Effect of annealing treatment at 550 °C on ferrite of thermally aged cast austenitic stainless steels and ageing kinetics of reverted cast austenitic stainless steels

R. Badyka (1, 2) , Sébastien Saillet (2) , C. Domain (2, 3) , Cristelle Pareige (1)

1 GPM - Groupe de physique des matériaux
2 EDF R&D MMC - Matériaux et Mécanique des Composants
3 EM2VM - Etude et Modélisation des Mécanismes de Vieillissement des Matériaux

Ageing of Cast Austenitic Stainless Steels (CASS) was attributed to the decomposition of the ferrite by spinodal decomposition and precipitation of G-phase particles. This leads to an increase in hardness and a decrease in Charpy-impact energy. It is possible to restore the mechanical properties of these steels by annealing treatment above the Fe-Cr miscibility gap in order to dissolve α' phase. In this work, an annealing treatment for 2 h at 550 °C followed by water quenching was applied to various Mo-free and Mo-bearing steels. This treatment allowed to restore almost completely the mechanical properties of Mo-free steels and partly Mo-bearing steels regardless of the initial ageing time. The mechanical property changes were attributed to the complete dissolution of spinodal decomposition and complete or partial dissolution of G-phase particles. After annealing, a re-ageing kinetics was studied. The preexisting G-phase particles have minor influence on the kinetic of spinodal decomposition until 2,400 h at 400 °C.

Domaines: Matière Condensée [cond-mat]; Science des matériaux [cond-mat.mtrl-sci]; Matériaux

R. Badyka, Sébastien Saillet, C. Domain, Cristelle Pareige. Effect of annealing treatment at 550 °C on ferrite of thermally aged cast austenitic stainless steels and ageing kinetics of reverted cast austenitic stainless steels. Journal of Nuclear Materials, 2020, 542, pp.152530. ⟨10.1016/j.jnucmat.2020.152530⟩. ⟨hal-02943308⟩