Rene Supersolvus Rene 95 Nickel Based Superalloy,E FORU

### **Supersolvus René 95 Nickel-Based Superalloy** #### **Overview** **Supersolvus René 95** is a specific thermomechanical processing variant of the classic high-strength, powder metallurgy (P/M) nickel-based superalloy. While standard René 95 is used in a **"Subsolvus"** (or "directly aged") condition featuring a fine grain structure, the **Supersolvus** heat treatment produces a coarser grain microstructure optimized for superior **creep resistance** and **damage tolerance** at the upper end of the alloy's temperature capability. This processing route involves solution heat treating the consolidated material at a temperature **above the gamma prime (γ') solvus**, completely dissolving the primary γ' precipitates. Upon controlled cooling, a uniform distribution of fine, secondary γ' precipitates forms within a coarse, often serrated grain structure. This trade-off sacrifices a small amount of ultimate tensile strength for significantly enhanced long-term performance under stress at high temperatures (~650-750°C / 1200-1380°F). --- #### **Chemical Composition (Weight % - Typical)** The chemical composition remains identical to conventional René 95; the difference lies entirely in the processing and heat treatment. | Element | Content (%) | | :--- | :--- | | **Nickel (Ni)** | **Balance** | | **Cobalt (Co)** | **8.0** | | **Chromium (Cr)** | **14.0** | | **Molybdenum (Mo)** | **3.5** | | **Tungsten (W)** | **3.5** | | **Aluminum (Al)** | **3.5** | | **Niobium (Nb)** | **3.5** | | **Titanium (Ti)** | **2.5** | | **Carbon (C)** | **0.05 - 0.15** | | **Boron (B)** | **0.01** | | **Zirconium (Zr)** | **0.05** | * **Aluminum, Niobium, Titanium:** Form the high volume fraction of the strengthening **gamma prime (γ')** phase. The supersolvus heat treatment controls the dissolution and reprecipitation of these elements. * **Cobalt:** Raises the γ' solvus temperature, enabling the high-temperature solution treatment. * **Chromium:** Provides essential oxidation and hot corrosion resistance. * **Molybdenum & Tungsten:** Provide solid solution strengthening to the gamma matrix. * **Carbon, Boron, Zirconium:** Key for grain boundary strength and stability, which is crucial in the coarse-grained supersolvus microstructure. --- #### **Physical & Mechanical Properties** The properties below are representative for the Supersolvus heat-treated condition and contrast with the subsolvus condition. | Property | Value / Description (Supersolvus Condition) | | :--- | :--- | | **Density** | ~8.3 g/cm³ | | **Melting Range** | ~1330 - 1360 °C (2425 - 2480 °F) | | **Gamma Prime (γ') Solvus** | ~1160 °C (2120 °F) | | **Grain Structure** | **Coarse, uniform ASTM 5-8.** (Subsolvus is much finer, ASTM 10-12). | | **Thermal Conductivity** | Low, similar to subsolvus condition. | | **Mean Coefficient of Thermal Expansion** | ~12.9 μm/m·°C (20-1000°C) | | **Tensile Strength (RT)** | **High,** ~1550 MPa (225 ksi) - *Slightly lower than Subsolvus* | | **Yield Strength (0.2% Offset, RT)** | **High,** ~1250 MPa (180 ksi) - *Slightly lower than Subsolvus* | | **Elongation (RT)** | ~12 - 18% | | **Creep Rupture Strength** | **Superior.** Significantly better than subsolvus material at temperatures **above 650°C (1200°F)**, offering longer life under stress. | | **Fatigue Crack Growth Resistance** | **Improved.** The coarse grain structure presents a more tortuous path for crack propagation. | --- #### **Key Characteristics & Applications** **Key Characteristics:** 1. **Coarse Grain Structure:** The defining feature of the supersolvus heat treatment. This structure is inherently more resistant to creep deformation and fatigue crack growth. 2. **Enhanced Creep Resistance:** The primary reason for selecting this processing route. It allows components to withstand higher stresses for longer durations at elevated temperatures. 3. **Improved Damage Tolerance:** The coarse grains slow the rate at which cracks propagate, a critical property for engine disk lifing and safety. 4. **Trade-off in Strength:** There is a deliberate trade-off: a slight reduction in low-temperature tensile and yield strength compared to the fine-grained subsolvus material is accepted to gain superior high-temperature creep performance. 5. **Solution Heat Treatment Window:** Requires precise control during the supersolvus solution treatment to achieve the desired coarse grain size without incipient melting. **Typical Applications:** Supersolvus René 95 is used for the most demanding high-temperature rotating components where creep and long-term durability are the primary design drivers, often in the hotter sections of the turbine. * **High-Pressure Turbine Disks (HPT Discs/Rotors):** Particularly the rim and web sections that see the highest temperatures and where creep is a dominant failure mode. * **Turbine Hubs and Spools:** Components that require a balance of strength and extended service life under thermal exposure. * **Compressor Disks (Final Stages):** In advanced engines where the rear compressor stages operate at very high temperatures. * **Integrally Bladed Rotors (IBRs/Blisks):** For applications where superior creep and crack growth resistance are prioritized over ultimate tensile strength. --- #### **International Standards** As a specific heat-treated condition of a proprietary alloy, Supersolvus René 95 is governed by stringent engine manufacturer (OEM) specifications that detail the entire processing chain. | Standard Type | Designation | Description | | :--- | :--- | :--- | | **Aerospace Material Specification (AMS)** | **AMS 7852** | This standard covers the chemistry of the powder precursor ("Superalloy Powder, Nickel Base, 62Ni - 14Cr - 8Co - 3.5Mo - 3.5Nb - 3.5W - 2.5Ti - 3.5Al, Vacuum Atomized"). It is the foundation for all forms of René 95. | | **Aerospace Material Specification (AMS)** | **-** | The specific requirements for supersolvus heat treatment, resulting grain size, and mechanical properties are typically not in public AMS standards but are controlled by proprietary OEM specifications. | | **Manufacturer Specifications** | **Various (OEM-specific)** | The definitive authority. These specifications rigorously control the supersolvus solution heat treatment temperature/time, cooling rate, and subsequent aging steps to ensure the required coarse grain microstructure and mechanical properties are consistently achieved. | --- #### **Summary** In summary, **Supersolvus René 95** represents a highly optimized processing path for a benchmark high-strength superalloy. By employing a solution heat treatment above the γ' solvus temperature, engineers tailor the microstructure to prioritize **high-temperature creep resistance** and **fatigue crack growth resistance** over ultimate tensile strength. This makes it an ideal choice for critical rotating components in the hot section of gas turbine engines, where long-term durability and stability under extreme thermal and mechanical stress are paramount. The existence of both Subsolvus and Supersolvus conditions for René 95 exemplifies the advanced microstructural engineering used in modern aerospace materials to meet specific performance requirements.

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 3201 gallon liquid totes Special package is available on request.