Duplex or Superduplex? 1.4462 and 1.4410 Compared

In petrochemicals, seawater applications and the chemical industry, classic stainless steels such as 1.4404 reach their limits. This is where duplex and superduplex steels come into play: they combine high strength with excellent corrosion resistance. We explain the difference between 1.4462 and 1.4410 – and when the more expensive superduplex is worth it.

What makes duplex steels special

Duplex steels have a two-phase microstructure consisting of roughly equal proportions of ferrite and austenite. This mixture combines the best of both worlds: the strength of the ferritic phase and the toughness and corrosion resistance of the austenitic phase. Compared with standard stainless steel, they offer around twice the yield strength and considerably higher resistance to stress corrosion cracking.

1.4462 (Duplex 2205)

Standard duplex 1.4462 (material number 1.4462, UNS S31803/S32205) is alloyed with around 22% chromium, 5% nickel and 3% molybdenum. It covers a large share of all demanding applications – from pressure vessels and heat exchangers to piping in aggressive media. Its pitting resistance equivalent number (PREN) is around 35.

1.4410 (Superduplex 2507)

Superduplex 1.4410 (UNS S32750) raises the alloy content further: around 25% chromium, 7% nickel, 4% molybdenum plus nitrogen. The PREN value is above 40. This allows the material to withstand chloride-rich media, seawater and higher temperatures. It is used wherever maximum resistance is required – for example in offshore installations, desalination and chlor-alkali chemistry.

Processing: what to watch for

Duplex steels weld well but require care with heat input and interpass temperature so that the phase balance is maintained. Excessive heat input can reduce toughness and corrosion resistance. For safety-relevant components, a qualified welding procedure with suitable filler materials is recommended.

Frequently Asked Questions

What is the difference between duplex and superduplex?

Both have a ferritic-austenitic microstructure. Superduplex (e.g. 1.4410) is more highly alloyed (more chromium, molybdenum, nitrogen) and has a PREN value above 40, which makes it more resistant to chlorides and seawater than standard duplex 1.4462 (PREN ~35).

When is 1.4462 sufficient and when do you need 1.4410?

1.4462 covers most applications in petrochemicals and the chemical industry. 1.4410 is chosen where there is extreme chloride exposure, seawater or higher temperatures, such as in offshore or desalination plants.

Are duplex steels weldable?

Yes. They are readily weldable but require controlled heat input and interpass temperature as well as suitable filler materials, so that the ferrite-to-austenite ratio and thus the corrosion resistance are maintained.