Inconel 718: properties, composition, uses and standards
Inconel 718 is a age-hardenable nickel–chromium alloy with niobium and molybdenum, chosen for very high strength at temperatures up to about 650 °C. UNS N07718, W.Nr 2.4668, density 8.19 g/cm³.
What is Inconel 718?
Inconel 718 is a age-hardenable nickel–chromium alloy with niobium and molybdenum. Engineers choose it for very high strength at temperatures up to about 650 °C. It is also known as Alloy 718, UNS N07718, W.Nr 2.4668, Precipitation-hardening nickel alloy.
- UNS
- N07718
- W.Nr
- 2.4668
- EN
- NiCr19NbMo
- Aerospace
- AMS 5596 (sheet) · AMS 5662/5663 (bar)
- Trade names
- Inconel 718
- Density
- 8.19 g/cm³
- Melting range
- 1260 – 1336 °C
- Magnetic
- Non-magnetic
Chemical composition and what each element does
| Element | Weight % |
|---|---|
| Nickel (+Co) | 50.0 – 55.0 |
| Chromium | 17.0 – 21.0 |
| Niobium + Tantalum | 4.75 – 5.50 |
| Molybdenum | 2.80 – 3.30 |
| Titanium | 0.65 – 1.15 |
| Aluminium | 0.20 – 0.80 |
| Carbon | 0.08 max |
| Iron | Balance |
Per ASTM B637 / B670 for UNS N07718.
Niobium forms the gamma-double-prime phase that doubles strength after ageing.
Keeps very high strength and creep resistance up to about 650 °C.
Ages slowly, so it can be welded without cracking during post-weld heat treatment.
718 is chosen for strength; for corrosion alone, 625 or 825 are usually better value.
Inconel 718 at a glance
See the Inconel 718 product page for every form we supply and its standard.
Mechanical properties
| Property | Value |
|---|---|
| Tensile strength | 1275 MPa · 185 ksi |
| Yield strength 0.2% | 1034 MPa · 150 ksi |
| Elongation | 12% |
Solution-treated and aged, minimum values. Values for pipe, bar and forgings differ slightly — see the product standard.
Where Inconel 718 is used
- Oil & gas. Wellhead parts, hangers and high-strength bolting. Industry →
- Aerospace. Turbine discs, casings and fasteners. Industry →
- Power. Gas-turbine and nuclear components. Industry →
- Tooling. Hot-work tooling and springs. Industry →
Welding 718
The matching filler is ERNiFeCr-2 (AWS A5.14). Post-weld solution treatment and ageing restore strength.
Keep heat input moderate and interpass temperature low, clean joints thoroughly, and pickle or passivate after welding where the service is corrosive.
Inconel 718 compared with similar grades
| Grade | PREN | Choose it for |
|---|---|---|
| Inconel 718 | — | Very high strength at temperatures up to about 650 °C |
| Inconel 625 | ≈ 51 | Seawater, high strength and high temperature in one alloy |
| Inconel 600 | — | High-temperature oxidation, caustic and nuclear service |
| Inconel 825 | ≈ 31 | Sulphuric and phosphoric acid service, chloride stress-corrosion cracking and sour gas |
Inconel 718 standards by product
| Product | Standard |
|---|---|
| Inconel 718 sheet | ASTM B670 · AMS 5596 |
| Inconel 718 plate | ASTM B670 · AMS 5596 |
| Inconel 718 coil | ASTM B670 |
| Inconel 718 pipe & tube | AMS 5589 (tube) |
| Inconel 718 fittings | Machined from B637 on request · ASTM B637 |
| Inconel 718 flanges | ASTM B637 |
| Inconel 718 fasteners | ASTM B637 |
Buying Inconel 718: what to specify
- The product standard and the UNS or designation — for example ASTM B670 · AMS 5596 UNS N07718.
- Size, thickness or schedule, and quantity in pieces and kg or metres.
- Heat-treatment condition where the standard offers a choice.
- Certificate: EN 10204 3.1 as standard, 3.2 if a third party must witness.
- NACE MR0175 / ISO 15156 compliance if the service contains H₂S.