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Poster De Conférence Année : 2003

Using thermodynamical modelisation to predict the evolution of Co-base superalloys’ microstructures at high temperature

Résumé

High temperature properties of superalloys more depends on their microstructure than their chemical composition. It’s especially true for cast cobalt-based alloys: several characteristics of the interdendritic carbides network govern their mechanical resistance. Quantities, morphologies and natures of carbides do not remain like they were just after solidification or heat treatment when exposed to high temperature for a long time. Indeed, they are evolving to reach the thermodynamically stable state corresponding to the considered temperature. Thermodynamical calculations are very useful to know the final microstructure the alloys are converging to, or to target the chemical compositions leading to thermodynamically-stable microstructures suitable to the wanted properties. The agreement between predicted stable metallurgical states and real microstructures was assessed. For this purpose, the natures and quantities of the different phases of several selected alloys held few hours at high temperatures were compared to those calculated by Thermo-Calc. Good fits were found for five different cobalt-based alloys, especially for the solidus temperatures. Concerning the nature of the phases, the expected carbide types were observed. Moreover, thermodynamical modelisation revealed for some compositions the presence of small quantities of others carbides not evidenced in the synthesised alloys. The rarefaction of carbides with an increasing exposition temperature is also confirmed by the simulation. Nevertheless values of carbides fractions are not similar, but it can be explained, at least for TaC carbides, by geometrical considerations.
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hal-04068601 , version 1 (14-04-2023)

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Paternité - Pas d'utilisation commerciale - Pas de modification

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  • HAL Id : hal-04068601 , version 1

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Patrice Berthod, Sylvain Michon, Lionel Aranda, Stéphane Mathieu, Jean-Claude Gachon. Using thermodynamical modelisation to predict the evolution of Co-base superalloys’ microstructures at high temperature. CALPHAD XXXII, May 2003, La Malbaie, Canada. . ⟨hal-04068601⟩
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