Super Austenitic vs. Duplex/Super/Hyper Duplex Stainless Steels

[FOM1]

I'm searching for the most definitive guide & reference for corrosion resistance factors, such as PREN, CCCT & CPT for the super austenitic (254/64SMO, 904L & AL6XN) vs. (2205,2507 & 2707).
I've been searching the net and find article for 1 or 2 of these materials, but nothing comprehensive or the article starts out with a couple of material references and later in the article, these references are missing or forgotten when doing graphs and charts.
We currently/commonly use the 2205/2507 SST and looking to upgrade to the austenitics for higher corrosion capabilities, but want to do a deep dive into their comparative properties and make a massive cross reference chart.

Best resources & location?

 

[SJones]

Manufacturers' datasheets for a start

Steve Jones
Corrosion Management Consultant

http://www.linkedin.com/in/drstevejones

All answers are personal opinions only and are in no way connected with any employer.

 

Google ACOM, the periodical where Avesta published many reports on the steels you are considering.

There are NiDI reports with material rankings for various corrosion tests. Just remember that rankings from standardized tests may not reflect the mileage you get in the real world.

Outokumpu Handbook of Stainless Steel

IMOA - Practical Guidelines for Fabrication of Duplex Stainless Steels 3rd Ed
There's a similar one for austenitic stainless steels

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[FOM1]

ironic metallurgist

I've not found the site for the ACOM, there are hundreds of hits and I've opened about 50 pages of meaningless dribble, any additional clues to this ACOM such as key words?

I've been thru the Outokumpu handbook, the NIDI, IMOA, EuroInox, Atlas, Nickel Institute, Arcelor Mittal, MetalTek, Penn Stainless, Haynes, Rolled Alloy, Allegheny Technologies Inc., Emerson/Fisher Controls, International Atomic Energy Agency, North American Stainless, Thyssen Krupp, BSSA, etc.

One location will list say 904L, then another AL6XN, or worse, they'll start with AL6XN & 254SMO, but 1/2 way thru the report, they'll drop one or the other, finding a comprehensive location, report, site for all the super austenitics has been painful to say the least.

 

[EdStainless]

ACOM and NiDI are the best places to start, but you will have to read very carefully.
There are many subtle differences in corrosion testing that end up with them being very different.
People publish preN values, but are they based on actual chemistries that mills use?
I could go one for a while ranting about this.
In the high corrosion resistant category you really have 654SMO, AL-6NX, 25-6hMO, and 1925Mo. (UNS S32654, N08367, N08926)
For the super duplex you have Zeron 100, 2507, 2707, and a few others. (UNS S32750, S32760, S32550, S32900)
When it comes to pitting and crevice corrosion is a high chloride aqueous environment there are all within a hair's breadth of each other.
How they are heat treated, fabricated, and cleaned will make the most difference.
The biggest problem with the higher alloy duplex SS is how difficult they are to HT correctly especially in large cross sections.
You have to quench directly (delay measured in seconds) into circulating ice water to have a hope of getting them correct.
The duplex are also sensitive to both low and high temps. Most rules only allow exposure between -40 (or -30F in some cases) and 600F.
These are firm limits never to be crossed, especially the upper one as damage is cumulative.


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P.E. Metallurgy, consulting work welcomed

 

Much of ACOM predates the interweb, but also Avesta has been swallowed by Outokumpu so it is defunct I think.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

Your best starting point is not trying to base it on research and standard tests, but what the rest of the industry is doing.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[FOM1]

I found some ACOM magazines; A CORROSION MANAGEMENT AND APPLICATIONS ENGINEERING MAGAZINE FROM OUTOKUMPU

 

[EdStainless]

https://www.scribd.com/document/97072652/AL-6XN-SourceBook

https://www.specialmetals.com/documents/technical-bulletins/incoloy/incoloy-27-7mo.pdf

https://www.carpentertechnology.com/alloy-finder/25ni-20cr-6mo

https://www.vdm-metals.com/fileadmin/user_upload/Downloads/Data_Sheets/Data_Sheet_VDM_Alloy_926.pdf

Just a sampling

I should have added, if your spec will include a corrosion test then you must be very specific about sample preparation and how the test is conducted.
Duplex SS should always be tested for phase balance and intermetallics (A923 low temp impact).

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed