Relationship between microstructural features in pipeline steel and hydrogen assisted degradation. (February 2019)

• Record Type: Journal Article
• Authors: Ohaeri, Enyinnaya; Eduok, Ubong; Szpunar, Jerzy
• Is Part Of: Engineering failure analysis. Volume 96(2019)
• Page Start: 496
• Page End: 507
• Publication Date: 2019-02
• Subjects: Pipeline steel -- Tensile test -- Corrosion -- Crystallographic texture -- Hydrogen embrittlement; System failures (Engineering) -- Periodicals; Fracture mechanics -- Periodicals; Reliability (Engineering) -- Periodicals; Pannes -- Périodiques; Rupture, Mécanique de la -- Périodiques; Fiabilité -- Périodiques; Fracture mechanics; Reliability (Engineering); System failures (Engineering); Periodicals; Electronic journals; 620.112
• DOI: 10.1016/j.engfailanal.2018.11.008
• Languages: English
• ISSNs: 1350-6307

Abstract

Abstract: The contributions of various microstructural features towards hydrogen-assisted degradation in API 5L X80 pipeline steel have been investigated. The current study was conducted on specimens obtained from the top surface and mid-thickness layers. After microstructural characterization on the RD-TD plane of each specimen, the mechanical response was investigated with and without in-situ hydrogen charging; before probing the electrochemical behavior in hydrogen producing and non-hydrogen producing corrosive environments. Despite reduced tensile and yield strengths, the mid-thickness layer showed relatively greater resistance to failure under both testing conditions. The increased susceptibility to hydrogen damage at the top surface layer was linked to higher strength and lower ductility. Also, the microstructure at the mid-thickness region contained mainly acicular ferrite, while the top surface was dominated by bainitic-acicular ferrite. In addition, the crystallographic orientation of grains spread towards 〈111〉‖ND and 〈110〉‖ND texture fibers (specifically, 〈123〉‖ND) at the mid-thickness; unlike the top surface which had mostly 〈001〉‖ND textured grains (specifically, 〈013〉‖ND). Highlights: Susceptibility to hydrogen degradation was higher at the pipeline steel surface than the mid-thickness. Electrochemical corrosion response of pipeline steel was lower at the mid-thickness relative to the surface. The surface layer of pipeline steel consists of specifically, 〈013〉‖ND oriented grains. Intensity of grain orientation deviated more towards 〈123〉‖ND at the mid-thickness layer.