Super Duplex stainless steels have a ‘duplex’ two-phase microstructure consisting of both austenitic and ferritic grains that gives them a combination of attractive properties.
Whilst duplex alloys were developed around a 22% Cr addition level, super duplex alloys utilise a higher base composition to increase the level of corrosion resistance.
They are twice as strong as more standard grades of stainless steels. They achieve good toughness and ductility, placing somewhere between the two.
Their corrosion resistance is also very good,with comparable levels of chromium, molybdenum and nitrogen in selected compositions. By increasing the level of chromium additions, combined with significant levels of molybdenum and nitrogen, super duplex stainless steels achieve a Pitting Resistance Equivalent number, which will match or beat all but the most stainless steels and often provide comparable performance to some nickel alloys.
Another advantage is their resistance to stress corrosion cracking.
The addition of copper to these grades results in additional corrosion resistance. It has been shown that the presence of copper can stop or slow the formation of pitting corrosion, and it also contributes to exceptional resistance to sulphuric acid.
Resistance to sulphuric, nitric and phosphoric acid makes these products attractive for a number of applications in the chemical processing industry.
Super duplex stainless steels offer a cost effective option for many demanding applications – as their design foregoes high nickel additions which are expensive and subject to price volatility.
This can benefit as a direct material cost saving, but can also contribute to overall design savings if the application involves suspended loads.
If you’d like more information on our Super Duplex Stainless Steels, please get in touch with our expert team today, who will be able to help you further.