What are super duplex stainless steels?

The phrase ‘Super-Duplex‘ was designed to describe highly alloyed, high-performance Duplex steel with a pitting resistance equivalent of >40 (based on Cr% + 3.3Mo% + 16N%). 

The History of Super Duplex Stainless Steels 

Langley Alloys developed the very first super duplex steel in the late 1960’s. This material was promoted as Ferralium 255, and it has provided more than 50 years of successful service in numerous highly aggressive environments. Its popularity increased with the discovery of oil and gas in the UK North Sea, an environment where high strength and corrosion resistance, plus competitive pricing, were all equally critical.

With a high level of chromium, Super-duplex steel provides superb resistance to acids, chlorides, caustic solutions and other environments in the chemical/petrochemical, pulp and paper industries, often replacing 300 series stainless steel, higher-nickel super austenitic steels and nickel-based alloys.

Its chemical composition exploits nitrogen as a lower cost addition, which improves the strength without impairing toughness. It also enhances the corrosion resistance. This approach means that super-duplex grades are extremely cost competitive versus alternatives that rely upon more expensive alloy additions, such as nickel or molybdenum, to achieve their properties

The two-phase microstructure guarantees higher resistance to stress corrosion cracking compared with austenitic stainless steels. Fabrication and welding can be readily undertaken as long as qualified procedures are followed.

Common Uses for Super Duplex Stainless Steels

Super duplex stainless steels are widely used in applications that can exploit their increased strength and corrosion resistance. They are widely used in the manufacture of valves, pumps, mixers and agitators, tooling and fasteners. Typically operating environments include Oil & Gas; chemical processing including fertiliser production; mining; water treatment and desalination facilities; flue gas desulphurisation and gas scrubbers; marine and naval applications.

Got any more Questions? Get in Touch

If you have any more questions about super duplex stainless steels, please don’t hesitate to contact a member of our team today. We supply super duplex alloys in pipe, tube and plate forms and can advise you on the best solution for your application.