Inconel 718 Tubes: Premium Nickel Alloy for High‑Temperature Service

Product Overview

Inconel 718 Tubes (UNS N07718) are precision‑formed, precipitation‑hardenable nickel‑chromium‑iron alloys engineered for critical applications in extreme environments. These seamless and welded tubes combine outstanding tensile strength, excellent fabricability, and superior resistance to oxidation, pitting, and stress‑corrosion cracking at temperatures up to 1300 °F (704 °C). Their ability to maintain mechanical integrity under rapid thermal cycling and under high mechanical loads makes Inconel 718 Tubes the material of choice for aerospace engine ducting, high‑pressure chemical reactors, nuclear steam generator tubing, and oil & gas downhole instrumentation lines.

Through a controlled solution annealing and aging (precipitation hardening) sequence, Inconel 718 Tubes achieve yield strengths exceeding 965 MPa and ultimate tensile strengths over 1379 MPa, while retaining ductility (elongation ≥ 25 %) and fracture toughness. The alloy’s balanced composition of 50–55 % nickel, 17–21 % chromium, 4.75–5.50 % niobium + tantalum, and carefully controlled levels of aluminum and titanium ensures a fine distribution of strengthening γ′ and γ″ precipitates. Combined with low carbon and sulfur limits, this yields exceptional performance in corrosive media such as superheated steam, chloride‑bearing process streams, and marine environments. Finished tube dimensions range from ½″ to 6″ OD with wall thicknesses from 0.028″ to 0.500″, all certified per ASTM and ASME standards for pressure‑containing systems.

Chemical Composition

Mechanical Properties

Physical Properties

Conformance Standards

• ASTM B163 — Seamless Inconel 718 Tubes

• ASTM B424/B424M — Welded Inconel 718 Tubes

• AMS 5663 / AMS 5596 — Special Quality UNS N07718 Tubing

• ASME SB-163 / SB-424 — Boiler and Pressure Vessel Code

Applications

Inconel 718 Tubes find extensive use in:

• Aerospace Propulsion: Hot‑section ducting, jet engine coils, afterburner fuel lines

• Chemical & Petrochemical: Heat exchanger tubing, reactor coil tubing, process piping

• Power Generation: Superheater and reheater tubes in steam turbines

• Marine & Offshore: Seawater coolers, desalination plant coils

• Oil & Gas: High‑pressure injection lines, downhole sensors, subsea manifolds

• Nuclear: Steam generator tubing, core internals in pressurized water reactors

Frequently Asked Questions

Q1: Why select Inconel 718 Tubes for high‑temperature applications?
A1: Their precipitation‑hardenable microstructure offers exceptional creep and fatigue resistance up to 704 °C, while retaining toughness and corrosion resistance in aggressive media.

Q2: Can Inconel 718 Tubes be joined by welding and brazing?
A2: Yes. Both TIG/GTAW and electron‑beam welding yield sound joints if post‑weld heat treatment protocols are followed. Silver‑based brazing alloys also produce gas‑tight seals.

Q3: What dimensional tolerances and finishes are available?
A3: Standard OD tolerances are ± 0.010″; wall thickness ± 10 %. Mill‑annealed, pickled finishes or electropolished surfaces are offered per customer requirements.