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

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

Thiswork focuses on an alloy based onNickel andCobalt in similar quantities, containing 30 wt.%Cr for its corrosion resistance, 1wt.%C and 1 wt.%Ta for obtaining many TaC carbides. In a first time thermodynamic calculations were performed to describe the microstructure development during solidification and solid state cooling. In a second time the real ally was elaborated by casting from pure elements. Thermodynamic calculations predicted that solidification should start not classically by the crystallization of matrix dendrites but by TaC carbides. This was effectively verified in the real alloy with the presence of blocky TaC carbides obviously of a proeutectic nature. This presence of TaCin the real alloy aswell as itsmatrix the chemical composition of which is of the same type as the high temperature austenitic matrix predicted by thermodynamic calculations show that the microstructure of the real alloy get frozen at about 1000°C during the cooling. The short temperature range of solidification determined by thermodynamic calculations did not allow the pro-eutectic carbides to migrate towards the periphery of the ingot during solidification under the decreasing electromagnetic stirring. TheVickers hardness of the real alloy is of about 30 Hv30kg.

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