Prediction of Hydrogen Embrittlement Susceptibility in Medium Strength Steels and Fasteners PDF Download
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Author: Hendarsin Lukito
Publisher:
ISBN:
Category :
Languages : en
Pages : 212
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Author: Hendarsin Lukito
Publisher:
ISBN:
Category :
Languages : en
Pages : 212
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Author: Tuhin Das
Publisher:
ISBN:
Category :
Languages : en
Pages :
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"Hydrogen embrittlement (HE) is identified as a serious problem even after decades of extensive research, in various industries starting from aerospace to fastener. HE is primarily responsible for the degradation of mechanical performances of a number of metals and alloys that are used nowadays. Among them, high strength steels owing to their widespread applications also suffer from HE failures to a great deal. Hence, this thesis focuses on fundamental issues influencing the susceptibility of three different grades of high strength steels designed for fastener applications.The present work includes investigation of mechanical properties both in presence and absence of hydrogen, microstructural characterisations and direct hydrogen quantification. The mechanical property test methodology is a modification of the ASTM F1624 standard test method to determine hydrogen embrittlement threshold in steels, which facilitates a unique approach to investigate the HE susceptibility of these steel grades. The microstructural characterisation process involves scanning electron microscopy (SEM), electron backscattered diffraction (EBSD) and transmission electron microscopy (TEM) to identify the potential hydrogen trap states in microstructure, both qualitatively and quantitatively. Microstructural characterisation also provides useful information to predict local microstructural evolution in the presence of hydrogen and stress. Altogether, a structure-property relationship has been developed for these materials employing a comprehensive investigation process. In addition to it, fracture surface mapping using SEM indicates the mechanisms of failure associated with HE process in these materials. And finally, direct hydrogen quantification methodology using thermal desorption spectroscopy (TDS) provides further experimental evidence to the above-mentioned facts. Thus, in this work a combined approach involving various research techniques and knowledge has been utilised to investigate the susceptibility of the steel grades and rank them according to their performances under the influence of hydrogen." --
Author: Salim Brahimi
Publisher:
ISBN:
Category :
Languages : en
Pages :
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"High strength steel fasteners characterised by tensile strengths above 1100 MPa are often used in critical applications, where a failure can have catastrophic consequences. Preventing Hydrogen Embrittlement (HE) failure is a fundamental concern implicating the entire fastener supply chain. Hydrogen embrittlement results in loss of ductility and, consequently, a loss of strength, caused by atomic hydrogen in combination with tensile stress that can lead to sudden and unexpected brittle fracture after certain time. This research aims to better define the relationship between chemical composition, microstructural characteristics and HE susceptibility of high-strength steel used for manufacturing mechanical fasteners. HE susceptibility is a function of the material condition, which is comprehensively described by the metallurgical and mechanical properties. Hardness/material strength have a first order effect on HE susceptibility which increases significantly above 1200 MPa and is characterised by a ductile-brittle transition. At a given hardness and for a given concentration of hydrogen, the critical strength above which the ductile-brittle transition begins can vary due to second order effects. In this work, testing and observations made on nine alloys, each quenched and tempered to four hardness levels, illustrate second order differences in susceptibility that are dependent on chemistry and heat treatment, and ultimately on microstructure." --
Author: Lamda Muchjin
Publisher:
ISBN:
Category :
Languages : en
Pages : 186
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Author: Tuhin Das
Publisher:
ISBN:
Category :
Languages : en
Pages :
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"Hydrogen Embrittlement (HE) is a serious engineering problem for a wide range of industries starting from fastener, oil & gas to aerospace and nuclear. After several decades of extensive research, the HE problem has not been mitigated to a satisfactory level. HE in general, comprises of numerous layers of complexities involving hydrogen metal interactions, hydrogen diffusion and fracture, where each of these phenomena are entangled with one another to a certain degree. High strength martensitic steels which are known for structural and critical engineering applications suffer premature failure due to HE, to a great extent. The interactions of the hydrogen with the complex microstructure of these martensitic steels further enhances the challenges of mitigation. Therefore, the aim of the current research is to develop a better understanding on the susceptibility and mechanism(s) of HE failure of these materials, by studying the key factors affecting their embrittlement. In order to carry out the investigation, a combined approach based on experiments and numerical modeling has been adopted. As a first step, the HE susceptibility of high strength martensitic steels was evaluated using conventional slow strain rate testing methodology, in bending. A stress coupled hydrogen diffusion finite element analysis (FEA) model integrated with a cohesive zone model was developed to simulate the HE test. The primary factors influencing material susceptibility to HE were studied using the model, and the evaluation of critical hydrogen concentration as a metric of material susceptibility was demonstrated. Following the first study, a new approach involving rapid fracture test in four-point bending was proposed to assess HE susceptibility and mechanism(s). Stress coupled hydrogen diffusion FEA was also performed to calculate both stress and hydrogen concentration distributions in the domain, while simulating the test. A mechanistic description rooted in hydrogen enhanced decohesion (HEDE) mechanism was used to corroborate the mechanical test results, and fundamental understanding on the role of strength, microstructure and plasticity influencing HE susceptibility of materials, was also developed.The difference in susceptibility obtained from the rapid HE test, for two different quench and tempered martensite steels with similar strength level and microstructural features were explained using advanced microstructural characterization techniques, FEA and nanoindentation. The role of local microstructure affecting the micromechanics of HE fracture was discussed.Finally, hydrogen diffusion along the interface boundaries in a typical martensitic microstructure was investigated using centroidal Voronoi based FEA model. The influences of packet boundaries and prior austenite grain boundaries on the output hydrogen flux and concentration were studied. The presence of retained austenite in the microstructure affecting the diffusion of hydrogen was also studied. An overall understanding on hydrogen diffusion characteristics in a martensitic microstructure was demonstrated for better prediction of HE fracture.Thus, the current research provides fundamental understanding on the HE susceptibility of martensitic steels, as well as mechanistic insights, that could be instrumental in tackling the HE problem"--
Author: A. R. Elsea
Publisher:
ISBN:
Category : Steel
Languages : en
Pages : 42
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This memorandum introduces the problem of delayed, brittle failures associated with hydrogen in steel, particularly high-strength steel. It is intended to help the steel user determine if he has such a problem. The effects of hydrogen on the mechanical properties of steel are dealt with, and the behavior of material susceptible to delayed, brittle failure is described. Also, the effects of such factors as strength level, magnitude of applied stress, hydrogen content, steel composition, test temperature, and strain rate on hydrogen embrittlement and the susceptibility to hydrogen-induced, delayed, brittle failure are discussed. Possible sources of hydrogen in steel and the types of tests useful in determining the susceptibility to delayed failure are outlined. (Author).
Author: Quentin Scott Allen
Publisher:
ISBN:
Category : Electronic dissertations
Languages : en
Pages : 60
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Advanced high strength steels (AHSS) have high susceptibility to hydrogen embrittlement, and are often exposed to hydrogen environments in processing. In order to study the embrittlement and recovery of steel, tensile tests were conducted on two different types of AHSS over time after hydrogen charging. Concentration measurements and hydrogen microprinting were carried out at the same time steps to visualize the hydrogen behavior during recovery. The diffusible hydrogen concentration was found to decay exponentially, and equations were found for the two types of steel. Hydrogen concentration decay rates were calculated to be -0.355 /hr in TBF steel, and -0.225 /hr in DP. Hydrogen concentration thresholds for embrittlement were found to be 1.04 mL/100 g for TBF steel, and 0.87 mL/100g for DP steel. TBF steel is predicted to recover from embrittlement within 4.1 hours, compared to 7.2 hours in DP steel. A two-factor method of evaluating recovery from embrittlement, requiring hydrogen concentration threshold and decay rate, is explained for use in predicting recovery after exposure to hydrogen. Anisotropic hydrogen diffusion rates were also observed on the surface of both steels for a short time after charging, as hydrogen left the surface through 001 and 101 grains faster than grains with 111 orientations. This could be explained by differences in surface energies between the different orientations.
Author: Mahmoud Y. Demeri
Publisher: ASM International
ISBN: 1627080058
Category : Business & Economics
Languages : en
Pages : 312
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Examines the types, microstructures and attributes of AHSSAlso reviews the current and future applications, the benefits, trends and environmental and sustainability issues.
Author: Jack E. Grochowski
Publisher:
ISBN:
Category :
Languages : en
Pages : 86
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Author: Edward J. Jankowsky
Publisher:
ISBN:
Category :
Languages : en
Pages : 9
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