Browse

31 - 40 of 162 items :

  • Chemical Engineering x
  • Materials Sciences x
Clear All
High temperature alloys stability testing in impure helium

Abstract

Within the national and international research program of materials for advanced nuclear reactors Czech organizations contributed with several tests of metallic alloys. The specimens of the alloys were first exposed in the long term (up to 1500 hours) in simulated advanced gas cooled reactor coolant environment at 750-900 °C. After exposure the degradation of tested materials was explored, especially changes in material microstructure, corrosion damage and corrosion layer composition and in some cases also changes in mechanical properties were observed. In this paper selected results of exposure tests in high temperature helium of alloy 800 H, austenitic steel 316L and high-temperature nickel alloys are presented.

Open access
Study of triacetate cinematographic films and magnetic audio track by infrared spectroscopy

Abstract

Most of the cinematographic film collections stored in film archives are made on a triacetate base, and from the 1950s to the 1980s, a magnetic track was used to record sound. With a large number of archive materials, archives often do not know the chemical composition of film bases, history of use and degradation rates. Therefore, the chemical composition of three films with a magnetic audio track and one representative of the modern film FOMAPAN were investigated by infrared spectroscopy. Selected samples were artificially aged at elevated temperatures and humidity, and the rate of degradation of the film was evaluated by infrared spectroscopy, dimensional changes and gravimetric analysis. Based on the measurements, all of the examined films were made from cellulose triacetate and the binder of the magnetic trackswas cellulose nitrate. To determine the degree of degradation of the binder of the audio track and the triacetate base, a degradation index was created which expresses the ratio of the bandwidths of the characteristic groups in the infrared spectra. It is shown that infrared spectroscopy makes it easy to determine the chemical composition of cinematographic films and to quantify the rate of degradation and the current state of the film base using a suitably chosen degradation index.

Open access
Analysis of resistance of T91 steel under load in liquid PbBi

Abstract

This paper describes behaviour of the ferritic-martensitic steel T91 after long-term exposure in liquid eutectic PbBi. Small specimens of the steel were pre-loaded according to the ISO Standard No. 7539-2 and subsequently exposed to PbBi. The experiment was carried out in a flowing and static liquid metal medium at 350°C. The experimental time was selected for the flowing environment at 1000 hours and for static environment at 2000 hours. After exposure, the specimens were analysed by use SEM and EDX. Surface changes of the specimens from different experimental conditions were compared and discussed. The initiation of the cracks wasn´t observed in the monitored expositions.

Open access
Analysis of the Coating for Heavy Liquid Metal Applications

Abstract

This paper deals with the behavior of the ferritic-martensitic steel T91 samples covered with an AlTiN black coating, which is mainly used for high temperature applications (> 800 ° C) because of its resistance to oxidation. The coating was applied by use of a combination of High Power Impulse Magnetron Sputtering (HiPIMS) and Direct Current Magnetron Sputtering (DCMS). Samples were subjected to a tensile test in a static tank CALLISTO. The environment was liquid PbBi eutectic at a temperature of 550° C. Two types of samples, with a notch in the middle and without a notch, were tested. After exposure, the samples were subjected to morphological and chemical analyzes on SEM and EDX. Although the coating cracked over the entire length of the sample, high adhesion of the layer was demonstrated, the coating was delaminated locally only in the notch.

Open access
Chromium Coating as a Surface Protection of Zirconium Alloys

Abstract

Increasing of nuclear safety, higher demands for longer nuclear fuel campaign and higher levels of burnout are based on improving the properties of zirconium alloys. Protective coatings appears to be a promising way to reduce their chemical reactivity and increase resistance to hydriding. In this work, a thin chromium coating applied to a standard Zr1Nb zirconium alloy was studied using in-situ impedance spectroscopy. Exposure was carried out at a temperature of 280 ° C and a pressure of 8 MPa in a simulated WWER primary coolant environment. The results show that the chromium-coated Zr1Nb alloy is under these conditions oxidized significantly slower than the non-coated alloy.

Open access
Electrochemical Corrosion Characteristics of High Strength Low Alloy Domex 700 Steel After Mechanical Surface Treatment in Chloride Environment

Abstract

Nowadays a large number of mechanical surface treatments of constructions materials is used in industry, mainly focusing on steel surface treatment. The aim of this study was to evaluate the effects of mechanical surface pre-treatment (grinding and shot peening) on corrosion resistance of high strength low alloy Domex 700 steel. Suitable mechanical surface treatment can by used for surface homogenization (eg. grinding) or for improvement of mechanical, strength and fatigue properties (shot peening). 0,1M NaCl solution of ambient temperature was used as an environment for electrochemical tests. Evaluation of the mechanical surface treatment effect on corrosion resistance of Domex 700 steel surface was realized by electrochemical tests: potentiodynamic polarization tests (using Tafel analysis) and electrochemical impedance spectroscopy (using equivalent circuit). From the obtained results it is possible to conclude, that the process of mechanical surface treatment by shot peening at choosen conditions has negative effect on corrosion resistance of Domex 700 steel.

Open access
Impact of AC Current Density on Material Corrosion of Distribution Pipelines

Abstract

Vliv střídavého indukovaného proudu na korozní rychlost oceli St3 a 17GS byl pozorován v simulovaných půdních elektrolytech typických pro Ukrajinu. Ocel St3 je citlivější na přirozené korozní napadení v půdě i na napadení vyvolané střídavým proudem. Byla stanovena nejhorší prostředí z hlediska koroze v elektrolytech obsahujících chloridy či směs chloridů se sírany.

Open access
Effect of hammer peening with tungsten coating on fatigue properties of carbon steel under rotating bending

Abstract

In the present study, we investigated the influence of hammer peening (HP) with tungsten carbide surface coating (WCSC) on high cycle bending fatigue performance of the carbon steel (CS) manufactured as specified in Bureau of Indian Standards BIS 2062 steel. Totally there are twenty-four numbers of specimens cast and tested to investigate fatigue performance. Constantly high cycle bending fatigue load (HBFL) were applied for all specimen, different range of bending stress applied to the specimen and the stress ratio maintained as R = 1. Investigation results show there is up to 40 percent of the fatigue life improvement possible by the surface treatments to the CS material. From the research to date the corrosion and pitting corrosion can be treated by modifying the surface layer of the metal by treating different peening methods and coating.

Open access
Evolution of microstructure and electrochemical corrosion characteristics of cold compacted magnesium

Abstract

The main advantage of magnesium and its alloys is high specific strength and biocompatibility. A modern approach to magnesium-based materials preparation is powder metallurgy. This technique allows preparation of new materials with a unique structure, chemical composition, and controlled porosity. In this study, cold compaction of magnesium powder was studied. Magnesium powder of average particle size of 30 μm was compacted applying pressures of 100 MPa, 200 MPa, 300 MPa, 400 MPa and 500 MPa at laboratory temperature. Influence of compacting pressure was studied with microstructural and electrochemical corrosion characteristics analysis. The resulting microstructure was studied in terms of light and electron microscopy. Obtained electrochemical characteristics were compared with those of wrought magnesium. Compacting pressure had a significant influence on microstructure and electrochemical characteristics of prepared bulk magnesium. With the increase in compaction pressure, the porosity decreased. Compacting pressures of 300 MPa, 400 MPa and 500 MPa led to the similar microstructure of the prepared material. Polarization resistance of compacted magnesium was much lower and samples degraded faster when compared to wrought magnesium. Also, the corrosion degradation mechanism changed due to the microstructural differences between the material states.

Open access
Materials for use in calcium looping technology for CCS – corrosion processes in high-temperature CO2

Abstract

Carbon Capture and Storage (CCS) technologies are a perspective solution to reduce the amount of CO2 emissions. One of promising methods is Ca-looping, which is based on carbonation and calcination reactions. During both of these processes, especially calcination, high temperatures (650-950°C) are required. This means high demands on the corrosion resistance of equipment materials. Therefore, we carried out a study to suggest materials with suitable properties for calciner construction, which have to be particularly heat resistant: stainless steels (AISI 304, AISI 316L and AISI 316Ti) and nickel alloys (Inconel 713, Inconel 738, Incoloy 800H). A special device simulating calciner environment was built for this purpose. Chosen materials were tested in temperature 900°C, atmospheric pressure and gaseous environment with composition that can be possible in a calciner. The surfaces of materials were evaluated to determine composition and properties of formed oxide layers. High temperature oxidation was observed on all tested materials and oxide exfoliation occurred on some of tested materials (304, 316L).

Open access