Inconel 718, also known as UNS N07718 or GH4169, is a high-performance nickel-based high-temperature alloy.
Chemical composition
The main chemical components of Inconel 718 include nickel (50%-55%), chromium (17%-21%), iron (balance, usually 15%-20%), niobium (4.75%-5.5%), molybdenum (2.8%-3.3%), titanium (0.65%-1.15%), and a small amount of aluminum, carbon, manganese, silicon and other elements. The precise proportion of these elements in the alloy enables it to perform well in high temperatures and harsh environments.
Physical and mechanical properties
Density: about 8.24g/cm³ (or 8.19g/cm³, depending on the specific process and composition).
Melting point: between 1260-1330°C.
Tensile strength: up to 1200-1400MPa at room temperature, and can maintain a high strength level at high temperature.
Yield strength: about 900-1150MPa at room temperature.
Ductility: about 25%, with good plastic deformation ability.
Hardness in the aged state, the hardness range is about 40-44HRC.
Features and advantages
High temperature strength: Inconel 718 can still maintain good strength and toughness at temperatures up to about 700°C, mainly due to its internal stable γ' phase and γ'' phase structure.
Low temperature stability: The alloy can also maintain its excellent physical and mechanical properties at extremely low temperatures.
Excellent welding and processing: It has good weldability and processing, and can be welded and machined in various forms, whether in the annealed state or the aged state.
Excellent corrosion resistance: It has good tolerance to a variety of corrosive environments, including oxidizing, reducing and salt spray environments.
Microstructure
Inconel 718 alloy is mainly composed of γ (austenite) matrix and γ' (Ni₃(Al,Ti)), γ'' (Ni₃Nb) and δ (Ni₃Nb) phase precipitation phases. These precipitation phases play a strengthening role in the alloy, giving it higher strength and hardness.
Application fields
Inconel 718 alloy is widely used in the following fields due to its excellent performance:
Aerospace: As a key component of aircraft engines and gas turbines, such as turbine blades, turbine disks and rotors.
Energy: Used in reactor pressure vessels, control rod drive mechanisms and various elastic elements in nuclear fuel cycle systems of nuclear power plants.
Chemical industry: In the petroleum and chemical industries, it is used to manufacture various high-temperature and corrosion-resistant equipment and pipelines.
Cryogenic engineering: Used in the manufacture of cryogenic storage containers such as liquid nitrogen and liquid hydrogen.
Mold manufacturing: Used to manufacture high-temperature molds to withstand high temperature and high pressure working environments.
