Stainless Steel is classified into numerous types based on the microstructure and chemical composition of the alloy. The main types of Stainless steel include Stainless Steel 409 Pipes. Duplex Stainless steel is an alloy with a dual-phase structure with properties similar to two other types of Stainless Steel viz., Austenitic and Ferritic. The Ferritic and austenitic properties and structure in Duplex SS is a proportionate 50%. Duplex Stainless Steel is further divided into three more subcategories or types. One of them happens to be “Super Duplex Stainless Steel”. This particular sub-type of Duplex SS has better corrosion resistance than Duplex Stainless steel due to its highly alloyed chemistry. Along with this, the mechanical strength is also off the charts.
This blog will help you differentiate between Duplex and Super Duplex grades of Stainless Steel.
Difference Between Duplex and Super Duplex SS
Both Duplex, as well as Super Duplex, have great corrosion resistance compared to regular austenitic grades. However, when it comes to differentiating between the two, Super Duplex Stainless Steel has an upper hand. This is possible as Super Duplex has an added quantity of chromium in its composition. However, adding excess chromium harms the structural integrity of the metal. This needs to be rectified by adjusting the proportions of all the alloying materials. Thus, Super Duplex SS is the pricier option between the two. An increased quantity of nickel and molybdenum simultaneously results in an increase in the overall price of the alloy.
There is no major difference in the welding procedure of Duplex and Super Duplex alloys. However, it is extremely tricky to weld these alloys keeping in mind the microstructural integrity that is at risk during welding. Thus, it is advised to allow only experienced workers to carry out the welding process.
The Difference in Corrosion Resisting Properties
As mentioned earlier, Super Duplex has an upper hand when it comes to pitting corrosion. The addition of fillers such as chromium, nickel, tungsten, nitrogen, and molybdenum is what enhances the corrosion-resisting properties of the metal alloy. Both Duplex and Super Duplex alloys are resistant to alkaline solutions, acidic environments, and various other temperature and atmospheric conditions.