Effect of heat treatment and irradiation temperature on mechanical properties and structure of reduced-activation Cr–W–V steels of bainitic, martensitic, and martensitic–ferritic classes

Effects of molybdenum replacement by tungsten in steels of the bainitic, martensitic, and martensitic–ferritic classes containing 2.5%, 8% and 11% Cr, respectively, were investigated. The phase composition and structure of the bainitic steels were varied by changing the cooling rates from the austenitization temperature (from values typical for normalization up to V=3.3 × 10−2°C/s) and then tempering. The steels were irradiated to a fluence of 4×1023 n/m2 (⩾0.5 MeV) at 270°C and to fluences of 1.3×1023 and 1.2×1024 n/m2 (⩾0.5 MeV) at 70°C. The 2.5Cr–1.4WV and 8Cr–1.5WV steels have shown lower values of the shifts in ductile–brittle transition temperature (DBTT) under irradiation in comparison with corresponding Cr–Mo steels. Radiation embrittlement at elevated irradiation temperature was lowest in bainitic 2.5Cr–1.4WV steel and martensitic–ferritic 11Cr–1.5WV steel. The positive effect of molybdenum replacement by tungsten at irradiation temperature ∼300°C is reversed at Tirr=70∘C.