718 has lower corrosion resistance than 625, and in 718 it may depend on the HT condition. There are three different aging treatments so be careful.
Why would you want to use 718?

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Edstainless, the reason for 718 is due to the strength. I need a material that has min 105K yield. The HT condition of the 718 in question would be solution treated and precipitation hardened per NACE MR-01-75.

Have you looked at 725? Or even work hardened 22 or 686?
What product form are you looking for?

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P.E. Metallurgy, consulting work welcomed

EdStainless, I just read up on the materials you have mentioned. It looks like 725 has similar corrosion properties as 625 with higher strength, which per the document in my initial post would be suitable for rich amines service. I'm a bit confused on why in lean amines the material is not suitable? Would 686 work with lean amines service as well?

Product form: bar. Will be used for the valve stem.

Thanks for the support!

There's a whole raft of high strength nickel alloys developed for high pressure systems that are, more or less, standard materials for subsea production systems: 716, 718, 725, etc, etc - the complete menu is in API Std 6ACRA which should be your go to document. Never seen them in a gas sweetening unit before, and not noted in European Federation of Corrosion Publication 46. Is super duplex stainless steel not an option - a bit less aggravation on the manufacturing quality control front, and more suppliers are likely to have Norsok M-650/ISO 17782 documentation. Of course, you will only get 80 ksi, but it may be quicker and easier.

Steve Jones
Corrosion Management Consultant

www.linkedin.com/in/drstevejones

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

Hi SJones, I did look into some super duplex stainless steel, but strength did not meet the requirement(105k Ksi). Like you have mentioned, they are mostly limited to 80Ksi. I will look into API Std 6ACRA.

Out of interest, why does it have to be 105 ksi in a gas sweetening unit?

Steve Jones
Corrosion Management Consultant

www.linkedin.com/in/drstevejones

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

SJones, the material is used for a valve stem, which requires 105 ksi.

Yes - you said that, but what pressure is this system working at to demand that sort of strength?

Steve Jones
Corrosion Management Consultant

www.linkedin.com/in/drstevejones

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

The pressure is 1480psig. The torque to operate the valve is high due to the application and seat materials.

I would look at cold worked Ni alloys.

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