Inconel 718 is a high-strength,corrosion-resistant nickel-chromium superalloy designed to perform in extreme environments.It is widely recognized as the “workhorse” of the aerospace and additive manufacturing industries due to its ability to retain its mechanical properties across a massive temperature spectrum,ranging from cryogenic freezing up to 1300°F (704°C).
Key Properties of Inconel 718
Chemical Composition of Inconel 718
| Ni | Cr | Fe | Nb + Ta | Mo |
| 50.0 – 55.0 | 17.0 – 21.0 | Balance | 4.75 – 5.50 | 2.80 – 3.30 |
| Ti | Al | Co | Mn | Si |
| 0.65 – 1.15 | 0.20 – 0.80 | ≤ 1.00 | ≤ 0.35 | ≤ 0.35 |
| Cu | C | P | S | B |
| ≤ 0.30 | ≤ 0.08 | ≤ 0.015 | ≤ 0.015 | ≤ 0.006 |
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Mechanical Properties of Inconel 718
The mechanical properties of Inconel 718 depend heavily on its heat-treatment condition,particularly whether it has undergone precipitation hardening.
In its fully age-hardened state,it displays extremely high tensile, yield, and creep-rupture strengths.Remarkably,it retains these high-performance properties at both cryogenic sub-zero temperatures and elevated temperatures up to 1300°F (704°C).
| Property | Ultimate Tensile Strength | Yield Strength | Elongation | Modulus of Elasticity | Hardness |
| Room Temperature | 1375 MPa 200 ksi | 1100 MPa 160 ksi | 12% – 25% | 200 GPa 29.0 Mpsi | 36 – 44 HRC |
| 650°C (1200°F) | Retains ~ 1100 MPa (160 ksi) | Retains ~ 980 MPa (142 ksi) | Decreases slightly to ~ 18% | Drops to ~ 165 GPa (24.0 Mpsi) | Maintains strong wear resistance |
Applications of Inconel 718 Pipes
Global Equivalent Grades for Inconel 718
| UNS | W.Nr. | EN | GB | JIS | AFNOR | BS |
| N07718 | 2.4668 | NiCr19Fe19Nb5Mo3 | GH4169 GH169 | NCF 718 | NC19FeNb | NA 51 |
Our Manufacturing Capabilities for Alloy 718 Tubes
Cold Drawing & Pilgering
- Capability:
Seamless tube reduction down to micro-diameter and ultra-thin wall specifications. - Technical Detail:
Utilizing multi-pass cold drawing and cold pilgering mills to achieve exceptionally tight dimensional tolerances and a mirror-like inner surface finish.This process refines the grain structure of Alloy 718, eliminating surface defects and boosting the raw fatigue strength required for aerospace hydraulic and fuel lines.
Welding & Cold Working
- Capability:
Automated,high-integrity continuous welding for large-diameter or cost-effective piping solutions. - Technical Detail:
Deploying automated GTAW / TIG or LBW under 100% inert gas shielding to prevent oxidation.
Post-weld,the tubes undergo severe cold working and intermediate annealing to fully recrystallize the weld seam,making the weld zone mechanically and chemically equivalent to the seamless parent metal.
Heat Treatment & Age Hardening
- Capability:
Custom thermal processing to precisely unlock required mechanical tempers. - Technical Detail:
Operating certified high-vacuum furnaces to execute multi-stage solution annealing and two-step precipitation age hardening.This controlled atmosphere prevents alpha-case formation and oxidation,allowing us to deliver tubes either in the soft,formable annealed state or the fully hardened, high-strength state.
NDT & Quality Testing
- Capability:
100% non-destructive inspection to guarantee defect-free lines for high-consequence environments. - Technical Detail:
Our facility is fully equipped for multi-method testing,including ECT for surface integrity,UT for internal volumetric flaws,and hydrostatic pressure testing exceeding 10,000 PSI.We ensure full compliance with critical global standards,delivering certified traceability for aerospace,oil & gas,and commercial industrial contracts.
Can Inconel 718 be welded?
Yes.Unlike most nickel-based superalloys that crack during thermal cycling,Inconel 718 has excellent weldability.This is because its niobium content causes a “sluggish” age-hardening response,allowing it to be welded without spontaneously hardening and cracking during cooling.
Should I choose Seamless or Welded Alloy 718 tubes?
Seamless tubes (manufactured under AMS 5589) offer the highest pressure thresholds and uniform strength,making them ideal for high-vibration aerospace or cryogenic rocket systems.
Welded tubes (manufactured under ASTM B517) are more cost-effective for large-diameter oil and gas pipelines,but they require severe cold working and recrystallization heat treatments to ensure the weld seam matches parent-metal strength.
In what condition are Alloy 718 tubes typically shipped?
They are usually shipped in the solution-annealed state.In this state,the alloy is softer and more ductile,making it significantly easier for fabricators to bend,flare,cut,or weld into the final required geometry.
How does Alloy 718 perform in freezing temperatures?
Exceptionally well.While carbon steels become brittle and shatter under intense cold,Alloy 718 maintains its structural ductility and high impact toughness down to cryogenic temperatures of -423°F (-253°C),making it a staple for liquid rocket propulsion.
Are Inconel 718 pipes compliant with sour gas regulations?
Yes.It fully complies with the NACE MR0175 / ISO 15156 standard.It resists hydrogen embrittlement and sulfide stress corrosion cracking,allowing it to safely transport toxic, corrosive sour oil from deep downhole wells.
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Should you have any questions regarding stainless steel pipes, including manufacturing processes, chemical composition or other unfamiliar matters, our staff will be happy to assist you.
