A steady state model of hydrogen-induced intergranular crack growth has been developed. It is assumed that the steady state growth of an intergranular crack, screened by dislocations, is controlled by the grain boundary and crack surface diffusion processes of hydrogen. A series of second-order differential equations controlling the diffusion processes of hydrogen in the intergranular crack regions is solved numerically to determine the hydrogen distribution along a steadily moving crack and thereby the change of the ideal work of fracture. The relationship of the stress intensity required for the crack growth to the crack velocity is established as a function of several values of the grain boundary and crack surface diffusivities, the crack length, and the grain size. It is found that while the susceptibility to hydrogen-induced intergranular crack growth increases with increasing hydrogen diffusivities, it decreases with increasing crack length and grain size. The effect of grain size on the growth characteristics of hydrogen-induced intergranular cracking are discussed in terms of the direction change of the hydrogen flux along the moving crack.
RCsum&--Nous dtveloppons un mod&e stationnaire pour la propagation d'une fissure intergranulaire induite par l'hydrogkne. Nous supposons que la propagation stationnaire d'une fissure intergranulaire, &rant&e par des dislocations, est contrBl6e par la diffusion de l'hydrogkne aux joints de grains et $ la surface de la fissure. Nous avons r&olu numkriquement la strie des tquations diff&rentielles du second ordre qui contrblent la diffusion de l'hydroghne au voisinage de la fissure intergranulaire afin de determiner la rkpartition de l'hydrogine le long d'une fissure en d&placement stationnaire, et de le fait le changement du travail idial de rupture. Nous avons