Seznam abstraktů 2022: POSTEROVÁ SEKCE D

Plasma electrolytic oxidation (PEO) coatings with and without calcium phosphate (CaP) were prepared on AZ31 magnesium alloy. The microstructure of both coatings was characterized using an electron scanning microscope with EDS (SEM/EDS). PEO coating revealed the presence of many pores and microcracks on its surface. The deposition of CaP on the PEO layer led to the cover of these microstructural defects. Potentiodynamic polarization in 0.15 M NaCl medium showed that CaP/PEO and PEO coatings led to the improvement in the corrosion resistance when compared to bare AZ31 alloy. However, the corrosion resistance of CaP/PEO duplex coating was lower than PEO coating even though the CaP crystals covered the pores and microstructural defects.

This paper present the issue of plasma treatment of the surface of polypropylene (PP) using AgO+CuO coating in order to antimicrobial activity. The analyzed coatings were deposited using High Power Impulse Magnetron Sputtering (HiPIMS). This method is characterized by high power density, high ionization and high plasma density, which enables the production of high-quality multi-component coatings. All CuO + AgO coatings, formed on the polypropylene (PP) surface by MS-PVD magnetron sputtering with various parameters, were tested in terms of morphology, chemical composition, mechanical properties and antibacterial properties. The conducted analysis showed a significant influence of the chemical composition on the structure, density and mechanical properties of the obtained coatings. The analysis of the continuity of different CuO+AgO coatings showed that its depending on chemical composition. Furthermore, different growth mechanisms of the coatings are observed. It was also found that plasma treatment of polypropylene (PP) with CuO+AgO layers allows to provide good antimicrobial properties.

The main goal of the study was to determine the effect of local laser treatment on bending stresses under load. The simulation results show that the different locations and number of laser tracks (internal rigidity ribs) on the thin-sheet surface had a influence on the stress distribution under bending loads. Finite element analysis of the equivalent von Mises stresses and bending of thin sheet steels confirms that specimens with internal stiffeners are more resistant to bending loading.

Micro-mechanisms are one of the main areas of development in manufacturing technology widely used in various production fields. The new microelements are made of superalloys which are difficult to machine materials. This work focuses on using WEDM machining in the formation of microelements. Conducted research was focused on analyzing the influence of wire electrical discharge machining on the parameters of selected surface topography features, which directly impact the tribological properties of the surface of micro parts. The effect of the WEDM parameters on the functional parameters of the surface texture: Sk - the roughness of the core, Spk roughness of the peak, Svk - the roughness of the valleys are presented and discussed.

Corrosion behavior of ferritic-martensitic steel Eurofer in stagnant liquid PbLi was studied. Eurofer is under consideration to be the structural steel for fusion reactors. The aim of this study was to describe behavior of the steel in a static liquid lead-lithium eutectic (PbLi) and improvement of corrosion resistance by application of protective coating. RF-ICP technology was used for deposition of the coating. The experiment was realized at 600 °C for 500 and 1000 hours, and post-test examination of surface and cross-section of the specimen was performed by Scanning Electron Microscope with Energy Dispersive Spectroscopy. Microscopical investigation identified the solution-based attack and Pb penetration into the material as the dominant corrosion damage of steel and coatings showed a promising resistance to the corrosive medium. Pb penetration zone deepened with increasing time of exposure. Evaluation of steel protected by Fe coating revealed no Pb penetration into the coating and no solution-based attack was found. Steel was protected from any kind of elemental dissolution or microstructural degradation.

Diamond-like carbon (DLC) coatings are currently used in many areas of the economy. Due to their unique properties, such as high hardness, low friction, and high wear resistance, they are also used in industry, especially on machine parts exposed to increased wear. DLC coatings are a metastable form of amorphous carbon, composed of sp2 hybridized bonds found in graphite and sp3 bonds found in a diamond. Depending on the proportion of these bonds, DLC exhibits different tribological properties. The hardest and most durable mixture is amorphous tetrahedral carbon (ta-C) (the content of sp3 bonds - approx. 70%). Coating with a ta-C layer with a thickness of 2 μm increases the resistance of stainless steel to abrasive wear, increasing its life cycle up to 85 years. Due to their carbon content, the DLC coatings themselves do not show high resistance to high temperatures. To improve their thermal stability, admixtures of non-metals (e.g. hydrogen, boron, nitrogen, phosphorus, fluorine, and sulfur) or metals (copper, nickel, tungsten, titanium, molybdenum, silicon, chromium, and niobium) are used. It can be concluded that DLC coatings can be used wherever necessary to reduce the coefficient of friction and the intensity of wear of parts. DLC coatings are applied to the surface of injection molds, and the electrical properties and biocompatibility cause a growing interest in using these coatings in medicine.
The paper presents the results of operational tests of diamond-like carbon coatings deposited in the physical vapor deposition (PVD) process on samples made of 4H13 stainless steel. The properties of DLC coatings were assessed based on microstructure analysis, nanohardness, roughness measurements, and tribological tests. The results obtained during the tests showed that using diamond-like coatings significantly improves the tribological properties. In addition, the coatings are free of pores and microcracks. In addition, DLC layers are characterized by high nanohardness and low roughness. This type of coating can be used on surfaces of machine parts.

High-strength alloy medium carbon structural steel 30KHGSA is commonly used in the manufacture of tools and machine parts. In this paper, the effect of electrolyte-plasma thermocyclic quenching on the surface hardening and modification of the microstructure of 30KHGSA steel is experimentally investigated. The research was carried out using optical microscopy, scanning electron microscopy, and X-ray diffraction analysis. Vickers microhardness tests were also carried out, and wear resistance was studied using the "ball-disc" method. An aqueous solution of 15% sodium carbonate Na2CO3 was used as the electrolyte. The principle of operation of thermocyclic electrolyte-plasma hardening consists in a periodic and cyclic increase in voltage and current values, at which the sample is heated above the temperature of the phase transition α→γ and subsequent rapid cooling, during which iron-based phases formed in the layer of the processed material, such as martensite and hardening phases, are fixed, and contribute to the improvement of operational characteristics of the material. It is revealed that the main morphological structural-phase component of the initial state of 30KHGSA steel is a ferrite-pearlite structure, and after thermocyclic electrolyte-plasma quenching, the phases of hardened martensite are formed.

This poster focuses on the characterization of chloride migration from the environment into different types of concrete. Chloride diffusion into reinforced concrete plays an important role in the degradation of reinforced concrete structures. Three types of concrete were tested: conventional concrete, conventional concrete with portland cement and concrete with the addition of microsilica. These additions led to a reduction in the rate of chloride diffusion. The diffusion rate was determined by means of an immersion test in a solution containing 3% chloride ions. Electrochemical impedance spectroscopy (EIS) was used to further describe the microstructure of the concrete. Open porosity was quantified based on the analysis of the data obtained and these results were correlated with the rate of chloride diffusion. The positive effect of the additives, consisting of limiting chloride migration, was confirmed by the reduction of pore permeability as seen in the EIS data.

Humic acid (HA) isolated from South Moravian lignite was dissolved in neutral aqueous solution. Potentiodynamic polarization (PDP) and immersion tests were performed on low carbon steel at different concentrations of HA in 0.1 M NaCl. The morphology and elemental composition of the corrosion products were characterized using scanning electron microscopy with energy dispersive spectroscopy.
The results showed that HA accelerated the corrosion of low carbon steel in 0.1 M NaCl, with a lower concentration of HA having a greater impact. The negative effect of HA was attributed to the complexation of the molecules with iron ions. After seven days, immersion tests revealed that steel in 0.1 M NaCl was covered with a discontinuous black film, whereas HA induced the formation of a continuous layer of brown corrosion products with low adhesion to the surface. The elemental composition of the black film and brown coating corresponded to Fe3O4 (magnetite) and FeOOH (lepidocrocite or goethite), respectively.

AZ31 alloy was subjected to potentiodynamic polarization and immersion tests in 0.9% NaCl with different glucose concentrations (0.1 - 5 g/L). The experiments were performed both at pH 7.4 and without pH adjustment of the solution and at 37 °C. Corrosion products (morphology and elemental composition) were investigated using scanning electron microscopy with energy dispersive spectroscopy.
Potentiodynamic polarization results showed that the corrosion current density or corrosion rate increased with increasing glucose concentration at pH 7.4. In saline solution without pH adjustment, the results indicated that low glucose content (0.1 g/L) could improve the corrosion resistance of AZ31 alloy; higher glucose content (above 0.2 g/L) accelerated the corrosion.
The surface of AZ31 alloy was covered with a compact layer of Mg(OH)2. The surface morphology of this layer was not affected by the presence of glucose.

The materials’ resistance to brittle fracture is a very important parameter for the characterization of PVD coatings. The fracture toughness of solid materials is determined by the critical value of the stress concentration coefficient KIc [1,2]. According to the literature, the fracture toughness of thin coatings must take the characteristic properties and features of the tested coating such as surface quality, thickness, and roughness. There are different models for determining the KIc coefficient of thin coatings. The most often used is the method proposed by Niihara [3] and Laugier [4].
Niihara model is based on measuring the total length of cracks emanating from the four vertices of a Vickers indentation as a consequence of applied load. The fracture toughness can be determined by measuring the crack lengths [3].
For smooth coatings, the best method of measuring the KIc coefficient is the nanoindentation method with the Berkovich indenter and Laugier [4] model. The fracture toughness coefficient is determined by the measurement of the generated crack lengths.
REFERENCES: [1] Standard: PN-87/H-4335.; [2] Zhu X.-K. et al., Engineering Fracture Mechanics 85 (2012)1-46.; [3] Niihara K. et al., Journal of Materials Science Letters 2 (1983) 221-223.; [4] Laugiera M.T. et al., Journals in Materials Science Letters 6(1987) 355-356.

Lead and its alloys have been highly employed from ancient times to the present day (various artefacts of everyday life, statues, coins, organ pipes, stained glass). Nowadays many of these artefacts are stored in museum and archive storage cabinets with atmosphere polluted with volatile organic compounds (VOCs). Protection of the lead stored under adverse conditions is based on the use of protective coatings. The aim of this work was to test long-term stability and corrosion protection efficiency of coatings with corrosion inhibitors (benztriazole (BTA), cyclohexylamine, thiourea and sodium benzoate), coatings of carboxylic acids and conversion coatings (microcrystalline wax and Paraloid B48N) with BTA, which are discussed in literature. The observation of the protective coatings on the lead and lead-tin alloy samples was carried out for 2 years in air conditions and 4 months in an acetic acid polluted atmosphere by the weight-loss measurement, contact angles measurement and measurement of color changes.

Electrical discharge machining is one of the advanced processing technologies widely used to machine micro-hole. However, advances in materials engineering that lead to the production of new nickel-based superalloys require the development of new machining technologies. In addition, new sustainable EDM conditions to achieve the desired geometric quality of manufacturing holes and material removal rate are needed. In this study, a series of experiments of EDM drilling of holes were performed. The influence of capacitor capacity, discharge time, and discharge break time on the diameter of manufacturing holes, material removal rate, and tool electrode wear was investigated and described.