Scanning electron microscopy and energy dispersive spectroscopy
(JEOL JSM 6460 SEM/EDS) techniques were used to analyse
the worn surfaces after testing. To avoid electron charging of the
samples due to the presence of silica particles (non-conductive
constituents), the samples were sputtered with gold. The surface
roughness values of the specimens were determined by means of a
Wyko 1100NT 3D optical surface profiler.