Coefficient of friction of different steels

In summary, there is a lot of variability in the friction coefficient (COF) for steel on steel, depending on factors such as temperature, surface finish, contamination, and relative motion. Measurements should be taken to accurately determine the COF for a specific situation. It is also important to consider both static and kinetic COF, as well as any differences between different types of steel.
  • #1
bill nye scienceguy!
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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.
 
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  • #2
Hi

i would do a measurement.
 
  • #3
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.
 
  • #4
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.
 

FAQ: Coefficient of friction of different steels

What is the coefficient of friction?

The coefficient of friction is a dimensionless scalar value that represents the amount of resistance to motion between two surfaces in contact with each other. It is a measure of the frictional force between the surfaces.

How is the coefficient of friction measured?

The coefficient of friction is typically measured by conducting experiments using a variety of techniques, such as the inclined plane method, the block-on-block method, or the drag method. These experiments involve applying a known force to a sample and measuring the resulting frictional force.

What factors affect the coefficient of friction of different steels?

The coefficient of friction of different steels can be affected by several factors, including surface roughness, lubrication, temperature, and load. The type of steel and its composition can also play a role in determining the coefficient of friction.

Why is the coefficient of friction important in engineering and design?

The coefficient of friction is an important factor to consider in engineering and design because it can affect the performance and durability of a product or structure. It can also impact the efficiency and safety of machines and systems.

How can the coefficient of friction be reduced?

The coefficient of friction can be reduced by using lubricants, polishing or smoothing surfaces, and using materials with lower coefficients of friction. Additionally, altering the design of a product or using different surface finishes can also help reduce the coefficient of friction.

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