Alloy 706,Inconel 706,UNS N09706,EFORU

### **Introduction to Alloy 706 (Inconel 706 / UNS N09706)** 

 Alloy 706, commonly known by its trade name **Inconel 706** and unified numbering system code **UNS N09706**, is a precipitation-hardenable nickel-iron-chromium superalloy. It was developed as a cost-effective alternative to Alloy 718, offering excellent mechanical properties, good weldability, and superior processability, particularly in machining and forging. The key characteristic of Alloy 706 is its ability to be strengthened by a two-step aging treatment, which precipitates gamma prime (γ') and gamma double prime (γ'') phases within the austenitic matrix. This provides high yield and tensile strength at temperatures up to about 650°C (1200°F). Its lower alloying content compared to Alloy 718 results in better forgeability and machinability, making it a preferred choice for large, complex components in the gas turbine industry. 

### **Introduction to Alloy 706 (Inconel 706 / UNS N09706)** 

 Alloy 706, commonly known by its trade name **Inconel 706** and unified numbering system code **UNS N09706**, is a precipitation-hardenable nickel-iron-chromium superalloy. It was developed as a cost-effective alternative to Alloy 718, offering excellent mechanical properties, good weldability, and superior processability, particularly in machining and forging. The key characteristic of Alloy 706 is its ability to be strengthened by a two-step aging treatment, which precipitates gamma prime (γ') and gamma double prime (γ'') phases within the austenitic matrix. This provides high yield and tensile strength at temperatures up to about 650°C (1200°F). Its lower alloying content compared to Alloy 718 results in better forgeability and machinability, making it a preferred choice for large, complex components in the gas turbine industry. 

 --- ### **Chemical Composition** 

 The properties of Alloy 706 are derived from its specific composition, which balances strength and processability. The typical composition is outlined below. 

 | Element | Content (%) (Typical) | Role & Function | 

| :--- | :--- | :--- | 

| **Nickel (Ni)** | 39.0 - 44.0 | Provides the austenitic matrix and base for precipitation hardening. | 

| **Iron (Fe)** | 35.0 - 40.0 | Balances cost and stability; forms a significant portion of the matrix. | 

| **Chromium (Cr)** | 14.0 - 17.5 | Imparts resistance to oxidation and corrosion. | 

| **Niobium (Nb)** | 1.5 - 3.0 | A key strengthening element, forming the gamma double prime (γ'') phase, Ni₃Nb. | 

| **Titanium (Ti)** | 1.5 - 2.0 | A key strengthening element, forming the gamma prime (γ') phase, Ni₃(Ti,Al). | 

| **Aluminum (Al)** | 0.2 - 0.6 | Works with Titanium to form the gamma prime (γ') phase. | 

| **Molybdenum (Mo)** | ≤ 1.0 | Provides solid-solution strengthening. | 

| **Carbon (C)** | ≤ 0.08 | Forms carbides for grain boundary control. | 

| **Manganese (Mn)** | ≤ 0.50 | Aids in deoxidation during melting. | 

| **Silicon (Si)** | ≤ 0.50 | Enhances resistance to oxidation. | 

| **Copper (Cu)** | ≤ 0.30 | Residual element. | 

| **Boron (B)** | 0.003 - 0.01 | Enhances creep strength and ductility. | 

| **Sulfur (S)** | ≤ 0.015 | Residual element (impurity). | 

 --- ### **Physical Properties** 

 The physical properties of Alloy 706 are typical for a nickel-iron based superalloy. 

| Property | Value / Condition | 

| :--- | :--- | 

| **Density** | 8.05 g/cm³ (0.291 lb/in³) | 

| **Melting Range** | 1365 - 1425 °C (2490 - 2600 °F) | 

| **Specific Heat** | 460 J/kg·K at 20°C | 

| **Thermal Conductivity** | 14.0 W/m·K at 100°C | 

| **Thermal Expansion** | 13.5 μm/m·K (20 - 100°C) | 

| **Modulus of Elasticity** | 205 GPa (29.7 x 10⁶ psi) at 21°C | 

 --- ### **Key Characteristics & Mechanical Properties** 

 Alloy 706 is primarily valued for its high strength, excellent manufacturability, and good weldability. *   

**High Strength via Precipitation Hardening:

** Achieves high yield and tensile strength through a two-step aging treatment (e.g., 720°C/8hrs, furnace cool to 620°C/8hrs, AC). *   

**Excellent Forgeability:** Superior to Alloy 718, allowing for the production of large, intricate forged components with less risk of cracking. *   

**Good Machinability:** In the annealed or solution-annealed condition, it is more readily machinable than many other high-strength superalloys. *   

**Good Weldability:** Can be welded using common methods, including resistance and fusion welding, without a strong tendency for post-weld age cracking. 

 **Typical Room Temperature Mechanical Properties (Solution Annealed & Aged):** *   

**Tensile Strength:** ≥ 1100 MPa (160 ksi) *   

**Yield Strength (0.2% Offset):** ≥ 1030 MPa (150 ksi) *   

**Elongation:** ≥ 15% --- ### **Product Forms and Applications** Alloy 706 is primarily available in forms suitable for forging and machining into critical rotating components. 

 **Product Forms:** *   

Bar, Billet, and Forging Stock *   

Rod and Wire *   

Forgings (Rings, Disks, Shafts) *  

 Plate 

 **Applications:** *  

 **Aerospace & Gas Turbines:**    *   

**Gas Turbine Discs and Wheels:** Its primary application, especially for large-diameter compressor and turbine discs.    *   

**Shafts and Spacers.**    *   

**Compressor Stators and Casings.** *   

**Power Generation:**    *   

Rotors and discs for land-based gas turbines. *   

**High-Strength Fasteners:**    *   

Bolts, screws, and studs for high-temperature service. 

 --- ### **International Standards** 

 Alloy 706 is covered by several key aerospace and industrial standards. 

| Product Form | Standard Number | Standard Title / Description | 

| :--- | :--- | :--- | 

| **Bar, Billet, Forgings** | **AMS 5703** | Nickel Alloy, Corrosion and Heat-Resistant, Bars, Forgings, and Rings 42Ni - 36Fe - 15Cr - 2.9Nb - 1.7Ti - 0.40Al Solution and Precipitation Heat Treated | 

| **Billet & Bar (Aircraft Quality)** | **AMS 5702** | Bars, Forgings, and Rings, Nickel Base Alloy, 42Ni - 36Fe - 15Cr - 2.9Nb - 1.7Ti - 0.40Al, Consumable Electrode or Vacuum Induction Melted, Solution Heat Treated, Forging Quality | 

| **Welding Wire** | **AMS 5834** | Wire, Welding, 42Ni - 36Fe - 15Cr - 3.0Cb - 1.7Ti - 0.40Al (INCONEL Alloy 706) | 

| **General Material** | **ASTM B637** | Standard Specification for Precipitation-Hardening Nickel Alloy Bars, Forgings, and Forging Stock for High-Temperature Service (Covers UNS N09706 and others) | | **Aerospace (French)** | **AIR 9181** | French Aerospace Standard for Alloy 706 | 

 --- ### **Conclusion**

 In summary, Alloy 706 (Inconel 706 / UNS N09706) is a high-strength, precipitation-hardenable nickel-iron superalloy that successfully balances performance with manufacturability. Its excellent forgeability and machinability, combined with robust mechanical properties up to ~650°C, have established it as a critical material for large rotating components in gas turbine engines, particularly where the processing advantages over Alloy 718 are a significant benefit.

Packing of Alloy 706 (Inconel 706 / UNS N09706)

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 1635 gallon liquid totes Special package is available on request.