The role of microstructure in sulfide stress cracking resistance of thermomechanically processed high strength low alloy steels

The sulfide stress cracking (SSC) behaviour of a high strength low alloy (HSLA) line pipe steel has been investigated to determine the role of microstructure, or, more precisely, the type of second phase. The SSC resistance, evaluated using uniaxial tensile tests at 1 bar H2S, exceeded 80% of the actual yield stress for all the given treatments. Nevertheless, it was found that the least SSC resistance was associated with the presence of certain pearlitic structures, either isolated or accompanied by bainite. Microstructures containing isolated islands of martensite displayed excellent SSC resistance. The relative behaviour of the different microstructures is discussed in terms of the observed modes of cracking.