A question about bearing coatings

[icrman]

Generally what is the material used in this process?
And approximatly what hardness? I would like to hear if anyone has done tests on coatings and what was discovered.
Just questioning some theorys here. HP power gains are advertized, but with a hydrodynamic bearing there is no contact with the material, if there was we would see bearings dying at very low mileage.

 

[ivymike]

a hydrodynamic bearing there is no contact with the material

That's not correct. Contact happens, or you'd never have wear. Contact happens at times other than startup, too. Also, the particles that occasionally come floating through are often larger in diameter than the min film thickness in the bearing (ie 8um vs 3um-5um). Contact isn't the only thing that can kill a bearing, though. Peak hydrodynamic stresses can fatigue the bearing material and cause chunks of it to come loose. Geometry changes can cause the oil to form bubbles which later pop, hammering away bits of material as they do. Bearings also need to be resistant to corrosion, and not react too strongly with chemicals that begin or end up in the oil. Different coatings and bearing materials can help with all of these problems.