Mechanical Property of F82H Steel Doped with Boron and Nitrogen

Abstract

Dependence of fracture properties and hardening was examined as a function of helium production in tensile specimens of a martensitic steel F82H (Fe-8Cr-2W-0.1C-0.04Ta) irradiated at 300 C to 2.3 dpa by neutron irradiation in the JMTR (Japan Materials Testing Reactor). The specimens used in this study were F82H, F82H+60 ppm 11 B, F82H+30 ppm ( 11 B+ 10 B) and F82H+60 ppm 10 B. The helium range produced from 10 B (n,) 7 Li reaction was from 5 to 330 appm in the specimens. The tensile testing was performed at 25 C. The radiation hardening due to helium production was detected at 330 appmHe. The degradation of fracture stress due to helium production was approximately evaluated from the fracture strength and the reduction area. Effect of specimen size on tensile and Charpy impact properties in F82H doped with 60 ppm boron and 200 ppm nitrogen was also examined. The JIS 14A and SS-J3 (Small Size-Japanese-3 type) were used for the tensile specimens, and half size (55 mm in length, 10 mm in height and 5 mm in width) and 0.5-1/3CVN (18 mm in length, 3.3 mm in height and 1.65 mm in width) were used for the Charpy impact testing. The tensile properties were a similar to each other. However, the ductile-brittle transition temperature measured in smaller size specimen was somewhat lower than that in the standard size specimen.

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 heat treatments on tensile properties of F82H steel irradiated by neutrons

“…The effects of the normalizing and tempering on tensile and impact behavior in martensitic steels before irradiation were reported by Schafer [8] and Gondi et al [9]. The mechanisms controlling the relationship between the changes of yield strength and shift of DBTT due to irradiation in these martensitic steels are not clear, and it is necessary to determine the effects of heat treatment on irradiation hardening and embrittlement [10][11][12]. The primary purpose of this study is to examine …”

Effects of heat treatment and irradiation on mechanical properties in F82H steel doped with boron and nitrogen

“…The B doping in steels, however, may cause the ductility loss, and mask the real effects of the irradiation. In a previous study, B doping of the martensitic steel F82H caused irradiation hardening [11], but the B doping degraded the original fracture toughness of the F82H [12]. The mechanical properties of F82H doped with B before irradiation should be almost equal with those of undoped F82H to evaluate He effects accurately.…”