | | **Melting Range** | ~1340 - 1380 °C (2445 - 2515 °F) | | **Thermal Conductivity** | 12.0 W/m·K (at 100°C) | | **Specific Heat (20°C)** | 450 J/kg·K | | **Mean Coefficient of Thermal Expansion** | 13.5 μm/m·°C (20-300°C) | | **Modulus of Elasticity** | 214 GPa (31 x 10⁶ psi) | | **Tensile Strength (HIP + Annealed, RT)** | ~655 - 760 MPa (95 - 110 ksi) | | **Yield Strength (0.2% Offset, HIP + Annealed, RT)** | ~280 - 350 MPa (40 - 51 ksi) | | **Elongation (HIP + Annealed, RT)** | ~40% - 50% | | **High-Temperature Capability** | Excellent oxidation resistance up to **1100°C (2010°F)**. | --- #### **Key Characteristics & Applications** **Key Characteristics:** 1. **Exceptional Stress Corrosion Cracking (SCC) Resistance:** Highly resistant to SCC in chloride-containing and high-purity water environments, making it a cornerstone material for nuclear applications. 2. **Outstanding Resistance to Oxidizing Environments:** The high chromium content provides excellent resistance to nitric acid, other oxidizing acids, and oxidizing salt solutions. 3. **Excellent Corrosion Resistance in Caustic Solutions:** Superior to most nickel alloys in hot alkaline environments. 4. **Good High-Temperature Oxidation Resistance:** Forms a stable, adherent oxide layer that protects against scaling in air and combustion atmospheres. 5. **Isotropic Properties:** The P/M HIP process ensures uniform corrosion resistance and mechanical properties in all directions, which is critical for complex-shaped components. **Typical Applications:** P/M Alloy 690 is used for critical components in industries where failure due to corrosion is not an option. * **Nuclear Power Industry (Primary Application):** * **Steam Generator Tubes:** The premier material for replacement tubes in Pressurized Water Reactors (PWRs) due to its proven immunity to chloride and caustic-induced SCC. * **Reactor Vessel Internals:** Components such as head penetrations, baffle-former bolts, and other core internal structures. * **Chemical Processing:** * Equipment for handling nitric acid, nitrates, and other strong oxidizers. * Components in plants producing hydrofluoric acid. * Caustic evaporator tubes and fittings. * **Thermal Processing:** * Radiant tubes, muffles, and retorts for heat-treating furnaces. * **Pollution Control:** Components in flue gas desulfurization systems. --- #### **International Standards** P/M Alloy 690 is covered by specific standards for powder and consolidated products, in addition to the well-established standards for its wrought form. | Product Form | ASTM (USA) | ASME (USA) | EN (European) | UNS | | :--- | :--- | :--- | :--- | :--- | | **Powder Preursor** | **ASTM B964** | - | - | N06690 | | **HIPed Billets & Shapes** | **ASTM B988** | - | **EN 10302 / NiCr29Fe** | N06690 | | **Wrought Tube/Plate** | ASTM B166 / B168 | SB-166 / SB-168 | EN 10302 / NiCr29Fe | N06690 | **Important Note:** While the P/M forms (ASTM B988) are ideal for creating near-net-shape components, the wrought forms (e.g., tube and plate) are governed by separate ASTM standards. The alloy composition remains consistent, but the manufacturing route (P/M vs. wrought) is chosen based on the component's geometry and performance requirements. For nuclear applications, stringent additional nuclear-grade qualifications (e.g., ASME Section III) are required. --- #### **Summary** In summary, **P/M Alloy 690 (UNS N06690)** is a highly specialized corrosion-resistant alloy whose properties are enhanced by the powder metallurgy manufacturing route. Its very high chromium content makes it the material of choice for resisting stress corrosion cracking in nuclear steam generators and for withstanding aggressive oxidizing chemicals. The P/M HIP process provides a homogeneous and isotropic microstructure, ensuring maximum reliability for critical, complex-shaped components in the nuclear, chemical processing, and thermal treatment industries. Its development and standardization represent a significant achievement in materials engineering for safety-critical 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 3205 gallon liquid totes Special package is available on request.