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

[摘要] 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 alpha' phase. In this work, an annealing treatment for 2 h at 550 degrees 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 degrees C. (C) 2020 Elsevier B.V. All rights reserved.

[发布日期] 2020-12-15

[关键词] Cast austenitic stainless steels;Atom probe tomography;Spinodal decomposition;G-phase precipitation;Annealing treatment