Thermodynamic calculations describing the solidification of a {m,m’}-based {30Cr, 1C, 15Ta} containing alloy and microstructure comparison with the alloy really elaborated. Part 2:{m,m’}={Co,Fe}

Author(s): Gaël Pierson, Kevin Duretz, Patrice Berthod

In this second part of the work, an alloy based on Cobalt and Iron with similar contents, containing 30 wt.% Cr again as well as 1 wt.%C and 1 wt.%Ta for obtaining many TaC carbides, was the subject of preliminary thermodynamic calculations to get a description of its microstructure development from the molten state to the solid state at 500°C. A real alloy was thereafter produced by casting from pure elements to allow characterizing the microstructure really obtained. Thermodynamic calculations predicted that solidification should start here too by TaC carbides, before thematrix development itself. Thiswas effectively verified in the real alloy with the presence of blocky TaC carbides which are of a pro-eutectic nature. However some disagreements appeared concerning the chromiumcarbides notably, which were seen much more present in the real alloy than predicted by thermodynamic calculations. The limitation of the outwards migration of the pro-eutectic carbides was less understood than in the first part, since no so obvious relation between the solidification temperature range and the amount of blocky carbides in the ingot core was revealed. The Vickers hardness of the real alloy is of about 430 Hv30kg.

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