Removing Mo without attacking W or Re 2

[huitball]

I am now trying to remove a Molybdenum mandrel from a piece that also contains Tungsten and Rhenium. Nital worked well for the Molybdenum but also attacked tha Rhenium. HCl, Hf, H2SO4 and Phosphoric acid were all tried and did not work at all. Anybody have any ideas?? Any input would be greatly appreciated.

 

[CoryPad]

How about heating the mandrel until the Mo melts (~2623 C)? Re doesn't melt until ~ 3200 C, and W doesn't melt until ~ 3400 C.

 

[huitball]

Interesting approach. The only thing we are worried about is the Re reacting with the Mo at such elevated temps and resulting in liquid embrittlement of the Re. The Re is in direct contact with the Mo, while the W is not.

 

[mcguire]

There's a large difference in thermal expansion between Re and Mo. Can that help? E.g.using cryogenic temps to create a greater physical separation. I don't know the geometry involved.

 

[huitball]

I ended up using liquid Argon to seperate the mandrel. It worked like a charm. Thanks mcguire!!

 

[cocobolorose]

Just for the record, the folks in the lighting industry dissolve out the Mo mandrels that tungsten wire is wound on by soaking in a HNO3/H2SO4 solution for a few minutes @50C. Doesn't affect the Re in W-3Re coils either.