Hydrogen-induced crack interaction and coalescence: The role of local crystallographic texture

The role of local crystallographic texture (microtexture) in hydrogen-induced crack interaction and coalescence is investigated in pipeline steels using stress simulation and orientation imaging microscopy. It is shown that, depending on the material's microtexture, crack interaction and coalescence can significantly depart from the conditions predicted by the mixed-mode fracture mechanics of isotropic linear elastic materials. The results of stress simulations and microtexture analyses conducted on several observed crack interaction zones show that the presence of cleavage planes and slip systems favorably oriented to the mixed-mode stresses can activate low-resistance transgranular paths along which cracks can merge. In such situations, the response of the material to the mixed-mode stress state resulting from crack interaction produces results drastically different to that predicted by the fracture mechanics of isotropic linear elastic materials. This evidences the need for considering the material's crystallographic texture when developing predictive models for the stepwise propagation of hydrogen-induced cracking in pipeline steels.