718-OP UNS N07718 Nickel Superalloy,AMS 5662, 5663, 5664. MIL-N-24469, RDT M2-18T, ASTM B 637.,E FORU

### **Product Introduction: 718-OP (UNS N07718) Nickel-Based Superalloy** **718-OP (UNS N07718)** is a precipitation-hardenable nickel-chromium superalloy in the overaged condition, specifically optimized for enhanced stress rupture properties and microstructural stability at elevated temperatures. As a variant of the widely used Alloy 718, the "OP" (Overaged) designation indicates a specialized heat treatment that provides superior long-term stability and creep resistance while maintaining excellent mechanical properties. This alloy is particularly valued for applications requiring sustained performance at temperatures up to 650°C (1200°F). The alloy derives its strength from the combined precipitation of gamma prime [γ'] and gamma double prime [γ''] phases, with the overaged condition providing optimal stability for extended service in demanding environments such as aerospace propulsion and power generation systems. --- #### **1. Chemical Composition (Weight %)** The typical chemical composition of 718-OP per AMS 5662 and related specifications is as follows: | Element | Content (%) | Element | Content (%) | |---------|-------------|---------|-------------| | **Nickel (Ni)** | 50.0 - 55.0 | **Niobium (Nb)** | 4.75 - 5.50 | | **Chromium (Cr)** | 17.0 - 21.0 | **Molybdenum (Mo)** | 2.80 - 3.30 | | **Iron (Fe)** | Balance | **Titanium (Ti)** | 0.65 - 1.15 | | **Cobalt (Co)** | 1.0 max | **Aluminum (Al)** | 0.20 - 0.80 | | **Carbon (C)** | 0.08 max | **Boron (B)** | 0.006 max | | **Manganese (Mn)** | 0.35 max | **Copper (Cu)** | 0.30 max | | **Silicon (Si)** | 0.35 max | **Phosphorus (P)** | 0.015 max | | **Sulfur (S)** | 0.015 max | | | --- #### **2. Physical & Mechanical Properties** **Physical Properties:** | Property | Metric Units | Imperial Units | |----------|-----------------|------| | **Density** | 8.19 g/cm³ | 0.296 lb/in³ | | **Melting Range** | 1260 - 1336 °C | 2300 - 2440 °F | | **Thermal Conductivity** | 11.4 W/m·K | 79.0 Btu·in/hr·ft²·°F | | **Coefficient of Thermal Expansion** | 13.0 μm/m·°C | 7.2 μin/in·°F | | **Modulus of Elasticity** | 200 GPa | 29.0 x 10⁶ psi | | **Specific Heat** | 435 J/kg·K | 0.104 Btu/lb·°F | **Mechanical Properties (Overaged Condition):** | Property | Value | |----------|-----------------| | **Tensile Strength** | 1240-1380 MPa | 180-200 ksi | | **Yield Strength (0.2% Offset)** | 1030-1170 MPa | 150-170 ksi | | **Elongation** | 12-20% | | **Reduction of Area** | 15-25% | | **Hardness (Rockwell C)** | 32-40 HRC | **Elevated Temperature Properties (at 650°C/1200°F):** | **Tensile Strength** | 960 MPa | 139 ksi | | **Yield Strength** | 825 MPa | 120 ksi | | **Stress Rupture Life (650°C/690 MPa)** | 100+ hours | --- #### **3. Key Characteristics & Product Applications** **Key Characteristics:** - **Enhanced Thermal Stability**: Superior microstructural stability in the overaged condition - **Excellent Creep Resistance**: Outstanding long-term load-bearing capability at elevated temperatures - **Good Fatigue Strength**: Excellent resistance to cyclic loading conditions - **Oxidation Resistance**: Good performance in oxidizing atmospheres up to 700°C - **Weldability**: Can be welded using conventional methods without post-weld cracking - **Stress Rupture Performance**: Optimized for extended service under stress at high temperatures **Product Applications:** 718-OP is extensively used in critical high-temperature applications: - **Aerospace Propulsion**: - Gas turbine engine discs and rotors - Compressor and turbine blades - Engine mounts and frames - Afterburner components - Jet engine fasteners and bolts - **Power Generation**: - Gas turbine components - Turbine wheels and shafts - High-temperature bolting - Steam turbine elements - **Nuclear Industry**: - Reactor core components - Nuclear fuel assembly hardware - Pressure vessel internals - **Oil & Gas**: - Downhole tool components - Wellhead equipment - High-pressure/high-temperature valves --- #### **4. International Standards & Specifications** 718-OP is covered by comprehensive international standards: **Aerospace Material Specifications (AMS):** - **AMS 5662**: Bars, Forgings, and Rings - **AMS 5663**: Solution Heat Treated and Overaged - **AMS 5664**: For Special Corrosion-Resistant Applications **Government & Industry Standards:** - **MIL-N-24469**: Military Specification for Nickel Alloy - **RDT M2-18T**: Nuclear Industry Specification - **ASTM B637**: Precipitation-Hardening Nickel Alloy **Other International Standards:** - **UNS**: N07718 - **ASME**: Code Case for Nuclear Components - **EN**: 2.4668 (NiCr19Fe19Nb5Mo3) - **ISO**: 6207 (NW 7718) --- #### **Summary of Key Advantages** - **Optimized Overaged Condition**: Enhanced stress rupture and creep properties - **Superior Thermal Stability**: Excellent microstructural stability for long-term service - **Proven Reliability**: Extensive service history in critical aerospace applications - **Good Fabricability**: Can be forged, machined, and welded using standard methods - **Comprehensive Standardization**: Covered by major international specifications - **Versatile Performance**: Suitable for aerospace, power generation, and nuclear applications **Technical Note**: The overaged heat treatment for 718-OP typically involves solution treatment at 950-980°C (1740-1795°F) followed by a two-step aging process at 720°C (1330°F) for 8 hours, furnace cool to 620°C (1150°F), and hold for 8 hours. This specialized thermal processing provides the optimal balance of strength and microstructural stability required for extended high-temperature service. The alloy maintains excellent weldability characteristics, with post-weld heat treatment recommended for 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 3157 gallon liquid totes Special package is available on request.