Materials Science Forum Vols. 537-538

Abstract: Duplex stainless steels are a famous group of the stainless steels. Duplex stainless steels consist of mainly austenitic and ferritic phases, which is resulted by high content of different alloying elements and low content of carbon. These alloying elements can effect a number of precipitations at high temperatures. The most important phase of these precipitation is the σ-phase, what cause rigidity and reduced resistance aganist the corrosion. Several orientation relationships have been determined between the austenitic, ferritic and σ-phase in duplex stainless steels. In this paper we tried to verify them by EBSD (electron backscatter diffraction).

Abstract: This paper shows the result of some metallographical examinations that have been carried out on low-alloyed Cr-Mo-V heat resistant steel. The aim of this research is to present and compare the advantages and disadvantages of the mainly applied metallographical methods. These techniques are optical microscopy, scanning electron microscopy, replica method and special applications of these methods. We have proved that using the investigated methods together gives much more information about the lifetime of the specimen than using these techniques particularly.

Abstract: In this study the main properties of coated coronary stents are shown, such as recoil, foreshortening, surface features and failures and the expansion properties. The types and the effects of active and passive coatings are introduced. The results of our examinations with different coated coronary stents are shown as well. The quality and the changing of the coatings were examined by different methods (stereomicroscopy, atomic force microscopy, scanning electron microscopy and EDS analysis).

Abstract: It is well known that during sliding friction the properties of rubbing surfaces are changed owing to transformations caused by applied loads, friction and wear processes. In the last years many research works were devoted to reveal the properties of the surfaces transformed during the friction and wear at the Budapest University of Technology and Economics in the Department of Machine Design. During these investigations the conditions of developing beneficial transformed surface layers and their operating boundaries were determined by experiments on metal sliding pairs in laboratory. The conditions of evolving large-scale adhesion junctions, scuffing and seizure were investigated on heavy-loaded surfaces at slow sliding velocity. During the experiments hard steel balls slid on dry or lubricated metal disks. Coefficient of friction and wear tracks were measured and structures and damages of sliding surfaces were evaluated using profilometry, SEM and normal microscope photographs, and micro-hardness measurement.

Abstract: The aim of the present work is to produce new types of solid nanomaterials for different purposes (coatings, fillers, foams, bulk pieces, etc.). Technologies such as RS Al flake production, high energy mechanical milling and high energy rate forming technology (HERF) for compacting are used. The products are analyzed mainly by XRD, SEM and TEM methods. It was shown that the new-type of RS Al “flake” material is suitable not only for pigments but also for powder metallurgical purposes, i.e. Al based nanocomposites. By choosing suitable parameters for mechanical alloying with the Fritsch Planetary mill 4, very fine, alloyed and composited nanostructures can be produced (Al-4.5w%Cu- 10w%Al2O3, Al-15w%Pb) Dynamic compaction (HERF) using explosive techniques seems to offer a good way for the compaction of Al (metal) matrix nanostructured composites.

Abstract: Nanostructured Langmuir-Blodgett (LB) films of Stöber-silica nanoparticles have been prepared on silicon and quartz glass substrates. The deposited layers were investigated using scanning angle reflectometry and UV-Vis spectroscopy. The reflectivity and the transmittance spectra of the LB films were evaluated using a model based on thin layer optics. Film thickness and effective refractive index of the films were determined. From the refractive index values the volume fraction of the particles in the film was estimated by effective medium approach.

Abstract: Diverse technologies in domestic enamelling production for machining, cutting and joining process are applied. The experiments presented in this paper focused on the opportunities of replacement of the drawn tubes built in heat exchangers longitudinal seam pipes produced by DUNAFERR Co. Ltd. The steel grade which satisfies the requirement of two-side enamelling, formability and after-fire sag resistance has been investigated. It has been shown that the coldrolled DC 04 EK-B steel grades stand all demands needed and therefore are able to replace the imported drawn tubes presently used.

Abstract: The macrosegregation is one of the most recurrent phenomena in continuous steel casting of slabs. It often impedes the further processing and has detrimental effect on the quality of rolled strip. The macrosegregation can be explained by the interpretation of unit steps of solidification in continuous casting slabs as well as on the basis of the interaction of the inclusions at the interface of solid and liquid phases. Development of solid shell and interaction between growing dendrites and MnS segregation has been presented. Only the pushing effect could be the real cause of MnS segregation among the three possible interactive mechanisms. The sulphur print could give misleading information on sulphur segregation.

Abstract: Three different types of austenitic stainless steel (SUS 304, SUS 304L and SUS 316) samples were cold formed in order to investigate the effect of cold forming on the grain boundary structure of the material. SUS 304L and SUS 316 samples were cold rolled, SUS 304 samples were tensile loaded in different manner at room temperature. Electron back scatter diffraction measurements have been carried out in order to obtain information about the boundaries of the treated specimen. The measurements showed that the frequency of the special Σ3n type CSLboundaries was significantly decreased by increasing the deformation of the samples.

Abstract: It is common for the most reactor pressure vessel (RPV) of light-water reactors used today, that the RPV made of ferrite-perlitic steel is cladded with an austenitic layer, which well resists corrosion influence. The cladding is manufactured by welding, the technology (mode of application, number of layers) is different by each manufacturer. This is the layer which comes into contact with the working media first, and is of course in cohesive contact with the RPV material. The aim of this study is to demonstrate the new approach, used for assessing the safety of the reactors today. This approach plays a decisive role in the lifespan calculation of already operating nuclear power stations, including the extension of their service period.