Super austenitic stainless steels
Austenitics with much more nickel, molybdenum and nitrogen than 316L, for acids, chlorides and seawater where 316L suffers pitting or stress corrosion cracking. PREN ranges from about 28 (Alloy 20) to over 42 (254 SMO).
Super austenitic stainless steels: alloys supplied by Dustre
Forms: Bar, Plate, Pipe, Forging and flange, Fitting. Click an alloy to see standards by form, composition, properties and equivalents.
| Material | UNS | W.Nr. / EN | Forms |
|---|---|---|---|
| 254 SMO / F44Super austenitic stainless · 6Mo super-austenitic stainless steel with nitrogen | S31254 | 1.4547 | Bar, Plate, Pipe, Forging and flange, Fitting |
| 904L stainless steelSuper austenitic stainless · Low-carbon Ni-Cr-Mo-Cu super-austenitic stainless steel | N08904 | 1.4539 | Bar, Plate, Pipe, Forging and flange |
| Alloy 20 (Carpenter 20)Super austenitic stainless · Niobium-stabilized Fe-Ni-Cr-Mo-Cu alloy | N08020 | 2.4660 | Bar, Plate, Pipe, Forging and flange, Fitting |
| Alloy 28Super austenitic stainless · 27Cr-31Ni-3.5Mo-Cu super-austenitic stainless steel | N08028 | 1.4563 | Bar, Plate, Pipe |
Did not find the alloy? See all materials or ask the technical team.
About super austenitic stainless steels
904L (N08904) and Alloy 20 (N08020) add copper to 20–38 % nickel and resist sulfuric and phosphoric acid. 254 SMO (S31254, forging F44) is the classic 6Mo grade, with nitrogen, for seawater and pulp bleaching. Alloy 28 (N08028) has more chromium and nickel for phosphoric acid and well tubing with H₂S. 6Mo alloys such as Alloy 926 and Alloy 31 follow the same logic, with even more molybdenum and nitrogen.
Like ordinary austenitics, they do not harden by heat treatment and are supplied solution annealed. Welding calls for overalloyed filler metal (ER385, ER320LR, ER383 or ERNiCrMo-3), so that the weld bead is not below the base metal in corrosion resistance.
See also
Frequently asked questions
904L or 254 SMO?
904L is better in sulfuric and phosphoric acid, thanks to copper. 254 SMO, with 6 % Mo and nitrogen, is better in chlorides and seawater: PREN of about 43, against about 35 for 904L.
Is a super austenitic a nickel alloy?
No. 904L, Alloy 20 and Alloy 28 get N-series UNS numbers because of their high nickel content, but they are iron based and classified as highly alloyed austenitic stainless steels.
