Inconel 718 is the workhorse nickel superalloy of aerospace turbine engines. Understanding why it punishes tools makes the difference between 5-minute and 50-minute tool life.
Why Inconel Is Hard to Machine
- Work hardening — Surface hardness can double from cutting forces (40 → 50 HRC)
- Low thermal conductivity — Heat stays in tool, not chip
- Chemical reactivity — Nickel diffuses into carbide at cutting temp
- Built-up edge — Forms readily, breaks off taking carbide chunks
Insert Selection (ISO S grades)
| Operation | Grade | Why |
|---|---|---|
| Roughing turning | Sandvik S05F or Kennametal KCS10B | Submicron carbide + AlTiN PVD |
| Finishing turning | Sandvik CC6190 (ceramic SiAlON) | Heat-resistant, high speed |
| Interrupted cuts | Iscar IC804 | Tough PVD nano-coating |
Cutting Parameters with HP Coolant
- Cutting speed: 30-60 m/min (carbide), 200-300 m/min (ceramic)
- Feed: 0.10-0.20 mm/rev
- Depth of cut: 1.0-3.0 mm (avoid below 0.5mm)
Critical: High-Pressure Coolant
Conventional flood coolant fails. Use HP coolant at 1000+ PSI through internal-coolant tooling. Drops cutting temperature 200-300°C and triples tool life. ROI in 3-6 months.
Always Cut Below the Hardened Layer
Each pass leaves a 0.05-0.1mm hardened layer. Subsequent passes must cut DEEPER than this layer or the tool just rubs.
See also titanium coolant strategy.
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