|
|
Zinc coatings
Zdařil, Lubor ; Trčka, Josef (referee) ; Zmrzlý, Martin (advisor)
The aim of this work is a description of corrosion as a major phenomenon in the degradation of the material and the description basic types of corrosion. Then the material protection possibilities are described using a suitable choice of surface treatment. From the wide field of coating systems, electrodeposited zinc based alloys coatings were emphasized. theirs subsequent increase of corrosion resistance by applying powder coatings. Alloy coatings that are in the focus of recent research were discussed.
|
|
|
Surface treatment of spherical pin
Plášil, Petr ; Kubíček, Jaroslav (referee) ; Žák, Ladislav (advisor)
Diploma thesis is worked-up as a part of master’s studies of engineering technology M2I – K, analyzing the possible methods of surface treatment of spherical pin, that increase its corrosion resistance. Spherical pin is mounted into several types of chassis components such as joints, control arms, etc. The current situation is inconvenient for manufacturers, insufficient corrosion protection increases the number of complaints and this may be reflected in the number of future orders. Via of suitable surface treatment is to achieve a higher corrosion resistance while maintaining the functional properties of pins used.
|
|
|
Galvanic zinc coating
Hamal, Jan ; Kubíček, Jaroslav (referee) ; Žák, Ladislav (advisor)
This thesis is based on analysing and description of galvanic zinc coating, operations and technologies used in them. The first part contains an analysis of corrosion and is aimed on physical-chemical process which takes place on the surface of coated part. The thesis also emphasize the choice of technology for zing coating and in conclusion analyzes defections in galvanic zinc layer.
|
|
|
Replacement of nickel alloy overlay by manganese alloy overlay
Hlobil, Albert ; Kubíček, Jaroslav (referee) ; Sigmund, Marian (advisor)
The thesis is focused on the issue of tuning the welding process of the 18.8. Mn alloy using the method 152. The welded component is the cylindrical throat of a Venturi tube made of ASME SA-106 Grade C carbon steel. A series of welds were performed, which were qualitatively evaluated and compared. Metallographic sections were made, and the dilution, excess, and width of the heat-affected zone were determined. Evaluation of microstructure and microhardness were also performed. Based on the tests performed, suitable welding process parameters were used. For comparison, a test for chemical and salt mist corrosion was undertaken, where the corrosion resistance of the 18.8. Mn alloy weld was compared to Inconel 625 alloy.
|
|
|
Synthesis of multiphase forsterite–spinel ceramics with improved properties
Nguyen, Martin ; Keršnerová, Lucie (referee) ; Nevřivová, Lenka (referee) ; Vejmelková, Eva (referee) ; Sokolář, Radomír (advisor)
This doctoral thesis is concerned with the synthesis of multiphase forsterite–spinel ceramics with improved properties in comparison with conventional forsterite ceramics. The objective of this work was to optimize the designed raw material mixtures in dependence on the production technology and resulting parameters, particularly in terms of phase composition, microstructure and refractory properties. The results of the research demonstrated an improvement in thermal shock resistance and modulus of rupture as a result of the synergistic effect of the individual phases in terms of the microstructure. In the end, the industrial applicability of the selected mixtures was verified by the corrosion resistance testing against several materials.
|
|
|
Influence of CaO Content on Specific LCC, ULCC and NCC Properties
Zemánek, David ; Nevřivová, Lenka
Castables are widely used refractory materials with variable applications. Three types of castables (low cement, ultra-low cement and no cement) were tested to compare their specific properties. Also, corrosion resistance test as an important factor influencing castables design was carried out. Potassium carbonate was used as a corrosive medium using static crucible method. The corrosion mechanisms were evaluated by Scanning Electron Microscopy (SEM) and X-ray Diffraction (XRD). The results confirmed that the presence of higher amount of calcium oxide from the Calcium Aluminate Cement (CAC) leads to formation of calcite and anorthite. The corrosion resistance was improved with decreasing or replacing the hydraulic bond.
|
|
|
Corrosion Resistance and Microstructure of Refractory Forsterite-Spinel Ceramics
Nguyen, Martin ; Sokolář, Radomír
This article examines the process for the synthesis of forsterite–spinel refractory ceramics utilizing fly ash and reactive alumina as raw materials. Raw materials were pre-treated, mixed, and sintered at 1 550 °C for 3 h. Sintered samples were characterized by XRD and SEM. Porosity, water absorption, bulk density, refractoriness, refractoriness under load, thermal shock resistance and corrosion resistance by iron and clinker as corrosive media were also investigated. The impact of different raw material mixtures was investigated in accordance with the resulting properties, microstructure, and corrosion resistance of all fired samples. Higher amount of spinel in fired samples led to improved microstructural and mechanical properties and thermal shock resistance.
|
|
|
Effect of microstructure on mechanisms of plastic deformation in fine-grained magnesium alloys
Minárik, Peter
In this work were studied effects of the grain refinement on the mechanical properties and the corrosion resistance of magnesium alloys potential for medical applications - AE21 and AE42. Mechanical properties changed after ECAP pressing in consistency with literature data. Enhanced corrosion resistance in AE42 alloy was achieved by the grain refinement. Corrosion layer created on the surface was observed by light and electron microscopy. Effect of the grain size on the character of the corrosion layer was investigated. AE42 alloy is suitable for further investigation as potential biodegradable material. AE21 alloy was excluded from further investigation due to low corrosion resistance even after ECAP treatment.
|
|
|
Physical properties of ultrafine-grained polycrystals of magnesium based alloys
Vrátná, Jitka
The objective of the thesis is the study of microstructure evolution, mechanical properties, defect structure and corrosion resistance of ultra-fine grained magnesium alloy AZ31 prepared by a combined two-step process: the extrusion and the equal-channel angular pressing (ECAP). The microstructure development was studied using light and transmission electron microscopy and electron backscatter diffraction (EBSD). Mechanical properties were studied by microhardness measurement and tensile tests and the defect structure by positron annihilation spectroscopy (PAS). The results of tensile tests indicates that the characteristic stress σ0.2 increases slightly with increasing number of ECAP passes only to the second pass and then decreases significantly with additional ECAP straining. This behaviour is in accordance with the results of PAS. EBSD measurements show that the microstructure of extruded and ECAPed material has a bimodal distribution of grain sizes. The bimodal distribution becomes homogeneous with increasing number of ECAP passes and no remaining large grains are observed after 8 passes. The average grain size in the specimen after 8 passes is in the submicrometer range and the fraction of high-angle grain boundary (HAGB) is approximately 80%. The extruded specimens after 8 ECAP passes show...
|
|
| |
guest ::
