Tribological properties of chromium implanted silicon nitride ceramics correlated with microstructure

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N₄ ceramic after chromium implantation were investigated for the dependence on implantation energy between 200 keV and 3 MeV at a fixed fluence of 10¹⁷ ions/cm². The wear of the modified material is reduced for a load of 2 N independent of ion energy accompanied by a slight increase of the friction coefficient. At higher loads only high-energy implantations result in improved wear behaviour. Structural investigations show the absence of any new phases formed by ion implantation. All energies result in an amorphous layer. For lower energies this amorphous layer reaches up to the surface whereas at higher energies it is covered by still-crystalline but damaged material. The observed wear behaviour can be explained with the amorphization of the near surface region and the stress generated by the volume swelling of the amorphous layer.