Etude Expérimentale et Simulation Numérique de la Cinétique de Précipitation γ' et de l'Evolution Microstructurale dans le Superalliage N18 au cours de la Trempe

Abstract
The high temperatures and stresses experienced within turbine discs require high temperature resistant Ni-base superalloys produced by Powder Metallurgy techniques. The alloy N18 we study has good overall mechanical properties at temperatures up to 700°C after appropriate heat treatment. These properties are derived from the precipitation of ordered γ' phase and are strongly dependent upon the microstructure produced during thermal treatments. The γ' precipitation kinetics is experimentally studied by dilatometry and transmission electron microscopy. The microstructural evolution of γ'precipitates during quenching is followed in a high quenching rate apparatus that permits to preserve the high temperature microstructure at room temperature. In the present work, a model is being developped and is experimentally verified in order to describe the intragranular γ' precipitation during quenching.