Super Duplex stainless steels have a ‘duplex’ two-phase microstructure consisting of both austenitic and ferritic grains that give 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 steel. 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 that matches or beats all but the most stainless steels and often provides 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.
For over 50 years, Langley Alloys have provided our clients with durable, high-quality alloys. Our products have been used in aerospace, defence, and many, many more fields. Today, we offer our products to clients across the world, and we have offices on several continents.
Contact Langley Alloys today for more information about super duplex stainless steels or any of our other products.