What insert should I use for duplex stainless 2205 / 2507?

A tough M-class PVD-coated carbide with a robust positive edge. Match the ISO M class across brands rather than the brand name and confirm the exact grade in the advisor.

Why is duplex harder to machine than 316?

Duplex is stronger and work-hardens more, generating higher cutting forces and heat. Run a lower speed band, a robust edge, and a rigid setup.

What cutting speed for duplex 2205 with carbide?

Roughly Vc 80–150 m/min and fn 0.10–0.30 mm/rev with high-pressure coolant — lower than austenitic stainless. Treat this as a starting band and confirm on a sample part.

How do I stop work-hardening in duplex?

Keep the depth of cut above the hardened layer, never let the tool dwell, and use a sharp robust edge with adequate speed.

ISO M — Stainless Steel · M10

M10 — Duplex stainless

Hardness range: 240–300 HB. Part of the ISO M — Stainless Steel group. Stainless steel presents work-hardening as the main challenge. Austenitic grades (304, 316L) built-up-edge and notch-wear rapidly. Positive, sharp geometry with high-pressure coolant at 15–20 bar is standard. Consistent depth of cut prevents re-cutting the hardened chip ramp.

Material profile — M10

ISO designation: M10 (ISO M — Stainless Steel)
Material: Duplex stainless
Hardness: 240–300 HB
ISO group colour: Stainless Steel

Tooling guidance — M-group

Group summary: Work hardening is the main challenge. Sharp positive geometry, high-pressure coolant 15–20 bar, consistent DOC.

Insert selection for duplex stainless (2205 / 2507) — starting point

ISO application class: M (stainless). Match the insert's ISO class, not the brand name. Sandvik, Kennametal, Iscar, Walter, Seco and Mitsubishi each publish an M-class grade — pick by ISO class, then confirm the exact grade for your condition.
Grade & coating: Tough PVD-coated carbide, a robust M-class grade. Duplex (2205 / 2507) is stronger and work-hardens harder than austenitic 304 / 316, so favour edge security over a keen finishing edge.
Geometry: Positive but robust honed edge, and a rigid setup — duplex generates high cutting forces. High-pressure coolant 15–20 bar.
Starting parameters: Vc ≈ 80–150 m/min (lower than 304 / 316 — duplex runs slower), fn ≈ 0.10–0.30 mm/rev. Typical starting band — confirm in the advisor or on a sample part.

duplex stainless (2205 / 2507): what goes wrong, and what to check first

Severe work-hardening: Worse than austenitic stainless. Keep DOC above the previously hardened layer, never let the tool dwell, and use a sharp but robust edge. See the tool-wear guide.
High cutting forces and deflection: Duplex is strong and pushes back. Shorten overhang, clamp rigidly, and use a robust edge to avoid deflection and chatter.
Notch wear at the depth-of-cut line: Vary the depth of cut between passes, ease Vc, and use a tougher grade.
Built-up edge at low speed: Raise Vc into the (lower) duplex band and aim coolant at the edge.

Reference data

Insert grade index ISO insert-code index CNMG120408 — general turning CCMT09T304 — positive finishing Tool-wear diagnosis

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