Duplex stainless steel, abbreviated as DSS, is a family of stainless steels characterized by a unique microstructure that consists of two phases: austenite and ferrite, present in roughly equal proportions. This "duplex" structure gives these alloys a superior combination of properties compared to traditional austenitic or ferritic stainless steels. Specifically, duplex stainless steels offer significantly higher strength (often double that of common austenitic grades like 304 or 316) and excellent corrosion resistance, particularly to chloride stress corrosion cracking and pitting corrosion, which can be problematic for other stainless steel types.
Their enhanced corrosion resistance is primarily due to higher levels of chromium (20-28%), molybdenum (up to 5%), and nitrogen (0.05-0.5%). The inclusion of nitrogen also contributes to their improved mechanical properties. While they contain less nickel than austenitic stainless steels, which helps with cost stability, careful control of their composition and heat treatment is crucial to maintain the optimal balance of austenite and ferrite for desired performance. Duplex stainless steels are widely used in demanding environments such as the offshore oil and gas industry, chemical processing, desalination plants, and structural applications where a combination of high strength and superior corrosion resistance is essential
