Alloy 718 (Inconel 718)
UNS N07718
Overview
Precipitation-hardenable nickel-chromium alloy with exceptional strength from cryogenic temperatures up to 700°C. The addition of niobium enables age hardening — delivering yield strength of 1034-1241 MPa in the heat-treated condition. The alloy of choice for gas turbine hot sections, aerospace fasteners, and high-pressure oil & gas wellhead components. Combines extreme strength with good corrosion resistance.
Chemical Composition (wt%)
| Element | Min | Max |
|---|---|---|
| Ni (Nickel) | 50 | 55 |
| Cr (Chromium) | 17 | 21 |
| Fe (Iron) | 13 | 19 |
| Nb (Niobium) | 4.75 | 5.5 |
| Mo (Molybdenum) | 2.8 | 3.3 |
| Ti (Titanium) | 0.65 | 1.15 |
| Al (Aluminum) | 0.2 | 0.8 |
| C (Carbon) | — | 0.08 |
Mechanical Properties
| Property | Value | Condition |
|---|---|---|
| Tensile Strength | ≥ 1275 MPa (185 ksi) | aged |
| Yield Strength (0.2%) | ≥ 1034 MPa (150 ksi) | aged |
| Elongation | ≥ 12% | aged |
| Hardness | ≥ 36 HRC | aged |
| Density | 8.19 g/cm³ | — |
Physical Properties
| Property | Value |
|---|---|
| Melting Range | 1260 – 1335 °C |
| Thermal Conductivity | 11.4 W/m·K (at 23°C) |
| Max Service Temp | 700°C (strength-limited) |
Corrosion Resistance
Good general corrosion resistance in many environments, including oxidizing acids and chloride-containing media. Excellent resistance to sulfide stress cracking in sour service (NACE MR0175 compliant). Good performance in seawater but susceptible to crevice corrosion under stagnant conditions. Not as corrosion-resistant as C-276 or 625 — strength is the primary selection criterion.
Typical Applications
Related Standards
Available Products in This Material
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