Inconel 718
Designated as UNS N07718 or W.Nr. 2.4668, Inconel 718, also known as “Alloy 718”, is a precipitation-hardenable nickel-chromium alloy containing significant amount of iron, niobium, and molybdenum along with lesser amounts of aluminum and titanium. The titanium and niobium are added to overcome strain-age cracking problems during welding and weld repair. Inconel Alloy 718 combines corrosion resistance and high strength with outstanding weldability, including resistance to postweld cracking. The alloy has excellent creep-rupture strength at temperatures up to 1300°F[700°C]. The Inconel 718 is fabricated for gas turbines, rocket motors, spacecraft, nuclear reactors, pumps and other piping tools. Most commonly, it is used for fasteners and springs.

Inconel 718 fasteners: hexagonal bolts with nuts.
1. Chemical Composition Requirements
| Element | Content, % |
|---|---|
| Nickel (plus Cobalt) | 50.00-55.00 |
| Chromium | 17.00-21.00 |
| Iron | Balance |
| Niobium (plus Tantalum) | 4.75-5.50 |
| Molybdenum | 2.80-3.30 |
| Titanium | 0.65-1.15 |
| Aluminum | 0.20-0.80 |
| Cobalt | ≤1.00 |
| Carbon | ≤0.08 |
| Manganese | ≤0.35 |
| Silicon | ≤0.35 |
| Phosphorus | ≤0.015 |
| Sulfur | ≤0.015 |
| Boron | ≤0.006 |
| Copper | ≤0.30 |
2. Physical Properties

Inconel 718 springs used in a trunnion mounted ball valve.
| Density, lb/in3 | Melting Range | Specific Heat at 70°F, Btu/lb °F | Curie Temperature, °F(°C) | Permeability at 200 oersted and 70°F | ||||
|---|---|---|---|---|---|---|---|---|
| Annealed | Annealed and Aged | °F | °C | at 21°C, J/kg °C) | Annealed Material | Annealed and Aged Material | Annealed Material | Annealed and Aged Material |
| 0.296 | 0.297 | 2300-2437 | 1260-1336 | 0.104(435) | <-320(<-196) | -170(-112) | 1.0013 | 1.0011 |
3. Product Forms and Related Standards of Inconel 718
| Products form | Standard |
|---|---|
| Rod, bar and wire | ASTM B166 |
| Plate, sheet and strip | ASTM B168, B906 |
| Seamless pipe and tube | ASTM B167, B829 |
| Billet and bar for reforging | ASTM B472 |
| Forging | ASTM B564 |
