Super duplex 2507 vs 654 SMO

Last verified 19 August 2026.

The comparison

Proof strength Rp0.2, minimum (EN) — different product forms — cold rolled coil and sheet against Quarto plate. The grades differ and so does what was tested, so the gap between these two numbers is not all material

Tensile strength Rm, minimum — different product forms — cold rolled coil and sheet against Quarto plate. The grades differ and so does what was tested, so the gap between these two numbers is not all material

Elongation A80, minimum — different product forms — cold rolled coil and sheet against Quarto plate. The grades differ and so does what was tested, so the gap between these two numbers is not all material

PREN — different documents — Outokumpu Forta range datasheet against Outokumpu Ultra range datasheet

Modulus of elasticity — different documents — Outokumpu Forta range datasheet against Outokumpu Ultra range datasheet

Density — different documents — Outokumpu Forta range datasheet against Outokumpu Ultra range datasheet

Thermal conductivity — different documents — Outokumpu Forta range datasheet against Outokumpu Ultra range datasheet

Where each side’s numbers come from

See Super duplex 2507 and 654 SMO — each page lists every source, every demotion and every gap. Nothing on this page is derived from anything not on those two, and our coverage limits are stated separately.

Where a PREN appears above, read it as a ranking number rather than a qualification: what PREN can and cannot tell you.

When to choose which

Super duplex 2507. Seawater and the aggressive end of chloride service, where 2205 is marginal. At the 550 MPa EN 10088-2 minimum it is also the strongest of the stainless grades on this site, so a strength-driven section in 2507 is thinner again than in 2205.

654 SMO. Hot, aerated seawater and the harshest bleaching and scrubbing duties, where 254 SMO and super duplex both have a service record of crevice attack. The usual comparison at this level is not against another stainless but against a nickel alloy or titanium, and 654 SMO wins on fabricability and on the fact that it is still a steel.

Against Super duplex 2507: Fabrication and supply, almost always. A narrower heat-input window than 2205, procedures that must be qualified specifically for it, and availability that is thin outside common thicknesses. A shop without a qualified procedure faces a new PQR and a lead time measured in weeks, and that is frequently decisive regardless of what the property table says.

Against 654 SMO: Price and everything that follows from it. Seven percent molybdenum and 22% nickel make it one of the most expensive alloys in any stainless catalogue, welding needs an overmatching nickel-base filler, and lead times are long because almost nobody stocks it. Every project that can be solved one grade down is solved one grade down.

What this comparison does not cover

• The ASTM plate minimum is not established here.
• Crevice corrosion, which PREN does not predict and which usually decides seawater work.
• Elevated temperature: super duplex carries the same 475 °C embrittlement and sigma-phase constraints as 2205, and they arrive sooner. Not sourced here.
• Fatigue, fracture toughness and stress corrosion cracking.
• Cost, which is materially above 2205 and moves with alloy surcharges.
• Composition limits, not established.
• Only plate minima are established here.
• Critical pitting and crevice temperatures, which are the whole basis for choosing this alloy.
• Corrosion rate data in the services it is bought for.
• Welding practice, filler selection and the properties of the resulting weld metal.

Generated from data/materials/2507.yaml and 654smo.yaml.