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, ma rtensitic, and martensitic-ferritic classes containing 2.5%, 8% and 11% Cr, respectively, were investigated. The phase composition and structure of th e bainitic steels were varied by changing the cooling rates from the austen itization temperature (from values typical for normalization up to V = 3.3 x 10(-2o)C/s) and then tempering. The steels were irradiated to a fluence o f 4 x 10(23) n/m(2) (greater than or equal to 0.5 MeV) at 270 degreesC and to fluences of 1.3 x 10(23) and 1.2 x 10(24) n/m(2) (greater than or equal to 0.5 MeV) at 70 degreesC. 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. Radiatio n embrittlement at elevated irradiation temperature was lowest in bainitic 2.5Cr-1.4WV steel and martensitic-ferritic 11Cr-1.5WV steel. The positive e ffect of molybdenum replacement by tungsten at irradiation temperature simi lar to 300 degreesC is reversed at T-irr = 70 degreesC. (C) 2000 Elsevier S cience B.V. All rights reserved.