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 ppm¹¹B, F82H+30 ppm (¹¹B+¹⁰B) and F82H+60 ppm¹⁰B. The helium range produced from ¹⁰B (n,α)⁷Li 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.