Most of the stainless steel products that require the greater resistance to chloride pitting and crevice corrosion, for example flatware, are in this group. The three significant components are carbon, chromium and nickel (or manganese). However, the high molybdenum and nitrogen content, together with the higher nickel content will result in a "superaustenitic" stainless steel for higher effective corrosion resistance, but the higher alloy content of superaustenitic means a higher cost as well. So, in this case, the duplex steels could be replaced because of the similar performance.
Ferritic stainless steel (magnetic)
Chromium is the main alloying component for this stainless steel type. There is low carbon content and very little nickel. It is the lowest cost stainless steel.
Martensitic stainless steel
The compositions are chromium, molybdenum and carbon. There is no nickel. Martensitic stainless steel is not corrosion resistant but it is extremely strong and hard; the drawback being that the carbon which makes it harder also makes it more brittle.
Precipitation-hardening martensitic stainless steel
The most common formula (14/4PH) contains chromium and nickel. It is corrosion resistant and also very strong, resisting impacts better than the ordinary martensitic grade.
This is the combination of austenitic and ferritic, making it strong and corrosion resistant. It can be used in a thinner section to save weight and cost.