Alloy 718 INCONEL® 718 – W. Nr. 2.4668 / UNS N07718 / ASTM B637, B670, B906
Alloy 718 INCONEL® 718
Alloy 718 INCONEL® 718 is a nickel-chromium alloy highly resistant to corrosion and high temperatures, with excellent mechanical strength, high workability, and excellent weldability. It can be used in a temperature range from -423°F (-253°C) up to 1300°F (704°C).
This alloy is particularly valued for its ability to maintain high mechanical properties thanks to precipitation hardening of secondary phases (gamma prime and gamma double-prime). The excellent combination of fatigue, tensile, creep, and stress-rupture strength makes it ideal for applications in the aerospace, nuclear, and oil & gas sectors.
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Reference standards:
- ASTM B637 (bars and forgings)
- ASTM B670 (sheets and strips)
- ASTM B906 (plates and slabs)
Chemical composition (%)
| Element | Content (%) |
|---|---|
| Nickel (Ni) + Cobalt (Co) | 50.00 – 55.00 |
| Chromium (Cr) | 17.00 – 21.00 |
| Iron (Fe) | Balanced |
| Niobium + Tantalum (Nb+Ta) | 4.75 – 5.50 |
| Molybdenum (Mo) | 2.80 – 3.30 |
| Titanium (Ti) | 0.65 – 1.15 |
| Aluminum (Al) | 0.20 – 0.80 |
| Cobalt (Co) | 1.00 max |
| Carbon (C) | 0.08 max |
| Manganese (Mn) | 0.35 max |
| Silicon (Si) | 0.35 max |
| Phosphorus (P) | 0.015 max |
| Sulfur (S) | 0.015 max |
| Boron (B) | 0.006 max |
| Copper (Cu) | 0.30 max |
Mechanical properties
| Temperature (°C) | Tensile strength (MPa) | Yield strength (MPa) | Elongation (%) |
|---|---|---|---|
| 20 | 1240 – 1515 | 825 – 1035 | 12 – 20 |
| 600 | 1035 | 720 | 16 |
| 800 | 880 | 665 | 15 |
| 1000 | 750 | 560 | 10 |
Heat treatments
INCONEL® 718 is a precipitation-hardenable alloy. The main heat cycles used to optimize mechanical properties are:
- Solution annealing at 1700-1850°F (925-1010°C), followed by rapid cooling and subsequent aging at:
- 1325°F (720°C) for 8 hours, furnace cooling to 1150°F (620°C) for a total of 18 hours, followed by air cooling.
- Solution annealing at 1900-1950°F (1038-1065°C), followed by rapid cooling and subsequent aging at:
- 1400°F (760°C) for 10 hours, furnace cooling to 1200°F (650°C) for a total of 20 hours, followed by air cooling.
Available forms
INCONEL® Alloy 718 is available in the following forms:
Industrial applications
Thanks to its combination of mechanical and corrosion resistance, INCONEL® 718 is used in various sectors:
- Aerospace and Defense: Turbine components for aircraft engines, jet engine exhausts, propulsion systems, and rockets.
- Power Generation: Heat exchangers, gas and steam turbine plants.
- Chemical and Pharmaceutical Industry: Components for chemical reactors and plants with high temperatures and corrosive environments.
- Motorsport: Critical components for racing engines and high-performance exhausts.
- Nuclear: Structural materials for nuclear reactors, control rods, and steam generator piping.
- Oil & Gas: Components for deep-sea drilling, piping, and fittings resistant to marine environments and high pressures.
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