Berlin 2008 – wissenschaftliches Programm
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DS: Fachverband Dünne Schichten
DS 33: Surface Modification
DS 33.1: Vortrag
Donnerstag, 28. Februar 2008, 14:45–15:00, H 2032
Surface properties of medical CoCr alloys after plasma immersion ion implantation — •Johanna Lutz1,2 and Stephan Mändl2 — 1Translationszentrum für regenerative Medizin, Universität Leipzig, Leipzig — 2Leibniz-Institut für Oberflächenmodifizierung, Leipzig
Different medical CoCr alloys were treated with nitrogen plasma immersion ion implantation (PIII), an implantation method where the sample is immersed in a plasma and negative high voltage pulses are applied to it. This leads to the formation of surface layers with nitrogen contents up to 30 at.% and a thickness of more than 1 micrometer after 1 hour at 400 ∘C. This layer should exhibit an improved biocompatibility and mechanical surface properties.
Analysing the nitrogen diffusion data from SIMS measurements as well as the phase information data from XRD measurements and mechanical properties from nanoindentation and wear measurements, several conclusions can be drawn: the thermal activation energy for the nitrogen diffusion of about 0.5 eV indicates an interstitial diffusion path; at temperatures lower than 400 ∘C, a lattice expansion of the fcc base structure is observed, at higher temperature CrN precipitates are formed. At the same time, the hardness of the surface layers increases by a factor of 3 from 5 (untreated material) to 16 GPa with a corresponding increase in the wear resistance, nearly independent of the process temperature.