Duplex stainless steels contain roughly 50% austenite and 50% ferrite. Ferrite is inherently much more resistant to chloride-induced SCC than austenite whereas Austenite provides toughness and ductility, helping prevent brittle cracking.
Compared with fully austenitic stainless steels, it has lower nickel content which helps to lower SCC susceptibility.
Duplex stainless steels bolts typically have higher chromium and molybdenum contents. Chromium forms a protective oxide passive layer whereas Molybdenum improves resistance to localized breakdown of that layer in chlorides. Ferrite is less susceptible to hydrogen embrittlement than austenite under many service conditions.
Duplex fasteners resist stress corrosion cracking because their ferrite-austenite microstructure simultaneously reduces crack initiation, slows crack propagation, stabilizes passivation, and lowers effective stress—a combination no single-phase stainless steel can match.
https://www.siddhgiritubes.com/uns-s31803-uns-s32205-duplex-steel-nut-studbolt-fasteners-manufacturer-supplier.html
- fastenersonline's blog
- Log in or register to post comments