The Microstructural Characterization of NiSi-Rich Sub-precipitates Within Cementite in Isothermally Aged Reactor Pressure Vessel Steel

Irradiation-induced solute-rich precipitates are harmful microstructural nanofeatures responsible for the irradiation embrittlement and hardening of reactor pressure vessel (RPV) steels. In this study, we found the formation of NiSi-rich sub-precipitates within the cementite of aged RPV steel. These sub-precipitates retained the same structure as the cementite. The segregation and precipitation of Si and Ni could reduce the energy of the cementite system and improve its stability. Moreover, these NiSi-rich sub-precipitates remain to be clusters.