On this page 13 sections
What is Inconel 718?
Quick answer
- Definition
- Inconel 718 (Alloy 718, UNS N07718) is a precipitation-hardenable nickel-chromium-iron alloy with very high yield, tensile and creep-rupture strength up to about 650 °C.
- Family
- Nickel-chromium (Ni-Cr) alloy
- Key strength
- Age-hardenable: yield strength above 1,000 MPa
- Main forms
- Pipes, Tubes, Plates, Sheets, Bars, Flanges
- Typical uses
- Aero-engine discs, shafts and casings; Oil and gas downhole tools and hangers; Wellhead and valve components (API 6A718)
Alloy 718 is strengthened by niobium-rich gamma-double-prime precipitates that form during ageing. Its slow ageing response means it can be welded and annealed without spontaneous hardening, which made it the most widely used superalloy for aero-engine discs, shafts and casings.
Outside aerospace, 718 is used for oil and gas completion tools, wellhead and valve components (API 6A718), high-strength bolting and cryogenic tankage. Most supply is bar, forgings and sheet to AMS or API specifications. Always specify the heat-treatment condition (solution-annealed, or solution-treated and aged).
Key characteristics
- Age-hardenable: yield strength above 1,000 MPa
- Excellent creep and fatigue strength to about 650 °C
- Weldable without strain-age cracking
- Mainly bar, forgings and sheet (AMS / API 6A718)
What are the specifications and equivalents of Inconel 718?
| Product form | Specification / designation | Product page |
|---|---|---|
| Pipes | To order (AMS / customer specification) | Inconel 718 pipes → |
| Tubes | AMS 5589 / 5590 | Inconel 718 tubes → |
| Plates | AMS 5596 / ASTM B670 | Inconel 718 plates → |
| Sheets | AMS 5596 / 5597 | Inconel 718 sheets → |
| Bars | ASTM B637 / AMS 5662 / 5663 / API 6A718 | Inconel 718 bars → |
| Flanges | ASTM B637 forgings | Inconel 718 flanges → |
| Bolts | ASTM B637 / AMS 5662 | Inconel 718 bolts → |
| Nuts | ASTM B637 | Inconel 718 nuts → |
| Washers | AMS 5596 | Inconel 718 washers → |
UNS N07718 · EN 2.4668 (cross-reference; limits are similar but not identical) · Inconel® is a trademark of Special Metals Corporation; generic material is supplied to the specification on your order.
What is the chemical composition of Inconel 718?
| Element | Limit (%) |
|---|---|
| Ni | 50.0 – 55.0 |
| Cr | 17.0 – 21.0 |
| Nb + Ta | 4.75 – 5.50 |
| Mo | 2.80 – 3.30 |
| Ti | 0.65 – 1.15 |
| Al | 0.20 – 0.80 |
| Co | 1.00 max |
| C | 0.08 max |
| Fe | Balance |
What are the mechanical properties of Inconel 718?
| Property | Value |
|---|---|
| Tensile strength | 1,275 MPa (185 ksi) |
| Yield strength (0.2% offset) | 1,034 MPa (150 ksi) |
| Elongation | 12% |
| Hardness | ≈ 36 HRC min |
Physical properties and service temperature
| Property | Value |
|---|---|
| Density (typical) | 8.19 g/cm³ (8190 kg/m³) |
| Magnetism | Non-magnetic. |
| Heat treatment | Supplied annealed or solution annealed, and age-hardened when specified. |
| Service temperature | High strength to about 650 °C; also excellent at cryogenic temperatures. |
How is Inconel 718 welded and fabricated?
Weldable by TIG, MIG and SMAW with matching or over-alloyed nickel fillers. Keep surfaces clean of sulphur and low-melting contaminants.
Always follow a qualified welding procedure (for example ASME Section IX) and the filler-metal recommendations for Inconel 718. Verify incoming material by PMI and check the mill test certificate against the specification.
Which Inconel 718 products do we supply?
Inconel 718 is available in 9 product forms, from ready stock or mill-sourced to your specification, with EN 10204 3.1 mill test certificates (3.2 with third-party inspection on request).
Inconel 718 PipesTo orderSpecification & sizes
How it's madeSeamless pipe is pierced from a solid billet and hot-finished or cold-drawn. Welded pipe is formed from strip or plate and welded longitudinally (ERW/HFW, TIG/plasma, EFW, LSAW) or spirally (SAWH). Stainless and nickel-alloy pipe is then solution annealed and pickled. Carbon and alloy steel pipe is supplied as-rolled, normalised, or normalised and tempered according to the specification.
- Specification
- To order (AMS / customer specification)
- Size range
- NPS ⅛" to 48" and larger (DN 6 – DN 1200+), schedules 5S to XXS, single random, double random and cut lengths
- Finish
- Annealed & pickled, bright annealed, mill finish, black, varnished, galvanised or 3LPE / FBE coated (by material)
- Ends
- Plain end (PE), bevelled end (BE, ASME B16.25), threaded (NPT / BSP), grooved
Testing & documents
- Chemical and mechanical (tension, flattening, flare/bend) tests
- Hydrostatic test or non-destructive electric test (UT/ET) on each length
- Dimensional and visual inspection
- Intergranular corrosion (stainless), impact (low-temperature), hardness (sour service) when specified
- PMI and third-party inspection on request
- EN 10204 3.1 certificate; 3.2 with third-party inspection
Inconel 718 TubesAMS 5589 / 5590Specification & sizes
How it's madeSeamless tubes are hot-extruded or pierced and then cold-drawn or pilgered to size. Welded tubes are formed from strip, welded (TIG/laser/HF), bead-worked and drawn or sized. Heat-exchanger and boiler tubes are annealed after final forming, and U-tubes are bent and stress-relieved as required.
- Specification
- AMS 5589 / 5590
- Size range
- OD 3 mm to about 127 mm (¼" to 5") typical, wall 0.5 mm to 12 mm; BWG or mm; straight lengths up to about 30 m, U-bent to drawing
- Finish
- Annealed & pickled, bright annealed (BA), polished (sanitary), cold-drawn
- Ends
- Plain square-cut, deburred; U-bends with stress-relieved bends on request
Testing & documents
- Eddy-current and/or ultrasonic testing on each tube
- Hydrostatic or pneumatic test
- Flattening, flaring and flange tests
- Grain size (H grades), IGC and hardness when specified
- Surface roughness (Ra) for sanitary and instrumentation tube
- EN 10204 3.1 certificate; 3.2 with third-party inspection
Inconel 718 PlatesAMS 5596 / ASTM B670Specification & sizes
How it's madeSlabs are hot-rolled on a reversing plate mill (or a Steckel/hot-strip mill for thinner plate), then heat treated (annealed, normalised, or quenched and tempered, depending on material), descaled and pickled or shot-blasted. Plates are cut to size by plasma, oxy-fuel, waterjet or shearing.
- Specification
- AMS 5596 / ASTM B670
- Size range
- Thickness about 3 – 150 mm (and heavier on request), widths 1,000 – 3,000 mm, lengths 2,000 – 12,000 mm; cut-to-size and profile-cut parts
- Finish
- No.1 (hot-rolled, annealed and pickled) for stainless; shot-blasted, mill scale or primed for carbon steel
- Ends
- Mill edge, sheared, plasma or waterjet cut, profile cut to drawing
Testing & documents
- Chemical analysis and tensile tests (per plate or heat)
- Impact tests for low-temperature and pressure-vessel plates
- Ultrasonic testing (e.g. ASTM A435 / A578) when specified
- IGC, HIC and simulated PWHT tests as required
- Flatness and dimensional inspection
- EN 10204 3.1 certificate; 3.2 with third-party inspection
Inconel 718 SheetsAMS 5596 / 5597Specification & sizes
How it's madeHot-rolled coil is cold-rolled to final thickness, then annealed and pickled (2B/2D) or bright annealed (BA), temper-passed, and polished or textured as needed. Coils are then levelled and cut into sheets.
- Specification
- AMS 5596 / 5597
- Size range
- Thickness about 0.3 – 6 mm, standard sizes 1,000 × 2,000, 1,219 × 2,438 (4 × 8 ft), 1,250 × 2,500 and 1,500 × 3,000 mm; custom cut lengths
- Finish
- 2B, 2D, BA, No.4 (brushed), HL (hairline), No.8 (mirror), embossed, PVC or laser-film protected
- Ends
- Sheared or slit edges; laser-cut blanks on request
Testing & documents
- Chemical and mechanical tests
- Surface and finish inspection
- Thickness and flatness checks
- Hardness and bend tests as specified
- EN 10204 3.1 certificate; 3.2 with third-party inspection
Inconel 718 BarsASTM B637 / AMS 5662 / 5663 / API 6A718Specification & sizes
How it's madeBillets are hot-rolled or forged to size, then heat treated (annealed, solution treated, or quenched and tempered) and finished by descaling, peeling, turning, cold-drawing or centreless grinding for bright bar with tight tolerance.
- Specification
- ASTM B637 / AMS 5662 / 5663 / API 6A718
- Size range
- Round bars about 3 – 500 mm diameter; hex 6 – 100 mm A/F; square and flat sections to order; lengths 3 – 6 m random or cut to size
- Finish
- Black (hot-rolled), peeled, bright drawn, centreless ground and polished (h9 / h11 tolerance)
- Ends
- Saw-cut, chamfered on request
Testing & documents
- Chemical and mechanical tests
- Ultrasonic testing for internal soundness
- Hardness, IGC and impact tests as specified
- Straightness and tolerance checks
- EN 10204 3.1 certificate; 3.2 with third-party inspection
Inconel 718 FlangesASTM B637 forgingsSpecification & sizes
How it's madeFlanges are forged from billets (or cut from plate for some blind and plate flanges), heat treated to the material specification, and machined: bore, face, raised face or ring groove, bolt holes and hub bevel.
- Specification
- ASTM B637 forgings
- Size range
- NPS ½" – 24" (B16.5), 26" – 60" (B16.47 Series A/B); Class 150, 300, 600, 900, 1500, 2500; EN 1092-1 PN 6 – PN 100 on request
- Finish
- Raised face (RF), flat face (FF) or ring-type joint (RTJ); serrated spiral or concentric face finish (typically 3.2 – 6.3 µm Ra)
- Ends
- Weld-neck bevel matched to pipe schedule; socket bore; threaded
Testing & documents
- Chemical and mechanical tests of the forging
- Dimensional inspection to ASME B16.5 / B16.47
- Hardness, impact and IGC tests as specified
- Ultrasonic testing of forgings on request
- EN 10204 3.1 certificate; 3.2 with third-party inspection
Inconel 718 BoltsASTM B637 / AMS 5662Specification & sizes
How it's madeCut from heat-treated bar (or forged and heat treated), then threaded by rolling or cutting, and coated if required.
- Specification
- ASTM B637 / AMS 5662
- Size range
- M6 – M100 and ¼" – 4" (larger on request); lengths to flange tables or drawing
- Finish
- Plain, black oxide, zinc, hot-dip galvanised, PTFE-based fluoropolymer, zinc-nickel
- Ends
- Chamfered points; full or partial thread
Testing & documents
- Chemical and mechanical tests of bar and finished bolts
- Hardness tests
- Proof-load and wedge tests where applicable
- Coating thickness and adhesion
- EN 10204 3.1 certificate; 3.2 with third-party inspection
Inconel 718 NutsASTM B637Specification & sizes
How it's madeHot-forged or cold-formed from bar, heat treated (for hardenable grades), tapped and coated if required.
- Specification
- ASTM B637
- Size range
- M6 – M100 and ¼" – 4"; heavy hex to ASME B18.2.2; metric to ISO 4032 / 4033
- Finish
- Plain, zinc, galvanised (tapped oversize), fluoropolymer
Testing & documents
- Proof-load tests
- Hardness tests
- Chemical analysis
- EN 10204 3.1 certificate; 3.2 with third-party inspection
Inconel 718 WashersAMS 5596Specification & sizes
How it's madeStamped or machined from plate or strip and heat treated where required.
- Specification
- AMS 5596
- Size range
- M6 – M100 and ¼" – 4" bolt sizes
- Finish
- Plain, zinc, galvanised
Testing & documents
- Hardness tests
- Dimensional checks
- EN 10204 3.1 certificate; 3.2 with third-party inspection
Where is Inconel 718 used?
Typical applications
- Aero-engine discs, shafts and casings
- Oil and gas downhole tools and hangers
- Wellhead and valve components (API 6A718)
- High-strength fasteners and springs
- Cryogenic tankage
Where do we supply Inconel 718?
Inconel 718 is regularly requested for projects in these markets:
What should you specify when buying Inconel 718?
- Grade and specification, e.g. To order
- Product form, size and tolerance
- Heat treatment / condition and surface finish
- Quantity, delivery location and required date
- Tests: PMI, hydro/NDT, IGC, impact or hardness as required
- Certificate type (EN 10204 3.1 / 3.2) and third-party inspection
See our RFQ checklist guide and what drives metal prices.
Explore more on Inconel 718
Inconel 718 products
Comparisons & articles
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Frequently asked questions
Is Inconel 718 heat treatable?
Yes. It's solution treated and then aged (typically a two-step age) to develop its high strength.
Inconel 718 vs 625: which is stronger?
Aged 718 is much stronger, with yield above 1,000 MPa against about 400–500 MPa for 625. 625 has better corrosion resistance and weldability.
What is Inconel 718 used for?
Aero-engine discs, shafts and casings, Oil and gas downhole tools and hangers, Wellhead and valve components (API 6A718), High-strength fasteners and springs. It's used across Aerospace, Oil & Gas, Power Generation, Nuclear.
What is the UNS number of Inconel 718?
Inconel 718 is designated UNS N07718; the closest EN cross-reference is 2.4668.
Which product forms is Inconel 718 available in?
Pipes, Tubes, Plates, Sheets, Bars, Flanges, Bolts, Nuts, Washers, to To order, AMS 5589 / 5590, AMS 5596 / ASTM B670 and related specifications.
What is the density of Inconel 718?
About 8.19 g/cm³ (8190 kg/m³), used for weight calculations.
Is Inconel 718 magnetic?
Non-magnetic.
What temperature can Inconel 718 withstand?
High strength to about 650 °C; also excellent at cryogenic temperatures.