Hydrogen effect on effective surface energy of microcracks propagation in α-iron solid solutions with phosphorus, sulfur and carbon

An attempt to evaluate the value (γsub(p)) of effective surface energy of microcrack propagation in α-iron and solid solutions with phosphorus, sulfur, and carbon has been made on the basis of theoretical representations and experimental data on regularities of internal microcrack development without external stresses under the action of molecular hydrogen pressure in crack. The cracks occur and develop during electrolytic saturation of α-iron with hydrogen, whereupon its concentration Csub(H) in solid solution and pressure Psub(Hsub(2)) of molecular hydrogen filling cracks may be controlled by the change of cathode current density (i). It has been established that hydrogen diffusion coefficient is not changed under the effect of investigated low concentrations of phosphorus, sulfur, and carbon in α-iron. In all studied alloys γsub(p) value is shown to drop with Csub(H) growth up to the definite limiting C*sub(H) value, at which limiting γsub(p) drop up to the value of γ*sub(p) is achieved