Hastelloy alloy 718,1

### **Introduction to Hastelloy®/INCONEL® Alloy 718 and Related Specifications** **Alloy 718** is a premier nickel-chromium superalloy strengthened by the addition of niobium, molybdenum, and titanium. It is a **precipitation-hardenable** alloy, meaning its exceptional strength is achieved through a specific heat treatment process that forms coherent precipitates of gamma double prime (γ'') and gamma prime (γ') phases. This gives Alloy 718 an outstanding combination of high tensile, creep, and rupture strength up to 1300°F (700°C), excellent fatigue resistance, and good oxidation and corrosion resistance. A key advantage of Alloy 718 is its excellent weldability and its resistance to post-weld strain-age cracking, a common issue with other precipitation-hardenable superalloys. This alloy is covered by numerous international standards for its base metal and welding consumables. --- ### **1. Base Metal: Alloy 718** The wrought forms of Alloy 718, such as bar, sheet, plate, and wire, are governed by Aerospace Material Specifications (AMS) from SAE International. ***Correction and Clarification on Standards:*** * **AMS 5755, 5786, 5787:** These specific AMS standards are for **Cobalt-Based Alloy 188**. For **Nickel-Based Alloy 718**, the correct and common AMS specifications are: * **AMS 5662:** Bars, Forgings, and Rings (Solution Heat Treated and Aged) * **AMS 5596:** Sheet, Strip, and Plate (Solution Heat Treated and Aged) * **AMS 5832:** Welding Wire #### **Chemical Composition (Weight %, typical per AMS 5662 / UNS N07718):** | Element | Minimum | Maximum | | :--- | :--- | :--- | | **Nickel (Ni)** | 50.0 | 55.0 | | **Chromium (Cr)** | 17.0 | 21.0 | | **Iron (Fe)** | Balance | --- | | **Niobium (Nb) + Tantalum (Ta)** | 4.75 | 5.50 | | **Molybdenum (Mo)** | 2.80 | 3.30 | | **Titanium (Ti)** | 0.65 | 1.15 | | **Aluminum (Al)** | 0.20 | 0.80 | | **Cobalt (Co)** | --- | 1.00 | | **Carbon (C)** | --- | 0.08 | | **Manganese (Mn)** | --- | 0.35 | | **Silicon (Si)** | --- | 0.35 | | **Copper (Cu)** | --- | 0.30 | | **Boron (B)** | --- | 0.006 | | **Sulfur (S)** | --- | 0.015 | | **Phosphorus (P)** | --- | 0.015 | *Balance is primarily Iron, making it one of the most iron-rich nickel superalloys.* #### **Physical Properties (Typical):** * **Density:** 8.19 g/cm³ (0.296 lb/in³) * **Melting Range:** 1260 - 1336 °C (2300 - 2440 °F) * **Electrical Resistivity:** 125 μΩ·cm at 21°C * **Thermal Expansion Coefficient:** 13.0 μm/m·°C (20-100°C) * **Thermal Conductivity:** 11.4 W/m·K at 100°C * **Modulus of Elasticity (Young's Modulus):** 205 GPa (29.8 x 10⁶ psi) at 21°C #### **Mechanical Properties (Typical at Room Temperature per AMS 5662 - Aged Condition):** * **Tensile Strength:** ≥ 1310 MPa (190 ksi) * **Yield Strength (0.2% Offset):** ≥ 1035 MPa (150 ksi) * **Elongation:** ≥ 12% --- ### **2. Welding Consumables: ERNiFeCr-2 and ENiFeCr-2** To weld Alloy 718, matching-composition welding electrodes and wires are used. These are standardized by AWS and ASME. The weld metal is also precipitation-hardenable and typically requires post-weld heat treatment (PWHT) to achieve optimal properties. #### **Key Standards for Welding Consumables:** * **AWS A5.14 / ASME SFA-5.14:** Specification for Nickel and Nickel-Alloy Bare Welding Electrodes and Rods. * **Product:** **ERNiFeCr-2** (Bare welding wire for GTAW/TIG, GMAW/MIG, SAW processes). * **AWS A5.11 / ASME SFA-5.11:** Specification for Nickel and Nickel-Alloy Welding Electrodes for Shielded Metal Arc Welding. * **Product:** **ENiFeCr-2** (Covered electrodes for SMAW/Stick welding). #### **Chemical Composition of Welding Products (Weight %, AWS Requirements for ERNiFeCr-2):** | Element | ERNiFeCr-2 (AWS A5.14) | | :--- | :--- | | **Nickel (Ni)** | 50.0 - 55.0 | | **Chromium (Cr)** | 17.0 - 21.0 | | **Iron (Fe)** | Balance | | **Niobium (Nb) + Tantalum (Ta)** | 4.75 - 5.50 | | **Molybdenum (Mo)** | 2.80 - 3.30 | | **Titanium (Ti)** | 0.75 - 1.20 (0.65 - 1.15 for ENiFeCr-2) | | **Aluminum (Al)** | 0.20 - 0.80 (0.70 max for ENiFeCr-2) | | **Cobalt (Co)** | 1.00 max | | **Carbon (C)** | 0.08 max | | **Manganese (Mn)** | 0.35 max | | **Silicon (Si)** | 0.35 max | | **Copper (Cu)** | 0.30 max | | **Boron (B)** | *Not Specified* | | **Sulfur (S)** | 0.015 max | | **Phosphorus (P)** | 0.015 max | --- ### **Product Applications** Alloy 718's unique combination of high strength, manufacturability, and weldability makes it indispensable in the most demanding applications: * **Aerospace & Jet Engines (Primary Market):** * Turbine blades, disks, and shafts * Compressor sections (rings, casings, blades) * Afterburner components * Cryogenic fuel tanks and structures * **Oil & Gas Industry:** * Downhole wellhead components (hangers, seals, valves) * Subsea equipment (manifolds, Christmas trees) * High-strength fasteners for sour service * **Power Generation:** * Gas turbine components * Nuclear reactor core components * **Rocket Motors & Spacecraft:** * Liquid-fueled rocket engine parts * Structural components for launch vehicles --- ### **Summary of International Standards** | Product Form | Standard | Governing Body | Designation | | :--- | :--- | :--- | :--- | | **Bar, Forgings, Ring** | AMS 5662 | SAE International | Alloy 718 (Aged) | | **Sheet, Strip, Plate** | AMS 5596 | SAE International | Alloy 718 (Aged) | | **Welding Wire** | AMS 5832 | SAE International | Alloy 718 | | **Bare Welding Wire** | AWS A5.14 / ASME SFA-5.14 | American Welding Society / ASME | **ERNiFeCr-2** | | **Covered Electrodes** | AWS A5.11 / ASME SFA-5.11 | American Welding Society / ASME | **ENiFeCr-2** | | **Bar & Shape** | ASTM B637 | ASTM International | UNS N07718 | | **Plate, Sheet, Strip** | ASTM B670 | ASTM International | UNS N07718 | **Note:** "INCONEL" is a registered trademark of Special Metals Corporation. "Hastelloy" is a registered trademark of Haynes International, Inc. While Alloy 718 is more commonly associated with the INCONEL brand, it is often generically referred to. The specifications mentioned are industry standards used to define the technical requirements for procurement and quality assurance.

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 3256 gallon liquid totes Special package is available on request.