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Picture for Hydrogen Permeation and Binding Energy Study on OCTG High Strength Steel
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Hydrogen Permeation and Binding Energy Study on OCTG High Strength Steel

Product Number: 51319-12908-SG
Author: Elizabeth Trillo
Publication Date: 2019
$20.00

Oil Country Tubular Goods (OCTG) high strength steels are susceptible to hydrogen assisted cracking (HAC) due to hydrogen ingress as a result of exposure to environmental conditions (cathodic protection (CP) and/or H2S environments) and as such are prone to failure. In order to address the potential cracking susceptibility a study was performed to understand fundamental parameters such as steady state hydrogen permeation flux hydrogen concentrations and hydrogen trap binding energies of the high strength steel under charging conditions. Electrochemical permeation testing was performed on unstressed and 80%AYS stressed C110 pipe steel using an applied charging current density of 0.5 mA/cm2 in a 1M H2SO4 test solution at 75 F. Comparisons between the stressed and unstressed samples showed that there were no significant differences in steady state flux (Jss) and calculated hydrogen concentration for this charging condition. Further testing was performed to measure hydrogen uptake and time to saturation under the same charging conditions using the Si Oil Method. Subsequent laser thermal desorption spectroscopy (LTDS) was performed at the saturation point and at several temperature scan rates in order to calculate the hydrogen trap binding energies (Eb). Similar testing was performed on P110 material to assess the possibility that differences in Eb are detectable and relatable to HAC.Key words: High Strength Steels Electrochemical Permeation Testing Hydrogen Assisted Cracking CP environment.

Picture for Hydrogen Pipeline In-Line Inspection Case Study
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Hydrogen Pipeline In-Line Inspection Case Study

Product Number: 51321-16820-SG
Author: Russell D. Morris; Tod Barker
Publication Date: 2021
$20.00
Picture for Hydrogen Stress Cracking Resistance of Precipitation Hardenable Nickel Alloys and Optimization
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Hydrogen Stress Cracking Resistance of Precipitation Hardenable Nickel Alloys and Optimization

Product Number: 51324-20719-SG
Author: Stephen McCoy; Brian A. Baker; William MacDonald
Publication Date: 2024
$40.00
The material trend in the Oil & Gas sector is for high strength materials with high levels of corrosion resistance to resist increasingly harsh sour downhole environments. Compared to sweet wells the presence of hydrogen sulphide, elemental sulphur and hydrogen generally requires material selection of tubular and bar products in high performance stainless steels and nickel base alloys to withstand the pressures and temperatures. The materials of choice must be corrosion resistant, cost effective, reliable and have the strength required for the well design conditions. The material selection for downhole and well head equipment such as hangers, sub-surface safety valves, pumps and packers require age-hardenable materials to obtain the strength in heavier cross sections which cannot be strengthened by cold work. The commonly used nickel alloys for the sour service applications are alloy UNS N09925 (925), alloy UNS N07718 (718) and alloy UNS N07725 (725) with the more recently developed alloy UNS N09945 (945) and alloy UNS N09946 (945X) designed for HP/HT and sour wells. The metallurgical stability and freedom from detrimental phases of these materials being increasingly important to optimise the mechanical and corrosion resistant properties, particularly as larger section thicknesses of higher strength materials. The effect of the microstructure of these materials is shown to have a significant effect on the resistance to hydrogen attack and corrosion in sour environments. Optimising the compositional control, thermomechanical processing and microstructure is shown to give significant improvements in resistance to sour corrosion and hydrogen stress cracking resistance of materials used for critical downhole components. Over recent years there has been increasing industry demand to improve quality control and categorise the various PH Nickel alloy grades resistance to Hydrogen Stress Cracking (HSC) for critical High Pressure-High Temperature environments. HSC is a complex corrosion mechanism with many factors including composition, strength, microstructure, and grain boundary cleanliness influencing susceptibility. Evaluation efforts have used multiple techniques to measure the effects of HSC resistance, with this paper focusing on the Slow Strain Rate Test (SSRT) method according to TM0198 Method C(1) and using the quality control standard API*6ACRA(2). The purpose of the paper is to present results using the TM0198:C slow strain rate test method in a hydrogen charging environment and show the HSC resistance of the grades 925, 718, 945, 945X, and 725. This paper shows how the composition can be controlled within the defined limits of the alloy grade to optimise the HSC resistance by reducing precipitation of deleterious phases and reduce mill heat batch variation. The SSRT results are compared with mechanical properties determined according to API6ACRA(2) and detailed microstructural analysis.
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Hydrogen Trapping in Heat Treated and Deformed Armco Iron

Product Number: 51319-13083-SG
Author: Wolfgang Siegl
Publication Date: 2019
$20.00

The purpose of this research was to investigate the influence of microstructure on hydrogen trapping in Armco iron by analyzing the trapping ability of grain boundaries and dislocations. Hydrogen traps were introduced into the material by systematically subjecting it to various grades of heat treatment and mechanical deformation. By combining different treatment steps (annealing at different temperatures cold rolling at various deformation degrees severe plastic deformation) a wide range of different grain sizes and dislocation densities was created.SEM EBSD TEM and XRD imaging were carried out to obtain a detailed characterization of the microstructure and an estimation of dislocation densities.Electrochemical permeation experiments and thermal desorption spectroscopy (TDS) were performed to render a classification and characterization of hydrogen traps. Electrochemical permeation yields information on the diffusivity of hydrogen in the material and the influence of traps on the diffusivity. An experimental setup according to Devanathan and Stachurski was used.TDS allows the estimation of the amount of hydrogen stored in the different traps and the determination of the trap’s binding energy for hydrogen.By combining the information on the microstructure obtained from the material characterization with the results of the permeation experiments and TDS as well as a model based data interpretation the trapping efficiency of grain boundaries and dislocations in iron can be precisely determined.