Surface Treatments
Certifications
- ISO 9001:2015
- NORSOK M-650
- NACE MR0175
- ISO 15156-3
- PED 2014/68/EC
- EN 10204 type 3.2
- AD 2000 W2/W7/W10
Ferralium 255 vs Duplex 2205, Super Duplex vs Standard Duplex Upgrade
Ferralium 255 (UNS S32550) is a super duplex stainless steel (PREN ≥ 40); Duplex 2205 (UNS S31803 / S32205) is the standard duplex grade one tier below (PREN ~35). The two are not direct substitutes, they sit at different tiers of the duplex / super duplex stainless steel family. The Ferralium 255 vs Duplex 2205 question is typically an upgrade decision: when do service conditions exceed Duplex 2205 limits and require super duplex?
Composition Comparison
| Element | Ferralium 255 (S32550) | Duplex 2205 (S31803 / S32205) |
|---|---|---|
| Carbon (C), max. | 0.04 | 0.030 |
| Chromium (Cr) | 24.0–27.0 | 21.0–23.0 |
| Nickel (Ni) | 4.5–6.5 | 4.5–6.5 |
| Molybdenum (Mo) | 2.9–3.9 | 2.5–3.5 |
| Copper (Cu) | 1.5–2.5 | not specified |
| Nitrogen (N) | 0.10–0.25 | 0.08–0.20 |
Full element-by-element table on the Duplex 2205 chemical composition page.
PREN Comparison
Ferralium 255 PREN = 25 + 3.3×3 + 16×0.2 = 38.1 minimum, ~41 typical per heat. Duplex 2205 PREN = 22 + 3.3×3 + 16×0.15 = 34.3 minimum, ~35 typical per heat. The 5+ PREN unit increase is the defining benefit of upgrading from Duplex 2205 to Ferralium 255, it extends Critical Pitting Temperature from ~25 °C (Duplex 2205) to ≥ 35 °C (Ferralium 255) per ASTM G48 method A.
Mechanical Properties
| Property | Ferralium 255 | Duplex 2205 |
|---|---|---|
| Yield strength (Rp0.2), min | 550 MPa | 450 MPa |
| Tensile strength (Rm), min | 760 MPa | 620 MPa |
| Elongation (A5), min | 15% | 25% |
| Hardness (NACE MR0175), max | 32 HRC | 32 HRC |
When to Upgrade from Duplex 2205 to Ferralium 255
Standard upgrade triggers from Duplex 2205 to super duplex (Ferralium 255 / 2507 / Zeron 100):
- Seawater service above 30 °C, Duplex 2205 CPT (~25 °C) marginal; super duplex CPT ≥ 35 °C provides safety margin
- Sour-gas service with H2S partial pressure exceeding NACE MR0175 thresholds for standard duplex
- Reducing-acid service, HCl, dilute H2SO4, brines, here Ferralium 255 specifically (Cu-bearing) outperforms Cu-free super duplex grades
- High chloride concentration, concentrated brines, evaporator service, geothermal
- NORSOK M-630 MDS D55 specification calling for super duplex per project spec
- High-velocity erosion-corrosion service where increased PREN provides additional margin
Cost & Availability
Ferralium 255 typically commands a 30–50% material premium over Duplex 2205 due to higher Cr / Mo / Ni / Cu loading and tighter manufacturing controls. For applications within Duplex 2205 service limits, the super-duplex upgrade is unjustified. For applications at or beyond those limits, the upgrade prevents in-service pitting failures whose lifecycle cost vastly exceeds the material premium. Both grades available from TorqBolt, see Ferralium 255 grade page or Duplex 2205 reference for details.
Need Ferralium 255 or Duplex 2205? Email info@torqbolt.com or WhatsApp +91-22-66157017 with form, dimensions, quantity, ASTM/EN spec, MTC level (3.1 / 3.2). NACE MR0175 sour-service stamp on every heat. NORSOK M-650 QTR on request. Per-heat EN 10204 type 3.2 MTC included with every consignment.
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