In this research, hydrogen induced cracking (HIC) behavior of an API X70 pipeline steel has been
studied. In order to create HIC cracks, an electrochemical hydrogen charging experiment was
carried out on X70 steel by using 0.2 M sulfuric acid and 3 g/l ammonium thiocyanate for 8 h.
Moreover, SEM, EDS and EBSD techniques were used to characterize the as-received (AR) steel
and investigate the different aspects of HIC phenomenon as well. The results showed that the
inclusions and precipitates which play a key role in HIC phenomenon have been distributed
randomly through the cross-section of tested steel. However, the concentration of them was
higher at the center of cross-section than other areas. All HIC cracks initiated and propagated
through the center of thickness where center segregation of elements has occurred. It is also
observed that HIC cracks were initiated from several special types of inclusions and precipitates
such as manganese sulphide and carbonitride precipitates. EBSD results showed that the
dominant local texture of center of thickness in RD-TD plane was {001}//ND and {111}//ND.
Moreover, HIC cracks propagate through differently oriented grains where the local texture is
random.