Does anyone have experience with AL6XN Stainless?

Discussion in 'Boat Design' started by Barry, Dec 5, 2018.

  1. Barry
    Joined: Mar 2002
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    Barry Senior Member

    During the process to find a suitable material to use in a submersed salt water environment, I ran across this alloy of stainless which promises extreme resistance to corrosion in a salt water environment and ultimate tensile strengths of 108,000 psi at 70 degrees F. Yields of 53,000 psi.
    Attached a copied reference
    AL-6XN® (AL6XN / UNS N08367) Super-Austenitic Stainless Steel
    • 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 AL-6XN 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.

    As there are often threads on this forum that deals with corrosion of stainless and my absolute
    inexperience with this alloy, ( I would have just bought 316 ss as a matter of course) I am wondering
    if anyone has used the alloy and could give some comments on it. And a query as to
    why, if it is as good as it is advertised to be, is it not the basis for most marine applications and hardware. Some information state that it is much cheaper than 316

    Of a technical nature, they note that the alloy contains nitrogen, so how does this exist in a metal, suspended? Attached to
    another element?
  2. Ad Hoc
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    Ad Hoc Naval Architect


    Never heard of that one before. But does look impressive. Pricewise though...i'd be very surprised if it is comparable to 316L.

    I assume you've looked at SAF 2205 as an alternative?
  3. Barry
    Joined: Mar 2002
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    Barry Senior Member

    I am looking at some of the duplex ss including 2205.

  4. daiquiri
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    Location: Italy (Garda Lake) and Croatia (Istria)

    daiquiri Engineering and Design

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