Role of HIP Parameters and Thermo-Mechanical Treatments on ODS Ferritic Steels Obtained with the STARS Route

摘要

Oxide Dispersion Strengthened Ferritic Stainless Steels (ODS FS) are promising candidates forstructural components in future nuclear systems. Their high mechanical and creep strength andresistance to radiation damage up to 750 °C are attributed to an ultrafine microstructure and a verystable dispersion of Y-Ti-O nanoparticles. STARS route (Surface Treatment of gas Atomized powderfollowed by Reactive Synthesis) under development at Ceit to produce ODS FS with composition 14Cr-2W-0.3Ti-0.3Y_2O_3 allows the production of ODS steels without Mechanical Alloying. However, thedensity of the nanoparticles dispersed in the ferritic matrix with this activity is low. In order to increasethat density HIP temperature has been tuned and hot deformation was applied to introduce high densityof dislocations, favorable nucleation sites for nanoparticles. Subsequently, final heat treatment at hightemperature promotes dissociation of metastable oxides and more profuse precipitation of Y-Ti-O nanooxides(mainly Y_2TiO_5) in the ferritic matrix.