HEAT-TREATMENT EFFECTS ON IMPACT TOUGHNESS OF 9CR-1MOVNB AND 12CR-1MOVW STEELS IRRADIATED TO 100 DPA

Plates of 9Cr-1MoVNb and 12Cr-1MoVW steels were given four different h eat treatments: two normalizing treatments were used and for each norm alizing treatment two tempers were used. Miniature Charpy specimens fr om each heat treatment were irradiated to approximate to 20 dpa at 365 degrees C and to approximate to 100 dpa at 420 degrees C in the Fast Flux Test Facility (FFTF). In previous work, the same steels were irra diated in FFTF to 4-5 dpa at 365 degrees C and 35-36 dpa at 420 degree s C. The tests indicated that prior austenite grain size, which was va ried by the different normalizing treatments, affected the impact beha vior of the 9Cr-1MoVNb but not the 12Cr-1MoVW. Tempering had relativel y little effect on the impact behavior of both steels. Conclusions are presented on how heat treatment can be used to optimize impact proper ties. (C) 1998 Elsevier Science B.V. All rights reserved.