P/M Low Carbon Astroloy, Supersolvus,,E FORU

### **P/M Low Carbon Astroloy, Supersolvus** #### **Overview** **P/M Low Carbon Astroloy, Supersolvus** is a high-strength, powder metallurgy (P/M) nickel-based superalloy designed for the most demanding high-temperature applications, primarily in the aerospace industry. It represents an advanced evolution of the conventional cast-and-wrought Astroloy, optimized through two key modifications: 1. **Powder Metallurgy (P/M) Processing:** The alloy is gas-atomized to form a fine, spherical powder, which is then consolidated via Hot Isostatic Pressing (HIP) and/or forging. This process eliminates the macro-segregation and inhomogeneity inherent in cast ingots, resulting in a fine, uniform microstructure with superior mechanical properties and greater reliability. 2. **Low Carbon & Supersolvus Heat Treatment:** A reduced carbon content minimizes the formation of primary, blocky carbide phases that can be initiation sites for cracks. The "Supersolvus" heat treatment is performed at a temperature above the gamma prime (γ') solvus temperature, causing all strengthening γ' precipitates to dissolve. Upon cooling, a coarse, uniform grain structure with very fine, intragranular γ' precipitates forms. This microstructure is optimized for exceptional **creep resistance** and **stress rupture strength** at high temperatures. This combination makes it a premier material for critical rotating components in gas turbine engines, where performance at extreme temperatures and stresses is non-negotiable. --- #### **Chemical Composition (Weight % - Typical)** The composition is tightly controlled to balance strength, microstructural stability, and processability. | Element | Content (%) | | :--- | :--- | | **Nickel (Ni)** | **Balance** | | **Cobalt (Co)** | **15.0 - 17.0** | | **Chromium (Cr)** | **14.0 - 16.0** | | **Molybdenum (Mo)** | **4.5 - 5.5** | | **Aluminum (Al)** | **3.5 - 4.5** | | **Titanium (Ti)** | **3.0 - 4.0** | | **Carbon (C)** | **≤ 0.03 (Low Carbon)** | | **Boron (B)** | **0.020 - 0.040** | | **Zirconium (Zr)** | **0.020 - 0.040** | * **Aluminum & Titanium:** Form the primary strengthening phase, Ni₃(Al,Ti), known as **gamma prime (γ')**. The high combined volume fraction of γ' is responsible for the alloy's remarkable high-temperature strength. * **Cobalt:** Increases the γ' solvus temperature, allowing for higher heat treatment temperatures and enhancing high-temperature strength. * **Chromium:** Provides resistance to oxidation and hot corrosion. * **Molybdenum:** Provides solid solution strengthening. * **Boron & Zirconium:** These elements segregate to grain boundaries, improving grain boundary strength and ductility, which enhances creep and stress-rupture life. --- #### **Physical & Mechanical Properties** The following table outlines the key properties of P/M Low Carbon Astroloy after Supersolvus heat treatment. | Property | Value / Description | | :--- | :--- | | **Density** | ~8.0 g/cm³ | | **Melting Range** | ~1330 - 1360 °C (2425 - 2480 °F) | | **Gamma Prime (γ') Solvus** | ~1160 - 1180 °C (2120 - 2155 °F) | | **Thermal Conductivity** | Low, typical of nickel-based superalloys (~11 W/m·K at 20°C) | | **Mean Coefficient of Thermal Expansion** | ~13.5 μm/m·°C (20-1000°C) | | **Tensile Strength (RT)** | ~1500 - 1650 MPa | | **Yield Strength (0.2% Offset, RT)** | ~1250 - 1400 MPa | | **Elongation (RT)** | ~10 - 20% | | **Creep Rupture Strength** | **Excellent.** Capable of sustaining high stresses for extended periods at temperatures **up to 815°C (1500°F)** and beyond. | --- #### **Key Characteristics & Applications** **Key Characteristics:** 1. **Exceptional High-Temperature Strength:** Offers one of the highest combinations of tensile, creep, and stress-rupture properties among commercially available disk alloys. 2. **Fine, Uniform Microstructure:** The P/M process ensures a homogenous distribution of alloying elements and γ' precipitates, leading to consistent and predictable performance. 3. **Coarse Grain Structure (Supersolvus):** The coarse grains formed during supersolvus heat treatment are optimal for resisting creep deformation, which is a critical failure mode for turbine disks. 4. **Improved Damage Tolerance:** The P/M process and controlled microstructure reduce the presence of defects, improving fatigue initiation resistance. **Typical Applications:** This alloy is exclusively used for the most critical rotating components in high-performance gas turbine engines: * **High-Pressure Turbine Disks (HPT Discs/Rotors):** The core application, where the disk operates under extreme centrifugal stress and high temperatures. * **Compressor Disks (Rear Stages):** In the highest-temperature stages of the compressor section. * **Turbine Spools and Hubs:** Other critical rotating structures in the hot section of the engine. * **Integrally Bladed Rotors (IBRs or Blisks):** Where the blades and disk are manufactured as a single piece from this high-performance material. --- #### **International Standards** As a proprietary, high-performance aerospace alloy, P/M Low Carbon Astroloy is typically governed by proprietary material specifications from engine manufacturers (e.g., GE, Rolls-Royce, Pratt & Whitney) and aerospace consortia. However, it is related to several overarching standards. | Standard Type | Designation | Description | | :--- | :--- | :--- | | **Aerospace Material Specification (AMS)** | **AMS 7952** | This standard is for "Superalloy Powder, Nickel Base, 55Ni - 15Cr - 16Co - 4Mo - 4Al - 3.5Ti, Vacuum Atomized," which is the powder precursor for Astroloy. | | **Aerospace Material Specification (AMS)** | **AMS 7850** | Covers the conventional (higher carbon) cast-and-wrought UNS N13017 form. The P/M Low Carbon variant is a distinct evolution. | | **UNS Number** | **UNS N13017** | This number is typically associated with the standard Astroloy composition. The "Low Carbon, P/M" version is a specific subset. | | **Manufacturer Specifications** | **Various** | The definitive processing and property requirements are usually detailed in Original Equipment Manufacturer (OEM) proprietary specifications, which control the powder production, HIPing, forging, and heat treatment parameters. | --- #### **Summary** In summary, **P/M Low Carbon Astroloy, Supersolvus** is a pinnacle material in the world of nickel-based superalloys for rotating engine components. Its development through powder metallurgy and advanced supersolvus heat treatment directly addresses the need for greater microstructural control and superior high-temperature mechanical properties. While it is challenging and expensive to process, its unmatched creep and rupture strength at temperatures around 815°C make it an enabling technology for the high-pressure turbine sections of modern military and advanced commercial jet engines, allowing for higher operating temperatures and improved efficiency.

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 3199 gallon liquid totes Special package is available on request.