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Microstructure et propriétés de l'Inconel 718 DA forgé en presse à vis dans le domaine subsolvus δ

Abstract : Due to their desirable properties at high temperature, polycrystalline nickel-based superalloys are widely used for aircraft engine turbine disk manufacturing. Among the nickel-based superalloys family, Inconel 718 is currently the most popular for civil aircraft engine disks. Such parts are obtained by a hot forging process. Microstructural evolutions occurring during this process are very sensitive to forging conditions (temperature, strain rate and strain level). Given that the microstructure and subsequent mechanical properties are strongly coupled, it is of utmost importance to establish the influence of forging conditions on microstructural evolutions. This relationship, once provided, makes it possible to control the final microstructure of industrial parts, and so their mechanical properties. This work deals with the screw press forging of Inconel 718, a process characterized by relatively high strain rates (1s-1 to 100s-1). In particular, this project aims at studying this kind of forging process compared to conventional forging performed at relatively lower strain rates (0.001s-1 to 0.1s-1). Microstructural evolution mechanisms and kinetics are relatively well known for these conventional methods, and so, the mechanical properties of forged components are controlled. The purpose of this current PhD thesis is to investigate the links that exist between the forging mode (i.e. the strain rate), the resulting microstructures, and, the mechanical properties they generate. Hot compression tests simulating forging operations have been performed. Accurate characterizations of microstructures produced during these compression tests have allowed the finding of the strain rate’s influence on microstructural evolutions. In particular, recrystallization kinetics differing from those reported in the literature have been elucidated. Tensile and creep properties were also evaluated on specimens taken from industrial forged parts. Accurate microstructural characterizations performed in these samples have led to discovering relationships between microstructural features and mechanical properties, and subsequently, have clarified connections to the forging mode.
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Submitted on : Monday, June 8, 2020 - 8:58:27 AM
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  • HAL Id : tel-02859830, version 1


Alexis Nicolay. Microstructure et propriétés de l'Inconel 718 DA forgé en presse à vis dans le domaine subsolvus δ. Mécanique des matériaux [physics.class-ph]. Université Paris sciences et lettres, 2019. Français. ⟨NNT : 2019PSLEM067⟩. ⟨tel-02859830⟩



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