In the field of high-temperature alloys, Inconel 718 bar remains one of the most widely used and trusted materials. Developed in the 1960s by Special Metals Corporation, this nickel-chromium-iron superalloy has become essential in aerospace, oil & gas, nuclear, and power generation industries.

This article provides a comprehensive overview of Inconel 718 bar, including its chemical composition, mechanical properties, heat treatment, machinability, standards, applications, and procurement considerations.

 

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What Is Inconel 718?

Inconel 718 (UNS N07718, W.Nr. 2.4668) is a precipitation-hardenable nickel-based superalloy strengthened primarily by:

• Gamma prime (Ni₃(Al,Ti))
• Gamma double prime (Ni₃Nb)

These fine precipitates form during aging heat treatment and provide exceptional strength and creep resistance.

One of the key advantages of Inconel 718 bar is its ability to maintain excellent mechanical performance from cryogenic temperatures up to approximately 705°C (1300°F). Unlike many high-strength superalloys, it also offers relatively good weldability.

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Chemical Composition of Inconel 718 Bar

The performance of Inconel 718 bar depends on strict control of alloying elements.

Element	Ni	Cr	Fe	Nb+Ta	Mo	Ti	Al	C	Mn	Si	P	S
Content (%)	50.0 – 55.0	17.0 – 21.0	Balance	4.75 – 5.50	2.80 – 3.30	0.65 – 1.15	0.20 – 0.80	≤ 0.08	≤ 0.35	≤ 0.35	≤ 0.015	≤ 0.015

For sour service applications in oil & gas environments, materials may comply with NACE MR0175 / ISO 15156 and API 6ACRA requirements.

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Mechanical Properties of Inconel 718 Bar

Mechanical properties vary depending on heat treatment condition, especially under AMS 5662 or AMS 5663 specifications.

Typical Room Temperature Properties (Aged Condition)

Tensile Strength: ≥ 1275 MPa (185 ksi)

Yield Strength (0.2% offset): ≥ 1034 MPa (150 ksi)

Elongation: ≥ 12%

Reduction of Area: ≥ 15%

 

Elevated Temperature Properties (649°C / 1200°F)

Tensile Strength: ≥ 1000 MPa

Yield Strength: ≥ 862 MPa

Elongation: ≥ 12%

 

Physical Properties

Density: 8.19 – 8.24 g/cm³

Melting Range: 1260 – 1336°C

Thermal Expansion Coefficient: approx. 13.0 µm/m·°C (20–700°C)

Thermal Conductivity: approx. 11.4 W/m·K at room temperature

These characteristics make Inconel 718 bar suitable for high-load structural components exposed to extreme temperatures.

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Heat Treatment of Inconel 718 Bar

The typical heat treatment process includes:

1. Solution Annealing: 927–1010°C (1700–1850°F), followed by air cooling

2. Aging Treatment:

• 718°C (1325°F) for 8 hours
• Furnace cool to 621°C (1150°F)
• Hold for additional aging time (total about 18 hours)

This treatment produces optimal precipitation strengthening.

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Machinability of Inconel 718 Bar

Inconel 718 bar is considered difficult to machine due to:

• Severe work hardening
• Low thermal conductivity
• High cutting forces
• Tool adhesion tendency

 

General machining recommendations:

• Use rigid setups and minimize tool overhang
• Maintain sharp cutting tools
• Apply sufficient coolant
• Use lower cutting speeds compared to carbon steel
• Prefer carbide tools for improved tool life

Its machinability rating is approximately 12–24% compared to free-cutting steel.

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Is Inconel 718 Bar Magnetic?

Inconel 718 is generally considered non-magnetic in annealed condition. However, slight magnetic response may occur after cold working or certain heat treatments.

This is significantly different from ferritic stainless steels and should be considered in applications requiring strict magnetic neutrality.

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Standards and Specifications for Inconel 718 Bar

Common standards include:

• AMS 5662 – Bars, forgings, rings (solution + aged)
• AMS 5663 – Higher strength requirements
• ASTM B637 / ASME SB-637 – Nickel alloy bars
• API 6ACRA – Corrosion resistant alloy applications
• NACE MR0175 / ISO 15156 – Sour service compliance

When purchasing Inconel 718 bar, always confirm the required specification and heat treatment condition.

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Typical Sizes of Inconel 718 Bar

Inconel 718 bar is available in: round bar, square bar, hexagonal bar and forged bar.

Typical diameter range: 6 mm to over 350 mm (custom sizes available).

Surface conditions:

• Black
• Turned
• Peeled
• Polished

Custom cut lengths can also be supplied based on project requirements.

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Applications of Inconel 718 Bar

Due to its high strength and corrosion resistance, Inconel 718 bar is widely used in:

Aerospace

• Turbine disks
• Compressor components
• Fasteners
• Structural fittings

 

Oil & Gas

• Downhole tools
• Packer components
• Valve stems
• Sour service equipment

 

Energy & Nuclear

• Reactor components
• High-temperature fasteners
• Pump shafts

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Price Factors of Inconel 718 Bar

The price of Inconel 718 bar depends on several variables:

• Nickel and alloying element market fluctuations
• Diameter and dimensional tolerances
• Heat treatment condition
• Certification requirements
• Order quantity
• Export destination

For accurate pricing, it is recommended to request a quotation based on specific size and standard requirements.

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Procurement Considerations

When sourcing Inconel 718 bar:

1. Confirm the required specification (AMS, ASTM, API)

2. Request Mill Test Certificate (MTC)

3. Verify heat number traceability

4. Evaluate supplier production capability

5. Consider machining allowance if secondary processing is required

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Conclusion

Inconel 718 bar remains one of the most reliable high-performance superalloys for demanding applications. Its unique precipitation-hardening mechanism, high strength at elevated temperatures, corrosion resistance, and weldability make it indispensable in aerospace and energy industries.

For engineers and procurement professionals, understanding the standards, mechanical properties, and processing characteristics of Inconel 718 bar is essential for ensuring long-term reliability and performance.