Effects of Nano-sized Microalloyed Carbonitrides and High-density Pinned Dislocations on Sulfide Stress Cracking Resistance of Pipeline Steels

Abstract

Sulfide stress cracking (SSC) resistance was investigated by comparing acicular ferrite (AF) and ferrite-pearlite (FP) in a microalloyed steel and in a non-microalloyedsteel. In microalloyed steel, AF exhibited better SSC resistance than FP, while in non-microalloyed steel, AF presented far worse SSC resistance than FP. In microalloyed steel, nano-sized carbonitrides and high-density pinned dislocations in AF were analyzed to behave as innocuous hydrogen traps, offering numerous sites for hydrogen redistribution and modifying critical cracking conditions. Dislocations in AF of microalloyed steel in the final analysis are attributed to pinning by the nano-sized carbonitrides.