Coefficient of friction of different steels

[bill nye scienceguy!]

I know the steel-steel COF is about 0.8. Are the tribological properties of different steels, eg austenitic and 9%Cr, sufficiently different that this difference should be taken into account in the design of a component that will slide over two different steels, or sufficiently similar that the difference is negligible?

I hope this question makes sense.

 

[Shockman]

Hi

i would do a measurement.

 

[AlephZero]

The friction coefficient is highly dependent on many things like temperature, surface finish, surface contamination, relative velocity, normal pressure, amplitude of relative motion if it is oscillating, etc. From my own experience I would take "about 0.8" to mean "anything between about 0.3 and 1.3, except for situations when it is outside of that range".

As Shockman said, if this is important to your design, measure it. Even better, change the design to make it less important, so it doesn't matter.

 

[nvn]

bill nye scienceguy: I know some sources list static coefficient of friction (COF) for steel on steel as 0.80, but I would be skeptical about that value. Are you referring to static COF, or kinetic COF? I would think a better estimate of kinetic COF for dry steel on steel is ~0.18. And I imagine an estimate of kinetic COF for dry stainless steel on stainless steel would perhaps be about 0.20 (?). Also, static COF is generally roughly 1.33 times kinetic COF.

But fortunately, COF is relatively easy to test.