A Comparative Study of the Role of Hydrogen on Degradation of the Mechanical Properties of API X60, X60SS, and X70 Pipeline Steels

Abstract

Three grades of high strength pipeline steel (API X60, X60SS, and X70) are subjected to cathodic hydrogen charging to determine the susceptibility of each steel grade to hydrogen-induced cracking (HIC). The specimens are subjected to tensile stress until failure to generate stress-strain, ductility, and toughness data. The fractured specimens are analyzed using a scanning electron microscope equipped with an EDS detector to determine crack initiation sites for the investigated grades of steel. The expectation that the X60SS steel grade will perform better than other grades is not met, instead it is found that under the cathodic hydrogen charging condition, the X60SS is more susceptible than the other two steel grades with respect to loss of toughness, ductility, and ultimate tensile strength. The presence of Ca-Albased inclusions is the most common along the fracture surfaces. Therefore, these inclusions also act as fairly strong trapping sites that under plastically strained conditions, they can result in fisheye features which severely impact the mechanical properties of the steel specimens.

Measurements by SKPFM and Finite‐Element Modeling of Hydrogen Atom Diffusion and Distribution in Ferrite and Bainite Contained in X80 Steel

“…The distribution and local trapping behavior of H atoms in the steel are critical to the HE occurrence. [14][15][16][17] Some advanced methods, such as secondary ion mass spectroscopy (SIMS), hydrogen microprint technique (HMT), and thermal desorption spectroscopy (TDS), are used to investigate the H-atom distribution in steels. The SIMS technique is based on a focused ion beam of elements that are not present in the test sample to bombard the sample surface and sputter out the secondary ions under ultrahigh vacuum conditions.…”

“…The distribution and local trapping behavior of H atoms in the steel are critical to the HE occurrence. [ 14–17 ]…”

Microstructure Characteristics and Corrosion Behavior of Low‐Alloy High‐Strength Steel used for Armor Layer under Exposure to H2S‐Saturated Solution

“…Corrosive electrolytes, such as chloride ions (Cl À ), carbon dioxide (CO 2 ), oxygen (O 2 ), and bacteria, can degrade pipeline steel and result in serious accidents. [1][2][3][4][5] H 2 S is formed in oil and natural gas through the decomposition of sulfur in sedimentary organic materials by sulfate-reducing bacteria. [6] The presence of H 2 S makes pipeline steel susceptible to surface corrosion such as pitting and to widespread corrosion.…”

In-Situ Hollow Sample Setup Design for Mechanical Characterisation of Gaseous Hydrogen Embrittlement of Pipeline Steels and Welds

“…Historically, HE of pipeline steels is mostly caused by absorption of hydrogen into the steel as a result of a cathodic potential that is applied to a pipeline to inhibit corrosion, or because of the presence of H 2 S gas in the transported medium [13,14]. This environment is often modelled in a laboratory environment by using a sample as the cathode in an electrolytic cell and applying either a constant current or potential [15][16][17].…”