okay so from the sounds of it, solid-solid contact is not ideal therefore it's best to have some lubrication that is dirt/grime free on top of the mated surface. When not sufficiently covered or there are design concerns therefore, metals or polymers might be used as a sacrificial layer where...
This may be rudimentary but how does the efficiency of a bearing material change if you were to go from a metal to a coated metal material if there already was a thin film boundary layer between the bearing and the wear surface?
