Effect of Microstructure on Hydrogen-induced Cracking Propagation and Hydrogen Trapping Efficiency of Pipeline Steel

The NACE TM 0284-2003 standard was used to test the hydrogen-induced cracking (HIC) sensitivity of X80 and X120 pipeline steels. The relationship between the crack propagation and the microstructure of the two kinds of pipeline steels was analyzed by optical microscopy and scanning electron microscopy. The hydrogen permeation test was used to quantitatively analyze the influence of microstructure of two types of pipeline steels on hydrogen atom capturing ability. The results show that the HIC resistance of X80 pipeline steel with acicular ferrite is better than that of X120 steel with ultra-low carbon bainite. The HIC crack propagates mainly along the polygonal ferrite in X80 steel while it along the prior austenitic grain boundaries in X120 steel. The X120 steel′s ability to trap hydrogen atoms is greater than X80 steel′s.