Dresden 2009 – wissenschaftliches Programm
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DS: Fachverband Dünne Schichten
DS 30: Application of Thin Films I
DS 30.6: Vortrag
Donnerstag, 26. März 2009, 15:30–15:45, GER 37
Anomalous Nitrogen Diffusivity During Plasma Nitriding of CoCr Alloys at High Temperatures — •Johanna Lutz1,2, Stephan Mändl1, and Bernd Rauschenbach1 — 1Leibniz Institute of Surface Modification, Leipzig, Germany — 2Translational Centre for Regenerative Medicine, University of Leipzig, Germany
Plasma immersion ion implantation is an important method to tailor and to increase the physical and chemical properties of numerous materials. In this presentation, the diffusion of nitrogen and the phase formation is investigated for face-centred-cubic CoCr alloys in the temperature range from 230 - 580 °C. Plasma immersion ion implantation was carried out using 10 kV pulse voltage and a process pressure of 0.5 Pa. X-ray diffraction patterns show two different phase structures depending on the temperature: a lattice expansion at temperatures lower than 450 °C while the decomposition of the base material into CrN precipitates and another Co-rich phase is observed at the upper end of the temperature range. A two-step nitriding process at different temperatures shows clearly that at a previous implantation at a temperature of 560 °C, no nitrogen diffusion is observed for a subsequent nitriding at any temperature. For preimplantation at 450 °C, normal diffusivities are observed during the latter process. This clearly indicates that the phase decomposition at elevated temperatures leads to a radical change in the nitrogen diffusivity.