AL-6XN® (UNS N08367)
AL-6XN super-austenitic stainless steel (UNS N08367)
- 6.3% molybdenum
- Over 25 years of proven seawater service
- Practical immunity to chloride stress cracking
- 50% stronger than stainless
- ASME coverage up to 800°F
- Easily welded
- Available in ALL product forms
AL-6XN® alloy (UNS N08367) is a low carbon, high purity, nitrogen-bearing "super-austenitic" stainless alloy. The AL6XN alloy was designed to be a seawater resistant material and has since been demonstrated to be resistant to a broad range of very corrosive environments. The high strength and corrosion resistance of the AL6XN alloy make it a better choice than the conventional duplex stainless steels and a cost effective alternative to more expensive nickel-base alloys where excellent formability, weldability, strength and corrosion resistance are essential.
Performance Profile
The levels of chromium, molybdenum and nitrogen in AL-6XN all serve to provide resistance to acidic oxidizing chloride solutions previously achieved only by the nickel base alloys. High nickel (24%) and molybdenum (6.3%) contents make AL-6XN a solution to chloride ion stress corrosion cracking. Because of its nitrogen content, AL-6XN has greater tensile strength than common austenitic stainlesses, while retaining high ductility and impact strength. The ASME allowable stresses for AL-6XN are up to 75% higher than for 316L stainless, and more than twice those for the copper-nickel alloys.
Chemistry
| Cr | Ni | Mo | C | N | Mn | Si | P | S | Cu | Fe | |
|---|---|---|---|---|---|---|---|---|---|---|---|
| MIN | 20.00 | 23.50 | 6.00 | -- | 0.18 | -- | -- | -- | -- | -- | |
| MAX | 22.00 | 25.50 | 7.00 | 0.03 | 0.25 | 2.00 | 1.00 | 0.04 | 0.03 | 0.75 | Balance |
Specifications
ASME SA 182, ASME SA 240, ASME SA 249, ASME SA 312, ASME SA 479, ASME SB 366, ASME SB 462, ASME SB 564, ASME SB 675, ASME SB 676, ASME SB 688, ASME SB 691
ASTM A 182, ASTM A 240, ASTM A 249, ASTM A 312, ASTM A 479, ASTM B 366, ASTM B 462, ASTM B 472, ASTM B 564, ASTM B 675, ASTM B 676, ASTM B 688, ASTM B 691, ASTM B 804
NACE MR0175
UNS N08367
Inventory
AL-6XN® Billet, AL-6XN® Concentric Reducers, AL-6XN® Fittings, AL-6XN® Forgings, AL-6XN® Pipe, AL-6XN® Plate, AL-6XN® Sheet, AL-6XN® Stub Ends, AL-6XN® Tees, AL-6XN® Welding Products
Common Trade Names
UNS N08367, AL6XN
Applications
FGD Scrubbers
Reverse Osmosis
Distillation Columns
Offshore Oil and Gas
Heat Exchangers
Fabrication
The low carbon and high nitrogen contents in AL-6XN alloy (UNS N08367) minimize the precipitation of carbides and secondary phases that can occur during welding. Therefore as-welded assemblies can be placed in service, provided a suitable over-matched filler metal, such as alloy 625 is used. AL6XN alloy can be welded in the field using procedures similar to those used with other austenitic stainless steels.
Rolled Alloys AL-6XN (UNS N08367) Fabrication Guide gives welding parameters, welding joint designs, machining, bending and forming data.
Corrosion Resistance
AL-6XN has excellent corrosion resistance in high chloride environments as well as many acids. Below is a quick summary of the critical pitting and crevice corrosion resistance compared to many other alloys. AL-6XN has improved properties over stainless steels and all duplex grades. The practical immunity to chloride stress corrosion cracking has pushed AL-6XN (UNS N08367) into many seawater applications including seawater reverse osmosis. The resistance to acid and chloride environments is proven by over 20 years of service in the flue gas desulfurization process at coal fired electric power plants.
| Alloy | % Mo | CCCT, °F | CPT, °F | PREN |
|---|---|---|---|---|
| 316L | 2.1 | < 28 | 68 | 24 |
| 2205 | 3.1 | 68 | 120 | 35 |
| 904L | 4.4 | 75 | 130 | 36 |
| ZERON 100 | 3.5 | 108 | 180 | 41 |
| AL-6XN | 6.3 | 110 | 172 | 44 |
| 625 | 9.0 | 113 | - | 51 |
* CCCT - 10% FeCl3 6H20, per ASTM G 48 Practice B, CPT - 1 M NaCl, per ASTM G 150, PREN = Cr + 3.3 Mo + 16N