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Nanoscale nickel-free austenitic stainless steel
|Maciej Tuliński 1, Karolina E. Jurczyk 2, Mieczysław Jurczyk 1|
1. Poznań Technical University, pl. Marii Skłodowskiej-Curie 5, Poznań 60-965, Poland
Recently, a new manufacturing process of nickel-free austenitic stainless steels with nitrogen absorption treatment has been developed . In this method, small devices can be precisely machined in a ferritic phase and than during nitrogenization of their surfaces in nitrogen gas at temperature approx. 1200oC they become nickel-free austenitic stainles steels with better mechanical and corrosion resistance properties.
In this work, a nanocrystalline nickel-free stainless steels has been synthesized by the combination of mechanical alloying (MA), heat treatment and nitrogenation of elemental microcrystalline powders. The process parameters, morphology and EDX-analysis of obtained powders were determined. Phase transformation from ferritic to austenitic was confirmed by XRD analysis. Changes of size and shape of the mechanically alloyed powder mixtures as a function of milling time was done by the SEM and AFM techniques. Human normal diploid fibroblasts were cultured onto each disk of nanostructured steels.
The microhardness of the final bulk material was studied using Vickers method. The result is almost two times greater than in austenitic steel obtained by conventional methods.
Mechanical alloying is a very effective technology to improve also the corrosion resistance of stainless steel. Decreasing the corrosion current density is a distinct advantage for prevention of ion release and it leads to better cytocompatibility.
According to existing conceptions, decreasing of material’s crystallites size to nanometric scale allows to achieve much better mechanical properties (e.g. microhardness) compared to conventional materials . With regard to austenitic stainless steels it could help to obtain better biomedical implants (e.g. stents) with better mechanical properties, corrosion resistance and biocompatibility.
 M. Sumita et al.: Materials Science and Engineering C 24 (2004) 753
Presentation: Poster at E-MRS Fall Meeting 2007, Acta Materialia Gold Medal Workshop, by Maciej Tuliński
See On-line Journal of E-MRS Fall Meeting 2007
Submitted: 2007-07-17 08:27 Revised: 2009-06-07 00:44