Extended Data Figure 7: Wear produced on the flat surface of the disk rubbing against the balls.
The optical micrographs at the top showing the physical condition and difference in wear track size in the three tests. The line scans and three-dimensional images below show the extent of wear damage more clearly. There is unmeasurable wear for the MoNx–Cu-coated flat surface. The steel surface tested in PAO 10 shows the highest wear loss, with a wider wear track and deep scratches; the flat surface tested in 5W30 oil shows a much smaller and narrower wear track.
