This effect is probably due to its high hardness and its wear
resistance properties [28,29]. Fig. 7 shows the qualitative analysis
of the UHMWPE surfaces (samples A) after the test under dry
conditions for pins' diameter of 6 mm in the case of materials of
pins were: (a) TiAl6V4; (b) AISI316L; (c) Al2O3. After a metrological
characterization of the worn surfaces during the tribological
tests, it was possible to calculate the groove volume left by the
pin on the UHMWPE samples. The several deformation processes
associated with different micro-structural characteristics and the
different hardness of the pin material are partially grounds for
the diverse values of the wear mass loss and for diverse shapes of