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Structural analysis of Fe48Cr28Ni16Mo4,5Si1,5C1,75 thermally-sprayed coatings on AZ91 magnesium alloy
Kobzinková, Eliška ; Doskočil, Leoš (referee) ; Buchtík, Martin (advisor)
The bachelor thesis deals with the analysis of thermally sprayed Fe48Cr28Ni16Mo4,5Si1,5C1,75 coatings on AZ91 magnesium alloy and evaluation of their structural and mechanical properties. The theoretical part deals with magnesium alloys, focusing on AZ91 alloy, thermal spray methods, specifically the High Velocity Oxygen Fuel method of depositing (HVOF), and Fe and Fe-Cr-Ni based materials. The theoretical part concludes with a review of current research in the field of Fe-based coatings deposited by the HVOF method. The experimental part is devoted to the structural analysis of AZ91 magnesium alloy and the Fe-based thermally sprayed coating deposited on this alloy. The microstructure was analyzed by light microscopy (LM) and scanning electron microscopy (SEM). Elemental and phase analysis was performed using energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). The hardness of the coating and alloy was measured by the Vickers method. The application of thermally sprayed coating increased the surface hardness from 87 ± 10 HV0.3 (AZ91) to 536 ± 94 HV0.3.
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Surface Characteristics and Materials of Internal Combustion Engines Piston Liners
Zloch, Jan ; Raffai, Peter (referee) ; Maršálek, Ondřej (advisor)
This work is professional research and addresses the issues of working surfaces of cylinders of internal combustion engines. It describes the technologies and concepts that are applied in the production of internal combustion engines currently. The characteristics of each of these technologies provides a description of the production process, finishing and the most common applications. Furthermore, the properties, structure, and achieved surface roughness created by these technologies are available.
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High temperature corrosion studies of HVOF sprayed coatings in molten sulphate salts environment
Lencová, K. ; Česánek, Z. ; Houdková, Š. ; Lukáč, František ; Mušálek, Radek
The generally applied requirements on lowering of emission production in the field of power industry have led, among others, into the application of low-emission combustion process of coal fired power plants. Besides the emissions reduction, this process has led to an increase of boilers parts corrosion degradation due to the reducing atmosphere in low-emission boilers, responsible for sulphide corrosion and molten salt attack. In such environment, the protection of the exposed surfaces gains importance. Among others, the thermal spraying technology can offer a suitable way of surface corrosion protection. In the present work, the high temperature corrosion behaviour of CoCrAlYTaCSi and Cr3C2-25%NiCr High Pressure/High Velocity Oxygen Fuel (HP/HVOF) sprayed coatings is evaluated and compared to the behaviour of bare structural steel (SPT360) substrate. The specimens were exposed to a molten salt environment, i. e., 12% Na2SO4 + 82% Fe2(SO4)3 at 690 °C under cyclic condition, simulating the working environment in low-emission boilers of coal-fired power plants. The thermogravimetric method was used to establish the kinetics of corrosion. X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS) techniques were used to analyse the corrosion products and determine the corrosion mechanism. The thermogravimetric measurement shows high oxidation rate of SPT360 steel. Cr3C2-25%NiCr coating provides slightly better performance compared to CoCrAlYTaCSi coating. Based on the obtained results, both coatings were found to have higher corrosion resistance than the SPT360 steel substrate, offering a sufficient surface protection in a given environment.
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Structural analysis of Fe48Cr28Ni16Mo4,5Si1,5C1,75 thermally-sprayed coatings on AZ91 magnesium alloy
Kobzinková, Eliška ; Doskočil, Leoš (referee) ; Buchtík, Martin (advisor)
The bachelor thesis deals with the analysis of thermally sprayed Fe48Cr28Ni16Mo4,5Si1,5C1,75 coatings on AZ91 magnesium alloy and evaluation of their structural and mechanical properties. The theoretical part deals with magnesium alloys, focusing on AZ91 alloy, thermal spray methods, specifically the High Velocity Oxygen Fuel method of depositing (HVOF), and Fe and Fe-Cr-Ni based materials. The theoretical part concludes with a review of current research in the field of Fe-based coatings deposited by the HVOF method. The experimental part is devoted to the structural analysis of AZ91 magnesium alloy and the Fe-based thermally sprayed coating deposited on this alloy. The microstructure was analyzed by light microscopy (LM) and scanning electron microscopy (SEM). Elemental and phase analysis was performed using energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). The hardness of the coating and alloy was measured by the Vickers method. The application of thermally sprayed coating increased the surface hardness from 87 ± 10 HV0.3 (AZ91) to 536 ± 94 HV0.3.
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Preparation and Characterization of Advanced Thermally-sprayed Coatings on Magnesium Alloys
Buchtík, Martin ; Hadzima, Branislav (referee) ; Fintová, Stanislava (referee) ; Ptáček, Petr (advisor)
The proposed dissertation thesis deals with the characterization of HVOF and APS-thermally sprayed coatings prepared on the AZ31 and AZ91 magnesium substrates. The theoretical part of the thesis describes in-detail Mg substrates used in the experimental part of the thesis. There are also characterized materials and coatings based on NiCrAlY and FeCrNiMoSiC metals, WC-CoCr cermets, and YSZ ceramic materials. At the end of the theoretical part, the literary research summarizing the characterization and analysis performed on thermally sprayed coatings on Mg alloys. Based on the theoretical knowledge, the characterization of Mg substrates and deposited coatings was performed in terms of the surface morphology, microstructure, and the chemical composition using the light microscopy (LM) and scanning electron microscopy with energy-dispersive spectroscopy (SEM+EDS). The phase composition of the coatings was analyzed using the X-ray diffraction (XRD). The diffractions corresponding to the sprayed coatings were compared with the feedstock powders, i.e. materials used for the spraying of the coatings. The characterization of the prepared coatings in terms of the mechanical and tribological properties was performed. The hardness and microhardness of the coatings as well as the coefficient of friction, and the wear rate were measured. The last chapter of the experimental part deals with the evaluation of the electrochemical corrosion properties by the potentiodynamic measurements in a 3.5% NaCl solution. In the case of exposed samples, the evaluation of the surface and coating/substrate interface was performed using LM and SEM with EDS. The mechanism of the corrosion attack and degradation was determined from the acquired knowledge and base on the results of the short-term measurements. Based on the measured results, it can be stated that the deposited coatings were successfully applied on the surface of both Mg alloys. All the coatings increase the surface hardness of the Mg alloys and significantly improve their tribological properties. However, except for FeCrNiMoSiC coatings, the corrosion properties of Mg alloys deteriorate due to the fact that the corrosion environment can pass through the coating to the less noble Mg substrate and the corrosion microcells are created.
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Thermal spray by electric arc
Eliáš, Vojtěch ; Sigmund, Marian (referee) ; Kubíček, Jaroslav (advisor)
This thesis deals with the issue of thermal spraying by means of an electric arc. First of all, a theoretical part is processed using a literary study dealing with corrosion and thermal spraying technology. The experimental part contains a description of the technological procedure and evaluation of four thermally sprayed samples. Zinacor 850, consisting of 85% zinc and 15% aluminum, was used as a coating. The evaluation involves measurements of thickness, adhesion and roughness as well as the macro-structural analysis of the coating. Two samples showed unusually low adhesion, and all samples also had a large fluctuation of the measured thicknesses. This was also confirmed by the macro-structural analysis, which showed that the sample with low adhesion also had high porosity. These defects may have multiple causes, but the recommendation for further practice is to reduce the spraying distance from the base material.
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Thermal spray coatings of bioceramics
Kašpárková, Kristýna ; Mrňa, Libor (referee) ; Kubíček, Jaroslav (advisor)
Bachelor´s thesis is focused on thermal spraying bioceramics. Bioceramic is designed to replace damaged parts of the human body. Practical use is mainly in orthopedics, jaw and facial surgery. This category of materials includes hydroxyapatite, which is characterized by biocompatibility and the ability to form a strong bond between the bone and the implant. The experimental part of the thesis was spraying 40 - pieces of dental implants for the company LASAK s.r.o. Plasma spraying technology was used to apply the hydroxyapatite coating. The required coating thickness was 60 m. The implant was sprayed and cleaned before spraying. Spraying was carried out in the laboratory of plasma coatings dental and skeletal implants ÚST FSI VUT Brno. A dimensional control was performed after plasma spraying.
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Corrosion protection by means of plasma spraying coatings
Bartoněk, Daniel ; Řehořek, Lukáš (referee) ; Jan, Vít (advisor)
This thesis is focused on making study of technologies used for applying metal coatings as corrosion protection and commonly used materials. By means of metalographic analysis compare microstructures of coatings thermal spraying by zinc based alloys. The thesis is describing basics of corrosion, means of corrosion protection and methods used for making zinc coatings for corrosion protection. Experimental part is comparing coatings made by thermal plasma spraying and thermal spraying with use of electric current.
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Suspension plasma spraying of sub-stoichiometric titania by hybrid water/argon stabilized plasma torch
Mušálek, Radek ; Ctibor, Pavel ; Medřický, Jan ; Tesař, Tomáš ; Kotlan, Jiří ; Lukáč, František
In this study, suspension plasma spraying of sub-stoichiometric titania was attempted using hybrid water/argon stabilized plasma torch (WSP-H). Porous coatings with fine cauliflower-like columnar microstructure were successfully deposited in two separate experiments with different power levels of the plasma torch. In both cases, high solid-load content (40 wt. %) of the water-based suspension resulted in considerable coating thickness increase per deposition cycle. Coating annealing and partial remelting of the surface asperities were also achieved by additional pass of plasma torch in front of the coating surface. According to X-ray diffraction, all coatings consisted dominantly of rutile phase. Detailed microscopic observation of the as-sprayed and annealed deposits showed that the local coloration of the coating (ranging from dark blue to beige) was driven by the local overheating of the rough coating surface which could also promote the oxygen intake. Moreover, sample annealing was also observed to increase the sample reflectivity as observed by UV-VIS-NIR scanning spectrophotometry
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Deposition of Titania from Solution by Hybrid Water-Stabilized Plasma Torch
Mušálek, Radek ; Medřický, Jan ; Tesař, Tomáš ; Kotlan, Jiří ; Lukáč, František
Thermal spraying with liquid feedstock presents a novel route for deposition of functional coatings. In this study, possibility of preparation of titania coatings from solution by hybrid water stabilized plasma torch is presented. Coatings were prepared from solution of titanium isopropoxide Ti[OCH(CH3)2]4 in anhydrous ethanol. Fragmentation of feedstock stream in the plasma jet was monitored by shadowgraphy. Deposition was carried out on steel samples mounted to the cooled rotating carousel. Cross-sectional images from SEM microscope showed successful formation of the deposit with dual morphology consisting of fine feather-like features combined with bigger droplets. X-ray diffraction revealed formation of nanometric rutile crystallites.
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