Effect of applied stress and microstructure on sulfide stress cracking resistance of pipeline steels subject to hydrogen sulfide

Effects of applied stress and microstructure on sulfide stress cracking resistance of pipeline steels subject to hydrogen sulfide were investigated by the single-edge notched tensile method using a microalloyed steel and a non-microalloyed steel. The failure time increased with the decreasing applied stress, and finally the threshold stress intensity factor was calculated for acicular ferrite (AF) and ferrite-pearlite (FP) in these two steels. The strength was not the dominant factor for the SSC, and aged microalloyed AF had the best SSC resistance in coincidence with the highest strength. The SSC resistance in sort ascending was non-microalloyed AF, non-microalloyed FP, microalloyed FP, microalloyed AF and aged microalloyed AF. The SSC was explained from hydrogen penetration and microstructural characteristic. The localized hydrogen concentration was enhanced by applied stress. The higher the applied stress, the more easily the SSC occurred. Carbonitrides and pinned dislocations contributed in better SSC resistance.