Stainless steel as the common ferritic and austenitic stainless steels due to their low chromium content. Duplex stainless steels have a mixed microstructure of austenite and ferrite, the aim usually being to produce a 50/50 mix, although in commercial alloys the ratio may be 40/60. They are characterized by high chromium (19–32%) and molybdenum (up to 5%) and lower nickel contents than austenitic stainless steels. Duplex stainless steels have roughly twice the strength compared to austenitic stainless steels. Their mixed microstructure provides improved resistance to chloride stress corrosion cracking in comparison to austenitic stainless steels Types 304 and 316. The properties of
Stainless steel can be deformed, broken and removed from parts of the component, exposing bare reactive metal. When the two surfaces are the same material, these exposed surfaces can easily fuse together. Separation of the two surfaces can result in surface tearing and even complete seizure of metal components or fasteners. Galling can be mitigated by the use of dissimilar materials (bronze against stainless steel), or using different stainless steels (martensitic against austenitic). Additionally, threaded joints may be lubricated to provide a film between the two parts and prevent galling. Also, Nitronic 60, made by selective alloying with manganese, silicon and nitrogen,