Microstructural evolution of P92 ferritic/martensitic steel under argon ion irradiation

Microstructural evolution of P92 ferritic/martensitic steel irradiated by Ar+ ion beams at doses from 0.6 to 230 displacements per atom (dpa) at room temperature was investigated with conventional transmission electron microscope technique. Selected-area electron diffraction combined with bright-field and dark-field contrast image indicated that carbide/matrix interfaces were more easily damaged. The carbide peripheries became partly amorphous at irradiation dose of 2.3 dpa and were almost complete amorphous at the dose of 11.5 dpa. The small carbides would re-precipitate in matrices at 34.5 dpa. Energy dispersive X-ray analysis revealed that segregation of Cr and W and depletion of Fe in carbides occurred under irradiation. With the irradiation dose increasing, the irradiation induced segregation and depletion became more severe, which would influence mechanical properties of the steel.