Metal finishing Q&As since 1989

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Stainless galling preventative

I'm looking for an extremely reliable way of preventing galling between several stainless alloy parts (13-8 and 15-5). The application is a 1 shot - but can't fail. The fits are tight .0005/.0010 clearance I'm cautious of spray on dry films. I've used platings in the past - nickel and chrome - But would like any suggestions on a cheaper solution. I recently read of Moly-fusion. Anyone have experience with this? Or any other potential solution?

Don McCrary
- Orlando, Florida
 

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Sorry, I'm not familiar with that process. Silver plating or the use of Nitronic or Gall-tough parts is a conventional answer.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

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1st of two simultaneous responses--You are looking for something that is extremely reliable, for a one time only , and you want it cheaper than nickel or chrome? I think that you may need to go shopping instead of asking for expert technical advise. GM

Guillermo Marrufo
Monterrey, NL, Mexico
 

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2nd of two simultaneous responses--  

Hello Don!

If you have light sliding loads, try PVD titanium nitride- Richter Precision do a fine job. Give Yury Madorsky a call. If you have heavy contact loads, or vibration, the PH stainless steel won't support the thin, 2 to 5 micron coating, and it could flake off.

Other things to consider include teflon co-deposited electroless nickel, and nitriding one of the stainless steel components. Remember that nitriding will reduce the corrosion resistance, however.

Good Luck!

Lee Gearhart
metallurgist - E. Aurora, New York

Try a sputtered on Titanium Carbide Graphite coating. That has been shown to reduce galling.

Norm Nicholas
- Elbert, Colorado
 

Stainless Steel by nature galls. However you can reduce the likelihood of the parts galling by not subjecting the parts to heat. Heat not only in application, but also in installation (i.e. high speed torque wrenches, air guns etc) It is best to apply parts by hand, and do not over tighten. You a can also have a light wax coating to the parts at about $.20/lb at most platers. This helps lubricate the parts during installation. Another proven way to reduce the galling is to mix different grades of stainless. For example, if you are using a bolt and nut, use a 304 Stainless Nut & a 316 Stainless Bolt. The chemical composition differences help to reduce the level of galling. If all else fails have the parts vacuum hardened, which also helps but it is not as economical.

James Weaver
- Santa Fe Springs, California, USA
2007