Think about a tapered roller wheel bearing- - - -precision ground hard steel rollers, running against glass-hard inner and outer races with grease as a lubricant. There are a few instances where a hardened part is runnig against a somewhat softer one, but I don't think that would be correct in this situation.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!