GTD 222 Centri-Vac Nickel Cobalt Based Alloy，1

### **Product Introduction: GTD-222™ Centri-Vac Nickel-Cobalt Based Alloy** **Overview** GTD-222™ is a premium nickel-cobalt-chromium superalloy specifically engineered for high-temperature strength and exceptional resistance to thermal fatigue and oxidation. The "Centri-Vac" designation signifies that components are manufactured using advanced centrifugal casting and vacuum melting processes. This results in a product with superior metallurgical soundness, fine grain structure, and excellent mechanical properties. GTD-222™ is designed to withstand the extreme conditions in the hot gas path of industrial gas turbines (IGTs), offering an outstanding balance of creep rupture strength, microstructural stability, and corrosion resistance at temperatures up to 1000°C (1800°F). --- #### **Chemical Composition (Typical % by Weight)** The composition of GTD-222™ is a sophisticated balance of solid-solution strengtheners and precipitation hardeners. | Element | Content (%) | Role & Benefit | | :--- | :--- | :--- | | **Nickel (Ni)** | Balance | Forms the stable austenitic (gamma) matrix, providing the fundamental high-temperature structure. | | **Cobalt (Co)** | 18.0 - 20.0 | Enhances high-temperature strength and microstructural stability by reducing the solubility of other hardening elements in the nickel matrix. | | **Chromium (Cr)** | 21.0 - 23.0 | Provides exceptional resistance to oxidation (scaling) and hot corrosion (sulfidation) by forming a protective Cr₂O₃ scale. | | **Tungsten (W)** | 3.5 - 4.5 | A potent solid-solution strengthener that significantly enhances high-temperature creep strength. | | **Tantalum (Ta)** | 1.5 - 2.0 | Contributes to strength through solid-solution hardening and the formation of stable carbides. | | **Niobium (Nb)** | 0.75 - 1.25 | Acts as a precipitation hardener and contributes to the formation of carbides for grain boundary strength. | | **Aluminum (Al)** | 1.00 - 1.50 | Combines with nickel to form the coherent gamma prime (γ') phase, Ni₃(Al, Ti), which is the primary source of precipitation strengthening. | | **Titanium (Ti)** | 2.75 - 3.25 | Works synergistically with aluminum to form and strengthen the gamma prime (γ') phase. | | **Carbon (C)** | 0.10 - 0.15 | Forms stable carbides (e.g., MC, M₂₃C₆) at grain boundaries, enhancing creep rupture strength. | | **Boron (B)** | 0.005 - 0.015 | Strengthens grain boundaries and improves creep ductility. | | **Zirconium (Zr)** | 0.01 - 0.05 | Further enhances grain boundary strength and stability. | *Note: GTD-222™ is a trademark of General Electric Company. "Centri-Vac" refers to a proprietary centrifugal casting and vacuum melting process.* --- #### **Physical & Mechanical Properties (Typical - Heat Treated Condition)** | Property | Value / Condition | | :--- | :--- | | **Density** | 8.10 g/cm³ (0.293 lb/in³) | | **Melting Range** | ~1350 °C (~2460 °F) | | **Thermal Expansion Coefficient** | 14.5 μm/m·°C (8.1 μin/in·°F) @ 20-600°C | | **Thermal Conductivity**| 18.0 W/m·K (125 BTU·in/hr·ft²·°F) @ 500°C | | **Tensile Strength (Room Temp)** | 965 MPa (140 ksi) min | | **Yield Strength (0.2% Offset, Room Temp)** | 690 MPa (100 ksi) min | | **Elongation (Room Temp)** | 10% min | | **Creep Rupture Strength** | Excellent, designed for long-term service at 850-1000°C | --- #### **International Standards and Specifications** GTD-222™ is a proprietary alloy, and its specifications are typically controlled by the manufacturer and end-users like major gas turbine OEMs. * **OEM Internal Specifications:** The primary controlling documents are proprietary material specifications from Original Equipment Manufacturers (e.g., General Electric, Siemens Energy). These define the exact chemistry, heat treatment, and mechanical property requirements for centrifugal castings. * **AMS 5398:** While not a direct match, this Aerospace Material Specification for a similar nickel alloy investment casting provides a reference for the quality and testing standards expected for such high-performance materials. * **ASTM A447 / A297:** These general standards for centrifugally cast and static cast heat-resistant alloys provide a broader industrial context. --- #### **Product Applications** GTD-222™ Centri-Vac castings are exclusively used in the most demanding high-temperature sections of industrial gas turbines. 1. **Industrial Gas Turbines (Power Generation & Mechanical Drive):** * **First and Second-Stage Turbine Nozzles (Vanes):** These stationary components direct hot combustion gases onto the rotating blades and are exposed to the highest temperatures, making GTD-222™'s oxidation resistance and thermal fatigue strength critical. * **Turbine Shrouds:** Stationary segments that form a ring around the turbine blades, requiring dimensional stability and resistance to thermal cycling. * **Transition Ducts:** Components that channel combustion gases from the combustor to the turbine section. #### **Key Advantages** * **Superior High-Temperature Strength:** Excellent creep and rupture strength, allowing for higher operating temperatures and efficiencies in gas turbines. * **Outstanding Thermal Fatigue Resistance:** Withstands repeated heating and cooling cycles without cracking, which is crucial for turbines that undergo frequent starts and stops. * **Exceptional Oxidation & Hot Corrosion Resistance:** The high chromium content provides long-term protection against degradation in the harsh turbine environment. * **Microstructural Stability:** The balanced composition ensures that the alloy retains its mechanical properties and does not form detrimental phases during long-term exposure at high temperatures. **Conclusion** GTD-222™ Centri-Vac alloy represents the pinnacle of materials technology for stationary hot-gas-path components in heavy-duty industrial gas turbines. Its optimized chemistry, combined with the high-integrity Centri-Vac casting process, delivers an unparalleled combination of strength, durability, and environmental resistance at extreme temperatures. For power generation and mechanical drive applications where reliability, efficiency, and long service intervals are paramount, GTD-222™ is a proven and critical material solution, governed by stringent OEM specifications to ensure peak performance.

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 3411 gallon liquid totes Special package is available on request.