Microstructure and crystallographic structure of ferritic steel subjected to stress-corrosion cracking

The article presents the results of studies on the microstructure and crystallographic texture of ferritic steel under stress-corrosion cracking (SCC). Using scanning electron microscopy (SEM), the size and type of non-metallic inclusions, the elemental composition of corrosion products, and the cracking mode in the SCC zone were determined. As a part of X-ray diffraction (XRD) analysis, during which the shape and size of grains-crystallites, crystallographic texture, atomic displacements, the Debye-Waller factor and instrumental broadening of lines using the Caliotti function for LaB6 were taken into account, parameters of the microstructure in the SCC zone were assessed. it is shown that the SCC zone is characterized by high density of introduced edge-type dislocations, strong elastic microdistortions of the crystalline lattice and a relatively small size of coherent scattering domains (CSD). It is found that the processes of texture formation in the pipeline during SCC are characterized by a set of Cube {001}<100>, Brass {110}<1<(1)over bar>1>, Copper {112}<<(1)over bar>1 (1) over bar>, rotated copper II {001}<1<(1)over bar>0>, Goss {001}<110> and CH (001}<2<(1)over bar>0> orientations. It is shown that when approaching the zone where there are no SCC traces, orientations of Goss {001}<110>, Copper {112}<<(1)over bar>1 (1) over bar and Rot G {011}<0<(1)over bar>1> type increase and orientations of Cube {001}<100>, H {001}<1<(1)over bar>0> and CH {001}<2<(1)over bar>0> type decrease.