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Inconel 718 CNC Machining: Properties, Tolerances and RFQ Checklist
Age-hardenable, aerospace-grade and the most requested alloy in our network. What buyers need to know before sending the drawing.
Quick facts
| Property | Typical value or note |
|---|---|
| UNS number | N07718 |
| Common designations | Inconel 718, Alloy 718, 2.4668, GH4169 |
| Strengthening mechanism | Precipitation (age) hardening after solution annealing |
| Common AMS callouts | AMS 5662, 5663 and 5664 cover bar and forging stock in various solution-treated and aged conditions. The drawing's exact callout controls, not this table. |
| Continuous service temperature | Up to roughly 700°C before strength drops off meaningfully |
| Weldability | Weldable, but less forgiving than 625 since the aging response in the heat-affected zone needs planning |
| Typical tolerance | ±0.02 to ±0.05 mm on most features |
Treat any spec number here as a starting reference, not a substitute for the drawing. See the glossary for what an AMS callout actually specifies, or read the full AMS specifications guide.
Why buyers specify 718
718 reaches the highest strength-to-weight ratio in the nickel family at continuous operating temperature, and it gets there through age hardening rather than composition alone. That combination is why it dominates aerospace and gas turbine work over every other nickel alloy combined in our network.
Turbine hardware
Discs, shafts, combustor and hot-section brackets that see sustained heat and load.
Aerospace fasteners
Engine bolts and fittings needing strength retention past where steel fasteners would soften.
Rings and retainers
Rotating hardware where strength and dimensional stability both matter under load.
Structural brackets
Hot-section airframe and engine mounting hardware in demanding thermal environments.
Machining considerations
718 is not a harder version of stainless. The age-hardening step changes what the material is doing on the machine at each stage of the job.
- Heat treat sequencingMany shops rough soft, age, then finish hard so aging movement lands before the critical dimensions are cut. Read the full sequencing guide
- Tool wear718 work-hardens fast and holds heat at the cutting edge. Ceramic or coated carbide tooling matched to nickel alloys is standard among shops that run it regularly.
- Cost driversTool wear, material price, the aging step and low-volume setup all stack together. See what actually drives the price
- Inspection scopeAerospace work usually means FAI, mill cert traceability and sometimes PMI on incoming stock. Call it out on the RFQ, not after quoting.
RFQ checklist for Inconel 718
Everything below on the first RFQ means fewer round trips before you get a real quote.
- Drawing and condition2D drawing plus 3D model. State the required final condition (solution annealed, or solution treated and aged) rather than just "Inconel 718."
- Spec calloutInclude the exact AMS or other spec number from the drawing if one exists, written exactly as it appears.
- Critical featuresBores, threads, sealing faces and any datum-driven tolerance tighter than ±0.02 mm.
- Stock formBar, forging, plate or another starting form, if already known.
- DocumentationMill cert traceability, PMI and FAI requirements, and whether they apply to every order or only the first article.
- Quantity and timelinePrototype quantities and realistic annual volume if the part repeats, plus when you need it.
Questions buyers ask about 718
What is Inconel 718 used for?
Mostly aerospace and gas turbine hardware: turbine discs, shafts, engine fasteners and hot-section brackets that need high strength at continuous elevated temperature. It is the most requested grade among the shops in our network.
What is the UNS number for Inconel 718?
N07718. Buyers also see it written as Alloy 718, 2.4668 or, in Chinese-standard drawings, GH4169. All describe the same base composition; the AMS or ASTM spec on the drawing pins down the exact condition and testing required.
Does Inconel 718 need heat treatment before or after machining?
Both, usually. Many shops rough the part in the solution-annealed condition, when it cuts easier, age it to full strength, then finish critical features once the part is at final hardness so aging-related movement does not affect the finished dimensions.
What tolerance can a shop hold on Inconel 718?
Roughly ±0.02 to ±0.05 mm is common on most features. Tighter is achievable but adds real machine time, not just inspection time, since every finishing pass is fighting work hardening from the pass before it.
Why does Inconel 718 cost more than a similar part in steel or stainless?
Tool wear, raw material price, the extra aging step and low-volume setup costs stack on top of each other. A 718 quote landing three to five times higher than the same geometry in stainless is normal, not padding.