Relationships between mechanical behavior and microstructural evolutions in Fe 9Cr-ODS during the fabrication route of SFR cladding tubes

A new martensitic ODS alloy (nominal composition Fe-9Cr-1W-0.2Ti-0.3Y2O3) has recently been developed at CEA Saclay to achieve the goals defined for GEN IV reactors. The aim of this paper is to present the main challenges involved in the manufacturing of 9Cr-ODS cladding tubes. Internal stresses have been measured as a function of the thermo-mechanical treatments. Control of microstructural evolutions by means of phase transformation and appropriate cooling rates appears to be critical to obtain favorable softened structure which can be further processed for cold working. The final cladding tubes present remarkable mechanical properties with tensile strength higher than 350 MPa at 750 °C in both longitudinal and circumferential directions.