Cutting parameters, tooling selection, and chip-management notes for super duplex stainless steel
Super duplex grades are notably harder to machine than the austenitic stainless steel benchmark of 304L: the mixed ferrite-austenite microstructure produces high cutting forces, the work-hardening tendency is severe at low feed rates, and the chip is tough and stringy. The machinability rating relative to free-machining 12L14 (rated 100%) is approximately 25 to 30% for Ferralium 255, similar to standard duplex 2205 and slightly worse than 316L (which rates ~45%). The practical consequences are slower cutting speeds, heavier feed rates than would be tempting on austenitic, copious flood coolant or high-pressure through-tool coolant, sharp positive-rake tooling, and a rigid setup with no chatter.
| Operation | Cutting speed (Vc) | Feed (fn) | DOC (ap) | Insert |
|---|---|---|---|---|
| Roughing turning | 60 to 80 m/min | 0.30 to 0.50 mm/rev | 2 to 5 mm | CNMG TM grade, P25 / P35 carbide |
| Finishing turning | 80 to 120 m/min | 0.10 to 0.20 mm/rev | 0.3 to 1.0 mm | CNMG WF, PVD-coated TiAlN |
| Threading (single-point) | 60 to 80 m/min | per thread pitch | 0.05 to 0.15 mm per pass | Full-form thread insert, PVD-coated |
| Drilling (carbide twist drill) | 15 to 25 m/min | 0.10 to 0.25 mm/rev | through | Solid carbide, TiAlN-coated, peck cycle 2 to 3 mm |
| Operation | Vc | fz (per tooth) | DOC | Insert |
|---|---|---|---|---|
| Face milling roughing | 50 to 80 m/min | 0.10 to 0.20 mm/tooth | 2 to 5 mm | Round insert, P30 / P40 grade |
| Face milling finishing | 80 to 120 m/min | 0.08 to 0.15 mm/tooth | 0.3 to 1.0 mm | Wiper insert, PVD-coated |
| End milling slotting | 40 to 60 m/min | 0.05 to 0.10 mm/tooth | 0.5 × cutter dia | 4 to 6 flute, TiAlN, full slot trochoidal preferred |
| Profile milling | 60 to 90 m/min | 0.08 to 0.15 mm/tooth | per geometry | Climb mill, PVD-coated |
