High temp caustic environment

[jimboux]

I looking to design some equipment that will be working in the following environment.
800-1,000 deg F
free sodium, Sodium Oxide, and Sodium Hydroxide, Ti-metal and NaCl (salt) mixture - all four are possible.

I need some guidance in corrosion compatibility for some high strength and wear components.

Right now I'm considering parts made from 304 SS, Nitronic 60, Inconel X-750, Inconel 718 and Inconel 800H clad with triballoy 400 or triballoy 800.

Any help would be appreciated.

 

[TVP]

A little more information on high strength components would be helpful. Pressure vessel? Stress state (tension, bending, compression, all of the above)? Moving parts or stationary? SS has relatively low strength at those temperatures, as does Inconel 800H.

 

[jimboux]

Some of it is pressure vessel but the pressures are low (30 psi at the high temp, 75 psi at the low temp).

The X-750 is primarily bending. The 718 is primarily torsion and with some bending. The Nitronic is for cylindrical bearing/moving against the 718 shaft and has some bending.
The triballoy will be self mated and clad to the 800H or 718 parts. The 800H part is primarily in compression, the 718 in bending.

 

[EdStainless]

How high is the pH?
Do you have data on 718 and X750 at those conditions?
I am concerned about attack of the secondary strengthening phases.

For high pH you need Cr, lots of it. How about alloy 33?
625 also does well.
I am not sure which alloys are allowed for construction of PV at those temps., that will be an issue.

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