galling in vacuum environment

[bnrg]

Hi,
I'm designing some parts that are to be fitted into a high vacuum system. They consist of a large (5 inch diameter) threaded part (like a bolt)and a mating nut-materials need to be stainless steel type. I have been planning on using Nitronic 60 for one of the parts but am not sure about the other. The Armco bulletin for nitronic (link below) indicates in table 1 that there is no difference for 440C, 303, 304, 17-4 (no HT specified) or self mated. Do any of you have experience with these materials in a vacuum? I was planning on trying a dry film lube (type TBD) as well. There is some high temp (250 F) exposure for a bake out period. The parts need to be infrequently disassembled, hence my concern about galling.

http://hpalloy.com/alloys/descriptions/NITRONIC60.html

Thanks,
Bob

 

[btrueblood]

Yes, N60 should work (keep its anti-gall properties) in high vacuum.

In previous experience with other alloys, a good dry film anti-gall/anti-sieze for vacuum oven use is powdered boron nitride, either aerosol spray or made into a water paste and brushed on.

 

[unclesyd]

Why not make both parts fron Nitronic 60?

 

[coatingengineer]

Hi.

I agree with Uncle Syd. Austenite Nitronic 60 is ideal, both surfaces. Not just for wear or galling, but to avoid electrochemical reaction of dissimilar metal, or metallurgical counter-face solubility.

Soft alloyed metals, like lead with tin or copper, applied electrolytically, could work. A good choice for low friction, especially when used at higher temperature, or under vacuum.

If you're considering dry film lubrication, stay inorganic, binder and all. Here, to help you: <a href="

http://www.industrialcoatingsworld.com/Low-Friction-Coatings/MoS2-Low-Friction-Coatings.html">MoS2

Low Friction Coatings</a>

I wish you well!

William Gunnar

http://www.IndustrialCoatingsWorld.com

 

[bnrg]

Thankyou all, I will use Nitronic for both parts and try the MoS2 coating. The HPA rep suggested using nitronic for both parts unless the assembly needed the strength of one of the heat treatable materials, but I do not.

Bob