Precipitation-Hardened Nickel Alloy for High-Strength and High-Temperature Applications

Inconel 718, also known as Alloy 718 or UNS N07718, is a precipitation-hardened nickel-iron-chromium alloy developed for applications requiring high tensile strength, excellent fatigue resistance, good creep performance, and reliable mechanical properties at elevated temperatures.

The alloy is widely used in aerospace, gas turbine, power generation, oil and gas, and other industries where components must withstand high mechanical loads, cyclic stress, vibration, and demanding thermal conditions.

What Makes Inconel 718 Different?

The primary characteristic of Inconel 718 is its precipitation-hardening mechanism. Unlike solid-solution-strengthened alloys, Inconel 718 obtains much of its strength through controlled heat treatment that forms strengthening phases within the nickel-based matrix.

The key alloying elements include:

• Nickel

• Chromium

• Iron

• Niobium

• Molybdenum

• Titanium

• Aluminum

Niobium plays a major role in the formation of strengthening precipitates. Titanium and aluminum also contribute to precipitation hardening. This metallurgical design allows Inconel 718 to achieve high strength while maintaining useful corrosion resistance and fabrication performance.

Typical Chemical Composition of Inconel 718

The exact chemical composition must be verified according to the relevant product standard and heat certificate.

Main Properties of Inconel 718

High Mechanical Strength

Inconel 718 can achieve very high tensile and yield strength after the required solution treatment and aging process. This makes it suitable for load-bearing components exposed to high stress.

Excellent Fatigue Resistance

The alloy is commonly selected for rotating parts, fasteners, shafts, discs, and other components exposed to cyclic loading.

Good Creep and Stress-Rupture Performance

Inconel 718 maintains useful strength at elevated temperatures and is widely used in applications involving sustained loads and thermal exposure.

Good Oxidation and Corrosion Resistance

The chromium content contributes to oxidation and corrosion resistance in many high-temperature environments. Nevertheless, material selection should always consider the actual chemical medium and operating temperature.

Suitable for Complex Engineering Components

Inconel 718 can be processed into bars, forgings, sheets, plates, rings, fasteners, and other engineered forms. Machining may be more demanding than with conventional steels because of its work-hardening tendency and high strength.

Typical Product Forms

• Round bars

• Forged bars

• Billets

• Plates

• Sheets

• Rings

• Forgings

• Shafts

• Fasteners

• Aerospace components

• Custom-machined parts

• Welding products, where applicable

Common Standards

Depending on the product form and end-use industry, Inconel 718 may be specified under:

• ASTM B637 — Nickel alloy bars, forgings, and rings

• ASTM B670 — Nickel alloy plate, sheet, and strip

• ASTM B637-related purchasing requirements for high-strength product forms

• AMS 5662 — Corrosion- and heat-resistant nickel alloy bars, forgings, and rings

• AMS 5596 — Nickel alloy sheet, strip, and plate

• UNS N07718

• ASME SB-637 or other applicable ASME specifications

The required standard should be selected according to the product form and intended application. Aerospace and power-generation buyers may also require AMS, OEM, or project-specific specifications.

Heat Treatment of Inconel 718

Inconel 718 is normally supplied in a controlled heat-treated condition when high mechanical strength is required. A typical industrial heat-treatment route may include:

1. Solution treatment

2. Controlled cooling

3. Aging treatment

4. Final inspection and mechanical testing

The exact temperatures, holding times, cooling method, and aging sequence must follow the applicable specification. Buyers should not rely on a generic heat-treatment description when purchasing material for safety-critical applications.

Machining Considerations

Inconel 718 is considered a difficult-to-machine alloy because it:

• Work-hardens rapidly

• Retains high strength during cutting

• Generates considerable cutting heat

• Can cause accelerated tool wear

• Requires rigid machine setup

• Benefits from suitable carbide or advanced cutting tools

• Requires carefully controlled cutting speed and feed

Machining parameters should be selected based on the supplied condition, hardness, geometry, tool material, coolant, and required surface finish.

Applications of Inconel 718

Inconel 718 is widely used for:

• Aircraft engine components

• Gas turbine discs

• Turbine shafts

• Engine fasteners

• High-temperature bolts

• Aerospace rings and forgings

• Oil and gas downhole tools

• High-pressure components

• Nuclear power equipment

• Cryogenic components

• Rocket engine parts

• Industrial gas turbines

• High-strength springs and structural components

Inconel 718 vs. Inconel 625

Selection guidance: Inconel 718 is often preferred for high-strength components subjected to mechanical and cyclic loads. Inconel 625 is often preferred when corrosion resistance, weldability, and resistance to aggressive chemical environments are the dominant requirements.

Purchasing Checklist for Inconel 718

A complete inquiry should include:

• UNS or material grade

• Product form

• ASTM, ASME, AMS, or OEM standard

• Dimensions and tolerances

• Heat-treatment condition

• Tensile and yield strength

• Elongation and reduction of area

• Hardness requirements

• Grain size requirements

• Ultrasonic or other NDT requirements

• Material test certificate requirements

• Traceability and batch identification

• Quantity and delivery schedule

Request a Quotation for Inconel 718

For Inconel 718 bars, plates, forgings, rings, or other product forms, contact Alloysfactory with your required grade, dimensions, standard, quantity, and application information.

Official website: alloysfactory.com

The sales team can help confirm the appropriate product form, supply condition, documentation, inspection requirements, and delivery options.