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Nickel Alloy

Inconel 718

Inconel 718 is an age-hardenable nickel-chromium superalloy delivering very high strength that holds up to about 700 degrees C. At 1375 MPa tensile and a hardened ~42 HRC it far outstrips solid-solution 625 in strength while retaining good corrosion resistance. Its strength-at-temperature and fatigue performance make it the dominant alloy for aerospace turbine and fastener applications.

How Inconel 718 machines

Machinability is 1/5. Like all nickel superalloys it work-hardens fast, generates extreme heat from low thermal conductivity, and abrades tooling. Use very low SFM, sharp coated carbide or ceramic, rigid setups, heavy positive feeds beneath the work-hardened skin, and flood coolant. Machine in the solution-treated state before age hardening where possible.

Manufacturing & processing

718 is processed by CNC, forging, and 3D printing, and is widely used in additive aerospace parts. It is precipitation hardened by solution treating then aging to develop full strength. Its sluggish aging response makes it more weldable than many age-hardening superalloys, and additive parts are typically HIP'd and heat treated for fatigue duty.

Typical applications

Best for high-strength hot turbine parts. Typical uses include gas-turbine discs, blades, and shafts, high-temperature bolts and fasteners, rocket-engine and aerospace structural components, and downhole oil-and-gas hardware where high strength and fatigue life must be maintained at elevated temperature.

When to choose it

Choose 718 when you need high strength retained at temperature, especially aerospace turbine and fastener duty. If the priority is weldable corrosion resistance rather than strength, 625 is better. If service is cool and only corrosion matters, cheaper stainless alloys will do.

Suitable surface finishes

Common finishes for Inconel 718: electropolishing, passivation. Use the finish selector →

FAQ

What makes Inconel 718 so strong at high temperature?
718 is precipitation hardened, forming strengthening phases during aging that resist softening up to about 700 degrees C. This gives it 1375 MPa tensile and excellent fatigue life at temperature, making it the workhorse for turbine discs and fasteners.
When should I machine 718 relative to aging?
Where possible, rough machine in the softer solution-treated condition, then age harden and finish. Fully aged 718 at ~42 HRC is extremely difficult to cut, so sequencing operations before final aging reduces tool wear and cycle time.
How does 718 differ from 625?
718 is age-hardenable and far stronger, while 625 is solid-solution strengthened with better weldability and corrosion resistance. Choose 718 for high-strength hot structural parts, and choose 625 for weldable corrosion resistance and high-temperature service where strength is secondary.

Property values are typical/nominal for early guidance and vary by temper, grade, supplier and heat treatment. Confirm critical specs against a certified datasheet or with an mfgiq engineer.