Papers by Keyword: Optical Microscopy

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Authors: V.V. Pikul, V.K. Goncharuk, I.G. Maslennikova
Abstract: A technique is developed for fabrication of a shell from glass-metal composite based on the borate glass and aluminum alloy. The metal–glass interface was studied by the optical and atomic force microscopy, it was found the presence of a diffuse layer with thickness of about 1 micron. The diffuse layer composition was studied by the XPS.
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Authors: Attila Bonyár, Péter J. Szabó
Abstract: Cold rolled steel specimens were investigated by color etching. We proved that in this sample ferrite grains with a surface normal close to the (111) orientation are etched with the slowest speed with Beraha-I type color etchant, and that after a sufficient over-etching these specific grains could be distinguished based on this feature. It was demonstrated, that it is possible to stop the color etching in a phase when only grains with (111) orientation show color due to the layer interference, while all the other grains are dull gray due to a thick and transparent layer. This observation was utilized to develop a method to identify and quantify ferrite grains with (111) orientation in cold rolled steel samples with the application of color etching, optical microscopy and digital image post-processing.
297
Authors: Ernst Plesiutschnig, Coline Beal, Stefan Paul, Günter Zeiler, Stefan Mitsche, Christof Sommitsch
Abstract: Over the past three decades a lot of effort was made to optimize the chemical compositionof 9% Cr martensitic steels, aiming to increase the operating temperature up to 923K and thus im-proving the efficiency of thermal power plants. Under these service conditions (high temperature andstress exposure), the creep strength of such steels is closely related to the long term stability of theirmicrostructure. The time to rupture can also be understood as an equivalent to the time of microstruc-ture deterioration. Optimization of the initial microstructure and understanding of the microstructureevolution during creep exposure are therefore decisive to improve the creep behavior of 9% Cr steels.Selected chemical compositions of MarBN steels (Martensitic 9% Cr steels strengthened by Car-bides, Nitrides and Boron) were subjected to different heat treatments to produce an optimized mi-crostructure to improve the creep rupture time. The initial microstructure before creep exposure wasinvestigated using optical microscopy, SEM and EBSD. Short term creep rupture tests at 923K and150MPa were performed, followed by systematic microstructure investigations.Comparative EBSD investigations confirm an optimized microstructure for creep exposure, pro-duced by an appropriate heat treatment. From comparative creep test results, it can be concluded thatadvanced microstructures increase the time to rupture of the selected MarBN steels by more than 10percent, without reduction of the ductility.
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Authors: Rosinei Batista Ribeiro, José Wilson de Jesus Silva, Luis Rogerio de Oliveira Hein, Eduardo Norberto Codaro, Nelson Tavares Matias
Abstract: Pit morphology on sensitized 310S stainless steel has been studied using an image processing method based on reflected light microscopy (profile and surface). Salt Spray test has been used to induce the pitting corrosion. Morphological pits character do not depend on sensitization heat treatments here applied. Nucleation rates and growth may be associated with quantity and distribution of chromium carbides. This being so, condition I (heating up to 1065o C during 1 h and air cooling) and condition II (heating up to 1065o C during 1 h and air cooling followed by reheating up to 670°C during 5 h and again air cooling) are the most susceptible to pitting, in particular the first one. In these two conditions, pits are nucleated in grains and in grain boundaries, while in condition III (heating up to 1065o C during 1 h and air cooling followed by reheating up to 620o C during 24 h and again air cooling), pits are preferentially nucleated in boundaries of small grains. Thence, pits usually grow more rapidly in depth than in width, being able to occur partial or total grains separation. Pits are mainly hemispherical, near-hemispherical, near-conical and near-cylindrical without significant geometric transition associated with an increasing exposure period.
446
Authors: E. Bolognesi, B. Fabbri, M. Macchiarola, P. Kotas
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Authors: Petr Rezek, Petr Martinec, Jiří Ščučka, Tereza Majstríková
Abstract: The paper deals with analyses of composition and structure of historic plasters from the convent building of the Želiv Monastery (Czech Republic). Composition and microstructure of plaster samples taken from the historic object have been assessed using both traditional and advanced analytical methods. The following techniques have been used for the assessment of binders and fine aggregates in plasters: optical microscopy of thin sections, mineralogical and petrographic analysis of separated components, infrared spectroscopy, and thermal analysis. Presented results show significant differences in character of the studied materials of varying age and demonstrate the effectiveness of the taken analytical approach.
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Authors: Mohd Asyadi Azam, Mohd Fuad Ibrahim, Muhammad Zaimi
Abstract: Oil and gas industry has been hugely contributing any government income and this industry is highly required to control corrosion failures in pipelines which may potentially cause substantial human and economic losses. The objective of this study is to study the effect of sulfuric acid (H2SO4) electrolyte concentration to corrosion behavior of the internal surface of natural gas pipeline by using Tafel extrapolation method. Surface morphology of the samples is studied using optical microscope and scanning electron microscope to investigate the correlation between the corrosion rate and surface morphology. As results, the corrosion rate increases with higher concentration of H2SO4. Microscopic analyses also confirmed the presence of pitting corrosion, and micrometer thick of corrosion product was developed on the surfaces. The data can be used to managing the pipelines effectively and prevention method can be taken in order to extend the life span of the pipeline.
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