Posted by John Swensen on August 23, 1999 at 14:29:34:
In Reply to: Re: Re: Re: Stuff that I've Wondered About posted by Leland on August 23, 1999 at 12:20:55:
From a corrosion perspective, using the same metals is superior. However, for sliding bearings (the only kind that tubists have in their valves), galling is often the greater problem. Here is one definition of galling that I pulled off the web:
Galling - Surface damage when two materials slide against each other,
resulting in localized welding of high spots. Typically refers to Al or
Cu sticking in wire drawing dies and the resultant drawn wire damage.
As for non-metals sliding in metals, as long as they have the same coefficients of expansion, they may work fine. Some manufacturers have tried plastic rotors, but these
hung up during hot weather, due to the plastic expanding more with heat than the brass casing.