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High entropy alloys fabricated via SPS compaction of high energy milled feedstock powders
Gubán, Ivan ; Hadraba, Hynek (referee) ; Čížek, Jan (advisor)
The subject of this thesis is preparation of CoCrFeMnNiNx high entropy mixtures via the methods of mechanical alloying and spark plasma sintering (SPS). Three series of specimens were fabricated in this thesis: samples milled in argon (benchmark materials), samples milled in nitrogen atmosphere (to observe their ability of nitrogen absorption) and samples microalloyed with CrN, FeN nitrides (to observe their dissociation into the solid solution potential). The fabricated powders and SPS compacts were subsequently observed by electron microscopy and their phase content by X-Ray diffraction (XRD) and elemental composition by EDS analysis were carried out. A method of reduction melting in inert atmosphere was used to determine the exact oxygen and nitrogen content in powders, while the respective particle size distribution measured by laser diffraction method. The influence of nitrogen content on the hardness of the samples was studied via the microhardness measured. After completing the process of mechanical alloying under the Nitrogen atmosphere was the maximal concentration of nitrogen in the structure 0,208% after 24 hours of milling (dependency on time was linear), which means, the method of milling under the Nitrogen atmosphere was successful. XRD of milled samples showed the existence of the only FCC single solid solution phase, while samples milled under the Nitrogen atmosphere showed the trend of the growth of the lattice parameter with the increasing nitrogen content. There was observed the presence of the chromium nitrides precipitates on the grain boundaries of the FCC phase in microalloyed samples. All specimen were contaminated by a mixture of metallic oxides and manganeese sulphides, which were present in the default manganeese powder. The greatest value of microhardness showed the duplex sample. The increase in values of microhardness (344 HV 0,3) in comparison with the standard sample (262,9 HV 0,3) was recorded on the samples milled under the nitrogen atmosphere, which conforms the positive influence of the nitrogen content on strength characteristics of this alloy.
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Process Gas Heating Systems in Cold Spraying
Babinský, Tomáš ; Ing. Tomas Denk, Glass Service Inc., Vsetin, CR (referee) ; Čížek, Jan (advisor)
The goal of this bachelor's thesis is to present ways of gas heating used in the cold spray technology. Primarily the work is focused on description of currently-used techniques of high-pressure gas heating in cold spray and introduction to commercial products. Part of the work is dedicated to the gas temperature influence on the coating process. Gas heating methods in various industrial applications are summarized in the final chapter for potential use in cold spray technology.
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Powder feeding analysis in RF-ICP
Zlatník, Rostislav ; Veverka, Jakub (referee) ; Čížek, Jan (advisor)
The work is focused on the problematics of inductively coupled plasma, which is used for deposition of layers. We focused on two goals in the work. The first one focused on powder feeder, which is working on the vibration principle and is used in an apparatus that is using inductively coupled plasma. The aim is to determine its properties, dependence on different input parameters and working conditions. Is important to verify the suitability of its use for this kind of application. The assumption was to find the ideal configuration of the feeder for the given powder. After an overall assessment of the feeder properties, it was recognized as inappropriate for this application. The second goal is to spray tungsten layers with three different tungsten powders. Layers made with an inductively coupled plasma technology delivers promising results, but this issue needs to be intensively addressed in the future.
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Characterization of suspension plasma sprayed coatings deposited using different organic carriers
Dukovský, Daniel ; Toma, Filofteia-Laura (referee) ; Čížek, Jan (advisor)
Cílem této bakalářské práce bylo charakterizovat a porovnat povlaky nanesené plazmovým žárovým nanášením ze suspenze s použitím různých organických nosičů. Teoretická část obsahuje stručný popis běžně používaných metod žárového nanášení a blíže se věnuje technologii hybridního vodou stabilizovaného plazmatu (hořák s touto technologií byl využit pro nanesení povlaků v tomto výzkumu). Druhá polovina teoretické části se zabývá věcným popisem povlaků a metodami nanášení prášku o velikosti částic v řádu nanometrů, kde hraje důležitou roli právě použití suspenze. Experimentální část je zaměřena na vliv použitého solventu v suspenzi na charakteristiky výsledného povlaku. V závěrečné části jsou prezentována a diskutována naměřená data a vyhodnoceny výsledky.
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Properties of quasicrystal-reinforced high entropy alloys
Adami, Martin ; Tesař,, Tomáš (referee) ; Čížek, Jan (advisor)
This diploma thesis deals with the processing of the high-entropy alloys with the addition of quasicrystals by the spark plasma sintering method. The aim of this thesis is to evaluate the influence of quasicrystals content on the microstructure and wear resistance. The literature review part is divided into several section. The first part is an overview of high-entropy alloys and quasicrystals, including their properties and production methods. The next part pertains to spark plasma sintering and the wear phenomenon. In the experimental part, spark plasma sintering compacts were produced at 1100 °C and an analysis was performed using scanning electron microscope as well as X-ray diffraction and their tribological properties were measured by the pin-on-disc method. It was found that increasing the content of quasicrystals triggered an improvement in the compacts’ wear resistance.
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Fatigue Properties of Materials with Protective Thermally Deposited Layers
Matějková, Michaela ; Kovářík,, Ondřej (referee) ; Čížek, Jan (advisor)
Titanium powder was deposited into low-carbon steel specimens using three thermal spray technologies: plasma spray, cold spray (USA, Singapore) and warm spray (denoted as PS, CSU, CS-S, and WS, respectively, in further text). The aim was to determine the influence of the coatings on the fatigue lives of the specimens. The experimental work was carried out in a symmetrical cantilever-beam bending setup using a computer-controlled SF-Test loading device. Further to that, the micro-morphology of coatings structure, their respective porosity content and the fracture surfaces of both coatings and substrate materials was carried out.
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Aluminium foams and their applications in engineering practice
Belák, Kristián ; Čížek, Jan (referee) ; Němec, Karel (advisor)
Bachelor thesis includes knowledge of aluminum foams and their practical use. The first part of the thesis is focused on the basic characteristics of aluminum and its alloys, consequently, there are characterized metal foams and stated their basic division. Further, there is also devoted considerable attention to selected methods of its manufacturing. Also, properties of these foams are mentioned, mainly the most important ones – mechanical. Thesis deals even about technological processing of foams and the last part contains description of selected applications of metal foams in technical practice.
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Ternary shape memory alloys powder feedstock fabrication by advanced mechanical alloying
Regináč, Jan ; Moravčík, Igor (referee) ; Čížek, Jan (advisor)
Prášková metalurgie může být použita jako alternativní metoda pro výrobu slitin s tvarovou pamětí s Cu-bází. Tato metoda poskytla lepší výsledky, co se týče celkového složení a velikosti zrn, než tradiční metoda lití. V této práci byl aplikován proces mechanického legování k přeměně směsí základních prášků Cu-Al-Ni na mechanicky legované směsi. Cílem práce bylo nalezení optimálních parametrů pro výrobu nejvhodnějšího práškového prekurzoru určeného k dalšímu zpracování. SEM, EDX a XRD analýzy byly použity pro zjištění účinku změny parametrů na výslednou strukturu a na případnou tvorbu nových fází. Bylo ukázáno, že vysokoenergetické legování je vhodnou metodou pro výrobu takových prekurzorů. Na základě výsledků bylo zjištěno, že tuhý roztok mědi byl formován nezávisle na změně mlecích parametrů. Výsledky dále odhalily, že vysoký energetický vstup ve formě otáček a dlouhých mlecích časů, může způsobovat vznik amorfních fází.
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Fabrication and characterization of solution precursor hydroxyapatite coatings deposited via hybrid water-stabilized plasma gun
Antoš, Zdeněk ; Tkachenko, Serhii (referee) ; Čížek, Jan (advisor)
Hydroxyapatite coatings have been used as a barrier between a metal core of replacement and living tissue for long time in medicine. Plasma spray is a typical technology for preparation these coatings. This thesis concerns a new plasma spray technology with hybrid system of arc stabilization (WSP-H). Simultaneously it uses an innovative method of feeding the initial material in a form of water suspension (SPPS). The aim of this thesis was to produce water solutions of hydroxyapatite and make coatings with WSP-H. These coatings were characterized in terms of their morfology, chemical and phase composition. Their biocompatibility was tested by a cultivation and an analysis of RAW 264.7 and MG-63 cells. The coatings made by SPPS have a very rough surface which is suitable for biological application. The biocompatibility testing discovered that the coatings will by tolerated in a human body very well. This method of production of hydroxyapatite coatings could be a good replacement of older methods after a better optimalisation of the processing parameters and after reaching purity of coating.
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