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Microstructure and microhardness evaluation for NiCrAlY materials manufactured by spark plasma sintering and plasma spraying
Hulka, Iosif ; Mušálek, Radek ; Lukáč, František ; Klečka, Jakub ; Chráska, Tomáš
NiCrAlY deposited by different thermal spraying methods is commonly used as the bond coat material in thermal barrier coatings (TBCs). In the present study, two experimental coatings were deposited by hybrid water stabilized plasma (WSP-H) and radio frequency inductively coupled plasma (RF-ICP) using the same feedstock powder. Spark plasma sintering (SPS) was used to manufacture a compact NiCrAlY from the same feedstock powder as a reference material. Microstructure, internal oxidation, phase characterization and quantification of the mechanical behaviour in terms of microhardness were studied. The investigations clearly showed microstructural and mechanical differences between the NiCrAlY samples manufactured by different plasma technologies. The results confirmed that SPS and RF-ICP provide dense structures with no oxides due to the fabrication under protective atmosphere and similar mechanical properties. Thus, RF-ICP may be used for deposition of very dense coatings with microstructure and hardness comparable to compacted materials prepared by SPS.
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Tungsten-steel and tungsten-chromium composites prepared by RF plasma spraying
Matějíček, Jiří ; Klečka, Jakub ; Čížek, Jan ; Veverka, Jakub ; Vilémová, Monika ; Chráska, Tomáš ; Ganesh, V.
For future fusion reactors, materials able to withstand harsh environments are needed. In particular, this concerns the plasma-facing components which are foreseen to consist of tungsten based plasma-facing armor and structural and cooling part made of steel. Currently, joining of these materials presents a significant challenge. The stress concentration at their interface, which arises due to thermal exposure and the difference in thermal and mechanical properties, can be reduced by composite/graded interlayers. Plasma spraying is among the prospective technologies for their preparation. In this work, tungsten-steel and tungsten-chromium composites were prepared by radio-frequency inductively coupled plasma (RF-ICP) spraying. Initial optimization of the spraying process for pure materials as well as their mixtures was carried out. Basic characterization of the layers for their structure, porosity and composition is presented.
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On tungsten spraying using inductively coupled plasma system - First results
Klečka, Jakub ; Mušálek, Radek ; Vilémová, Monika ; Lukáč, František
Thanks to its unique properties such as high melting point and density, tungsten and tungsten-based alloys are commonly used in a wide range of applications. Among others, these materials are promising candidates for the plasma facing components in the future fusion reactors. One of considered ways of production of these parts is plasma spraying. There are however several limitations for conventional gas stabilized torches, mainly in plasma enthalpy (i.e. the ability to efficiently melt tungsten particles in considerable feed rates) and susceptibility of tungsten to oxidation (which complicates spraying in oxidizing open-air atmosphere). The radio frequency inductively coupled plasma torch (RF-ICP) is a unique system which can potentially overcome both these problems and can be used for efficient tungsten spraying. The tungsten powder, which can be finer than the one used for the conventional systems, is fed axially into the hot plasma core, both factors lead to a more efficient melting of the particles. The deposition is performed in a chamber with controlled atmosphere of inert gas or decreased pressure, the oxidation is therefore suppressed. In this first study carried out with the newly commissioned RF-ICP system TekSpray 15 (Tekna), samples of tungsten coatings on graphite substrates were prepared. The X-ray diffraction and SEM images of the free surfaces and cross-sections were obtained, documenting high purity of the deposits and appropriate flattening of the splats leading to a dense coating microstructure. The effect of substrate preheating on the microstructure, porosity and hardness was also studied.
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Systémy detekce průniků
Klečka, Jakub ; Doucek, Petr (advisor) ; Pacík, Jan (referee)
Vzhledem k rostoucímu trendu využívání Internetu, nejen k získávání dat a informací, ale i jejich zneužití, roste význam jednotlivých prvků zabezpečení. Důležitou součást obrany informačního systému tvoří Systémy detekce průniku (IDS - Intrusion Detection System), které v reálném čase sledují provoz na síti a jsou schopny vyhodnotit a odfiltrovat nežádoucí komunikaci. Nasazení IDS je komplexní proces, který má dopad na celou organizaci a proto je třeba důkladně zvážit všechna jeho specifika a rozhodnout, zda-li bude IDS skutečně přínosem.
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Analysis of security requirements for payment card industry and problems with their implementation
Klečka, Jakub ; Doucek, Petr (advisor) ; Krob, Jan (referee)
Rapid development of new technologies and their easy implementation introduces new risks that must be faced. This diploma thesis concentrates at payment card industry. Payment card industry come through significant development. Billions of dollar each year flow through these systems. New technologies like contactless cards, prepaid brand cards are emerging, ATM and payment terminal support new services and products. Merchant are looking for new opportunities. This situation brings along new threats and introduces new vulnerabilities. These are not necessarily new, only the whole environment got much more complicated and digger. Unfortunately the acting threats and vulnerabilities were not eliminated. Missing legislation measures and restricted enforceability are not sufficient to effectively fight against crime in this area. On the other hand sever organizations are aware of these threats and tries to face them. New security requirements were introduced for each separate subjects of payment card industry so that the risks are eliminated or their impact is reduced to an acceptable degree. Some of these requirements were already implemented and are in the scope of this work. The goal of this work is to explore these requirements. To find out what risks they are affecting and how effective they are. And in case of need help to implement the appropriate security measure. This work is practically oriented and can help responsible persons to ensure compliance with the requirements and face all effecting threats.
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