Description
Inconel 718/2.4668 (UNS N07718) is a nickel-chromium alloy known for its high strength, corrosion resistance, and excellent mechanical properties at elevated temperatures. It is a precipitation-hardenable superalloy that can maintain its properties in extreme environments, making it ideal for high-temperature applications. This alloy is particularly notable for its ability to withstand creep, fatigue, and oxidation, which makes it a preferred choice in industries such as aerospace, power generation, and oil and gas. The DIN designation for Inconel 718 is 2.4668.
Chemical Composition
The chemical composition of Alloy 625 is as follows:
Nickel (Ni): 50.0 - 55.0%
Chromium (Cr): 17.0 - 21.0%
Iron (Fe): Balance
Molybdenum (Mo): 2.8 - 3.3%
Niobium + Tantalum (Nb+Ta): 4.75 - 5.5%
Titanium (Ti): 0.65 - 1.15%
Aluminum (Al): 0.2 - 0.8%
Cobalt (Co): ≤ 1.0%
Manganese (Mn): ≤ 0.35%
Silicon (Si): ≤ 0.35%
Carbon (C): ≤ 0.08%
Phosphorus (P): ≤ 0.015%
Sulfur (S): ≤ 0.015%
Copper (Cu): ≤ 0.3%
Boron (B): ≤ 0.006%
Mechanical Properties
Tensile Strength: 1,275 MPa (min)
Yield Strength (0.2% offset): 1,035 MPa (min)
Elongation: 12% (min)
Hardness: 331 HB (max)
Creep Rupture Strength: 725 MPa at 650°C
Thermal & Physical Properties
Density: 8.19 g/cm³
Melting Range: 1,260 - 1,325°C
Thermal Conductivity: 11.4 W/m•K at 20°C
Coefficient of Thermal Expansion: 13.0 x 10⁻⁶ /°C (20 - 1000°C)
Specific Heat Capacity:435 J/kg•K at 20°C
Electrical Resistivity:1.29 µΩ•m at 20°C
Other Designations
DIN:2.4668
UNS: N07718
ASTM : B637, B670
AMS: 5662, 5663
Fabrication and Heat Treatment
Formability: Inconel 718 can be readily formed using conventional techniques.
Weldability: Exhibits good weldability, suitable for welding by all common methods including TIG, MIG, and resistance welding.
Machinability: The alloy is difficult to machine, and it requires the use of carbide-tipped tools and low cutting speeds.
Solution Annealing: Heat to 980°C - 1,050°C and air cool.
Aging Treatment: Typically aged at 720°C for 8 hours, followed by furnace cooling at 50°C/hour to 620°C, held for 8 hours, and air-cooled.
Applications
Aerospace: Jet engines, turbine blades, and other components exposed to high temperatures and pressures.
Power Generation: Gas turbines, steam turbines, and nuclear reactors.
Oil & Gas: Downhole tools, valves, and other components used in harsh environments.
Automotive: High-performance engine parts.
Chemical Processing: Equipment exposed to corrosive environments at elevated temperatures.
Supplied Forms
Round Bars
Flat Bars
Square Bars
Hexagonal Bars
Forged Bars
Features
High Strength: Maintains strength at elevated temperatures up to 700°C.
Corrosion Resistance: Excellent resistance to oxidation and corrosion, particularly in environments containing acids and corrosive gases.
Fatigue and Creep Resistance: Exceptional resistance to creep and fatigue, making it ideal for cyclic loading applications.
Good Weldability: Can be welded using standard welding techniques without the need for post-weld heat treatment.
