Showing papers on "Stress corrosion cracking published in 2019"

Influence of different heat-affected zone microstructures on the stress corrosion behavior and mechanism of high-strength low-alloy steel in a sulfurated marine atmosphere

Abstract: The stress corrosion cracking (SCC) behavior and mechanism of the simulated heat-affected zone (HAZ) of high-strength low-alloy (HSLA) steel in a sulfurated marine atmosphere were surveyed in detail using electrochemical measurements and slow strain rate tensile (SSRT) tests combined with microstructure analysis. The SCC of the simulated HAZs is controlled by both anodic dissolution (AD) and hydrogen embrittlement (HE), which are attributed to the synergistic effect of Cl− and SO42−, as Cl−-induced localized dissolution causes microcrack initiation, and SO42--catalyzed acid regeneration facilitates microcrack propagation. The intercritical HAZ and fine-grained HAZ present high crack numbers because of the high amount of prior austenite grain boundaries (PAGBs), lath bainite boundaries (LBBs), and martensite/austenite (M/A) constituents, which act as preferential sites for hydrogen trapping and crack initiation. However, coarse-grained HAZ exhibits the highest SCC susceptibility because of the coarse PAGBs, wide lath bainites (LBs), and high local dislocation density, which promote crack propagation.

Important Factors on the Failure of Pipeline Steels with Focus on Hydrogen Induced Cracks and Improvement of Their Resistance: Review Paper

Abstract: Currently, thousands of kilometers of pipeline steels are transferring hydrocarbon fluids such as oil and natural gas in the world. Due to the fact that these pipes transport corrosive and high-pressure fluids from harsh environments, they are damaged and eventually degraded. Previous studies showed that sulphide stress cracking, hydrogen induced cracking (HIC) and stress corrosion cracking are the main destructive factors in these types of pipes. This paper focused on the HIC related failure in pipeline steel, since the role of texture and grain boundary character has not been completely recognized. Moreover, if pipeline damage is occurred by hydrogen cracks, besides the environmental pollutions, it will cost a lot to repair or replace the damaged pipeline steels. In this research, the factors influencing the initiation and propagation of the HIC cracks, such as hydrogen traps, inclusions, precipitates, microstructure and texture of steel have been investigated. Also, the existing solutions for improving the steel resistance to the HIC have been investigated based on the control of micro-alloy elements, texture and grain boundary engineering. For instance, some special dominant texture components and coincidence site lattice boundaries decrease the HIC susceptibility by providing the resistant path for crack propagation.

Laser Shock Peening and its Applications: A Review

Abstract: In this paper Laser Shock Peening (LSP), as a surface treatment technique for metals and alloys is reviewed. A brief introduction covering LSP process, LSP on various materials and some innovative applications of LSP have been discussed. Critical laser parameters for LSP such as laser energy, pulse width, wavelength, overlap rate, role of sacrificial coating and transparent overlay are presented towards parameter optimization perspective. A small section has been devoted to detail the development of a pulsed Nd:YAG laser that was built in house, exclusively for the LSP applications. Role of LSP in improving the material properties such as fatigue, Stress Corrosion Cracking (SCC), Inter Granular Corrosion (IGC) besides, rejuvenation of fatigue life of pre fatigued specimens and hybrid technique to rejuvenate the SCC damaged components are discussed. Further, results on oblique laser peening along with its successful application to the interior of cylindrical geometry specimens for improving the SCC resistance are also discussed.

Effects of Different Parameters on Initiation and Propagation of Stress Corrosion Cracks in Pipeline Steels: A Review

Abstract: The demand for pipeline steels has increased in the last several decades since they were able to provide an immune and economical way to carry oil and natural gas over long distances. There are two important damage modes in pipeline steels including stress corrosion cracking (SCC) and hydrogen induced cracking (HIC). The SCC cracks are those cracks which are induced due to the combined effects of a corrosive environment and sustained tensile stress. The present review article is an attempt to highlight important factors affecting the SCC in pipeline steels. Based on a literature survey, it is concluded that many factors, such as microstructure of steel, residual stresses, chemical composition of steel, applied load, alternating current (AC) current and texture, and grain boundary character affect the SCC crack initiation and propagation in pipeline steels. It is also found that crystallographic texture plays a key role in crack propagation. Grain boundaries associated with {111}∥rolling plane, {110}∥rolling plane, coincidence site lattice boundaries and low angle grain boundaries are recognized as crack resistant paths while grains with high angle grain boundaries provide easy path for the SCC intergranular crack propagation. Finally, the SCC resistance in pipeline steels is improved by modifying the microstructure of steel or controlling the texture and grain boundary character.