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Thermomechanical fatigue of nickel-based superalloys
Pech, Filip ; Škorík, Viktor (referee) ; Šulák, Ivo (advisor)
The main objective of present bachelor thesis is to compile literature review of thermomechanical fatigue of nickel-based superalloys. Superalloys were developed to work at high temperatures, where sufficiently high strength, oxidation resistance, creep resistance, and resistance to other high temperature adverse effects have to be ensured. Superalloys are despite efforts to find alternatives still widely used and therefore it is necessary to know their properties and limitations. The present review compiles basic overview of nickel-based superalloys based on specialized publications. First of all, classification of Ni-based superalloys, chemical composition, along with an overview of the most important phases, which are affecting properties of superalloys were studied in detail. The second chapter describes basics of isothermal fatigue of materials, its definition, description of mechanism and basic fatigue life curves. Penultimate chapter of this literature review deals with thermomechanical fatigue and the structure of text is similar to chapter about isothermal fatigue. In the last chapter is given an overview of thermomechanical fatigue of different types of nickel-based superalloys.
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Basic Mechanism of Fatigue and Combined Fatigue/Creep Damage of Ni-based Superalloys MAR-M 247 and IN 713LC
Horník, Vít ; Kohout, Jan (referee) ; Pantělejev, Libor (referee) ; Kunz, Ludvík (advisor)
The thesis is focused on clarifying fatigue damage mechanisms and fatigue-creep damage mechanisms of MAR-M 247 and IN 713LC polycrystalline Ni-based superalloys. This thesis begins with basic information about nickel-based superalloys and their microstructure, followed by a description of fatigue and creep mechanisms and their mutual interaction. The next part contains experimentally obtained results describing the behavior of MAR-M 247 and IN 713LC superalloys under various sets of conditions. Three testing temperatures - 800, 900 and 950 °C were used for the measurement of fatigue properties under symmetrical loading cycle, because in the temperature range 800 – 950 °C, the mechanism of fatigue crack propagation of both superalloys should change from the originally crystallographic at "lower" temperatures (800 °C) to non-crystallographic at "higher" temperatures (950 °C). In addition the effect of processing technology on fatigue properties was studied on the superalloy IN 713LC. High-frequency cyclic loading (about 120 Hz) with high mean stress at elevated temperatures was applied to induce fatigue-creep interaction. The combined fatigue-creep loading was performed on the IN 713LC superalloy at 800 °C and on the MAR-M 247 superalloy at 900 °C.
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Relationship between Structure and Properties of cast Ni-alloys
Smékalová, Jana ; Hutařová, Simona (referee) ; Podrábský, Tomáš (advisor)
Nickel superalloys are developed for conditions which request the corrosion resistance, the heat-resisting and the creep-resisting material. They are used for components of air turbine motors and internal combustion turbines. The efficiency of these mechanisms is elevated with increasing combustion temperature so their development is accentuated. This thesis is concerned with a relationship between a structure and properties of nickel superalloys Inconel 713LC and Inconel 738LC in this thesis.
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Classification of microstructure of nickel-base superalloys with image analysis using
Volf, Milan ; Čelko, Ladislav (referee) ; Němec, Karel (advisor)
During operational conditions of internal combustion turbines of turbojet engines, the impeller are stressed by load cycles which vary in time, temperature and stress. In the course of operation, the blades are exposed to a considerable number of degradation effects, particularly high-temperature corrosion, fatigue processes and creep. The presented work is aimed at the study of the structure cast nickel-base superalloy INCONEL 713 LC, creep tests exposured. The structural changes (degradation) was clasification by the help of image analyses. Operational conditions of heat parts, used in gas turbines and turbo-compressors, were simulated by creep tests of Inconel 713 LC nickel superalloy during a constant load of temperatures ranging from 750 up to 950°C. Changes in the structure dependent upon time, temperature and stress applied were analysed by means of light and electron microscopy methods and image analyses after the fracture of test bars.
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Structure and Properties of Cast Nickel-base Superalloys
Fukátková, Pavla ; Němec, Karel (referee) ; Hutařová, Simona (advisor)
This thesis is focused on changes of microstructure of nickel - base superalloys (alloy ZH6K) from the point of view of quantitative and qualitative classification. These phases especially phase ´ and the carbides significantly influence mechanical and other characteristics during the strain and temperature load action. Specimens were observed after thermal and thermal-strain exposition by light microscope and by scanning electrone microscope. There was used the image analysis for the following classification. The part of the thesis is the theoretical summary of the microstructure, chemist and the characteristic of the nickel - base superalloys.
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Study of AlSi protective coating after degradation
Vítková, Gabriela ; Řičánková, Veronika (referee) ; Hutařová, Simona (advisor)
Materials used for high temperature applications works in a very aggressive environment (oxidation, hot corrosion, erosion, fatigue, creep). Demands on these materials are very high. Nickel-based superalloys show the certain stability in this environment. Improved resistance to oxidation and hot corrosion can be achieved by using protective layers such as diffusion barriers. This thesis is focused on changes of microstructure and properties of AlSi layer applied by „slurry“ method on nickel-based superalloy Inconel 713 LC, due to long-term thermal exposition at 800, 900 a 1000 °C.
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Analysis of the influence of temperature cycles on the elimination of recast layer on materials used in aerospace
Slavíková, Barbora ; Martin,, Grepl (referee) ; Horník, Vít (advisor)
This bachelor thesis is dealing with the analysis of the influence of temperature cycles on the elimination of recast layer on materials used in aerospace. This thesis was created in cooperation with Honeywell Aerospace Company in Olomouc. The aim of this work was to prepare the study about influence of the brazing heat cycle on recast layer removing which was caused by laser cutting process. In first part of this bachelor thesis the unconventional machining methods, materials and related brazing processes used in Honeywell Aerospace Olomouc were described. Second part of the thesis consists of experimental measurement of the recast layer provided on a test specimens including their evaluation and interpretation of the results. The conclusions of this bachelor thesis will be used as future reference for next technological research in Honeywell Aerospace Company in Olomouc.
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Fatigue-creep interaction in Ni superalloys and TiAl alloys
Šmíd, Miroslav ; Věchet, Stanislav (referee) ; Kunz, Ludvík (referee) ; Obrtlík, Karel (advisor)
The present doctoral thesis is focused on the effect of dwells on the low cycle fatigue behaviour of advanced high temperature materials. 10 minutes strain holds are introduced into the cyclic straining of cast Ni-based superalloy IN792-5A and cast intermetallic alloy TiAl-7Nb which were chosen as experimental material. Fatigue experiments were conducted in strain control mode with constant total strain amplitude and strain rate. IN792-5A was subjected to continuous cyclic loading test as well as fatigue tests either with tensile peak strain holds or compressive peak strain holds at temperature 800 °C. TiAl-7Nb was experimentally examined by continuous cyclic loading tests and also by fatigue test with tensile peak strain hold times at temperature 750 °C. Cyclic hardening/softening curves, cyclic stress-strain curves, Manson-Coffin curves and Basquin curves were obtained. Stress relaxation data were measured during hold times. Mean stress evolution was observed and documented. Microstructure of both alloys was observed in as-received state and also after cyclic loading by means of SEM and TEM. Surface relief investigation revealed cyclic plastic strain localisation as well as fatigue crack initiation sites. Fatigue crack propagation was described using fracture surface and longitudinal gauge section observations. Dislocation structures developed in the course of fatigue tests were studied and documented.
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