High pH stress corrosion cracking initiation and crack evolution in buried steel pipelines: A review

摘要

High pH Stress Corrosion Cracking (HpHSCC) was identified in the 1960 s for the first time and is considered to be a significant threat for buried pipelines. When certain specific conditions arise in the pipeline's environment and loading it leads to intergranular cracking on the axial-radial plane. These cracks can grow under continued adverse loading and eventually result in fast rupture or leakage. Large numbers of field investigations, exper imental studies, and simulations have been conducted to delineate and understand the circumstances that lead to HpHSCC. This paper will provide a review of the circumstances, conditions, and events that pipelines experiencing HpHSCC may undergo during the course of this phenomenon. HpHSCC cracks failure happens over an extended time period, and the life cycle of the vulnerable pipe involves five sequential stages viz. incubation stage, crack initiation and early stage of crack growth, preparation stage for mechanically derived crack growth, sustainable crack growth caused by mechanical driving force, and rapid crack propagation to failure. This paper discusses the mechanisms at each stage of HpHSCC from the environmental, metallurgical, and mechanical loading points of views. The interactions and sometimes synergistic effects of different parameters are discussed during the entire life cycle of the pipes. The central focus of this review is to correlate the events at each stage of crack propagation to loading conditions and their variability, which play a crucial role in estimating the remaining life of the susceptible linepipe to HpHSCC. The discussion will include how the cyclic-loading conditions can alter the steel properties and assist in intergranular crack initiation. The changes in the geometry of subcritical cracks and subsequent alteration in mechanical driving force for crack propagation are detailed. The contributing mechanisms that cause sustainable crack growth are expanded. The modeling of HpHSCC crack growth is discussed and outlined. The gaps in knowledge about HpHSCC are highlighted at the end along with necessary future research to improve the modeling of HpHSCC.