Effects of Helium Production and Heat Treatment on Neutron Irradiation Hardening of F82H Steels Irradiated with Neutrons

Abstract

The influcence of addition of 10 B and 11 B on radiation hardening as a function of irradiation temperature was examined in reducedactivation martensitic F82H+B steels (8Cr-2W-0.2V-0.04Ta-0.1C-0.006B). Specimens used were 10 B doped, 10 B+ 11 B doped and 11 B doped F82H steels. Helium concentration produced in the specimens through 10 B(n, ) 7 Li reaction was measured from about 15 to about 330 appm. Radiation hardening of the specimens irradiated at 300 C to 2.3 dpa and 150 C to 1.9 dpa was observed. Increment of radiation hardening possibly due to helium in the specimen irradiated at 300 C tended to increase slightly with increasing helium production in tensile test at 20 C, but it was not observed for 150 C irradiation. Therefore, it can be mentioned that the enhancement of radiation hardening in the 10 B( 11 B) doped steels depends on irradiation temperature. The dependence of radiation hardening on tempering time was also examined for F82H-std irradiated at 150 C to 1.9 dpa. Increment of yield strength of F82H-std tended to increase with increasing tempering time. The relation between the shift of DBTT and the increment of yield strength due to irradiation suggest that the extension of tempering time or the increase of tempering temperature would be beneficial for mechanical properties of F82H-std.

Radiation hardening and -embrittlement due to He production in F82H steel irradiated at 250°C in JMTR

“…It may be necessary to perform a further investigation on the effect of lithium on DBTT in F82H. In this study, the enhancement of radiation hardening and the shift in DBTT is shown in the F82H steel irradiated at 250°C to 2.3 dpa with helium up to about 330 appm He, however, the enhancement is reduced by increasing irradiation temperature at 300°C [42]. This trend with increasing irradiation temperature matches with previous studies of Shiba and Rieth [5,9].…”

Mechanical properties of small size specimens of F82H steel

“…However, there was a possibility that the addition of boron or nickel may cause severe irradiation embrittlement. In this experiment, there are no effects of chemical additional element on DBTT [16,17], the shift of DBTT [11], the increment of irradiation hardening [18,19] and defect clusters [20,21] as reported in previous studies. It is therefore concluded that helium production can affect the shift of DBTT.…”

Effect of gas atoms and displacement damage on mechanical properties and microstructures of F82H

“…These systems are desired to operate at relatively higher temperatures. It is reported that helium atoms can affect DBTT [3][4][5][6][7], swelling behavior [8][9][10][11][12][13][14][15] and irradiation hardening [16][17][18][19][20][21][22][23] in martensitic steels. To study the synergistic effects of displacement damage and helium on mechanical properties and microstructure, there are some specific experimental methods.…”