Staff Scientist, Metallurgy Division, AERE Harwell, Oxfordshire,
Pye-Unicam Ltd., Cambridge,
Pages: 27 Published: Jan 1982
The strength and microstructural stability of three 10–12%Cr ferritic-martensitic stainless steels have been characterised following fast reactor irradiation to damage levels of 30 displacements per atom (dpa) at temperatures in the range 380°–615°C.
Irradiation results in either increases or decreases in room temperature hardness depending on the irradiation temperature. These strength changes can be qualitatively rationalised in terms of the combined effects of irradiation-induced interstitial dislocation loop formation and recovery of the dislocation networks comprising the initial tempered martensite structures. Precipitate evolution in the irradiated steels is associated with the non-equilibrium segregation of the elements nickel, silicon, molybdenum, chromium and phosphorus, brought about by solute-point defect interactions. The principal irradiation-induced precipitates identified are M6X, intermetallic chi and sigma phases and also α'(Cr-rich ferrite). The implications of the observed microstructural changes on the selection of martensitic stainless steels for fast reactor wrapper applications are briefly considered.
ferritic steels, fast reactors, microstructure, precipitation, microchemical evolution, radiation-induced segregation, radiation hardening
Paper ID: STP34347S