|
|
The using protection paste during carburization of chain segments on their properties after welding
Kovář, Tomáš ; Kubíček, Jaroslav (referee) ; Slováček, Marek (advisor)
This thesis is focused on assessing whether it is possible to remove Condursal paste from the manufacturing process in order to reduce costs and save time. For the study, the area of the crossbar – C-shape weld was selected, where the C-shape is cemented and then welded to the crossbar. From this area, samples were produced by pewag s.r.o., which were subjected to subsequent tests and measurements. There was an evaluation of the macrostructure and microstructure as well as a tensile test, toughness, hardness inside and on the surface of the sample and measurement of residual austenite. After evaluating the tests and measurements, it was necessary to carry out another test measuring the carbon quantity in the surface layer due to an inappropriate hardness result. The hardness test and measurement of the carbon quantity confirmed the poorly prepared samples by the company, because the hardness in the surface layer did not reach the required value set by the company and the carbon quantity was also less than required. Subsequently, it was evaluated that Condursal paste can be excluded only in the case of supplied samples. In other circumstances, it cannot be said whether it is possible to exclude Condursal paste or not.
|
|
|
Refractory high entropy alloys - preparation and properties
Urbancová, Kateřina ; Jan, Vít (referee) ; Dlouhý, Ivo (advisor)
Tato diplomová práce zkoumá mikrostrukturu a mechanické vlastnosti dvou vysokotavitelných vysokoteplotních slitin (RHEA), MoNbTaVW a HfNbTaTiZr, připravených mechanickým legováním a slinováním (SPS). Teoretická část shrnuje hlavní koncepty vysokoentropických slitin a zaměřuje se především na RHEA, jejich metody přípravy, mikrostrukturu, mechanismy zpevnění a mechanické vlastnosti. V experimentální části termodynamické předpovědi a rovnovážné diagramy potvrdily stabilitu jednofázových tuhých roztoků u obou slitin při nepřítomnosti jiných příměsí. Byla provedena analýza procesu mechanického legování v závislosti na době mletí pomocí zkoumání prášku elektronovou disperzní spektrometrií spolu s rentgenovou difrakcí. Tato analýza ukázala, že MoNbTaVW vytvořil homogenní pevný roztok po 20 hodinách, zatímco HfNbTaTiZr vyžadoval delší dobu mletí. Připravené slitiny vykazovaly vyšší tvrdost, než se uvádí v literatuře, což bylo způsobeno modifikací jejich struktury dalšími fázemi, které vznikly během slinování. Měření lomové houževnatosti naznačila, že MoNbTaVW má vyšší houževnatost ve srovnání s HfNbTaTiZr, přičemž hodnoty se zvyšovaly s délkou mletí. Zavedení železa do MoNbTaVW významně ovlivnilo mikrostrukturu a mechanické vlastnosti. Vedlo to ke složitějšímu fázovému složení a zvýšené tvrdosti, která dosáhla maximální hodnoty 1077,8 HV v kombinaci s lomovou houževnatostí 4,3±0,3 MPa·m0,5. Tato slitina vykazuje rovnováhu mezi vysokou tvrdostí a střední lomovou houževnatostí, což dokazuje její potenciál pro aplikace vyžadující odolnost proti opotřebení. Tato práce zdůrazňuje důležitost vzájemného působení složení slitiny, délky mletí a podmínek spékání při úpravě mikrostruktury a vlastností RHEA pro pokročilé aplikace.
|
|
|
Oxigen cutting of high strength steels
Lupták, Jakub ; Izák, Josef (referee) ; Kubíček, Jaroslav (advisor)
The work focuses on the issue of thermal cutting and its use for high-strength steels. Plasma cutting is most commonly used for cutting these materials, and this work explores the alternative possibility of cutting with oxygen. The theoretical part discusses high-strength steels, the possibilities of their thermal cutting, the selection of methods for the practical part, and their principles of operation. Specific methods for the experimental part are selected and detailed in terms of their principles of operation. The experimental part involves cutting selected samples of high-strength steels using oxygen and plasma at two different cutting speeds. Changes in hardness at the cutting edge are analyzed, and the size of the heat-affected zone for both technologies is evaluated. Finally, the suitability of oxygen cutting technology for high-strength steels is assessed.
|
|
|
Relationship between tensile strength and hardness of aluminium alloys
Růžička, Martin ; Jetela, Václav (referee) ; Klement, Josef (advisor)
This thesis deals with relationship between tensile strength and hardness of aluminium alloys. The introduction provides an overview of aluminum aloys and their properties. In the following section there is an analysis of the processing of aluminum alloys. A large part is devoted to the course of precipitation hardening. The second part of the thesis contains a practical part, which describes the methodology of measuring hardness and tensile strength. The measurement process is described below. At the end, the measured data are processed into various graphs and their results are evaluated.
|
|
| |
|
|
Advanced Abrasion Resistant Coatings for Vacuum Systems
Hégr, Eduard ; Kudláček,, Petr (referee) ; Hrubý, Vojtěch (referee) ; Švejcar, Jiří (advisor)
The thesis is focused on research of advanced surface resistant coatings which have a direct effect on increasing of functional properties of vacuum systems (eg reducing wear of individual pump components, surface inertia to aggressive gases/molecules). But they can also secondarily affect other important pump properties (eg reducing pump temperature). The studied layers/coatings are divided into three areas (i) hard anodic layer, (ii) hard anodic layer with PTFE coating and (iii) DLC coating. The initial material (substrate) is an aluminum-based alloy, which was used for this purpose. In presented thesis, the influence on increase of material and physical properties was demonstrated, such as the increase of hardness and abrasion resistance of the surface after the application of the anodic layer with PTFE coating. The theoretical part of thesis describes the basic principles of preparation of abrasion-resistant layers/coatings and also introduces the vacuum physics. It shows the basic principles of obtaining vacuum, which give a comprehensive picture of the importance of working with advanced coatings. The experimental part is divided into the evaluation of the microstructure of the sample material and the second part is focused on the experiments needed to obtain/measure the required properties, which can be further used to predict damage of the layers/coatings.
|
|
|
Influence of thermal processing to microstructure of various steels
Kocman, Lukáš ; Havlík, Petr (referee) ; Štěpánek, Roman (advisor)
This bachelor thesis deals with the heat treatment of steel, especially measuring the influence of individual heat treatment technologies on changes in the microstructure of steels. The theoretical part of the work presents alloys of iron and carbon, furthermore describes their phase transformations in the solid state, particularly the transformation diagrams of steels. In another part of theoretical part, the basic heat treatment technologies and their influence on the mechanical properties and microstructure of steels are described. The experimental part deals with the preparation of metallographic samples and presents results of examining the microstructure and measuring the hardness of individual samples. At the end of the work the synthesis of the theoretical part and results of the experimental part is used for the partial and overall evaluation of the influence of heat treatment on the microstructure of steels.
|
|
|
Effect of heat treatments on the microstructure and hardness of high-entropy alloy
Jesenská, Mária Ľudmila ; Adam, Ondřej (referee) ; Moravčíková de Almeida Gouvea, Larissa (advisor)
V tejto práci je študovaná neekviatomická Al0.2Co1.5CrFeNi1.5Ti vysoko entropická zliatina, ktorá bola vyrobená pomocou vákuového indukčného tavenia. Zliatina v odliatom stave bola analyzovaná a tepelne spracovaná pri teplote 1000 °C po dobu 5h, a následne podrobená tepelnému spracovaniu pri teplote 750 °C po dobu ďalších 5h, s cieľom skúmania vplyvu teploty a doby tepelného spracovania na fázové zloženie, mikroštruktúru a mechanické vlastnosti. Na vyhodnotenie možných fáz prítomných v zliatine bol použitý pseudobinárny fázový diagram (CALPHAD). Mikroštruktúra zliatin bola charakterizovaná a chemicky analyzovaná pomocou röntgenovej difrakcie (XRD), elektrónovej mikroskopie (SEM) a energeticky disperznej spektroskopie. Výsledné vyhodnotenie tvrdosti materiálu prebehlo pomocou skúšok mikrotvrdosti a nanoindentácie.
|
|
|
Preparation and Characterization of Porous Magnesium Based Materials
Březina, Matěj ; Pacal, Bohumil (referee) ; Vojtěch, Dalibor (referee) ; Ptáček, Petr (advisor)
Bulk magnesium materials produced nowadays via powder metallurgy are based on a vastly extensive technological spectrum, which makes it possible to create a wide range of materials. This work focuses on the preparation of bulk materials from magnesium powder by cold pressing and hot pressing, sintering and field assisted sintering. The bulk materials were prepared in a series of compacting pressures from 100 MPa to 500 MPa and the sintering temperatures were selected in the range of 300 ° C to 600 ° C in order to characterize the influence of the manufacturing conditions and technology on the final properties of bulk materials. Prepared materials were evaluated in terms of microstructure, hardness, microhardness, three-point bend test, and fractography. From the hot pressed materials, the samples prepared at 400 and 500 MPa and 400 °C had the highest strength and hardness. The classic sintering of magnesium in the furnace with argon atmosphere proved to be ineffective due to the oxide layer on the surface and the presence of oxygen in technical argon. The SPS sintering (Spark Plasma Sintering) was the more effective with the lower applying pressure used to make the preforms and with the higher applied pressure during the SPS process itself. Highest strength and hardness were achieved in this case of materials sintered at 600 ° C prepared from free powder and the most porous preform (100 MPa). The bulk materials were prepared using all methods used, but the properties of these materials varied considerably depending on the technology used.
|
|
|
Surface hardening of steels by high power diode laser
Bazalová, Lucie ; Daněk, Ladislav (referee) ; Mrňa, Libor (advisor)
The master thesis deals with the technology of surface hardening of steels by high power diode laser. The thesis is an experiment of surface hardening of steel 12 050 on various parameters of speed movement of the laser head and used power. At first, the work deals with the possible technology of surface hardening, industrial lasers and possible methods for measuring hardness. It describes the material used and the evaluation of the macrostructure and microstructure of the samples and evaluates the achievement of hardness, depending on the distance from the surface. The results are used to assess the suitability of the parameters during quenching.
|
guest ::
