Material Family

Nickel-Chromium-Niobium-Molybdenum Precipitation-Hardenable Superalloy

Gains its extreme strength from a controlled aging heat treatment, not just from solid solution.

Common Designations

UNS N07718, Inconel 718, W.Nr. 2.4668, GH4169 (China)

The benchmark for high-strength, fabricable superalloys.

Chemical Composition (Typical wt.%)

Ni: 50.0 - 55.0 (Balance)
Cr: 17.0 - 21.0
Fe: Remainder (~18.5)
Nb (+Ta): 4.75 - 5.50
Mo: 2.80 - 3.30
Ti: 0.65 - 1.15
Al: 0.20 - 0.80
C: ≤ 0.08

Niobium (Nb) is the primary strengthening element for forming the γ" phase. Iron (Fe) content lowers cost and improves workability.

Mechanical Properties (Solution Annealed & Aged Plate - Typical)

Tensile Strength (Rm): ≥ 1240 MPa
Yield Strength (Rp0.2): ≥ 1035 MPa
Elongation (A): ≥ 12%

Strength is more than double that of solid-solution alloys like 625. High strength is achieved post-fabrication via heat treatment.

Physical Properties

Density: 8.19 g/cm³
Melting Range: 1260 - 1336 °C
Effective Service Temp: -250°C to 700°C (-420°F to 1300°F)

The optimal strength range is up to ~650°C (1200°F); above this, strength declines as strengthening phases dissolve.

Key Performance Attributes

• Ultra-High Strength & Excellent Creep Rupture Strength• Superior Resistance to Strain-Age Cracking After Welding• Good Oxidation & Corrosion Resistance up to ~700°C• High Fatigue Strength and Fracture Toughness

The premier alloy for high-stress, moderate-temperature applications requiring weldability.

Key Standards (Plate)

AMS 5596 / ASTM B637 (Heat-Treated), ASTM B670 (Solution Annealed)

Aerospace Material Specification (AMS 5596) is the most common procurement standard for aged material.

Heat Treatment Condition

Typically supplied in Solution Annealed condition for fabrication, then Aged (e.g., 720°C/8hrs, furnace cool to 620°C, hold 8hrs, air cool).

Critical: Final properties are developed by the customer's specific aging cycle post-fabrication.

Form Availability

Plate, Sheet, Bar, Forging, Billet, Ring

Often used for machined components, frames, casings, and welded structures.

Typical Applications

• Gas Turbine Engine Components (disks, blades, casings, frames)
• High-Strength Fasteners, Bolts, and Rings
• Rocket Motor Casings & Cryogenic Storage Tanks
• Nuclear Reactor Core Components & Tooling for Isothermal Forging

The dominant material for critical rotating and structural aerospace parts.