reproducible (Figure ). After 10,000 revs, the CoF values steadily increase until coating failure becomes apparent; the friction trace in the 20,000 rev sliding tests increases from ~ 0.16 at 10,000 revs to > 0.4 at the test end. The resulting partial wear tracks on 100-12,800 sliding tests are shiny and bright copper in colour, with the track from the 20,000 test run appearing dulled.