Precipitates change of P92 steel under 3.5 MeV Fe13+ ion irradiation at 400 °C

Abstract

9–12% Cr ferritic/martensitic steels are promising candidate materials for applications in fourth generation nuclear reactors. 9%Cr ferritic/martensitic steel P92 was normalized at 1050 °C for 0.5 h and subsequently tempered at 765 °C for 1 h. The precipitates of the normalized-and-tempered steel after 3.5 MeV Fe13+ ion irradiation at 400 °C to 0.66 dpa were studied using transmission electron microscopes. After irradiation, the number of precipitates increased, especially for the number of large-sized precipitates, and there was an increase in the overall size of precipitates. Pre-existing Cr-rich M23C6, Nb-rich MX and V-rich MX precipitates in the normalized-and-tempered steel still existed in the irradiated steel, and the M23C6 precipitates remained almost unchanged in their composition. Irradiation-induced Nb-rich M6C5 carbide with a base-centered monoclinic structure, V-rich M2X (V2C type) carbonitride with a simple orthorhombic crystal structure, and Fe71Cr26(Mo,W)3 (σ-FeCr type) intermetallic compound with a simple teragonal crystal structure were identified in the irradiated steel. The formation of these irradiation-induced phases is also discussed.