Inconel 718 (UNS N07718): Precipitation-Hardening Ni Superalloy
ASTM B637 / AMS 5662 · Updated: 2026-05-25
Inconel 718 is the most widely used precipitation-hardening nickel superalloy, accounting for approximately 35% of all superalloy production by weight. Composition: 50-55% Ni, 17-21% Cr, 4.75-5.5% Nb+Ta, balanced Fe. Strengthened primarily by gamma double-prime (γ'')—metastable Ni3Nb precipitates formed during a two-step aging treatment (720°C/8h + 620°C/8h). The slow precipitation kinetics of γ'' provide the '718 advantage': minimal quench cracking sensitivity compared to gamma-prime-hardened alloys like Waspaloy, excellent weldability for a superalloy, and the ability to produce complex forged shapes that are then aged to full strength. Used for gas turbine disks, compressor blades, nuclear reactor core components, and cryogenic valves (maintains toughness to -253°C). Service limit: 650°C due to γ'' coarsening and transformation to stable delta phase above this temperature.
Quick Facts
| Category | Nickel Alloy |
| Standard | ASTM B637 / AMS 5662 |
| Density | 8.19 g/cm³ |
| Yield Strength | 1,034 MPa (150 ksi) aged |
| Tensile Strength | 1,275 MPa (185 ksi) aged |
Global Equivalents & Cross-Reference
| Alternative Standard / Grade | Action |
|---|---|
| EN NiCr19Fe19Nb5Mo3 | Compare |
| DIN 2.4668 | Compare |
| JIS NCF718 | Compare |
| GH4169 | Compare |
| ISO NiCr19Fe19Nb5Mo3 | Compare |
Related Materials
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Calculate the weight based on this material's density: 8.19 g/cm³
Frequently Asked Questions
What is the difference between Inconel 718 and Waspaloy?
Waspaloy (UNS N07001) is a gamma-prime (γ') strengthened alloy with approximately 50°C higher temperature capability (700°C vs 650°C for 718). However, Waspaloy has poor weldability (strain-age cracking), requires water quenching from solution temperature (higher residual stress), and costs more. 718 dominates for components below 650°C due to superior fabricability. Waspaloy is specified for the hottest compressor and turbine disks where 718's γ'' coarsening is unacceptable.