Inconel 718 Machining Guide – Cutting, Drilling and Turning
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Inconel 718 Machining Guide – Cutting, Drilling and Turning
Inconel 718 is a nickel-based superalloy used in demanding engineering applications where strength, corrosion resistance and performance at elevated temperatures are important. However, these characteristics can also make machining more challenging than machining many conventional engineering steels.
For component manufacturers, successful Inconel 718 machining depends on selecting appropriate cutting tools, controlling heat, maintaining a stable setup and following parameters suitable for the material condition.
This guide covers key considerations for turning, drilling and milling Inconel 718, also known as Alloy 718 and identified by UNS N07718.
What Makes Inconel 718 Difficult to Machine?
Inconel 718 is a precipitation-hardenable nickel-based alloy. Its machining behaviour depends on the heat-treatment condition, workpiece hardness, component geometry and cutting operation.
Several characteristics need attention during machining.
1. High strength
Inconel 718 can retain substantial strength at elevated temperatures. Cutting tools therefore need to withstand the mechanical loads generated during material removal.
Tool selection should account for the material condition, depth of cut, feed rate and machine rigidity.
2. Heat concentration at the cutting zone
Nickel-based superalloys can generate significant heat during cutting. A large proportion of this heat may remain concentrated near the cutting edge, increasing tool wear if cutting conditions are unsuitable.
Effective coolant delivery, appropriate tooling and stable cutting parameters can help manage the machining process.
3. Work hardening
Under unsuitable cutting conditions, the surface can become harder as the material is deformed during machining. Repeatedly rubbing or making very light cuts over a work-hardened surface can increase tool wear.
Use a machining strategy appropriate to the material and avoid allowing the tool to rub against the workpiece instead of cutting effectively.
4. Tool wear
Cutting-edge wear can progress quickly if tooling, cutting speed, feed and coolant are poorly matched to the operation.
Manufacturers should monitor tool condition and surface finish rather than relying only on machining time.
Turning Inconel 718
Turning is commonly used to produce cylindrical components such as shafts, sleeves and precision-machined parts.
When turning Inconel 718, consider the following factors.
Machine rigidity: A rigid machine and secure workholding help reduce vibration and unstable cutting.
Tool selection: Use cutting tools recommended by the tooling manufacturer for nickel-based superalloys and the actual material condition.
Cutting parameters: Select speed, feed and depth of cut using tooling guidance and controlled trials. Avoid adopting parameters intended for ordinary carbon steel without validation.
Coolant delivery: Apply coolant as recommended for the tool and operation, ensuring it reaches the cutting zone effectively.
Tool wear monitoring: Inspect cutting edges and the machined surface at appropriate intervals to identify wear before quality deteriorates.
The correct parameters depend on the machine, tooling, workpiece hardness and geometry. There is no single cutting speed or feed rate that is suitable for every Inconel 718 turning operation.
Drilling Inconel 718
Drilling can be challenging because the cutting tool operates within a confined area where heat and chips must be managed.
Important considerations include:
- Select a drill designed for the material and hole requirements.
- Ensure the workpiece is securely clamped.
- Use cutting parameters recommended by the tool manufacturer.
- Provide suitable coolant delivery where required by the operation.
- Plan chip evacuation, particularly for deeper holes.
- Monitor tool wear and hole quality during production.
For deep holes or tight-tolerance components, the machining strategy may require additional planning and specialist tooling. Pilot drilling, pecking or other methods should be selected according to the tool manufacturer’s guidance and the specific hole geometry.
Milling Inconel 718
Milling involves interrupted cutting, so the tool experiences repeated engagement and disengagement with the workpiece. This can place additional demands on the cutting edge.
To improve process stability:
- Use tooling intended for nickel-based superalloys.
- Minimise vibration through secure workholding and suitable tool overhang.
- Follow the tool manufacturer’s recommendations for engagement, feed and speed.
- Avoid unnecessary dwell or rubbing at the cutting surface.
- Monitor chip formation, cutting-edge wear and surface finish.
- Adjust the machining strategy to the component geometry and material condition.
Toolpath strategy matters. A method that works well for one component may not perform equally well for another because engagement, rigidity and heat dissipation can differ.
Why Material Condition Matters
Inconel 718 can be supplied in different conditions depending on the applicable product specification and intended application. Its hardness and machining behaviour may change with heat treatment.
Before machining, confirm:
- The alloy designation and applicable material specification
- The supplied heat-treatment condition
- The hardness or mechanical requirements, where specified
- Whether rough machining or finishing is planned before or after heat treatment
- The final dimensional and surface-finish requirements
Machining allowances should be planned with the component designer and heat-treatment provider where dimensional change or finishing operations are important.
Do not assume that all Inconel 718 stock will machine identically. Confirm the actual material condition before finalising production parameters.
Common Inconel 718 Machining Problems
| Problem | Possible contributing factor | Practical response |
|---|---|---|
| Rapid tool wear | Unsuitable tooling or cutting conditions | Review tool selection and manufacturer-recommended parameters |
| Poor surface finish | Tool wear, vibration or unstable cutting | Check rigidity, tool condition and finishing strategy |
| Chipping at the cutting edge | Interrupted cutting or excessive mechanical loading | Review tool geometry, engagement and setup |
| Difficult chip control | Inappropriate feed, geometry or chip-breaking strategy | Use tooling and parameters suited to the operation |
| Dimensional variation | Workholding, heat, tool wear or process instability | Check setup, inspection frequency and process sequence |
These are general troubleshooting suggestions, not a substitute for diagnosing the actual machining process. Investigate the specific machine, tool, workpiece and cutting conditions before changing production parameters.
How to Specify Inconel 718 for Machining
Before purchasing material for a machined component, provide the supplier with the correct technical information.
A useful enquiry includes:
- Material: Inconel 718 / Alloy 718
- UNS designation: N07718
- Product form: Round bar or other required form
- Dimensions: Diameter, length and tolerances
- Material condition: As specified by the drawing or purchase order
- Quantity: Pieces, total length or approximate weight
- Documentation: Material test certificate and any required inspection records
- Application: Component type and any relevant technical requirements
The required product specification must be confirmed against the drawing or purchase order. Do not assume that the alloy designation alone establishes compliance with every aerospace, pressure-equipment or customer-specific requirement.
For further material information, consult Special Metals’ technical resources.
Sourcing Inconel 718 from Manan Steel & Metals
Manan Steel & Metals, based in Mumbai, India, handles industrial metal sourcing enquiries. If your machining project specifies Inconel 718, share the required dimensions, quantity, material condition and applicable specification with our team.
You can also review the existing Inconel 718 supplier information on our website and contact us with your specific requirement.
Price, material condition, documentation and availability should be confirmed against the actual order requirements before purchase.
Request an Inconel 718 Enquiry
Manan Steel & Metals
Address: Shop No. 2, Hira Building, 97 Khetwadi Main Road (Nanubhai Desai Road), Girgaon, Mumbai – 400004, Maharashtra, India
Phone: +91 7977369869
Email: manansteel@gmail.com
Website: www.manansteel.com
Send your material grade, dimensions, quantity and specification to discuss your requirement.
Frequently Asked Questions
Why is Inconel 718 difficult to machine?
Its strength, work-hardening behaviour and heat concentration at the cutting zone can make machining more demanding than machining many conventional steels.
Can Inconel 718 be turned and milled?
Yes. Turning and milling are used for suitable Inconel 718 components, but the tooling, cutting parameters and machine setup must suit the alloy and its condition.
Can ordinary steel cutting parameters be used for Inconel 718?
They should not be transferred without validation. Use recommendations intended for nickel-based superalloys and confirm parameters for the actual operation.
Does heat treatment affect Inconel 718 machining?
Yes. Material condition and hardness can affect cutting behaviour. Confirm the supplied condition and plan machining around any required heat-treatment steps.
What information should I provide when buying Inconel 718 for machining?
Provide the alloy designation, applicable specification, product form, dimensions, quantity, material condition and documentation requirements.
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Alt text: CNC machining of Inconel 718 nickel-based alloy round bar
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Technical note: Machining parameters must be selected for the actual material condition, tooling, machine and component geometry. This guide provides general process considerations rather than a production-ready cutting schedule.