Acoustic emission monitoring of wet H2S cracking of linepipe steels: Application to hydrogen-induced cracking and stress-oriented hydrogen-induced cracking

cited By 9International audienceAcoustic emission (AE) was used for monitoring steel cracking during exposure to wet hydrogen sulfide (H2S) environments. A method for filtering AE data related to hydrogen-induced cracking (HIC) was presented and applied for several case studies. In a series of tests on unstressed sweet service steels, evolution of AE indicated three successive HIC phases. An initial incubation period corresponded to hydrogen entry in the steel, during which no cracking occurred. Then two cracking phases were detected. The first was associated with decohesion of weak steel interphases. The second was identified as crack propagation under high internal hydrogen pressure. Crack propagation decreased and eventually ceased over time. Analysis of AE data was then used to evaluate the extent of HIC after sour exposure. Correlation was found when appropriate data filtering was applied. AE analysis was also applied to sour service steels under an applied load. The first steel exhibited HIC AE signals. Its fracture surface was typical of a stress-oriented hydrogen-induced cracking (SOHIC) mode of failure, in good agreement with AE results. For the second steel, which also failed during the test, no AE related to HIC was detected. Fracture surface was typical of sulfide stress cracking (SSC), also in good agreement with AE findings. © 2011, NACE International

Contribution of acoustic emission to the understanding of sulfide stress cracking of low alloy steels

cited By 17International audienceThe acoustic emission technique was applied to standard tests devoted to evaluate sulfide stress cracking susceptibility of steels for oil and gas industry. The mapping of the density of AE signals vs. their location on the specimen gauge length as a function of time allowed early detection of cracking, and gave meaningful information on incubation times and propagation rates. Sulfide stress cracking initiation was correlated with the presence of critical surface defects. A mechanism involving plastic strain and/or metal dissolution was proposed to account for crack propagation. © 2011 Elsevier Ltd

Evaluation of potential of high Si high C steel nanostructured bainite for wear and fatigue applications

The present study is concerned with the potential of high carbon, high silicon steel grades isothermally transformed to bainite at low temperature (<300 C). The first part gives an overview of the design principles, allowing very high strength and ductility to be achieved while minimising transformation duration. Wear and fatigue properties are then investigated for over 10 variants of such materials, manufactured in the laboratory or industrially. The results are discussed against published data. Tensile strengths above 2 GPa are routinely achieved, with, in one case, an exceptional and unprecedented total elongation of over 20%. Bainite plate thickness and retained austenite content are shown to be important factors in controlling the yield strength, though additional, non-negligible parameters remain to be quantified. Rolling-sliding wear performances are found to be exceptional, with as little as 1% of the specific wear rate of conventional 100Cr6 isothermally transformed to bainite. It is suggested that this results from the decomposition of retained austenite in the worn layer, which considerably increases hardness and presumably introduces compressive residual stresses. Fatigue performance was slightly improved over 100Cr6 for one of the two industrially produced materials but significantly lower otherwise. Factors controlling fatigue resistance require further investigations. © 2013 Institute of Materials, Minerals and Mining Published by Maney on behalf of the Institute.Peer Reviewe

Impact of COVID-19 on cardiovascular testing in the United States versus the rest of the world

Objectives: This study sought to quantify and compare the decline in volumes of cardiovascular procedures between the United States and non-US institutions during the early phase of the coronavirus disease-2019 (COVID-19) pandemic. Background: The COVID-19 pandemic has disrupted the care of many non-COVID-19 illnesses. Reductions in diagnostic cardiovascular testing around the world have led to concerns over the implications of reduced testing for cardiovascular disease (CVD) morbidity and mortality. Methods: Data were submitted to the INCAPS-COVID (International Atomic Energy Agency Non-Invasive Cardiology Protocols Study of COVID-19), a multinational registry comprising 909 institutions in 108 countries (including 155 facilities in 40 U.S. states), assessing the impact of the COVID-19 pandemic on volumes of diagnostic cardiovascular procedures. Data were obtained for April 2020 and compared with volumes of baseline procedures from March 2019. We compared laboratory characteristics, practices, and procedure volumes between U.S. and non-U.S. facilities and between U.S. geographic regions and identified factors associated with volume reduction in the United States. Results: Reductions in the volumes of procedures in the United States were similar to those in non-U.S. facilities (68% vs. 63%, respectively; p = 0.237), although U.S. facilities reported greater reductions in invasive coronary angiography (69% vs. 53%, respectively; p < 0.001). Significantly more U.S. facilities reported increased use of telehealth and patient screening measures than non-U.S. facilities, such as temperature checks, symptom screenings, and COVID-19 testing. Reductions in volumes of procedures differed between U.S. regions, with larger declines observed in the Northeast (76%) and Midwest (74%) than in the South (62%) and West (44%). Prevalence of COVID-19, staff redeployments, outpatient centers, and urban centers were associated with greater reductions in volume in U.S. facilities in a multivariable analysis. Conclusions: We observed marked reductions in U.S. cardiovascular testing in the early phase of the pandemic and significant variability between U.S. regions. The association between reductions of volumes and COVID-19 prevalence in the United States highlighted the need for proactive efforts to maintain access to cardiovascular testing in areas most affected by outbreaks of COVID-19 infection

Composition Design of Nanocrystalline Bainitic Steels by Diffusionless Solid Reaction

NANOBAIN is the term used to refer to a new generation of advanced steels capable of producing by isothermal transformation at low homologous temperatures, T/Tm ∼ 0.25 where Tm is the absolute melting temperature, a nanocrystalline microstructure, composed exclusively of two phases, thin plates of bainitic ferrite separated by C enriched austenite. Such alloys are exclusively designed on the basis of bainitic transformation theory and some physical metallurgy principles. In this work, by designing a new set of alloys capable of producing such microstructure, a further step toward the industrialization of NANOBAIN is taken. Some important industrial requirements, including circumventing the inclusion of expensive alloying elements and the need for faster transformations, are also considered. For all the alloys, the experimental results validate the design procedure and they illustrate that the NANOBAIN concept is a step closer to industrialization, probing that it is possible to obtain nanocristalline bainite in simpler alloy systems and in shorter times than those reported previouslysupport of the European Research Fund for Coal and Steel and the Spanish Ministerio de Economia y Competitividad Plan Nacional de I+D+I (2008-2011) for funding this research under contracts RFSR-CT-2008-00022, and MAT2010 – 15330, respectively. also acknowledges the Spanish Ministry of Science and Innovation for financial support in the form of a PhD research grant (FPI)Peer reviewe

Industrialised nanocrystalline bainitic steels. Design approach

Nanostructured microstructures consisting of a mixture of very thin plates of bainitic ferrite separated by C enriched austenite are the main characteristics of the so called NANOBAIN steel family. This paper shows the theoretical approach followed in the design of a new, industrially viable, generation of NANOBAIN steels, a process in which industrial demands such as, simpler chemical compositions, faster transformation kinetics and suffice hardenability have been also considered. The microstructural and mechanical characterization of the bainitic microstructures obtained by isothermal transformation at different temperatures, come to confirm and to validate the theoretical approach usedsupport of the European Research Fund for Coal and Steel and the Spanish Ministerio de Economia y Competitividad Plan Nacional de I+D+I (2008-2011) for funding this research under the contracts RFSR-CT-2008-00022, and MAT2010 - 15330 respectivelyPeer reviewe

Hydrogen induced cracking (HIC) testing of low alloy steel in sour environment: Impact of time of exposure on the extent of damage

cited By 43International audienceHydrogen induced cracking (HIC) of line pipe steel was investigated through immersion testing and hydrogen permeation measurements. At constant pH and hydrogen sulphide partial pressure (pH2S), the extent of HIC was found to depend on exposure time until a stable level was reached. The time to reach this stable value is affected by pH and pH2S. Results of permeation experiments confirmed that HIC is linked with the increase of hydrogen concentration in the steel. It is also shown that low severity requires longer exposures to reach equilibrium. This must be taken into account for HIC testing in mildly sour environment. © 2009 Elsevier Ltd. All rights reserved