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- Duplex & Super Duplex
Duplex & Super Duplex
Roughly twice the yield of austenitic stainless with much better chloride resistance — and a narrow heat-treatment window that not every foundry can hold.
Duplex 2205 and super duplex 2507 are austenitic-ferritic grades with a 50/50 structure that delivers roughly twice the yield strength of CF8M and significantly better resistance to chloride pitting and stress corrosion cracking. Super duplex adds chromium and molybdenum to reach a PREN above 40.
The applications are specific: seawater cooling, desalination intake and brine rejection, produced water, and high-chloride process streams. In these services CF8M will pit and crack; duplex will not, at least not at the temperatures where duplex is allowed to operate.
That temperature limit is real. Duplex is generally limited to about 280 °C because above that the microstructure begins to transform, and to about −50 °C because the ferritic phase raises the ductile-to-brittle transition. Outside that window the correct grade is austenitic or a nickel alloy.
The manufacturing difficulty is the heat treatment: solution annealing must be held in a narrow band, then quenched fast enough to avoid sigma and other intermetallic phases. We control and report ferrite content and phase balance on every duplex casting, and we welcome third-party metallurgical review.
Key properties
| Property | Value |
|---|---|
| 2205 (CD3MN) PREN | ~ 32 – 35 |
| 2507 (CE3MN) PREN | > 40 |
| Specified min yield (2205) | 450 MPa |
| Ferrite content | 35 – 55 % typically |
| Solution anneal | ≈ 1 040 – 1 120 °C, rapid quench |
| Intermetallic control | Phase balance reported per casting |
Where you meet this grade
Send the piping class, not the part number
We check the dimensions, the material and the standard before we price — which is the part that decides whether the valve actually fits. RFQ answered within one working day.