Inconel 718
2.4668THE most widely used aerospace superalloy. Precipitation-hardened Ni-Cr-Fe alloy strengthened by gamma-prime and gamma-double-prime phases (Nb). Unique slow aging kinetics allow welding without cracking. UTS >1275 MPa aged. Used for gas turbine discs, jet engine components, rocket motors, cryogenic tanks, and oil/gas downhole tools. Service to 700°C.
International equivalents
| Flag | Standard | Country | Grade | Number | Match |
|---|---|---|---|---|---|
| 🇺🇸 | ASTM | USA | UNS N07718 | N07718 | REF |
| 🇪🇺 | EN | Europe | NiCr19Fe19Nb5Mo3 | 2.4668 | 100% |
| 🇺🇸 | AMS | USA | AMS 5662/5663/5664 | — | 100% |
| 🇫🇷 | AFNOR | France | NC19FeNb | — | 95% |
Sources: ASTM B637, DIN 17752, AMS, AFNOR
Chemical composition comparison (wt%)
Side-by-side: Inconel 718 (ASTM) (ASTM B637) vs NC19FeNb (AFNOR)
| Element | Inconel 718 (ASTM) | NC19FeNb (AFNOR) | Overlap |
|---|---|---|---|
| C | 0–0.08% | — | — |
| Si | 0–0.35% | — | — |
| Mn | 0–0.35% | — | — |
| Cr | 17–21% | — | — |
| Mo | 2.8–3.3% | — | — |
| Ni | 50–55% | — | — |
| Cu | 0–0.3% | — | — |
| Al | 0.2–0.8% | — | — |
| Ti | 0.65–1.15% | — | — |
| Nb | 4.75–5.5% | — | — |
| B | 0–0.006% | — | — |
| Co | 0–1% | — | — |
| Fe | — | — | — |
Mechanical properties
Precipitation hardened
| Property | Value | Unit |
|---|---|---|
| Tensile Strength | ≥ 1275 | MPa |
| Yield Strength | ≥ 1034 | MPa |
| Elongation | ≥ 12 | % |
| Hardness HB | ≥ 331 | HB |
| Elastic Modulus | ≥ 205 | GPa |
| Density | ≥ 8.19 | g/cm3 |
Heat treatment
| Process | Temperature | Medium | Holding Time | Notes |
|---|---|---|---|---|
| solution_treating | 940–1010 °C | air | 1 hour min | AMS 5662: 940-1010°C, air cool |
| aging_step1 | 718–718 °C | furnace | 8 hours | Furnace cool 55°C/hr to 621°C |
| aging_step2 | 621–621 °C | air | 8 hours | Air cool. Double-aging gives peak strength. |
Compatibility verdict
Inconel 718 and NC19FeNb: 95% composition match
Close equivalents but NOT identical.
Related materials
Hastelloy C-22
2.4602Improved version of Hastelloy C-276 with better resistance to oxidizing media and higher chromium. Considered the most versatile Ni-Cr-Mo alloy for chemical processing. Resists both oxidizing and reducing acids, chlorides, and mixed media. Used for flue gas desulfurization, pharmaceutical, and universal chemical processing.
Alloy 20 / Carpenter 20
2.4660Austenitic Ni-Fe-Cr alloy specifically developed for sulfuric acid resistance. Nb-stabilized against sensitization. Cu addition gives outstanding resistance to H2SO4 at all concentrations up to 80%. Used for sulfuric acid piping, heat exchangers, mixing tanks, pickling equipment, and pharmaceutical processing.
Nimonic 80A
2.4952Nickel-chromium age-hardenable alloy with Ti + Al for gamma-prime strengthening. Developed originally for gas turbine blades. Good creep resistance to ~700°C. Used for exhaust valves, springs at elevated temperatures, nuclear engineering fasteners, and gas turbine components. ≈ UNS N07080.
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