Relationship between microstructure and hydrogen induced cracking behavior in a low alloy pipeline steel

Hydrogen induced cracking (HIC) behaviors of a high strength pipeline steel with three different microstructures, granular bainite & lath bainite (GB + LB), granular bainite & acicular ferrite (GB + AF), and quasipolygonal ferrite (QF), were studied by using corrosion experiment based on standard NACE TM 0284. The HIC experiment was conducted in hydrogen sulfide (H2S)-saturated solution. The experimental results show that the steel with GB + AF and QF microstructure present excellent corrosion resistance to HIC, whereas the phases of bainite lath and martensite/austenite in LB + GB microstructure are responsible for poor corrosion resistance. Compared with ferrite phase, the bainite microstructure exhibits higher strength and crack susceptibility of HIC. The AF + GB microstructure is believed to have the best combination of mechanical properties and resistance to HIC among the designed steels. (C) 2017 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.