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Assessment and evaluation of mobilities for diffusion in the bcc Cr-Mo-Fe system
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
Swerea KIMAB.
2012 (English)In: Journal of Phase Equilibria and Diffusion, ISSN 1547-7037, Vol. 33, no 5, 375-389 p.Article in journal (Refereed) Published
Abstract [en]

An assessment of the diffusion mobility functions for diffusion in the bcc Cr-Fe-Mo system ispresented. The optimization of the mobility parameters is performed by utilizing experimentaldiffusion data available in literature. New diffusion data for the Mo diffusion is produced by adiffusion couple experiment and is accounted for in the optimization. Agreement between calculatedand measured diffusion coefficients is found. An M6C coarsening experiment is performedand the measured coarsening rate can be reproduced by diffusion calculation using the DICTRA software and the developed kinetic description. The mobility parameters are shown tohave a strong influence on the calculated coarsening rate.

Place, publisher, year, edition, pages
ASM International, 2012. Vol. 33, no 5, 375-389 p.
Keyword [en]
assessment, coarsening, DICTRA modeling, Mo carbides, multicomponent diffusion, tool steels
National Category
Metallurgy and Metallic Materials
URN: urn:nbn:se:kth:diva-103317DOI: 10.1007/s11669-012-0107-zISI: 000308969200005ScopusID: 2-s2.0-84870656570OAI: diva2:559698

QC 20121010

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