Effect of neutron radiation and hydrogen on the brittle fracture properties of Cr-Ni-Mo-V steel

The results of fracture toughness tests of Cr-Ni-Mo-V steel from a set of 8 identically treated heats were subjected to statistical processing. The measurements were accomplished on an Instron 1342 hydraulic tensile testing machine. Two cleavage fracture mechanisms were found to operate at any temperature and in all conditions of the material, i.e. in the untreated material, in the irradiated material as well as in the hydrogenated material: the one mechanism (with a lower fracture toughness value) is probably initiated by fracture of a particle from the carbide phase, whereas the other is initiated by disturbance of the inclusion-matrix boundary. The degrading effect of cathode hydrogenation is identical with that of neutron irradiation. (Z.M.). 3 figs., 2 tabs., 6 refs