Inconel 718 · UNS N07718 · W. Nr. 2.4668 · GH4169 · NiCr19NbMo
Inconel 718 (N07718): composition, properties, fittings and flanges
Inconel 718 (UNS N07718, W. Nr. 2.4668, Chinese GH4169) is the most widely used precipitation-hardening nickel-based superalloy and accounts for roughly a third of all superalloy tonnage produced worldwide. Its nominal chemistry is 50-55 % nickel, 17-21 % chromium, 2.8-3.3 % molybdenum, 4.75-5.5 % niobium plus tantalum, with…
- UNS
- N07718
- W. Nr.
- 2.4668
- Density
- 8.19 g/cm³ (0.296 lb/in³)
- Key strength
- 1275 MPa / 185 ksi
Identification and standards
| Short form | Inconel 718 · UNS N07718 · W. Nr. 2.4668 · GH4169 · NiCr19NbMo |
|---|---|
| Classification | Precipitation-hardenable nickel-chromium-iron superalloy (gamma prime / gamma double prime) |
| UNS | N07718 |
| Werkstoff number | 2.4668 |
| Material family | Inconel Alloys |
Chemical composition
| Element | Composition (wt %) | Why it is there |
|---|---|---|
| Nickel (Ni) | 50.0 - 55.0 | Austenitic matrix former |
| Chromium (Cr) | 17.0 - 21.0 | Oxidation and hot corrosion resistance |
| Iron (Fe) | Balance | Cost control without loss of phase stability |
| Niobium + Tantalum (Nb+Ta) | 4.75 - 5.50 | Forms gamma double prime Ni3Nb, the main strengthening precipitate |
| Molybdenum (Mo) | 2.80 - 3.30 | Solid-solution strengthening, pitting resistance |
| Titanium (Ti) | 0.65 - 1.15 | Forms gamma prime Ni3(Al,Ti) |
| Aluminium (Al) | 0.20 - 0.80 | Forms gamma prime, improves oxidation resistance |
| Cobalt (Co) | 1.00 max | - |
| Carbon (C) | 0.08 max | - |
| Manganese (Mn) | 0.35 max | - |
| Silicon (Si) | 0.35 max | - |
| Copper (Cu) | 0.30 max | - |
| Boron (B) | 0.006 max | Grain boundary strengthening |
| Phosphorus (P) | 0.015 max | - |
| Sulphur (S) | 0.015 max | - |
Note Single figures are maximum limits unless shown as a range. Always confirm against the heat-specific EN 10204 3.1 certificate supplied with your order.
Mechanical properties
| Tensile strength, min (solution treated + aged bar, ASTM B637) | 1275 MPa / 185 ksi |
|---|---|
| 0.2 % yield strength, min | 1035 MPa / 150 ksi |
| Elongation in 4D, min | 12 % |
| Reduction of area, min | 15 % |
| Typical hardness after ageing | 331 - 401 HB (about 36 - 42 HRC) |
| Typical impact energy at -196 °C | 40 - 60 J |
| Useful temperature range | -253 °C to 650 °C (strength), to 980 °C (oxidation) |
Warning Values depend on product form, section thickness and heat treatment. Larger sections generally achieve lower strength than thin product; always design against the applicable code allowable stress rather than these figures.
Physical properties
| Density | 8.19 g/cm³ (0.296 lb/in³) |
|---|---|
| Melting range | 1260 - 1340 °C (2300 - 2444 °F) |
| Modulus of elasticity | 200 GPa (29 x 10⁶ psi) |
| Thermal conductivity at 20 °C | 11.4 W/m·K |
| Mean coefficient of thermal expansion, 20-100 °C | 13.0 µm/m·°C |
| Specific heat capacity | 435 J/kg·K |
| Electrical resistivity at 20 °C | 1.26 µΩ·m |
Specifications by product form
| Bar / rod / forgings | ASTM B637 / ASME SB-637, AMS 5662, AMS 5663, API 6A 718 |
|---|---|
| Plate / sheet / strip | ASTM B670 / ASME SB-670, AMS 5596, AMS 5597 |
| Seamless pipe & tube | ASTM B983, AMS 5589 / 5590 (hydraulic tubing) |
| Forgings & flanges | ASTM B637, ASTM B564 by agreement, API 6A / 17D |
| Butt weld fittings | ASTM B366 (WP718) where applicable; often machined from bar or forging |
| Fasteners | AMS 5662 with cold work before ageing |
| Welding consumables | ERNiFeCr-2 wire (AWS A5.14), ENiFeCr-2 electrode |
| UNS / EN / China | UNS N07718 · EN NiCr19NbMo · W. Nr. 2.4668 · GB GH4169 |
Product forms available
Hangbo supplies this grade in the following forms. Sizes outside the listed range can often be produced to order.
- Forged discs, rings, blocks, turbine discs and step shafts
- Bolting and fasteners (hot or cold worked before ageing)
- Seamless tube and hydraulic tubing to AMS 5589 / 5590
- Machined components produced to customer drawing
- Fittings and flanges to customer drawing or API specification
Typical applications
- Aero-engine turbine discs, shafts, blades, casings and thrust reversers
- Land-based gas turbine hot section components
- Rocket motors, turbopump impellers and cryogenic tankage hardware
- Oil and gas wellhead equipment, tubing hangers, gate valves, Christmas trees (API 6A)
- Downhole tools, MWD/LWD collars and perforating gun carriers
- Cryogenic tank supports and superconducting magnet structures
- Nuclear reactor core internals and steam generator supports
Welding, forming and machining
- Heat treatment
- Standard practice per AMS 5662 is solution anneal at 955-1010 °C for one hour then oil, water or air cool, followed by ageing at 720 °C for 8 hours, furnace cool at 55 °C/h to 620 °C, hold 8 hours, then air cool - roughly 18 hours total. Direct-age variants exist for oil patch requirements.
- Welding
- Weld in the solution annealed or over-aged condition, then age the completed assembly with standard ERNiFeCr-2 filler. Electron beam and inertia friction welding are used for rotating parts. Avoid post-weld stress relief in the 595-815 °C band, which promotes strain-age cracking.
- Hot forming
- Hot work between 1120 °C and 900 °C with adequate reduction to break up the as-cast structure; forgings are finish forged near 980 °C to refine grain size.
- Machining
- Machine in the solution treated or over-aged condition where possible for best tool life. The fully aged condition produces higher cutting forces and tool wear but better surface finish.
Buy Inconel 718 from Hangbo
Material is supplied with full heat-number traceability, solution annealing or ageing performed under calibrated furnace control, and an EN 10204 3.1 certificate covering chemical analysis, mechanical properties, heat treatment records and the agreed NDT scope. Positive material identification and third party inspection and test reports from SGS are available for critical service.
Inconel 718 frequently asked questions
Is GH4169 the same as Inconel 718?
GH4169 is the Chinese GB designation for the UNS N07718 composition. Chemistry limits, heat treatment window and mechanical properties are equivalent, so GH4169 forgings and bar can generally substitute for Inconel 718 as long as the governing standard is stated on the order and shown on the EN 10204 3.1 certificate.
Why is Inconel 718 preferred over Inconel 625 for wellhead equipment?
Ageing roughly doubles the yield strength - 1035 MPa against 414 MPa - allowing smaller, lighter pressure-containing parts while retaining NACE MR0175 sour service qualification at high strength levels.
Can Inconel 718 be welded without cracking?
Yes, far more readily than most age-hardenable superalloys. The gamma double prime phase forms slowly enough that the heat affected zone relaxes stress instead of cracking. Standard practice is to weld in the solution annealed condition and carry out the 720 / 620 °C double age afterwards.
What hardness is Inconel 718 supplied at?
Typical aged hardness is 331-401 HB, about 36-42 HRC. For NACE MR0175 sour service, API 6A 718 is commonly limited to a maximum of 40 HRC, controlled through solution temperature and ageing parameters.
What is the maximum service temperature for Inconel 718?
It retains useful creep strength to about 650 °C and oxidation resistance to roughly 980 °C. Above 650 °C the gamma double prime phase coarsens and strength falls away quickly, at which point Inconel 625, 718Plus or Nimonic grades are considered.
Do you offer alternative melt routes for Inconel 718?
Yes. Hangbo supplies VIM+ESR and, for rotating aerospace parts, triple melted VIM+ESR+VAR material with documented cleanliness control and full traceability from melt to finished component.