Seamless Inconel 718 Pipe (UNS N07718) – High-Performance Nickel Alloy Solution
On this page:Overview · Key Advantages · Specifications · Applications · Quality & Certification
Size Range: OD 6–457 mm · WT 0.6–35 mm
Overview of Seamless Inconel 718 Pipe
Seamless Inconel 718 pipe (UNS N07718) is a high-performance, precipitation-hardenable nickel-based superalloy pipe manufactured from a solid billet through a seamless process. Unlike welded pipes, seamless manufacture eliminates the longitudinal manufacturing weld seam; pressure capability and service life depend on dimensions, material condition, inspection acceptance criteria, the design code and operating conditions.
Designed for extreme environments, Inconel 718 offers good resistance to oxidation and corrosion with useful mechanical properties from cryogenic conditions up to about 704 °C (reference service temperature); elevated-temperature design values must come from the applicable design code.
Strength comes mainly from strengthening precipitates formed during controlled ageing (solution treatment plus age hardening); properties depend on the specified delivery condition. This makes it a preferred material in aerospace, subsea oil & gas, and nuclear industries.
Key Features and Technical Advantages
- High Strength & Creep Resistance
Precipitation hardening provides exceptional tensile and yield strength; wall-thickness optimization must be confirmed by the applicable design code (corrosion allowance, buckling, fatigue). - Excellent Corrosion Resistance
Good resistance to chloride-induced SCC, pitting and crevice corrosion. H₂S (sour) service suitability is not automatic — it requires review of the applicable requirements (e.g. NACE MR0175 / ISO 15156-3), the material condition, hardness limits and the actual environment. - Outstanding Thermal Stability
Mechanical properties are maintained from cryogenic temperatures up to about 704 °C (reference service temperature); high-temperature design values must come from the applicable design code, not the room-temperature table. - Dimensional Requirements (ASTM B829 general requirements + ordered standard)
Tolerances follow ASTM B829 and the ordered product specification — B829 is a common-requirements standard, not a pressure rating. - Good Weldability
Compared to other precipitation-hardening alloys, Inconel 718 exhibits strong resistance to post-weld cracking.
Product Specifications and Data
To provide a comprehensive overview of this high-performance material, here are the detailed technical specifications and performance data for Inconel 718 .
Equivalent Grade
| UNS | Common grade name | EN material number | EN steel name | JIS grade | GB/T grade |
|---|---|---|---|---|---|
| N07718 | Inconel 718 | 2.4668 | NiCr19Fe19Nb5Mo3 | – | NS4301 / GH4169 |
Grade correspondence does not make ASTM, ASME, EN, JIS and GB delivery requirements interchangeable. Confirm chemistry, heat treatment, mechanical properties, dimensions, testing and certification against the purchase specification. See the grade designation index.
Chemical Composition
The composition of Inconel 718 is carefully balanced to achieve its superior strength and corrosion resistance.
| Ni | Cr | Fe | Mn | Nb | Mo | Ti | C | Si | S | P | Co | B | Al | Cu |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 50.0-55.0 | 17.00-21.00 | Bal | ≤0.35 | 4.75-5.50 | 2.80-3.30 | 0.65-1.15 | ≤0.08 | ≤0.35 | ≤0.015 | ≤0.015 | ≤1.0 | ≤0.006 | 0.20-0.80 | ≤0.30 |
Source: SAE AMS 5589G, Table 1 (composition of the 718 seamless-tubing alloy, similar to UNS N07718), consistent with published ASTM B637 limits for UNS N07718. Single values are maximum content unless a range is shown. Aluminium 0.20–0.80 % and copper ≤ 0.30 % are included; iron is determined arithmetically by difference.
Mechanical Properties (Specification Limits)
Inconel 718 is specifically designed to maintain its strength and shape in high-stress, corrosive environments.
| Condition (AMS 5589 / ASTM B637 route) | Tensile Strength, min | Yield Strength (0.2% offset), min | Elongation in 50 mm (2 in.), min | Hardness |
|---|---|---|---|---|
| Solution heat treated (delivery condition) | 1069 MPa (155 ksi) max | 655 MPa (95 ksi) max | 30 % | — |
| Solution treated + precipitation hardened | 1276 MPa (185 ksi) | 1034 MPa (150 ksi) | 12 % | ≥ 36 HRC |
Source: SAE AMS 5589G (Nickel Alloy, Corrosion and Heat-Resistant, Seamless Tubing — 52.5Ni-19Cr-3.0Mo-5.1Cb(Nb)-0.90Ti-0.50Al-18Fe, composition similar to UNS N07718), Table 2 and Table 3. The solution heat treated condition carries maximum tensile/yield limits of 155 ksi (1069 MPa) / 95 ksi (655 MPa) with 30 % elongation minimum; after precipitation hardening the minimums are 185 ksi (1276 MPa) / 150 ksi (1034 MPa) with 12 % elongation minimum and hardness not lower than 36 HRC. ASTM B983 does not cover Alloy 718 — it is a specification for precipitation-hardening cobalt-containing alloys; it has been removed from this page. 718 pipe/tube is normally ordered to AMS 5589 (aerospace tubing) or, for bar and forgings, ASTM B637 / AMS 5662. Precipitation heat treatment: 718 ± 8 °C (1325 ± 15 °F) for 8 h, furnace cool to 621 ± 8 °C (1150 ± 15 °F), hold to 18 h total, air cool.
Physical Properties (Reference)
These physical properties highlight the material’s ability to perform reliably under a wide range of conditions.
| Density | Melting Point | Thermal Expansion | Thermal Conductivity | Modulus of Elasticity | Electrical Resistivity |
|---|---|---|---|---|---|
| 8.22 g/cm³ | 1260 – 1336 °C | 13.0 μm/(m·°C) (20–100 °C) | 11.4 W/(m·K) (20 °C) | 200 GPa | 1.20 × 10-6 Ω·m (20 °C) |
Size Tolerance Chart (mm)
Cold-Finished Pipes and Tubes:
| Specified/Calculated Nominal OD (Inches) | Permissible Variation (Inches) | Specified/Calculated Nominal OD (mm) | Permissible Variation (mm) |
|---|---|---|---|
| 0.500 to 5⁄8, excl. | ±0.005 | 12.7 to 15.8, excl. | ±0.127 |
| 5⁄8 to 1 1⁄2, incl. | ±0.0075 | 15.8 to 38.1, incl. | ±0.190 |
| Over 1 1⁄2 to 3 1⁄2, incl. | ±0.010 | Over 38.1 to 88.9, incl. | ±0.254 |
| Over 3 1⁄2 to 4 1⁄2, incl. | ±0.015 | Over 88.9 to 114.3, incl. | ±0.381 |
| Over 4 1⁄2 to 6, incl. | ±0.020 | Over 114.3 to 152.4, incl. | ±0.508 |
| Over 6 to 6 5⁄8, incl. | ±0.025 | Over 152.4 to 168.3, incl. | ±0.635 |
| Specified/Calculated Nominal OD (Inches) | Permissible Variation (Inches) | Specified/Calculated Nominal OD (mm) | Permissible Variation (mm) |
|---|---|---|---|
| 2 1⁄2 to 5 1⁄2, excl. | ±0.031 | 63.5 to 139.7, excl. | ±0.787 |
| 5 1⁄2 to 9 1⁄4, incl. | ±0.047 | 139.7 to 234.9, incl. | ±1.19 |
| Condition | Specified/Calculated Nominal OD (Inches) | Permissible Variation (Wall Thickness) |
|---|---|---|
| Cold-Finished | 0.500 to 5⁄8, excl. | ±15.0% |
| 5⁄8 to 4 1⁄2, incl. | ±10.0% | |
| Over 4 1⁄2 to 6 5⁄8, incl. | ±12.5% | |
| Hot-Finished | 2 1⁄2 to 9 1⁄4, incl. | ±12.5% |
Common Industrial Applications
Seamless Inconel 718 pipes are widely used in demanding industries requiring high strength and corrosion resistance:
Aerospace & Defense
Jet engine components, fuel lines, rocket engine systems
Oil & Gas (Upstream & Subsea)
Downhole tools, wellhead equipment, subsea control systems, sour gas service
Nuclear Power
Reactor components, high-strength fasteners, pressure systems
Chemical Processing
Heat exchangers, reactors, and piping systems handling aggressive media
Quality Assurance & Certification
Inspection and documentation are defined by the ordered specification and the agreed inspection plan. The quotation will identify included tests, acceptance criteria and inspection documents.
- Defined by the ordered specification
e.g. hydrostatic or non-destructive electric testing, tensile and hardness tests as required, with EN 10204 3.1 mill test certificate and heat-number traceability - Confirmed in the quotation (optional)
additional PMI, ultrasonic / eddy-current testing with agreed acceptance criteria, impact, flattening / flaring or intergranular corrosion testing, EN 10204 3.2 documentation - Coordinated in advance
third-party inspection or witnessing by recognized agencies (e.g. ABS, DNV, BV, TÜV, Lloyd’s Register)
Additional PMI, ultrasonic testing, third-party witnessing or EN 10204 3.2 documentation must be agreed before order placement.
Need tubing specified by actual outside diameter and wall thickness? See our Inconel 718 seamless tube range.
Ready to Request a Quotation?
Send the NPS and schedule (or actual OD and wall), quantity, length, end finish and the inspection items you need as acceptance criteria — you will get a written quotation stating the specification and edition, delivery condition, documents included and lead time.
