What is super duplex material?

‘Super duplex’ is a shorthand term for a family of high-performance stainless steels designed with around 25% chromium content in the alloy’s makeup. As the duplex name suggests, this family of alloys have a microstructure made up of both austenitic and ferritic grains of steel. This duplex nature provides Super Duplex’s unique combination of physical and mechanical properties.

History of Super Duplex Materials

The original duplex stainless steel was developed in Sweden for use in the sulfite paper industry. These early alloys were developed to combat corrosion problems common in that industry as a result of chloride-bearing cooling waters. However, while these duplex stainless steels proved to be an excellent development in the field, they did not meet all needs. As a result, further innovation was needed.

That innovation took the form of super duplex stainless steel. The original alloy of that range, Ferralium 255, was developed by Langley Alloys itself in the 1960s. However, the term ‘super duplex’ was not widely used until the 1980s, when it was used to describe highly alloyed, high-performance Duplex steel with a pitting resistance equivalent of >40 (based on Cr% + 3.3Mo% + 16N%).

A number of other grades were subsequently developed in addition to the original Ferralium 255 (UNS S32550, F61)including  SAF2507 (UNS S32750, F53) and S32760 (F55, Zeron 100).

Practical Uses of Super Duplex Stainless Steel

Owing to its high level of chromium, this new type of duplex stainless steel provides superb resistance to acids, acid chloride and caustic solutions, as well as other aggressive operating environments in the chemical/petrochemical, pulp and paper industries. Super duplex stainless steels feature superior resistance to stress corrosion cracking compared with more commoditised austenitic (3xx series) stainless steels, as well as enhanced mechanical properties – even compared with regular duplex stainless steels (S32205).

Today, super duplex materials are typically used in applications such as pumps, valves, fasteners, pipework, connectors, plus components in the oil and gas, petrochemical/chemical, pulp, and paper industries.

Langley Alloys stocks the most complete range of super duplex material, including solid bars up to 16” (406.4mm) diameter, plate up to 3” thickness, plus access to pipes, flanges and fittings through our supply chain.

These are available in Ferralium 255 (UNS S32550, F61), SAF2507 (UNS S32750, F53) and S32760 (F55, Zeron 100).

Got Any Questions? Get in Touch With Us

As the creator of Super Duplex Stainless Steel, there is no better source of information about this family of alloys than Langley Alloys.

For more information about super duplex materials, download our introduction guide to super duplex stainless steels by filling in your details to get instant access. Otherwise, please don’t hesitate to contact us today. We would be happy to answer any questions that you may have regarding specifications and common applications.