UDIMET alloy 720 Nickel Base Alloy, 1

### **Product Datasheet: UDIMET® Alloy 720 (U720)** **A Premium High-Strength Wrought Nickel-Based Superalloy for Critical Rotating Components** --- #### **1. Overview** UDIMET® Alloy 720 (U720) is a high-strength, precipitation-hardenable nickel-based superalloy primarily supplied in the wrought form. It is renowned for its exceptional combination of **ultra-high tensile strength**, **excellent low-cycle fatigue (LCF) resistance**, and **good creep properties** at intermediate to high temperatures. This superior balance of properties makes it a leading material for the most critically stressed rotating components in modern gas turbine engines, particularly turbine disks. The alloy is typically produced using a "triple melt" process (VIM + VAR + ESR) to achieve the utmost cleanliness and homogeneity, which is essential for the reliability of these high-integrity parts. The specifications referenced (**EMS 55477; EMS 73105; MSRR 7252; C50TF105; MTS 5013**) are proprietary standards from major aerospace OEMs like Safran, Rolls-Royce, and others, which dictate precise manufacturing, heat treatment, and quality control requirements for this material. #### **2. Chemical Composition (Typical Weight %)** The composition is carefully balanced to form a high volume fraction of the strengthening γ' (gamma prime) phase. | Element | Content (%) | Role in the Alloy | | :--- | :--- | :--- | | **Nickel (Ni)** | Balance | Austenitic matrix. | | **Chromium (Cr)** | ~16.0 | Provides essential oxidation and hot corrosion resistance. | | **Cobalt (Co)** | ~14.7 | Solid solution strengthener; reduces γ' solvus temperature. | | **Molybdenum (Mo)** | ~3.0 | Potent solid solution strengthener. | | **Tungsten (W)** | ~1.25 | Solid solution strengthener. | | **Titanium (Ti)** | ~5.0 | Primary strengthening element; forms the γ' phase (Ni₃(Al,Ti)). | | **Aluminum (Al)** | ~2.5 | Primary strengthening element; forms the γ' phase (Ni₃(Al,Ti)). | | **Carbon (C)** | ~0.025 | Forms primary MC and secondary M₂₃C₆ carbides for grain boundary control. | | **Boron (B)** | ~0.025 | Significantly enhances creep life and grain boundary strength. | | **Zirconium (Zr)** | ~0.035 | Further improves creep resistance and grain boundary cohesion. | | **Iron (Fe)** | ≤ 0.5 | Residual element. | *Note: A low-carbon version, U720**Li** ("Li" for Low Carbon), is also widely used to improve ductility and damage tolerance at high strength levels.* #### **3. Physical Properties (Typical)** | Property | Value / Condition | | :--- | :--- | | **Density** | 8.05 g/cm³ (0.291 lb/in³) | | **Melting Range** | ~1330 - 1360 °C (~2425 - 2480 °F) | | **γ' Solvus Temperature** | ~1160°C (~2120°F) | | **Thermal Expansion Coefficient** | ~13.2 μm/m·°C (20 - 100°C) | | **Thermal Conductivity** | ~13.5 W/m·K (at 100°C) | | **Modulus of Elasticity** | ~220 GPa (32 x 10⁶ psi) at 20°C | #### **4. Mechanical Properties** Properties are highly dependent on the heat treatment, which is optimized for specific applications. The following are representative for a high-strength heat treatment of U720Li bar stock. **At Room Temperature:** * **Tensile Strength:** > 1515 MPa (220 ksi) * **Yield Strength (0.2% Offset):** > 1170 MPa (170 ksi) * **Elongation:** > 15% * **Reduction of Area:** > 18% **At Elevated Temperature (e.g., 650°C / 1200°F):** * **Tensile Strength:** ~1310 MPa (190 ksi) * **Yield Strength (0.2% Offset):** ~1100 MPa (160 ksi) * **Creep & Fatigue:** Exhibits exceptional resistance to low-cycle fatigue and sustained peak loads at operational temperatures. #### **5. Heat Treatment** UDIMET 720 undergoes a complex heat treatment to achieve its optimal microstructure and properties: 1. **Solution Treatment:** Performed at a subsolvus temperature (e.g., 1100°C / 2010°F) to control grain size and create a bimodal γ' distribution. This is followed by a rapid quench. 2. **Aging Treatment:** A multi-stage aging process (e.g., 760°C / 1400°F for 16 hours, then 650°C / 1200°F for 24 hours) is used to precipitate a fine, secondary γ' phase, providing maximum strength. #### **6. Product Applications** UDIMET 720 is the material of choice for the most demanding rotating components in aerospace and industrial gas turbines: * **High-Pressure Turbine (HPT) Disks / Discs** * **Compressor Disks** (later stages) * **Spools and Shafts** * **Turbine Blades (forged)** * **Integrally Bladed Rotors (IBRs)** #### **7. International and Proprietary Standards** This alloy is covered by both common international standards and critical proprietary specifications from engine manufacturers. * **AMS:** **AMS 4082** (Bar and Billet), **AMS 4083** (Die Forgings) * **UNS:** **N07720** * **Proprietary Specifications (as referenced):** * **EMS 55477; EMS 73105:** Likely Safran (Snecma) material specifications for raw material or forgings. * **MSRR 7252:** A Rolls-Royce material standard. * **C50TF105; MTS 5013:** Proprietary specifications from other aerospace OEMs (e.g., possibly GE Aviation, MTU). These documents specify exact chemical ranges, mechanical property minima, non-destructive testing (NDT) requirements, and manufacturing processes. --- **Disclaimer:** The information provided herein is for reference purposes only. Properties can vary based on manufacturing process, heat treatment (subsolvus vs. supersolvus), and product form. The proprietary specifications listed (**EMS, MSRR, C50TF, MTS**) are the controlling documents for specific applications and override all other general data. For design and procurement, the official, latest issue of the relevant material specification must be consulted. UDIMET is a registered trademark of Special Metals Corporation (a PCC company).

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 3363 gallon liquid totes Special package is available on request.