Alloy 718
Also known as Inconel® 718, Nickelvac 718, UNS N07718, Werkstoff 2.4668
Alloy 718 is a precipitation-hardened nickel-chromium superalloy that keeps high strength and corrosion resistance to about 750°C.
Alloy 718 combines high tensile, fatigue and creep strength with acceptable corrosion resistance, and stays workable and weldable thanks to a slow age-hardening response.
We supply it in the solution-treated or age-hardened condition. We stock bar in the UK and USA; plate, tube and fittings are available on enquiry, with forgings and castings to order.
- High strength from cryogenic temperatures to about 750 C
- Excellent creep-rupture and fatigue properties
- Good resistance to pitting, crevice corrosion and oxidation
- Outstanding weldability with low risk of post-weld cracking
- Readily age-hardened to high hardness
| Element | Min | Max |
|---|---|---|
| Chromium (Cr) | 17.00 | 21.00 |
| Nickel (Ni) | 50.00 | 55.00 |
| Molybdenum (Mo) | 2.80 | 3.30 |
| Cobalt (Co) | - | 1.00 |
| Niobium (Nb+Ta) | 4.70 | 5.50 |
| Titanium (Ti) | 0.65 | 1.15 |
| Copper (Cu) | - | 0.30 |
| Carbon (C) | - | 0.08 |
| Manganese (Mn) | - | 0.35 |
| Silicon (Si) | - | 0.35 |
| Phosphorus (P) | - | 0.015 |
| Sulphur (S) | - | 0.015 |
| Aluminium (Al) | 0.20 | 0.80 |
| Iron (Fe) | Bal | |
| Boron (B) | - | <0.006 |
| Calcium (Ca) | - | <0.003 |
| Magnesium (Mg) | - | <0.006 |
| Lead (Pb) | - | <0.005 |
| Selenium (Se) | - | <0.0003 |
| Bismuth (Bi) | - | <0.00003 |
| Property | Imperial | Metric |
|---|---|---|
| 0.2% Proof stress (min) | 125 ksi | 827 N/mm² |
| 0.2% Proof stress (max) | 145 ksi | 1000 N/mm² |
| Tensile strength (min) | 150 ksi | 1034 N/mm² |
| Elongation | 20% | 20% |
| Reduction of area | 35% | 35% |
| Hardness | 32-40 HRC | 32-40 HRC |
| Impact, Charpy V-notch (-60°C, longitudinal, <3in) | 50 ft·lb avg (45 min) | 68 J avg (61 J min) |
| Impact, Charpy V-notch (-60°C, transverse, ≥3-10in) | 35 ft·lb avg (30 min) | 47 J avg (41 J min) |
| Property | Imperial | Metric |
|---|---|---|
| 0.2% Proof stress (min) | 125 ksi | 827 N/mm² |
| 0.2% Proof stress (max) | 145 ksi | 1000 N/mm² |
| Tensile strength (min) | 150 ksi | 1034 N/mm² |
| Elongation | 20% | 20% |
| Reduction of area | 25% | 25% |
| Hardness | 32-40 HRC | 32-40 HRC |
| Impact, Charpy V-notch (-60°C, transverse, ≥3-10in) | 30 ft·lb avg (27 min) | 41 J avg (37 J min) |
| Property | Imperial | Metric |
|---|---|---|
| 0.2% Proof stress (min) | 140 ksi | 965 N/mm² |
| 0.2% Proof stress (max) | 150 ksi | 1034 N/mm² |
| Tensile strength (min) | 165 ksi | 1138 N/mm² |
| Elongation | 20% | 20% |
| Reduction of area | 35% | 35% |
| Hardness | 34-40 HRC | 34-40 HRC |
| Impact, Charpy V-notch (-60°C, longitudinal, <3in) | 50 ft·lb avg (45 min) | 68 J avg (61 J min) |
| Impact, Charpy V-notch (-60°C, transverse, ≥3-10in) | 35 ft·lb avg (30 min) | 47 J avg (41 J min) |
| Property | Imperial | Metric |
|---|---|---|
| 0.2% Proof stress (min) | 140 ksi | 965 N/mm² |
| 0.2% Proof stress (max) | 150 ksi | 1034 N/mm² |
| Tensile strength (min) | 160 ksi | 1103 N/mm² |
| Elongation | 20% | 20% |
| Reduction of area | 25% | 25% |
| Hardness | 34-40 HRC | 34-40 HRC |
| Impact, Charpy V-notch (-60°C, transverse, ≥3-10in) | 30 ft·lb avg (27 min) | 41 J avg (37 J min) |
| Property | Value |
|---|---|
| Density (kg/m³) | 8230 |
| Magnetic permeability (20°C) | <1.002 |
| Young's modulus (kN/mm²) | 200 |
| Specific electrical resistance, 20°C (µΩ-m) | 1.25 |
| Mean coefficient of thermal expansion, 20-100°C (m/m/°C) | 12.1 x 10-6 |
| Specific heat, 20°C (J/kg.K) | 435 |
| Thermal conductivity, 20°C (W/m.K) | 11.1 |
| Curie temperature (°C) | -112 (aged) |
Alloy 718 was developed by the International Nickel Company in the late 1950s and introduced in the early 1960s. Its advance was a niobium-strengthened precipitation response slow enough to allow welding without the cracking that affected earlier nickel superalloys.
It became the workhorse of the gas-turbine and oil and gas industries, and remains the most-produced nickel superalloy today.
Equivalents & cross-references
Standard designations
- UNS
- N07718Unified Numbering System
- Werkstoff
- 2.4668German/European material number
- ASTM
- B637Bar, rod and wire
- AMS
- 5662Bar, rod and wire - annealed 5663Bar, rod and wire - precipitation hardened
- NACE
- MR0175 / ISO 15156Sour service
- API
- 6ACRACorrosion-resistant alloy
Alloy 718 is also designated UNS N07718, Werkstoff 2.4668, ASTM B637, AMS 5662, AMS 5663, NACE MR0175 / ISO 15156 and API 6ACRA.
Trade name equivalents
-
Inconel 718
Special Metals Corporation
Inconel 718 is a trade name of Special Metals Corporation for Alloy 718.
-
Nickelvac 718
ATI Allvac (ATI)
Nickelvac 718 is a trade name of ATI Allvac (ATI) for Alloy 718.
Common questions
What is the UNS number for Alloy 718?
Alloy 718 is a high-strength, corrosion-resistant nickel-chromium alloy covered by UNS N07718, ASTM B637, AMS 5662, AMS 5663 and Werkstoff No. 2.4668, and is listed in NACE MR0175/ISO 15156 and API 6A CRA. It is supplied in the hot worked, solution annealed and age hardened condition, with niobium, titanium, aluminium and nickel forming precipitates that give significantly higher strength and hardness than alternative nickel alloys. Langley Alloys stocks it as bar; plate, tube and fittings are available on enquiry, and forgings and castings are to order.
What is Alloy 718 used for?
Alloy 718 is used for oil and gas wellhead components, gate valves, choke stems, fasteners, packers, clamps, tubing hangers and downhole equipment; power generation fasteners and turbines; aerospace components; and nuclear power plant containment vessels and valves. It is suited to engineering applications between cryogenic temperatures and 750°C.
Is Alloy 718 suitable for sour service?
Yes. Alloy 718 offers acceptable corrosion resistance in environments including seawater, hydrogen sulphide, CO2, elemental sulphur and chloride ions, and is resistant to sulphide stress cracking, capable of passing the test to NACE TM0177 Method C Solution A. It is supplied to meet both NACE MR0175 and API 6A standards, combining resistance to stress corrosion cracking with high strength, high creep resistance and weldability. It is non-magnetic and spark resistant.
Over what temperature range can Alloy 718 be used?
Alloy 718 maintains its tensile and creep rupture properties from cryogenic to elevated temperatures, making it suitable for applications between -250°C and 750°C. It offers good strength and ductility from sub-zero temperatures to over 760°C and retains high fatigue strength in seawater. It is supplied in age hardened 120 ksi and 140 ksi conditions.
What is Inconel 718?
Inconel 718 is a registered trade name of Special Metals Corporation for UNS N07718, a precipitation-hardened nickel-chromium alloy. Langley Alloys stocks this alloy as Alloy 718 and supplies it to ASTM B637, AMS 5662 (annealed) and AMS 5663 (precipitation hardened).
Is Nickelvac 718 the same as Alloy 718?
Yes. Nickelvac 718 is a trade name used by ATI Allvac for UNS N07718, the same precipitation-hardened nickel-chromium alloy that Langley Alloys stocks as Alloy 718 to ASTM B637, AMS 5662, and AMS 5663.
What is the UNS number for Inconel 718?
The UNS number for Inconel 718 is N07718. It is also designated Werkstoff No. 2.4668, AMS 5662/5663, and ASTM B637, and is listed in NACE MR0175/ISO 15156 and API 6A CRA. Langley Alloys stocks this alloy as Alloy 718.
What is AMS 5663?
AMS 5663 is the SAE aerospace material specification for UNS N07718 (Alloy 718) bar, rod and wire in the precipitation-hardened condition. AMS 5662 covers the same material in the annealed condition. Langley Alloys supplies Alloy 718 to both specifications as well as ASTM B637 and API 6A CRA.
What is the density of Alloy 718?
Alloy 718 has a density of approximately 8.22 g/cm³ (8220 kg/m³).
Is Alloy 718 magnetic?
No. Alloy 718 is non-magnetic.
Datasheets
The vacuum-remelted nickel superalloy
In this Technical Corner, metallurgist Rodney explains Alloy 718: a precipitation-hardening nickel alloy that holds its strength and corrosion resistance from around -250°C to 600°C and beyond.
First developed for aerospace, it is now widely used in oil and gas and chemical processing. High-performance but demanding to machine, it is vacuum-remelted for a clean, high-integrity structure.
Visit our YouTube channelHot worked, solution annealed and age-hardened; each bar ultrasonically tested and visually inspected.
Processing capability
Cutting
CNC sawing at all sites, plus water-jet cutting for plate in the USA. Cut to length and to your sizes.
Cutting servicesInspection & testing
Ultrasonic, dye-penetrant, tensile, Charpy impact and micrographic testing, with 3.2 third-party witness certification.
Inspection & testingHeat treatment
Available heat treated to your specification, with certification, when your application calls for a specific condition.
Added-value processing
Tools for this grade
Sour-service screen (NACE MR0175)
Sour-Service Screen
Work out whether a service is sour from the H2S partial pressure, and see each alloy's NACE MR0175 / ISO 15156 status and hardness limit. A first-pass screen for oil & gas material selection - the full environmental envelope for a grade is set in ISO 15156-3 Annex A.
Candidate grade
| Grade | Family | NACE status | Hardness limit |
|---|
First-pass screen only. This shows whether the service is sour (from H2S partial pressure) and each material group's NACE MR0175 hardness limit and general suitability. It does not reproduce the full environmental windows (maximum H2S partial pressure, temperature, chloride, in-situ pH per grade) - those are in ISO 15156-3 Annex A and must be checked there for the specific grade, product form and condition. Qualification also depends on heat treatment, cold work and welding.
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