Thermodynamic and experimental study of cobalt-based alloys designed to contain TiC carbides
Résumé
Two alloy compositions, {Co(bal.)-25Cr-0.25C-1Ti} and {Co(bal.)-25Cr- 0.50C-2Ti}, were studied using Thermo-Calc. In parallel the corresponding real alloys were elaborated by foundry and their microstructures, in their as-cast state or after a long stage at 1000 or 1200 °C, were characterized. Thermodynamic calculations and real experiments were globally in good agreement. They both demonstrate that the two alloys are highly refractory, that solidification starts by the crystallization of the alloy matrix in all cases and that all titanium carbides precipitate at the end of solidification and belong to a {matrix + TiC} eutectic compound. The TiC carbides remain stable during long exposure at elevated temperature, for both temperatures for the {0.50C-2Ti}-alloy but only at 1000 °C for the {0.25C-1Ti}-alloy. This observation suggests potential high mechanical properties of the {0.50C-2Ti}-alloy at elevated temperature. Many of the collected experimental data – temperature range of melting or solidification, microstructures stabilized at high temperature (natures, fractions and chemical compositions of the phases) – will be of interest for testing and improving databases.
Domaines
Chimie
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