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The effect of nitrogen on the coarsening rate of precipitate phases in iron-based alloys with chromium and vanadium: experimental and theoretical investigations
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
Swerea KIMAB.
2013 (English)In: International Journal of Materials Research - Zeitschrift für Metallkunde, ISSN 1862-5282, Vol. 105, no 5, 442-451 p.Article in journal (Refereed) Published
Abstract [en]

A comparison of the coarsening of nitrogen-rich vanadium precipitates and the coarsening ofcarbon-rich vanadium precipitates is presented. The precipitate phases are studied experimentally,via fabrication of model alloys, and theoretically, via simulations utilizing the DICTRA software.The experimental investigations indicate that the nitrogen-rich precipitates exhibit a slowercoarsening behaviour than the carbon-rich precipitates. Analysis using thermodynamic andkinetic modelling shows that this can be explained by the higher thermodynamic stability of thenitrogen-rich precipitate compared to the carbon-rich precipitate. The calculated coarsening ratesare compared with the measured rates, and found to be in satisfactory agreement using reasonablevalues for the interfacial energies. The investigations are motivated by the ne precipitate sizedistribution of nitrides and carbonitrides characteristic for high nitrogen alloyed tool steels producedby means of powder metallurgy.

Place, publisher, year, edition, pages
2013. Vol. 105, no 5, 442-451 p.
Keyword [en]
Tool steels, Powder metallurgy, Nitrogen, HIP, Coarsening, DICTRA
National Category
Metallurgy and Metallic Materials
URN: urn:nbn:se:kth:diva-103319DOI: 10.3139/146.110885ISI: 000320346600003OAI: diva2:559704

QC 20121010. Updated from accepted to published 20131212. 

Available from: 2012-10-10 Created: 2012-10-10 Last updated: 2013-12-02Bibliographically approved
In thesis
1. Multicomponent diffusional reactions in tool steels: Experiment and Theory
Open this publication in new window or tab >>Multicomponent diffusional reactions in tool steels: Experiment and Theory
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Many phenomena determining the microstructure of a tool steel and consequently the properties of the material, are governed by multicomponent diffusion. The diffusion driven reactions that take place during, for example, tempering of a hot-work tool steel or when the microstructure develops during hot isostatic pressing of cold-work tool steel, are dependent on the types and amounts of alloying elements. In order for computational methods to be usable, these alloying effects need to be understood and incorporated in the models.

In this work the influence of some typical tool steel alloying elements on the coarsening behavior of precipitates is investigated. Experimental coarsening studies are performed and the impact of the diffusion mobility descriptions and the thermodynamic descriptions are investigated by means of DICTRA coarsening calculations. The kinetic descriptions for diffusion in the body centered-cubic phase in the case of the chromium-iron-vanadium system and the chromium-iron-molybdenum system are improved by assessments of diffusion mobility parameters, and are shown to have a large impact on the calculated coarsening rate for vanadium-rich and molybdenum-rich precipitates.

The effect of cobalt is examined by a coarsening experiment for vanandiumrich carbides and by a diffusion couple experiment for the investigation of the vanadium interdiffusion. The presence of cobalt is experimentally shown to have retarding effect on the coarsening rate of the carbides, but not on the vanadium diffusion.

The coarsening rate of nitrogen-rich precipitates is compared to the coarsening rate of carbon-rich precipitates, and a lower coarsening rate for nitrides compared to carbides can be confirmed. Correlation between coarsening calculations and experiments is obtained suggesting that the thermodynamic description of the two systems is the underlaying reason for the different coarsening rates.

Further, calculations utilizing the DICTRA software are combined with experimental investigations in order to study the possibility to apply computational methods for compound material development and explore application areas for high nitrogen alloyed tool steels produced by powder metallurgy.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2012. vii, 67 p.
hot-work tool steel, precipitation hardening, DICTRA, coarsening, mobilities, CALPHAD, cobalt, PM tool stees, nitrogen, compound materials
National Category
Engineering and Technology
urn:nbn:se:kth:diva-103328 (URN)978-91-7501-504-0 (ISBN)
Public defence
2012-10-26, B3, Materialvetenskap, Brinellvägen 23, KTH, Stockholm, 10:15 (English)

QC 20121011

Available from: 2012-10-11 Created: 2012-10-10 Last updated: 2012-10-11Bibliographically approved

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