The coefficient of friction (CoF; μ) of the CMMCs was measured by reciprocating Pin-on-Disc (PoD) sliding in ~40% RH, under a normal load of 1 N (~511 MPa maximum Hertzian contact pressure) selected to attempt to prolong the low-friction phase in the early phases of testing. Cu Ref coatings typically show a rapid increase of friction after run-in, achieving μ > 0.3 in less than 500 revs and stabilising at ~0.6 until testing was stopped at 10,000 revs (Figure ). GO-CMMC gave tentative performances as a low-friction lubricating surface.