Abstract
Abstract Silicon nitride ceramic ( β -Si 3 N 4 ) with Y 2 O 3 and Al 2 O 3 as sintering additives was implanted with Cr or Ti ions to a fluence of 10 17 cm −2 at energies ranging from 200 keV to 2 MeV. Changes in the phase composition in the near surface layer due to the implantation and subsequent annealing at 1000 and 1200 °C and their correlation with the behaviour of hardness and wear were investigated. Implantation results in amorphization of the near surface layer, which is buried for MeV implantations. For Ti-implanted samples, annealing leads to oxidation, resulting in the formation of γ -YSi 2 O 7 and cristobalite besides the β -Si 3 N 4 . In the case of Cr implantation with MeV energies, the amorphous layer recrystallizes to α -Si 3 N 4 already at 1000 °C catalyzed by the chromium. This causes a significant suppression of the oxidation. Consequently, the hardness and the tribological behaviour of Ti- and Cr-implanted samples, respectively, are affected differently by the annealing process. For chromium, the improved wear behaviour due to the high-energy implantation remains after annealing while the reduced hardness as result of the amorphized surface is partly recovered. For titanium, the oxide formation leads to a poorer hardness and tribological behaviour.
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