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Iskalni niz: "ključne besede" (corrosion resistance) .

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Ultra-high strenght TWIP steel with high chromium content
Pavel Podaný, Tomáš Studecký, Tomas Gregor, Radek Prochazka, Aleksandra Kocijan, 2023, izvirni znanstveni članek

Povzetek: A new ultra-high strength steel with a fully austenitic microstructure and twinning-induced plasticity (TWIP) effect has been developed. TWIP effect gives this steel a good combination of high strength of over 1000 MPa and ductility of over 35%. This new steel has a high chromium content, which increases its corrosion resistance. By combining cold rolling and annealing, the steel has achieved a very fine austenitic microstructure with an average grain diameter of 2.85 µm. This steel could be used for structural applications or components that need to withstand high levels of stress, deformation and corrosion environment.
Ključne besede: TWIP steels, corrosion resistance, microstructure, tensile strength, plasticity
Objavljeno v DiRROS: 31.01.2024; Ogledov: 346; Prenosov: 204
.pdf Celotno besedilo (1,44 MB)
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Improving the surface properties of additive-manufactured Inconel 625 by plasma nitriding
Danijela Anica Skobir Balantič, Črtomir Donik, Bojan Podgornik, Aleksandra Kocijan, Matjaž Godec, 2023, izvirni znanstveni članek

Povzetek: As a surface-hardening technique, plasma nitriding is a common procedure for improving the properties of conventional Ni-based alloys. The diffusion of nitrogen hardens a layer on the surface of the alloy, leading to better wear resistance and a higher coefficient of friction, as well as a higher surface hardness. This study reports the effect of plasma nitriding on additive-manufactured (AM) Inconel 625 (IN625) compared to its conventional manufactured and nitrided counterparts. The samples produced with the laser powder-bed fusion (LPBF) process were subsequently plasma nitrided in the as-built condition, stress-relief annealed at 870 °C and solution treated at 1050 °C. The plasma nitridings were carried out at 430 °C and 500 °C for 15 h. The growth kinetics of the nitride layer of the AM samples depends on the prior heat treatments and is faster in the as-built state due to the specific cellular structure. The lower nitriding temperature leads to the formation of expanded austenite in the nitride layer, while at the higher nitriding temperature, the expanded austenite decomposes and CrN precipitation occurs. The XRD and SEM analyses confirmed the presence of two layers: the surface layer and the diffusion layer beneath. The lower nitriding temperature caused the formation of expanded austenite or a combination of expanded austenite and CrN. The higher nitriding temperature led to the decomposition of the expanded austenite and to the formation/precipitation of CrN. The higher nitriding temperature also decreased the corrosion resistance slightly due to the increased number of precipitated Cr-nitrides. On the other hand, the wear resistance was significantly improved after plasma nitriding and was much less influenced by the nitriding temperature.
Ključne besede: additive manufacturing, powder-bed fusion, plasma nitriding, expanded austenite, wear and corrosion resistance, Ni-based alloy
Objavljeno v DiRROS: 31.01.2024; Ogledov: 354; Prenosov: 138
.pdf Celotno besedilo (7,98 MB)
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Corrosion monitoring of steel structure coating degradation
Bojan Zajec, Mirjam Bajt Leban, Tadeja Kosec, Viljem Kuhar, Andraž Legat, Stanislav Lenart, Karmen Fifer Bizjak, Gavin Kenneth, 2018, izvirni znanstveni članek

Povzetek: An important aspect regarding the sustainability of steel structures is to ensure the structure is protected from corrosion. A number of surface coatings are availablethat play an important role in protecting these structures. An important part of the management of these structures is reliable and regular inspection along with methods forearly detection of corrosion processes. In this paper, a development and application of sensors for monitoring the steel coating degradation and corrosion damage to steelsubstrate are presented. An encapsulated corrosion kit with integrated EIS sensors and ER probes was developed. To test its efficiency, steel probes were coated withselected coatings in the laboratory and their performance was assessed under various aggressive atmospheres, including; salt, industrial and humid atmosphere.
Ključne besede: coatings, corrosion, electrochemical impedance spectroscopy, electrical resistance probes, railways, steel structures
Objavljeno v DiRROS: 13.12.2023; Ogledov: 297; Prenosov: 146
.pdf Celotno besedilo (2,45 MB)
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The corrosion resistance of dental Ti6Al4V with differing microstructures in oral environments
Mirjam Bajt Leban, Tadeja Kosec, Matjaž Finšgar, 2023, izvirni znanstveni članek

Povzetek: The impact of the microstructural properties of a Ti6Al4V alloy on its electrochemical properties, as well as the effect of the α- and β-phases present within it, is still unclear. With the introduction of new, emerging technologies, such as selective laser melting and post heat treatments, the effect of the microstructure on an alloy's corrosion properties has become increasingly interesting from a scientific perspective. When these alloys are produced through different methods, despite an identical chemical composition they have diverse microstructures, and consequently display varying resistance to corrosion. In the present research study, Ti–6Al–4V alloy specimens produced by three different processes, leading to the formation of three different microstructures were investigated: heat treated specimen fabricated by selective laser melting, wrought and cast specimens. The impact of the microstructure of these alloys when immersed in artificial saliva was studied through the use of various electrochemical techniques, by microscopical examinations, and time-of-flight secondary ion mass spectrometry. Corrosion properties were investigated by the measurement of open circuit potential, linear polarization, and potentiodynamic curve measurements followed by microscopical examinations, and time-of-flight secondary ion mass spectrometry examination was conducted to reveal spatial distribution of alloying species on oxide film. It was found that the difference between specimens containing an α+β microstructure was small and not dependent on the aspect ratio of the β-phase, alloy grain size, and vanadium partitioning coefficient, but rather on the size, shape, and content of this phase.
Ključne besede: Ti6Al4V, dental alloy, microstructure, corrosion resistance, heat treatment, ToF-SIMS
Objavljeno v DiRROS: 26.10.2023; Ogledov: 658; Prenosov: 337
.pdf Celotno besedilo (8,12 MB)
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Development of an electrical resistance sensor from high strength steel for automotive applications
Tadeja Kosec, Viljem Kuhar, Andrej Kranjc, Vili Malnarič, Branko Belingar, Andraž Legat, 2019, izvirni znanstveni članek

Povzetek: This work focuses on a demonstration of the monitoring of corrosion processes taking place in high strength steel in automotive applications. This is performed by means of a corrosion sensor, which operates as an electrical resistance sensor. It was developed from the same type of material that is used for the high-strength steel parts produced in the automotive industry. Using the sensor, real time corrosion processes can be measured. It is attached to a location inside the vehicle’s engine and is equipped with a data logger, which enables wireless transfer of the measured data. In this study the development, operation, and evaluation of the monitoring process are presented. Corrosion estimation is verified by means of electrochemical methods. A metallographic investigation was included in order to verify the similarity between the microstructural properties of the sensor and those of the as-received high-strength steel sheet.
Ključne besede: high strenghth steel, automotive, electrical resistance sensor, corrosion
Objavljeno v DiRROS: 24.10.2023; Ogledov: 649; Prenosov: 219
.pdf Celotno besedilo (2,33 MB)
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Monitoring the corrosion of steel in concrete exposed to a marine environment
Nina Gartner, Tadeja Kosec, Andraž Legat, 2020, izvirni znanstveni članek

Povzetek: Reinforced concrete structures require continuous monitoring and maintenance to prevent corrosion of the carbon steel reinforcement. In this work, concrete columns with carbon and stainless steel reinforcements were exposed to a real marine environment. In order to monitor the corrosion processes, two types of corrosion probes were embedded in these columns at different height levels. The results from the monitoring of the probes were compared to the actual corrosion damage in the different exposure zones. Electrical resistance (ER) probes and coupled multi-electrodes (CMEs) were shown to be promising methods for long-term corrosion monitoring in concrete. Correlations between the different exposure zones and the corrosion processes of the steel in the concrete were found. Macrocell corrosion properties and the distribution of the separated anodic/cathodic places on the steel in chloride-contaminated concrete were addressed as two of the key issues for understanding the corrosion mechanisms in such environments. The specific advantages and limitations of the tested measuring techniques for long-term corrosion monitoring were also indicated. The results of the measurements and the corrosion damage evaluation clearly confirmed that the tested stainless steels (AISI 304 and AISI 304L) in a chloride-contaminated environment behave significantly better than ordinary carbon steel, with corrosion rates from 110% to 9500% lower in the most severe (tidal) exposure conditions.
Ključne besede: corrosion in concrete, steel reinforcement, long-term exposure, field exposure, electrical resistance (ER) probes, coupled multi-electrodes
Objavljeno v DiRROS: 21.08.2023; Ogledov: 419; Prenosov: 211
.pdf Celotno besedilo (4,42 MB)
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Sensor development for corrosion monitoring of stainless steels in H2SO4 solutions
Miha Hren, Tadeja Kosec, Mari Lindgren, Elina Huttunen-Saarivirta, Andraž Legat, 2021, izvirni znanstveni članek

Povzetek: Equipment made of different stainless steels is often used in the hydrometallurgical processing industry. In this study, an electrical resistance sensor was developed for monitoring corrosion in acidic solutions at high temperature. Two types of stainless steel were used as the electrode materials, namely grade 316L stainless steel (EN 1.4404) and grade 2507 duplex stainless steel (EN 1.4410). The materials and sensors were exposed to a 10% H2SO4 solution containing 5000 mg/L of NaCl at various temperatures. Results from the sensors were verified using electrochemical techniques and postexposure examination. Results showed that the microstructure played an important role in the interpretation of corrosion rates, highlighting the importance of using an appropriate stainless steel for the production of sensors. Electrochemical tests and postexposure examination both showed that the grade 2507 had a significantly lower corrosion rate compared to the grade 316L. Under industrial‑process conditions, the results for the grade 2507 sensor were promising with respect to sensor durability and performance, despite the extremely harsh operating environment.
Ključne besede: stainless steel, hydrometallurgical industry, sulphuric acid, electrical resistance sensor, corrosion
Objavljeno v DiRROS: 05.07.2023; Ogledov: 458; Prenosov: 248
.pdf Celotno besedilo (5,12 MB)
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Application of electrochemical methods for studying steel corrosion in alkali-activated materials
Shishir Mundra, Gabriel Samson, Giulia Masi, Rebecca Achenbach, David M. Bastidas, Susan A. Bernal, Maria Chiara Bignozzi, Maria Criado, Martin Cyr, Nina Gartner, Stefanie von Greve‐Dierfeld, Andraž Legat, Nikoonasab Ali, John L. Provis, Michael Raupach, Gregor J. G. Gluth, 2023, izvirni znanstveni članek

Povzetek: Alkali‐activated materials (AAMs) are binders that can complement and partially substitute the current use of conventional cement. However, the present knowledge about how AAMs protect steel reinforcement in concrete elements is incomplete, and uncertainties exist regarding the application of electrochemical methods to investigate this issue. The present review by EFC WP11‐Task Force ‘Corrosion of steel in alkali‐activated materials’ demonstrates that important differences exist between AAMs and Portland cement, and between different classes of AAMs, which are mainly caused by differing pore solution compositions, and which affect the outcomes of electrochemical measurements. The high sulfide concentrations in blast furnace slag‐based AAMs lead to distinct anodic polarisation curves, unusually low open circuit potentials, and low polarisation resistances, which might be incorrectly interpreted as indicating active corrosion of steel reinforcement. No systematic study of the influence of the steel–concrete interface on the susceptibility of steel to corrosion in AAMs is available. Less common electrochemical methods present an opportunity for future progress in the field.
Ključne besede: alkali-aktivated materials, alkali‐activated materials, anodic/cathodic polarisation, concrete, linear polarisation resistance, open circuit potential, reinforcement corrosion, resistivity
Objavljeno v DiRROS: 29.05.2023; Ogledov: 431; Prenosov: 216
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