These color plots represent image data taken from two different materials subjected to identical wear test conditions in a reciprocating tester.

The wear pattern on the metal specimen is uniform. The groove takes the shape of the carbide ball slider. The green and blue colors indicate where material has piled up on the surface next to the wear track.This deposit also inhibits further wear in that location.

The wear pattern on the silicon nitride / graphite composite is different. Material that comes off does not pile up but fractures instead. These pieces can either form an abrasive or a lubricating film depending on surface properties. Because the ceramic does not smear like a metal the wear pattern is much rougher. This is also exaggerated by the scale factors used in the plots. Note that the Z axis for the plot is ± 10µm, whereas the Z axis for the cast iron sample is ± 250µm. Although the trace looks rough, the actual amount of material removed from the ceramic composite part was much less.