GH4169 Superalloy
GH4169 is a Chinese-grade precipitation-hardening nickel-based superalloy, equivalent to the internationally recognized Inconel 718. It is widely used in aerospace, energy, and industrial sectors due to its exceptional combination of high-temperature strength, creep resistance, corrosion resistance, and weldability. Below is a detailed overview:
1. Chemical Composition
GH4169’s composition is carefully balanced to achieve its superior properties, with key elements and their typical ranges as follows:
Element Content Range (%) Role in the Alloy
Nickel (Ni) 50.0-55.0 Forms the austenitic matrix, providing ductility, toughness, and a base for strengthening precipitates.
Chromium (Cr) 17.0-21.0 Enhances corrosion and oxidation resistance by forming a protective Cr₂O₃ oxide layer.
Iron (Fe) Remainder (~10-15%) Improves workability and reduces cost while stabilizing the austenitic structure.
Niobium (Nb) + Tantalum (Ta) 4.75-5.50 (Nb); ≤1.0 (Ta) Primary strengtheners: Niobium forms the intermetallic phase γ″ (Ni₃Nb), the key to high-temperature strength. Tantalum enhances γ″ stability.
Molybdenum (Mo) 2.80-3.30 Solid-solution strengthener; improves resistance to pitting and crevice corrosion in chloride environments.
Titanium (Ti) 0.65-1.15 Aids in forming γ′ (Ni₃Ti) precipitates, complementing γ″ for additional strength.
Aluminum (Al) 0.20-0.80 Promotes γ′ formation and enhances oxidation resistance.
Carbon (C) ≤0.08 Improves grain boundary strength via carbide formation (e.g., NbC).
2. Physical Properties
Density: Approximately 8.2 g/cm³
Melting Point: 1260-1320°C
Thermal Conductivity: 11.4 W/(m·℃) at 20°C; increases to 19.0 W/(m·℃) at 800°C
Coefficient of Linear Expansion: 11.4×10⁻⁶/℃ (20-100°C) to 16.0×10⁻⁶/℃ (20-800°C)
Magnetic Property: Non-magnetic in all heat-treated conditions
3. Mechanical Properties
GH4169 exhibits excellent mechanical performance across a wide temperature range:
Room Temperature (Aged Condition)
Tensile Strength: ≥1240 MPa
Yield Strength (0.2% offset): ≥1030 MPa
Elongation: ≥12%
Hardness: ~35 HRC
High-Temperature Performance
At 650°C: Tensile strength ≥965 MPa; yield strength ≥827 MPa
Creep Resistance: Excellent up to 650-700°C (e.g., creep rupture strength ≥100 MPa for 1000 hours at 650°C)
Fatigue Strength: ~480 MPa at 10⁷ cycles (room temperature), suitable for rotating components
4. Performance Characteristics
Corrosion Resistance: Resistant to pitting, crevice corrosion, and stress corrosion cracking (SCC) in chloride environments, seawater, and sulfuric acid. Performs well in oxidizing atmospheres up to 800°C.
High-Temperature Stability: Maintains strength and creep resistance at elevated temperatures, making it suitable for long-term service in gas turbines and rocket engines.
Fabricability: Excellent weldability (using techniques like GTAW and GMAW) and formability, with good machinability despite its high strength.
5. Heat Treatment
The standard heat treatment process optimizes GH4169’s strength through precipitate formation:
Solution Annealing: 982-1066°C for 1-2 hours, water-quenched.
Intermediate Aging: 720°C for 8 hours, furnace-cooled to 621°C.
Final Aging: 621°C for 8 hours, air-cooled.
6. Application Fields
GH4169 is widely used in critical engineering applications:
Aerospace: Gas turbine engine components (blades, disks, casings), rocket engine thrust chambers, and aircraft fasteners.
Energy: Oil and gas downhole tools, nuclear power plant components, and gas turbine parts.
Industrial: High-temperature furnace fixtures, pressure vessels, and chemical processing equipment.
In summary, GH4169 (equivalent to Inconel 718) is a versatile superalloy valued for its exceptional combination of strength, corrosion resistance, and processability, making it indispensable in high-performance engineering applications.
