Download or read book Determination and Understanding of the Role of Alloying Elements on the Passive Behavior of Ni based Alloys by Electrochemical Investigation written by Zhiheng Zhang and published by . This book was released on 2021 with total page 149 pages. Available in PDF, EPUB and Kindle. Book excerpt: Ni-based alloys are widely used in various engineering applications, such as oil and gas, nuclear power plant and chemical process, due to their excellent corrosion resistance and good mechanical properties at elevated temperature. To extend the sustainability and the versatility of Ni-based alloys, development of new grades or improvement of the existing ones is still ongoing. To carry out the alloy design, the study on the role of alloying elements on nickel-based alloys properties and corrosion resistance remains the best scientific approach. Within this framework, the main objective of this thesis is to develop a methodology based on electrochemical characterization and analysis for understanding the role of the alloying elements on the corrosion behavior and on the passive film properties of Ni-based alloys. The proposed methodology relies on successive electrochemical impedance spectroscopy measurements and advanced analyses of the impedance data, to follow the evolution of the passive film properties grown on different binary (Ni-Cr) and ternary (Ni-Cr-Fe) alloys at different potentials. The obtained impedance diagrams were interpreted with enhanced graphical method and fitted with Power-Law Model for giving physical meanings to passive film. This experimental procedure provides supplementary data from conventional polarization curves, such as evolution of the passive film thickness and resistivity profiles through the film. In this work, the role of alloying elements, especially chromium and iron, on the passive film properties and reactivity is studied. Understanding how alloying elements act on the passive film nature, structure and properties will provide some guidelines to engineers and scientists for designing or choosing the more adapted alloys. Finally, the proposed experimental method is also applied on certain commercial alloys. Their responses are compared with that of the closest binary and ternary alloys to evidence the discriminating factors that control the passive behavior.
Download or read book The Influence of Alloying Elements on the Crevice Corrosion Behaviour of NI CR MO Alloys written by Nafiseh Ebrahimi and published by . This book was released on 2015 with total page 388 pages. Available in PDF, EPUB and Kindle. Book excerpt: To enhance its corrosion resistance in aggressive media, Ni is alloyed with various amounts of Cr and Mo along with small amounts of other alloying elements such as W, Cu, and Fe. While the resulting alloys (known as Ni superalloys) show excellent passive behaviour, the function of individual alloying elements in resisting localized corrosion processes, in particular crevice corrosion is not fully understood. This study focuses on the electrochemistry and corrosion of a series of Ni-Cr-Mo (W) alloys with various Cr and Mo contents. Several electrochemical and surface characterization techniques were used to investigate the role of major alloying elements on maintaining passivity and protecting the alloy under crevice corrosion conditions. To initiate crevice corrosion, either galvanostatic or galvanodynamic polarization was used. Using these techniques to apply an electrochemical current the cathodic reaction on the counter electrode is controlled simulating the cathodic reaction needed to drive the anodic crevice corrosion reaction. A comparison of the crevice corrosion behaviour, controlled galvanostatically, of C22 (Ni-22Cr-13Mo-3W), BC1 (Ni-16Cr-22Mo) and C625 (Ni-21Cr- 9Mo) in 5 M NaCl solution at 150°C shows that crevice initiation is mainly controlled by the Cr content of the alloy while both Cr and Mo (Mo +W) synergistically determine the crevice activation rate. Once the crevice is activated, the corrosion damage propagation profile is dominantly influenced by the Mo (Mo + W) content of the alloy and also by the applied current. Higher currents and a higher Mo + W content lead to shallower and more laterally distributed corrosion damage. A series of weight change measurements on BC1, galvanostatically crevice corroded to a constant applied charge, show that internal proton reduction plays a key role in supporting active alloy dissolution, with more than 50% of the corrosion damage supported by this reaction. The results indicate that the alloy resists initiation of crevice corrosion, but once initiation has occurred it can continue to propagate spontaneously. The properties of the oxide films anodically formed on the alloys were investigated before and after a period of dissolution at pH 7 and 9 using electrochemical impedance spectroscopy (EIS), X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES). The purpose of these experiments was to determine the properties of the passive film formed on the alloy after transpassive dissolution. While Cr is the main element in maintaining passivity, the corrosion resistance of the reformed passive film after transpassive break down is enhanced mainly by Mo. Investigation of the crevice corrosion damage morphology beneath corrosion products, showed intergranular corrosion initiated preferentially on high energy random grain boundaries. Transmission electron microscopy (TEM) and electron energy loss spectroscopy (EELS) analyses of grain boundaries showed needle shaped inclusions enriched in oxygen and depleted in nickel were present on these boundaries but not on the dominant 3 boundaries.
Download or read book Electrochemical Corrosion Behavior of Alloys Formed by Ion Implantation written by United States. Bureau of Mines and published by . This book was released on 1979 with total page 28 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book IN SITU INVESTIGATION OF THE PASSIVATION OF ALLOY C22 AND OF THE PASSIVE FILMS FORMED ON ALLOY C22 IN ACIDIC ELECTROLYTES AT ROOM TEMPERATURE AND AT 90 DEGREES C written by S. Harrington M. Miyagusuku (and T. M.) and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The passive films formed on Alloy C22 in several acidic solutions were investigated by a combination of five in situ techniques: cyclic polarization, electrochemical impedance spectroscopy, Mott-Schottky analyses, electrochemical quartz crystal microbalance measurements, and surface enhanced Raman spectroscopy. Similar tests were conducted on unalloyed samples of nickel, chromium and molybdenum, which are the main alloying elements of Alloy C22. The results of the tests conducted on nickel, chromium, and molybdenum helped to determine the roles of these elements in the passivation of Alloy C22. In general, the corrosion resistance of C22 was superior to that of unalloyed chromium. Although chromium is an important component of the passive film on Alloy C22, the other elements figure prominently in the corrosion resistance of C22 in acidic solutions. The passivity of Alloy C22 was detrimentally affected by increasing concentrations of hydrogen ions, chloride ions, and increasing temperature. The results of this study provide understanding of the resistance/susceptibility of Alloy C22 to corrosion by the aggressive solutions that can develop inside pits and crevices.
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1995 with total page 426 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Modifications of Passive Films written by P. Marcus and published by CRC Press. This book was released on 2023-06-09 with total page 360 pages. Available in PDF, EPUB and Kindle. Book excerpt: The modification of passive films is a promising method of improving the corrosion resistance of metallic materials. As well as reviewing a wide spectrum of film modifications and their effects on passivity and to corrosion resistance, papers presented at this international symposium deal with chemical composition, chemical states and electronic properties of passive films.
Download or read book Improvement of the Corrosion and Oxidation Resistance of Ni based Alloys by Optimizing the Chromium Content written by Fethi Hamdani and published by . This book was released on 2015 with total page 108 pages. Available in PDF, EPUB and Kindle. Book excerpt: This fundamental study is focused on the understanding of the influence of the chemical composition of Ni-based alloys on their corrosion and oxidation mechanisms. This work is not dedicated for a particular application. It is well known for instance that Ni-based alloys are susceptible to intergranular stress corrosion cracking (IGSCC) in primary water. Thus, Alloy600 (Ni-16Cr-9Fe), used in steam generator (SG) tubing, was replaced by higher chromium content material Alloy690 (Ni-30Cr-9Fe). This later shows a better resistance to IGSCC which may be linked to the growth of more protective oxide layer as chromium content is increased to 30 wt.%. The main goal of this study is to investigate: i) the influence of chromium content, ii) impact of iron addition on the corrosion and oxidation resistance of Ni-based alloys in primary water and superheated steam at 700°C. Furthermore, analytical approach in acidic solution is conducted at room temperature. This allowed to establish a relationship between alloying elements and physical properties of the oxide layers. For this purpose, Ni-xCr (14 ≤ x≤ 30 wt.%), Ni-xCr-8Fe (x=14,22 and 30 wt.%) model alloys and industrial material Alloy600 have been studied. To characterize the oxide scales, conventional technics were used: SEM, STEM, EDX, Potentiodynamic, EIS, Chronoamperometry, Mott-Schottky. Furthermore, steam oxidation kinetics was evaluated by means of weight gain measurements. To uncouple the effect of surface cold-work and the chemical composition of the base metal, mirror and electro polishing were carried out. In primary water, critical chromium content (20 wt.%), which corresponds to the minimum amount of chromium required to the transition from non-protective to protective and compact Cr-oxide layer, is determined. However, the analytical approach, using electrochemical technics, at room temperature elucidated the existence of optimum chromium content (26 wt.%) in terms of corrosion resistance. In superheat steam, oxidation kinetics and oxide scale characteristics showed the existence of optimum chromium content (24 wt.%) in terms of oxidation resistance. The corrosion and oxidation resistance is degraded as chromium content was increased more than optimal amount. Iron addition (8 wt.%) had a detrimental effect on the protectivess of the resulting oxide scales. Finally, this study showed that optimizing of chromium content is more appropriate method for enhancing corrosion and oxidation resistance, that increasing chromium content to high level is not necessary beneficial to those parameters. This work provides a useful knowledge to design new alternative materials. For this purpose, more investigations should be conducted to test other parameters such as: weldability, fabricability, thermal conductivity,etc.
Download or read book Physics Briefs written by and published by . This book was released on 1990 with total page 866 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Nanomaterials and Nanocomposites written by Rajendra Kumar Goyal and published by CRC Press. This book was released on 2017-10-30 with total page 351 pages. Available in PDF, EPUB and Kindle. Book excerpt: The main aims of this book are to summarize the fundamentals, synthesis methods, properties and applications of nanomaterials, so as to provide readers with a systematic knowledge on nanomaterials. In addition, the book covers most commonly used characterization tools pertaining to nanomaterials. Further, it deals with relevant aspects of nanocomposites which contains dispersion of nano-sized particulates, and carbon nanotubes (CNTs) in the matrices (polymer, metal and ceramic). It also discusses development of smart nano textiles (intelligent textiles), self-cleaning glass, sensors, actuators, ferro-fluids, and wear resistant nano coatings. Aimed at senior undergraduate and graduate students, the key features on this book include: Top-down and bottom-up approaches for the synthesis of nanomaterials included Illustrates sample preparation and basic principle of characterization tools for nanomaterials Explains calculation of ratios of surface area to volume and surface atoms to bulk atoms Reviews synthesis, properties and applications of carbon nanotubes and magnetic nanomaterials Discusses size effect on thermal, mechanical, optical, magnetic and electrical properties
Download or read book Development of New Electrochemical Techniques to Detect the Depletion of Alloying Elements in Nickel chromium molybdenum tungsten Alloys written by and published by . This book was released on 2006 with total page 136 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Ni-Cr-Mo-W based Alloy 22 will be used for the outer wall of Nuclear Waste Package containers planned for use at the Yucca Mountain Nuclear Waste Reporitory. Corrosion has been identified as the most likely cause of failure of WPs. Although Alloy 22 is stable at low temperatures, it can form topologically close packed (TCP) phases like mu, P, sigma etc. and Cr rich carbides during welding and heat treatments. These microstructural changes could make it susceptible to localized corrosion, jeopardizing the projected 10,000 year service life. It is important to correlate these microstructural changes with the corrosion resistance of the alloy using non-destructive and rapid electrochemical tests. This investigation identifies a rapid, non-destructive, in-situ testing technique, to evaluate Cr and Mo depletion and intergranular corrosion susceptibility of Alloy 22.
Download or read book Corrosion Resistance of Nickel and Nickel Alloys Against Acids and Lyes written by Michael Schütze and published by John Wiley & Sons. This book was released on 2015-01-27 with total page 363 pages. Available in PDF, EPUB and Kindle. Book excerpt: Derived from the online reference "Corrosion Handbook", this handbook brings together all the relevant information on corrosion protection and prevention for nickel-based materials, all in a convenient and easy-to-use format. As such, it provides scientists and engineers manufacturing and utilizing these materials with comprehensive information, including tabulated data and references, on their corrosion behavior when in contact with acids and hydroxides.
Download or read book International Aerospace Abstracts written by and published by . This book was released on 1996 with total page 1012 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Bulk Metallic Glasses written by Michael Miller and published by Springer Science & Business Media. This book was released on 2007-09-26 with total page 243 pages. Available in PDF, EPUB and Kindle. Book excerpt: Bulk metallic glasses are a new emerging field of materials with many desirable and unique properties. These amorphous materials have many diverse applications from structural applications to biomedical implants. This book provides a complete overview of bulk metallic glasses. It covers the principles of alloy design, glass formation, processing, atomistic modeling, computer simulations, mechanical properties and microstructures.
Download or read book Energy Research Abstracts written by and published by . This book was released on 1993 with total page 754 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Government Reports Announcements Index written by and published by . This book was released on 1982 with total page 576 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Saline Water Conversion Report for written by United States. Office of Saline Water and published by . This book was released on 1964 with total page 652 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Saline Water Conversion Report for written by and published by . This book was released on 1962 with total page 718 pages. Available in PDF, EPUB and Kindle. Book excerpt:
