Looking for Design Guide for Sliding Contact/Friction/Galling

[h2omike]

I'm working on a biomedical device that uses unlubricated sliding surfaces as a short (0.050")declutch mechanism. I inherited the design, which currently uses a mixture of stainless steels as the components and experiences galling during the declutch. Other than basic calculations for Hertz stresses, I'm having difficulty finding literature that can give guidance to material selection and surface finish based on the contact stress or applied forces. Can anyone provide a good online or published design reference?

 

[unclesyd]

The quickest way to get out of you problem is to change materials. You need to consider Nitronic 60 or Gall-Tough for any sliding SS components.
Galling and wear properties of Austenitic SS is generally given in tables taken from actual tests as the threshold galling stress is so low.

http://www.hpalloy.com/Alloys/Nitronic60/Brochure/Galling Resistance.htm

http://cartech.ides.com/datasheet.aspx?i=103&e=250&c=TechArt

Here is a site to get started from.

http://www.tribology-abc.com/

 

[h2omike]

Unclesyd,

We are in the process of having the suspect component fabricated from Nitronic-60, as it looks to have the highest galling resistance of the SS family. We don't have a friction/wear expert in our company, so the Nitronic material selection was based on a threshold galling stress table from the ASM SS handbook. I've been on the tribology-ABC website, but would still like to find some definitive design literature that could give some guidelines to someone without years of experience in tribology. There are several textbooks offered on the website....I may buy all of them to get what I need...

Some other facts that might give you insight. We had a significant number of units (90) of the current design that performed flawlessly, and then made 150 more to validate the design..all of which performed miserably. The sliding surfaces were 17-4 H900 and 303....the differences between the two groups were a different piece of bar stock, and in the first group the 303 parts were not passivated. We've considered that material variability in the 303 may have contributed (hardness tests showed similar values) but from my limited knowledge of sliding/friction mechanism I would have thought that passivation would help rather than hinder.

Thanks for your suggestion for material...it at least validates that we are on the right track.