In cases of good affinity between the nanomaterial and the matrix, the nanomaterial blocks dislocation movement in the metal matrix, and hence increase the hardness which in turn increase the wear resistance.
The increasing of the hardness of nanomaterials also due to the increased of density. This is observe in nano material coating. An increase in density increased bonding strength between particle, and hence the particle not easy to separate from each other and pluck out from surface, and consequently increase in wear resistance.