Overview
AL6XN is a superaustenitic stainless steel with outstanding resistance to chloride pitting, crevice corrosion and stress corrosion cracking. AL6XN is a 6 moly alloy that was developed for and is used in highly aggressive environments. It has high nickel (24%), molybdenum (6.3%), nitrogen and chromium contents that give it excellent resistance to chloride stress corrosion cracking, chloride pitting, and exceptional general corrosion resistance. AL6XN is primarily used for its improved pitting and crevice corrosion resistance in chlorides. It is a formable and weldable stainless steel.Because of its nitrogen content, AL6XN has greater tensile strength than common austentitic stainlesses, while retaining high ductility and impact strength.
Alloy AL6XN is a low carbon, high purity, nitrogen-bearing"super-austenitic"nickel-molybdenum alloy with excellent resistance to chloride pitting and crevice corrosion. Alloy AL6XN's high strength and corrosion resistance makes 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.
The high nickel and molybdenum contents provide improved resistance to chloride stress-corrosion cracking. Copper (Cu) has been intentionally kept to a residual level for improved performance in seawater40. The high alloy composition of the AL-6XN alloy resists crevice corrosion and pitting in oxidizing chloride solutions to a degree previously achieved only by nickel-base alloys and titanium.
Specification
ASTM B690-18 Standard Specification for Iron-Nickel-Chromium-Molybdenum Alloy (UNS N08367) Seamless Pipe and Tube.
Which include:
ASME SA : 182, 240, 249, 312, 479
ASME SB : 366, 462, 564, 675, 676, 688, 691
ASTM A : 182, 240, 249, 312, 479
ASTM B : 366, 462, 472, 564, 675, 676, 688, 691, 804
NACE : MR0175
UNS : N08367
Chemical Composition
Ni | Cr | Mo | C | N | Mn | Si | P | S | Cu | Fe |
|---|---|---|---|---|---|---|---|---|---|---|
23.5-25.5 | 20.00-22.00 | 6.00-7.00 | 0.03 Max | 0.18-0.25 | 2.0 Max | 1.00 Max | .040 Max | 0.03 Max | 0.75 Max | Remainder |
Mechanical Properties
Temp. °F (°C) | Ult. Tensile Strength | .2% Yield Strength | Elongation in 2” | Charpy V-Notch Toughness |
|---|---|---|---|---|
-450 (-268) | 218,000 | 142,000 | 36 | 353* |
-320 (-196) | 196,000 | 107,000 | 49 | 85 |
-200 (-129) | - | - | - | 100 |
70 (21) | 108,000 | 53,000 | 47 | 140 |
200 (93) | 99,900 | 49,400 | 47 | - |
400 (204) | 903,000 | 40,400 | 46 | - |
600 (316) | 86,000 | 36,300 | 47 | - |
800 (427) | 87,000 | 36,000 | 48 | - |
Corrosion Resistance
Chromium, molybdenum, nickel and nitrogen all contribute to overall resistance to corrosion by various media. Chromium is the principal agent for conferring corrosion resistance in neutral or oxidizing environments. Chromium, molybdenum and nitrogen increase resistance to pitting corrosion. Nickel imparts the austenitic structure. Nickel and molybdenum both provide increased resistance to chloride stress corrosion cracking in reducing environments.
Applications
1. Reverse osmosis desalination equipment and pumps.
2. FGD Scrubbers.
3. Chemical process tanks and pipelines.
4. Seawater heat exchangers.
5. Tall oil distillation columns and packing.
6. Offshore oil and gas production equipment.
7. Pulp bleaching plant washers, vats, press rolls and pipelines.
