Inconel 718 (also known as UNS N07718 or GH4169) is a precipitation hardening nickel based high-temperature alloy. Since its development by International Nickel Corporation (INCO) in the late 1950s, it has become a core material in extreme working conditions such as aerospace and energy. Its core features and applications are as follows:
Ⅰ.Basic characteristics
Chemical composition
Using nickel (50% -55%) as the matrix, chromium (17% -21%) provides oxidation resistance, iron (about 17% -21%) reduces costs, and reinforcing elements such as niobium (4.75% -5.5%), molybdenum (2.8% -3.3%), titanium (0.65% -1.15%), and aluminum (0.2% -0.8%) are added. Niobium forms the “γ” phase (Ni ∝ Nb), while molybdenum/titanium/aluminum assists in the formation of the “γ” phase (Ni ∝ (Al, Ti)), collectively forming the precipitation hardening core mechanism.
Physical and mechanical properties
- Density: 8.19-8.24 g/cm ³, melting point: 1260-1340 ℃;
- High strength: The tensile strength at room temperature is ≥ 1250 MPa, and it still maintains 1375-1450 MPa at 700 ℃;
- Temperature resistance range: Long term applicable -253 ℃ to 704 ℃, short-term able to withstand high temperatures of 982 ℃;
- Resistance to creep and fatigue: Excellent stability below 650 ℃, strong resistance to cyclic loading.
Ⅱ.Core advantages
- Résistance à la corrosion : Chromium forms a dense oxide film, which resists corrosion in acid, alkali, salt spray, and sulfide environments;
- Processing performance: Supports forging, welding, and machining, with high feasibility for manufacturing complex components;
- Organizational stability: Optimization of precipitation phase distribution through aging treatment (955 ℃ solid solution+720 ℃/620 ℃ two-stage aging).
Ⅲ.Key application areas
1. Aerospace
Aircraft engine turbine discs, blades, combustion chambers, and rocket nozzles are resistant to high temperature and high pressure impacts.
2. Energy industry
Nuclear reactor pressure vessels and gas turbine components are suitable for radiation and creep environments.
3. Petrochemical industry
Cracking furnace pipelines, deep-sea drilling equipment, resistant to high-strength corrosive media.
4. Special Scenarios
Liquid hydrogen fuel storage tank (-253 ℃) and seals for supercritical power generation units.
Ⅳ.Technological evolution
The new modification directions include: adding tungsten to enhance strength above 760 ℃, optimizing fatigue resistance through laser additive manufacturing; Low cobalt variants are suitable for nuclear fusion reactor requirements.
Inconel 718 achieves a balance between strength, corrosion resistance, and processability in extreme environments through its unique composition design and strengthening mechanism, continuously driving the development of high-end equipment.
