Inconel 718 (Alloy 718 / UNS N07718): Instrumentation Fittings, Valves & Tubing

Inconel 718 (UNS N07718) is a nickel-chromium superalloy that gains its strength through precipitation hardening, also called age hardening. A γ″ (Ni₃Nb) precipitate does the work here, giving the alloy very high strength alongside good resistance to corrosion and elevated temperatures. On this page, Inconel 718 refers specifically to Alloy 718 as a material of construction for instrumentation fittings, valve components, and tubing. It doesn't cover bar, sheet, plate, or pipe mill products. Nor is it interchangeable with Inconel 625, 825, or Monel K-500, each of which is its own distinct grade.

Crestflo manufactures instrumentation components in high-nickel alloys, including Alloy 718. This page lays out the extractable metallurgy: composition, mechanical and physical properties, temperature envelope, and sour-service caveats, along with product-form specifications. From there it points you to the instrumentation forms Crestflo actually supplies, with an RFQ ready for your exact requirement.

Reviewed by the Crestflo Engineering Team

What Is Inconel 718? Age-Hardenable Nickel Superalloy Explained

Inconel 625 is a solid-solution alloy, but Alloy 718 works differently. It's a wrought nickel-chromium superalloy with iron and niobium added in, which makes it precipitation hardenable. Its strength comes from a solution anneal followed by a two-step age (precipitation) heat treatment. That treatment precipitates the γ″ phase (body-centered-tetragonal Ni₃Nb) throughout the matrix, with a secondary contribution from γ′ (Ni₃(Al,Ti)). This microstructure lets aged 718 reach strengths far above stainless steels, and it still holds onto useful corrosion and oxidation resistance. It stays weldable too.

The result: a superalloy built for strength first. It's suited to high-pressure, high-load instrumentation service across the range from cryogenic to elevated temperatures, covering valve springs and stems, fasteners, and cone-and-thread and high-pressure fitting components. Here, mechanical strength is the deciding factor, not maximum resistance to wet corrosion.

Inconel 718 Is Also Known As: Alloy 718, UNS N07718, Werkstoff 2.4668

Alloy 718 goes by more names than most engineers realize. National bodies and standards organizations each apply their own designation, and buyers use whatever term their supply chain favors. You'll hear it called Inconel 718, Inconel® 718, 718 Inconel, Alloy 718, 718 alloy, Nickel Alloy 718, Ni Alloy 718, plain "718", IN718, IN-718, Inco 718, or Ni-Cr Alloy 718. Metallurgists tend to stick with the UNS number instead: UNS N07718 or UNS 07718. Others prefer Werkstoff (W.Nr.) notation or the EN chemical-symbol designation. A handful of proprietary trade names cover this exact UNS N07718 chemistry too. Whatever the label, it's the same age-hardenable nickel superalloy underneath.

INCONEL® is a registered trademark of Special Metals Corporation. The other trade names here belong to their respective owners, registered marks all of them. Crestflo has no affiliation with these owners and isn't endorsed by them. Throughout this page, "Alloy 718" refers to the generic UNS N07718 material. AMS designations appear for identification only; they aren't a claim of AMS-qualified supply. Values follow the applicable standard, though they can be customized to your requirement.

Inconel 718 Chemical Composition (UNS N07718)

The nominal makeup of Alloy 718 centers on nickel and chromium, balanced with iron, plus niobium, molybdenum, titanium, and aluminum additions that drive precipitation hardening. The table lists the standard published limits for UNS N07718.

Composition follows the standard UNS N07718 chemistry. Heat-specific values appear on the material test certificate issued for each lot.

Inconel 718 Mechanical Properties: Tensile, Yield Strength & Hardness (Aged vs Annealed)

Alloy 718's properties change a lot depending on condition. Solution-annealed material stays comparatively soft and easy to form, whereas the precipitation-hardened, or aged, condition is what gives the alloy the high strength it's known for. The table lists standard published room-temperature values. Actual delivered properties depend on product form and condition, though, and should be confirmed on the certificate.

Aged 718 outperforms most stainless steels by a wide margin, and that extra strength is what makes it suitable for high-pressure, high-load instrumentation components. In sour service, though, hardness isn't set by peak-aged values. It's governed by NACE MR0175 / ISO 15156, so check the sour-service section below for details. Values follow whichever standard applies, and they can be adjusted to suit specific requirements.

Inconel 718 Physical Properties: Density, Melting Range & Modulus of Elasticity

The physical constants below are standard published values for Alloy 718.

Values per applicable standard; customizable to requirement.

Inconel 718 Temperature Range: Cryogenic to ~700 °C Service

Alloy 718 spans a strikingly wide range of temperatures. At the cold end, it keeps its toughness and strength even in cryogenic conditions, which makes it a solid fit for LNG and liquefied-gas instrumentation. Strength stays high up to about 650 °C (1200 °F), and the alloy can still do useful work at roughly 700 °C (1300 °F). Past that point, though, the γ″ strengthening phase starts to over-age and coarsen. That's why engineers don't turn to 718 for the very-high-temperature oxidation jobs handled by grades like Inconel 601.

Within its envelope, 718's strength at both room temperature and elevated temperatures is exactly what allows small instrumentation cross-sections to carry high internal pressures. That's the mechanical basis for cone-and-thread fittings and other high-pressure fitting components.

Inconel 718 Sour Service, Corrosion Resistance & NACE MR0175

Alloy 718 holds up well against general corrosion and oxidation, and it beats 300-series stainless steels when it comes to chloride stress-corrosion cracking and pitting. Still, it's a strength alloy, not a maximum-corrosion alloy. For severe reducing or oxidizing acids, specify Inconel 625 or Hastelloy C-276 instead.

The table maps its behavior by environment and names a better alternative wherever 718 isn't the leading choice.

Sour-service (NACE) note, stated honestly: NACE MR0175 / ISO 15156-3 does cover age-hardened UNS N07718 among nickel-based alloys, but only within limits on hardness, heat-treat condition, and environmental factors such as H₂S partial pressure, temperature, and chloride content. A maximum hardness near 40 HRC for qualifying conditions is the figure most often cited. Where the envelope actually falls depends on the specified condition and the service at hand, so confirm the certified condition against NACE MR0175 sour-service requirements and ISO 15156 age-hardened alloy limits before relying on it for your application. Our sour-service material selection guide lays out that decision logic in full. PREN, for what it's worth, is a stainless and duplex metric and doesn't carry much weight for a nickel superalloy; strength and resistance to stress corrosion cracking are what actually drive the choice of 718, not PREN.

Inconel 718 ASTM & AMS Specifications: B637, B983 & AMS Grades

Crestflo procures Wrought Alloy 718 to ASTM and AMS specifications, sorted by product form. Those specs serve as the reference standard for the alloy. Each instrumentation component Crestflo builds uses material that meets the specification for its particular form.

Every part carries a heat/lot number, and it ships with an EN 10204 3.1 material test certificate (MTC) as standard. A 3.2 certificate is available on request. Values follow the applicable standard, and we're happy to adjust them to suit your requirement.

When to Choose Inconel 718 vs Inconel 625, 825, Monel K-500 or 17-4PH

Go with Inconel 718 whenever mechanical strength is the deciding factor. Think high-pressure cone-and-thread parts, valve springs and stems, fasteners. It also suits components running anywhere from cryogenic to elevated temperatures, where high loads need to be carried in a small cross-section.

Specify an alternative when:

• You need maximum wet-corrosion resistance in oxidizing or mixed acids: Inconel 625 for sour & oxidizing service.
• You need acid and sour resistance at moderate strength: Incoloy/Inconel 825 for acid service.
• You need age-hardened marine strength at lower cost than 718 → Monel K-500.

Need age-hardened strength, but at a lower cost and a lower service temperature than 718, in a benign environment? Reach for 17-4PH stainless. It's a precipitation-hardening martensitic stainless, not a nickel superalloy.

• You face aggressive reducing acids → Hastelloy C-276 for aggressive acids.

The quick-selection table condenses this:

For a direct comparison, consult the Inconel vs Monel selection guide or the Hastelloy vs Inconel comparison.

Available Inconel 718 Product Forms from Crestflo: Fittings, Valves & Tubing

Crestflo supplies Alloy 718 strictly as instrumentation forms: compression and tube fittings, high-pressure and cone-and-thread components, instrumentation valve components, and instrumentation tubing. Alloy 718 bar, sheet, plate, pipe, and other mill products fall outside the US instrumentation scope. They aren't offered.

We test compression tube fittings per ASTM F1387 fitting qualification, covering dimensional fit and performance interchange. Instrumentation valves don't follow that path. They qualify against the valve standards that actually apply, ASME B16.34 and API, since F1387 is a compression-tube-fitting standard, not a valve standard. Finish options run from material finish and electropolish to passivation and silver anti-galling plating. Standard items ship from stock; specials are made to order, with delivery running 6-8 weeks. Need exact OD, wall thickness, and end configuration? Request an Inconel 718 quote.

Inconel 718 Machining, Welding & Heat Treatment

Alloy 718 behaves like a tough superalloy. It work-hardens fast, so it demands rigid setups, positive tooling, and tightly controlled feeds and speeds; Crestflo machines it in-house on CNC, VMC, and EDM equipment, so parts arrive finished and already in the specified temper. GTAW handles it well too, and it shows comparatively low sensitivity to strain-age and post-weld heat-treatment cracking next to many other superalloys. Its hot forgeability holds up well within a controlled forging window, and that's why 718 valve stems, springs, and high-pressure bodies are commonly made from forged stock. Peak strength comes from a solution anneal followed by a two-step, or double, age. Condition governs both hardness and NACE and PED eligibility, so finished parts get supplied in the correct heat-treat condition for the service. Inconel 718 is also a common additive-manufacturing superalloy, but Crestflo supplies machined and forged instrumentation components in 718, not additively manufactured ones.

Inconel 718 Applications & Industries

Alloy 718 shows up in downhole and subsea oil-and-gas components, high-pressure hydraulic and control-line parts, valve springs, stems and fasteners, and cryogenic and aerospace-grade instrumentation. Wherever very high strength has to sit alongside corrosion and temperature resistance, this is the material that gets picked. In instrumentation, that means high-pressure fittings, valve internals, and tubing built for oil and gas, subsea, LNG and cryogenic, and aerospace and defense service.

Why Crestflo for Inconel 718 Instrumentation Components

Crestflo is the instrumentation arm of an export house with four decades behind it, recognized by the Government of India, with a proven record of delivery across the Middle East. That heritage sits behind a brand focused squarely on instrumentation. We manufacture and supply Alloy 718 instrumentation directly, selling factory-direct to buyers in the US. No distributor markup, no stockist markup. You deal straight with the people who make the part. Here's what that means for Alloy 718 instrumentation:

• ASTM F1387-backed interchange on compression tube fittings: a dimensional and performance drop-in match for the major brands.
• 6-8 week delivery: standard items ship from stock, specials are built to order, and both beat the 20+ weeks typical at the majors. See our 6, 8-week lead time methodology.
• Small MOQ + private label, see the private-label & OEM program.
• Heat-number traceability on every part with EN 10204 3.1 MTC standard, 3.2 on request.
• In-house machining and testing, CNC/VMC/EDM, PMI, hydraulic and pneumatic proof, and NDT.
• ISO 9001 / 14001 / 45001 & PED certified.

Origin, stated honestly: Indian origin; US and European melt are available on request, with full material traceability. Crestflo serves the US market and is engineered for US drop-in replacement. Houston, TX is our US sales-contact city. We never claim "made in USA." Where domestic-melt or TAA compliance is required, US or European-melt options are available on request. Our post-tariff cost advantage keeps Alloy 718 landed cost competitive. We Engineer Confidence.

Inconel 718 FAQ

Related Materials, Standards & Resources

• All instrumentation fitting materials
• Inconel 625 for sour & oxidizing service · Incoloy/Inconel 825 for acid service · Monel K-500, age-hardened for marine strength · Hastelloy C-276 for aggressive acids
• Inconel vs Monel: a selection guide · Inconel 625 vs 825 · Hastelloy vs Inconel, compared · choosing a material by service condition
• what NACE MR0175 requires for sour service · ISO 15156 limits on age-hardened alloys · EN 10204 3.1/3.2 material test certificates · ASTM F1387 fitting qualification
• Cross-reference a competitor 718 part · 6–8 week lead time
• Request an Inconel 718 quote · request a sample