Stainless Steel is a steel alloy, primarily made from Iron and Carbon (max 1.2% by mass) with a major input of Chromium (min 10.5% by mass, max upto 25%) to obtain a corrosion- resistant product.
Duplex Stainless Steel, characterised as special stainless steel is a mixture of Austenite and Ferrite microstructure on a 50:50 ratio. It contains high levels of chromium, low levels of nickel and added with molybdenum.
Nickel is known for its Strength, Toughness and Resistance to Corrosion. Almost all Stainless Steel grades contain Nickel ranging from 5% to 30% for its above properties. Nickel based alloys generally contain minimum of 55% Nickel.