High Temperature High Strength Alloy 1

[jmoon]

I am designing a small vessel that is rated for 40,000 psig internal pressure, 600F. I am attempting to justify the use of Alloy 718 however I am concerned about chloride attack at elevated temperatures. The exposure to 25% CaCl2 will not be continuous, parts will be cleaned after use.

Any thoughts or comments?

Jeff Moon, P.E.

 

[EdStainless]

I do not like 718 for for high stress Cl service. I have seen it attacked both in auq solutions and by molten salts. What pH range are you working with?
I would feel better about 725 or heavily cold worked NiCrMo (C-22, 686, 59).

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Corrosion never sleeps, but it can be managed.

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[metengr]

To help with your question, could you provide some additional information regarding service conditions of the vessel or process.

Under normal service, what are the vessel contents?

When will CACl2 be introduced and under what service conditions?

 

[jmoon]

Thanks for the reply.

I tend to agree, however I need an alloy that exhibits high UTS and 0.20%YS at 600F. I also need a non-magnetic alloy since a magnetic drive is involved.

The exposure to 25% CaCl2 + Water + Lime will tend to be brief (<1 day exposure), long enough to perform rheological tests. Afterwards, the parts will be washed and neutralized. For the most part, the fluids in contact with the 718 are water or oil based drilling muds.

I need to keep the wall thickness to a minimum. I will probably use a liner & jacket approach, pre-stressing the liner. Other alloys, such as Alloy 725, simply do not have the strength. Other choices tend to be magnetic.

Jeff

 

[jmoon]

Some additional details on the application:

The vessel ID is 2.25in, OD 5.00in, liner and jacket design, final dimensions still subject to change based on FEA results. Closure involves is an straight ACME thread and high pressure seals.

The application is a HPHT rheometer, used to determine the rheology (viscosity) of drilling fluids under downhole conditions. A typical test involves temperature and pressure ramps during which the measurements are made. All tests last less than a day, although I can see cases where longer term tests might be involved. In the case of the CaCl2 solution, I plan to mandate that exposure be kept to a minimum.

In our industry, Alloy 718 is commonly used, particularly for magnetic drives used to to couple to an inner shaft and downhole tools.

The Cl content of the brine solution requested by my client caught my attention. I decided to post this to see if anyone can suggest alternatives.

Jeff

 

[metengr]

I would probably go with alloy C22, ASME SB 564. Considering your elevated temperature, aqueous solution with even a low level of chlorides, Inconel 718 would be susceptible to intergranular stress corrosion cracking.

 

[jte]

jmoon-

You might want to also get in touch with the tech staff at

http://www.rolledalloys.com/index.aspx.

jt

 

[unclesyd]

Take a look at Carpenter MP35N.
I would call them about your application.

Here is the Carpenter Data Sheet

http://carpenter.idesinc.com/datasheet.asp?i=2&e=3

AMS 5758
AMS 5844
AMS 5845
ANSI/ASTM F562

 

[jmoon]

Unclesyd,

Actually, MP35N was my first choice. I can't seem to find 5" bar stock without purchasing a mill run. Do you have any sources that can help me? MP35N will definitely solve the problem.

Thanks

Jeff

 

[unclesyd]

I try to check some other companies.

Here is one that list it and MP159

http://www.falcon-metals.com/Nickel/NickelAlloyAvailability.htm

 

[unclesyd]

Here are some others. I think you may have to get it forged from a rod billet.

http://www.steelforge.com/products/step2.asp?Family=Super+Alloy

http://www.magellanmetals.com/nickelalloy.htm

http://www.nationalspeciality.com/index.html

You are not as lucky as I was when I had to build some “bombs”, really. I made mine from a slightly bent 5" dia. screw from a screw jack. Had a threaded sleeve and screw-in plug, made from the same screw, for a 2 piece cap and used a self-energizing gasket. Fortunately they were only used to around 22,000 psi.

Make sure you put in a vent, I know where a very large bomb under better than 1,000,000 psi is buried.

 

[EdStainless]

If you are looking at MP, don't forget Elgiloy

= = = = = = = = = = = = = = = = = = = =
Corrosion never sleeps, but it can be managed.

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