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During the three years of this NANOPREC project, several new methods were explored for the: selective extraction and analysis of cementite from the steel matrix; selective extraction and analysis of Ti, V and Nb based precipitates; quantitative analysis of precipitates by XRD; quantitative analysis of the non-metallic element in precipitates by combustion analysis of filters; quantitative analysis of the C/N ratio within mixed precipitates. We learned that cementite is very comparable to iron with respect to its chemical and electrochemical stability. The procedure developed for its selective extraction is therefore very specific. The methods for extraction of Ti, V and Nb based precipitates were evaluated and a good correspondence between the labs (scatter < 10 %) was obtained. Combustion analysis was used to determine the concentration of precipitated carbon. During the project we learned that: using a glass filter with a pore size of 700 nm, good results were obtained for cementite; the drawback of this method is incomplete recovery of the extracted small precipitates; alumina filters are less suitable although they give a better recovery. Quantitative XRD, based on a direct comparison method, was used for the analysis of cementite in steel. Measurements are performed directly on the steel sample. A good correspondence between XRD, chemistry results and expected value was obtained. The detection limit of this method is approx. 2 wt %. For other types of precipitates, XRD was performed on extracted precipitate fractions and on synthetic powders. TEM work was concentrated on the determination of the C/N ratio within combined precipitates. Several approaches were followed: combined TEM/EELS experiments; combined TEM/EDX analysis of the N peak only (+ calculated C); determining the lattice parameters in HRTEM. No correspondence was found between the techniques and it is difficult to decide which is the most accurate.

Additional information

Authors: DE VYT A, OCAS, Zelzatte (BE);PAIVA P, ISQ, Oeiras (PT);BARROS L, ISQ, Oeiras (PT);RAVAINE D, Arcelor Research, Maizières-lès-Metz (FR);SCOTT C, Arcelor Research, Maizières-lès-Metz (FR);FLUCH J, Voestalpine, Linz (AT)
Bibliographic Reference: EUR 22376 EN (2006), 94 pp. Euro: 15
Availability: Katalogue Number: KI-NA-22376-EN-S The paper version can be ordered online and the PDF version downloaded at:
ISBN: ISBN: 92-79-02644-5
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