Dresden 2006 – scientific programme

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DS: Dünne Schichten

DS 24: Poster presentation

DS 24.64: Poster

Tuesday, March 28, 2006, 15:00–17:30, P2

Grain Size as Proxy for Intragrain Nitrogen Diffusion in Ion Nitrided Austenitic Stainless Steel — •Darina Manova, Dietmar Hirsch, Stephan Mändl, Horst Neumann, and Bernd Rauschenbach — Leibniz-Institut für Oberflächenmodifizierung, Leipzig, Germany

Nitrogen insertion at low energies and temperatures between 350 and 380 ^∘C in austenitic stainless steel results in the formation of thick modified layers with outstanding mechanical properties and excellent corrosion resistance. The main characteristics of these layers are an anisotropic lattice expansion a concentration dependent diffusion rate. In this investigation nitrogen plasma immersion ion implantation was performed into austenitic stainless steel X5CrNi18.10 (DIN 1.4301) for different microstructures of the base material. This was achieved by annealing the as-received material at different temperatures ranging from 900 to 1200 ^∘C. Results from investigations of metallographic cross sections are presented together with nitrogen depth profiles obtained from SIMS measurements. Additionally, XRD spectra are shown. A strong influence of microstructure on the nitrogen diffusivity in austenitic stainless steel was found as a smaller grain size increases diffusion. However, an additional effect of defects like twin boundaries and dislocations must be employed as the diffusion occurs within single grains (nitrogen range 1 – 5 µm vs. grain size of 10 – 40 µm) and the grain size is only a proxy of the underlying effect.