On the Influence of Crystallographic Texture on HIC

Abstract

This work presents the results of ongoing investigations aimed at determining the influence of crystallographic texture, microtexture and mesotexture on hydrogen induced cracking (HIC) in low carbon pipeline steels. HIC samples of two steels were investigated using X-ray diffraction texture measurement and Orientation Imaging Microscopy (OIM™). The first steel is a low strength API 5L X46 retired from service and the second is a low sulfur ASTM A106 steel. The results of this work confirm the feasibility of improving the HIC resistance of pipeline steels through crystallographic texture control and grain boundary engineering. Controlled rolling schedules can be proposed in order to induce a crystallographic texture dominated by the {112}//ND, {111}//ND and {011}//ND fibres. Such a texture is expected to decrease significantly the steel susceptibility to HIC by: (i) reducing the number of available transgranular and intergranular low resistance cleavage paths provided by the {001}//ND oriented grains, (ii) reducing the probability of crack coalescence and stepwise HIC propagation and (iii) increasing the number of high resistance intergranular crack paths provided by coincidence site lattice (CSL) and low angle boundaries with the lowest possible energy.