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Structure and Properties of Sintered Tungsten Carbides
Novotná, Hana ; Klakurková, Lenka (referee) ; Čelko, Ladislav (advisor)
This bachelor thesis deals with the structure and properties of sintered tungsten carbides. The literature review section concerns the development of sintered carbides, their composi-tion and structure, different types of carbides, the steps of the production of sintered car-bides, sintering technology and alternative materials for cutting tools. The experimental section deals with composition of WC-Co and is ascertained by the dependency coercivity on WC grain size and also on cobalt content. This work describes the measurement of WC grain size and measurement of the coercivity, one of the fundamental properties of sintered carbides.
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The analysis of couses of the damage of stroller welded construction
Štarhová, Martina ; Juliš, Martin (referee) ; Klakurková, Lenka (advisor)
This bachelor thesis deals with analysis of causes of damage of aluminum welded structures of baby carriages. The theoretical part contains a summary of information concerning the most frequently used aluminum alloys and their heat treatment. Furthemore, it deals with possibilities of welding and testing of welded joints, corrosion resistance of aluminum alloys. Basic information on the most frequently used surface treatment, anodic oxidation, is also mentioned. The experimental part of the work deals with a complex material analysis of three frames of baby carriages. This analysis is focused on mapping the occurrence of the most common defects and determining their contribution to damage or destruction of the baby carriage frame.
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Research and development of surface modifications of bearing steels by means of ion nitridation
Klimčáková, Kateřina ; Klakurková, Lenka (referee) ; Doležal, Pavel (advisor)
Basic requirements placed on rolling bearing components include the high fatigue limit, the wear resistance and the corrosion resistance. As full production of bearings from materials with these attributes would be quite expensive, surface modifications are used to improve mechanical characteristics. This thesis deals with application of layers to the bearing steel by means of ion nitridation. It studies effects of input conditions of the ion nitridation and of the surface condition on tribological characteristics of the bearing steel with the above mentioned finishing. The study employed the interaction light microscopy, the scanning electron microscopy equipped by energy dispersive chemical microanalysis, the hardness measurement by Vickers, the glow discharge optical emission spectroscopy, and methods of the phase analysis by means of the X-ray diffraction were used.
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Methods to increase the visibility of the original austenite grain boundaries in steels
Gamanov, Štěpán ; Klakurková, Lenka (referee) ; Juliš, Martin (advisor)
This thesis deals with methods of revealing prior austenite grains in steels. The objective was to describe and demonstrate these basic methods on samples. The theoretical part deals with the importance of austenite grain and its size, with description of base methods of revealing austenite grains, and with methods of determination of grain size. The practical part consists of pictures and commentary of samples wich were made with some of the base methods described in the theoretical part. Conclusion consists of comparison of our and external results and also expanding commentary on individual methods.
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Design, production and characterization of the adhesive layer for the deposition of ta-C coating by the magnetron sputtering method
Drásalová, Kateřina ; Juliš, Martin (referee) ; Klakurková, Lenka (advisor)
The topic of this thesis is improving the adhesion parameters of the DLC (diamond-like carbon) coating, specifically for its non-hydrogenated form ta-C (tetra amorphous carbon), for the deposition of ta-C coating by the magnetron sputtering with a central rotating cathode method. A possible solution is the creation of a chrome adhesive layer between this coating and the substrate. Effects of the adhesive layer on the coating are controlled by change settings of a process parameters as temperature, voltage, or time of deposition. The aim of the experiment was the production of such an adhesive layer that will increase the adhesion of the ta-C coating without worsening its other properties. The resulting properties of the deposited coating were analysed using a calotest for thickness measuring, Rockwell test and scanning electron microscopy (SEM) to assess adhesion and cohesion parameters, instrumented penetration tests to determine hardness and bent-strip method to calculate internal stress. By evaluating the prepared samples, depending on the resulting useful properties of the coating, the best deposition parameters were determined.
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Design of material for drawing tools
Petrecký, Adam ; Juliš, Martin (referee) ; Klakurková, Lenka (advisor)
Bachelor thesis deals with optimalization of material choice and its heat treatment for cold work forming tools. The thesis deals with specific failure of seizure during the cold forming of high strenght steel for automotive. First part deals with theory of cold forming and tool steels made for this purpose. The main goal of the thesis was to discover cause of the failure and deduce solution as choice of alternative material with its proper heat treatment and surface coating. Solution has to show higher lifespan and also has to deliver economical benefit.
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Influence of cooling rate on microstructure and mechanical properties of castings from magnesium alloys AZ91, WE43B and Elektron21 produced by investment casting
Jakubcová, Eliška ; Klakurková, Lenka (referee) ; Juliš, Martin (advisor)
This master's thesis deals with the effects of the cooling rate on the grain size of magnesium alloys based on Mg–Al (AZ91E) and Mg–Zr–RE (WE43B and Elektron21). The effects of the cooling rate are analyzed on samples of varying thickness for different cooling methods (forced–air–cooling, cooling into polymer, natural air cooling). We also evaluated the final microstructure, porosity, hardness, and mechanical properties for investment castings. Based on the evaluated grain sizes, we demonstrated a significant difference in the cooling rate influence on the grain size for the alloy AZ91E. Compared to Zirconium-based alloys (WE43B and Elektron21), for which the zirconium content influences grain size the most. For the alloys based on Mg–Zr–RE, it is possible to prefer casting conditions, without negative enlarging of the grain size.
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Deposition and analysis of AlCrN coatings
Drásalová, Kateřina ; Juliš, Martin (referee) ; Klakurková, Lenka (advisor)
The topic of this thesis is the deposition process and methods of quality assessment of AlCrN surface coatings produced by methods of (i) magnetron sputtering, (ii) magnetron sputtering with arc enhanced glow discharge, and (iii) high power magnetron sputtering with the movable magnetic field. The main focus is placed on categorizing properties of the produced coatings based on the production method (which vary in the ionization level). Qualities of the surface coatings are assessed by adhesion and cohesion parameters testing of coarseness using AFM (Atomic Force Microscopy), depth measuring using a calotest, measuring internal tension using the Bent Strip Method and Instrumented indentation test for hardness.
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The analysis of couses of the damage of stroller welded construction
Štarhová, Martina ; Juliš, Martin (referee) ; Klakurková, Lenka (advisor)
This bachelor thesis deals with analysis of causes of damage of aluminum welded structures of baby carriages. The theoretical part contains a summary of information concerning the most frequently used aluminum alloys and their heat treatment. Furthemore, it deals with possibilities of welding and testing of welded joints, corrosion resistance of aluminum alloys. Basic information on the most frequently used surface treatment, anodic oxidation, is also mentioned. The experimental part of the work deals with a complex material analysis of three frames of baby carriages. This analysis is focused on mapping the occurrence of the most common defects and determining their contribution to damage or destruction of the baby carriage frame.
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Nondestructive testing in current industrial practice
Jakubcová, Eliška ; Klakurková, Lenka (referee) ; Juliš, Martin (advisor)
The bachelor thesis is focused on personnel certification of non-destructive testing according to valid standards. The theoretical part compares the Czech certification system for non-destructive testing with systems in other countries and evaluates their differences. Problems that occur during certification according to ČSN EN ISO 9712 are also discussed. In the practical part of the thesis the evaluation of the test sample is documented by means of radiographic test, magnetic particle test and leak test. At the end of the thesis the results are evaluated and discussed and also described in the form of measuring protocols.
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