Duplex and super duplex stainless steels
Duplex and super duplex alloys are composed of iron and chromium or molybdenum. They also have an amount of austenite stabilisers, such as nickel or nitrogen, to achieve a balance between the ferritic and the austenitic phases. The creep limit is increased by nitrogen, while decreasing the speed of formation of brittle intermetallic compounds. Thanks to molybdenum, resistance to pitting corrosion increases.
This type of alloy was developed due to the austenitic steels’ vulnerability to SCC (stress corrosion cracking in chloride environments), as well as the brittleness and difficulty of ferritic welding. Even though austenitic steels have a high degree of weldability and ferritic steels are highly resistant to SCC, duplex steels combine some of these characteristics, giving rise to a compound that is very useful in industry. Austenite provides ductility, while ferrite contributes resistance to SCC. This balance between the two processes provides great benefits in terms of temperature and chloride content, whereas austenitic stainless steels do not provide optimal results.
The main benefits of use of duplex steels include:
- a high degree of weldability and malleability.
- a high level of mechanical resistance (by comparison to austenitic steels) and higher resistance to SCC, although in this case resilience, ductility, and weldability decrease.
- by comparison to austenitic and ferritic steels, duplex steels display greater resistance to traction and yield stress, as well as to general and pitting corrosion.
- as for corrosion due to chloride-induced stress, it displays a medium resistance level.
- strong resistance to erosion and abrasion.
- thanks to its low carbon content, it is also highly resistant to integranular corrosion.
Thanks to these properties, this type of alloys are mainly used in different types of pipes, in the chemical industry, petrochemical plants, etc.
Duplex and Superduplex alloys in industries and applications:
Castinox works with different kinds of steels and special alloys, such as duplex and superduplex, so we can produce high-quality cast parts for the power industry, the water processing industry, the paper industry, the construction industry and the mining industry. These are some of the components that we manufacture:
- Ball valves
- Rising plug valves
- Rotary valves
- Butterfly valves
- Guillotine valves
- Globe cryogenic valves
- Check gate valves
Components for Turbines
- Parts for Kaplan Turbines
- Parts for Pelton Turbines
- Parts for Francis Turbines
- Fluid pump pieces
Duplex and superduplex alloys