I agree with the previous responses to your post. Hardness is not the only factor to consider regarding wear resistance, friction coefficient is also inextricably linked. I would consider coating the two surfaces with a low fiction coating. Diamond-like carbon deposited by PVD or PACVD has...
Teer Coatings Ltd provide equipment in many sizes to deposit graphite, the tradename of the coating is Graphit-iC.
This is their website,
http://www.teercoatings.co.uk
PVD theory can be read here,
http://www.pvd-coatings.co.uk
