Seznam abstraktů 2026: SEKCE D - POVRCHOVÉ INŽENÝRSTVÍ

The work reviews phase evolution, mechanical, electrical, thermal and tribological properties of NbMoTaW100-z(CN)z coatings deposited using reactive DC magnetron co-sputtering. The concentrations of the metals were not equimolar, therefore, the resulting material was attributed to the compositionally complex compounds instead of high-entropy stabilized ceramics. The concentrations of anions was the result of the combination of carbon co-sputtering at 300 W and 600 W power levels on carbon target and variable flows of nitrogen. Depending of the carbon and nitrogen additions, the coating compositions transformed from metallic alloy doped by carbon and nitrogen with bcc structure up to carbo-nitrides with variable stoichiometry with fcc structure. The stoichiometry was even exceeded at high carbon and nitrogen additions supply due to the formation of free carbon phase. Nanoindentation measurements of hardness and indentation moduli exhibited additive effects of carbon and nitrogen. The difference between two carbon levels was around 5 GPa. The changes in hardness due to nitrogen were more pronounced due to wider addition range. Superhardness of ~ 50 GPa was obtained in the slightly sub-stoichiometric carbon-rich carbonitride coatings exhibiting fcc structure. Electrical resistance of the coatings decreased when temperature decreased and a transition to superconductive state occurred. Transition temperatures, Tc, increased almost linearly from ~4K in the low stoichiometry coatings to 9 K in the near-stoichiometric carbonitrides. Thermal conductivity of the studied coatings also depended on phase composition and decreased with the increase of nitrogen concentration from 10 W/K.m to 5 W/K.m. The coefficients of dry friction (COF) against alumina were in a narrow range 0.15 - 0.30 and depended on coating stoichiometry and applied load. Friction and wear mechanisms included adhesion combined with the tribochemical reactions leading to the formation of transfer films in the wear track.
ACKNOWLEDGMENT: This work was supported by the EU NextGenerationEU through the Recovery and Resilience Plan for Slovakia under project No. 09I03-03-V04-00281 and by the Slovak Research and Development Agency (projects APVV 21-0042 and APVV-24-0038).

The improvement of surface quality in difficult to cut materials is critically important for enhancing service life. Plasma electrolytic polishing (PeP) is a promising surface finishing technology that provides high quality and eco-friendly smoothing of metal surfaces. This study presents the effects of PeP parameters on the surface modification of Ti-6Al-4V alloys. The PeP parameters were determined as cycle stages (1, 3, and 6) and stirring speeds (0 and 300 rpm). Other constant parameters were cathode material (SS304), voltage (300 V), electrolyte type (hydroxylamine hydrochloride and sodium fluoride), electrolyte concentration (5% and 0.8%), electrolyte temperature (80°C), and polishing time (6 min). Surface roughness, gloss, and material removal rate (MRR) were selected as output parameters. In addition, the current time graph was recorded during the polishing process. The experimental results shown that the surface roughness value decreased significantly after PeP. Moreover, an increase in the number of cycle stages led to an improvement in surface roughness. Similarly, a considerable rise in surface gloss was observed, demonstrating the direct influence of process parameters on gloss. The MRR value was determined to be directly proportional to the number of cycles. Additionally, a reduction in thickness occurred in the portions of the samples immersed in the electrolyte after the PeP process.

Electromagnetic interference (EMI) poses a significant threat to the operational stability and reliability of modern electronic and communication systems. The increasing integration density of electronic components, particularly in aerospace, defense, and portable technologies, necessitates the development of lightweight, mechanically robust, and highly efficient shielding materials as alternatives to conventional bulk metals.
In this study, three-dimensional (3D) printed Polylactic Acid (PLA) and Polyethylene Terephthalate Glycol (PETG) polymers were metallized via an electroless plating process to enhance their electromagnetic shielding effectiveness (SE). To ensure strong interfacial adhesion between the metallic coating and the polymer substrate, surface pretreatment steps including chemical etching and palladium-based catalytic activation were employed. These treatments improved surface roughness and facilitated uniform nucleation during subsequent metal deposition.
Activated PETG specimens were coated in an electroless nickel (Ni) bath at 60 °C for 30 minutes, while PLA specimens were metallized with electroless copper (Cu) using a bath containing disodium EDTA as a complexing agent at 55 °C for 20 minutes. The deposited metallic layers formed continuous and conductive networks on the polymer surfaces.
The electromagnetic shielding performance of the coated composites was evaluated over the investigated frequency band, and the effects of both the polymer matrix and coating type were comparatively analyzed. The results revealed that shielding performance was strongly influenced by coating conductivity, layer continuity, and frequency-dependent skin depth effects. Under optimized conditions, shielding effectiveness values reaching up to approximately 60 dB were achieved. These findings demonstrate that electroless-metallized 3D-printed polymer structures provide lightweight, structurally adaptable, and highly effective EMI shielding solutions suitable for advanced engineering applications.

Although CoCrFeNi high-entropy alloy (HEA) exhibits excellent ductility due to its face-centered cubic (FCC) crystal structure, its relatively low strength limits its applicability in certain industrial applications. To enhance its bulk mechanical performance, alloying additions can be introduced, while various surface modification techniques can be employed to improve its surface properties. In this study, CoCrFeNi HEA was produced by vacuum arc melting, followed by homogenization at 1150 °C for 24 h. Zr additions ranging from 1 to 4 wt.% were introduced to promote grain refinement and improve bulk hardness. The addition of Zr resulted in a moderate increase in hardness, from approximately 150 HV to 250 HV. To further enhance surface properties, a low-temperature aluminizing treatment was carried out at 700 °C for 4 h. This process led to the formation of Co- and Ni-based aluminide intermetallic phases on the surface, resulting in a significant increase in hardness from 250 HV to approximately 700 HV. In addition to Vickers hardness testing, scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses were performed for structural and microstructural characterizations.

Magnesium alloys represent promising materials for temporary biomedical implants due to their biocompatibility and mechanical properties resembling natural bone. However, their rapid and uncontrolled degradation in physiological environments remains a key limitation for their clinical application. In this context, a protective duplex coating system was investigated on Mg-1Zn-0.4Ca (ZX10) and referential Mg-4Y-3RE-0.4Zr (WE43) alloys, combining a plasma electrolytic oxidation (PEO) layer with subsequent polymer sealing. Porous ceramic-like PEO layers were initially formed in a phosphate-based electrolyte, followed by the deposition of polylactic acid (PLA) and chitosan layers using a dip-coating technique. The surface morphology, chemical composition of the coatings, and their long-term corrosion resistance were evaluated using SEM-EDX, Raman spectroscopy and electrochemical impedance spectroscopy (EIS). Microstructural analysis confirmed that the applied polymers partially penetrated and sealed the porous structure of the PEO layers, leading to a more compact surface. Electrochemical measurements conducted in 0.9% NaCl solution demonstrated a significant improvement in corrosion resistance for the polymer-coated samples compared to both bare and solely PEO-treated materials. Furthermore, a comparison of the two polymers revealed differences in their sealing behaviour and corrosion response, highlighting the influence of polymer properties on the overall performance of the coating system. The combination of PEO and biodegradable polymer layers therefore provides a highly effective strategy for tailoring the degradation kinetics of magnesium implants.

Thermal energy storage (TES) systems used in industrial applications, such as power plants, must store large amounts of thermal energy. Meeting demands for high heat capacity, low thermal diffusivity, and structural stability at elevated temperatures requires selecting optimal nanostructures. Conventional planar graphene is a well-known material for its exceptionally high thermal conductivity and has been extensively investigated. However, to enhance energy retention and storage efficiency, it is necessary to adopt advanced three-dimensional (3D) architecture. This study investigates molecular dynamics (MD) simulations of optimized, conventional pillared graphene (PG) nanostructures designed to improve thermal energy storage. While previous research has mainly examined PG as a thermal conductor, the present research focuses on PG architecture composed of parallel graphene layers connected by carbon nanotube (CNT) pillars, exploiting their three-dimensional geometry to localize phonons and reduce thermal dissipation. The unit-cell models, featuring systematic changes in pillar length, spacing between pillars, and CNT chirality, are investigated using MD simulations. The systems are equilibrated under an NVT ensemble using the AIREBO potential, incorporating heat flux to identify regions of thermal accumulation. The key performance indicators include specific heat capacity obtained from energy fluctuations, the stability of the potential energy, and structural robustness evaluated through the mean squared displacement (MSD). These results demonstrate the significance of the pillared graphene structure as an advanced material or high-temperature coating for TES systems, expanding their potential use in industrial thermal management while offering environmental benefits. Future studies will explore more advanced structural modifications to further improve thermal storage performance.

Ensuring high strength at low weight in aircraft joints presents a constant challenge for designers and researchers. One widely used material in this industry is 2xxx series aluminum alloys. This study investigates the effects of shot peening on the surface layer properties of FSW-welded butt joints made from EN AW-2024 aluminum alloy in the T3 temper, both with and without Alclad coating. The methodology involved shot peening the welded joint for 3 minutes at a pressure of 0.6 MPa using 1.5 mm diameter bearing balls. The treatment generated compressive residual stresses in both material variants. Analysis of stress magnitude and FWHM values revealed greater strain hardening in the unclad alloy. This trend was also evident in surface layer microhardness measurements. Surface roughness parameters improved significantly after shot peening in both cases, with particularly pronounced effects observed for the Alclad variant. The Ra value for the aluminum with Alclad was 0.811 μm at the weld, which is more than twice as low as the untreated weld (Ra = 1.9 μm).

Aluminothermic (AT) rail welding is a well-established process for joining and repairing rails and can, in principle, be regarded as a casting process, where the molten metal is poured into a mould mounted around the rail ends to be joined. The characteristics of the resulting weld profile, particularly the fusion zone (FZ) and heat-affected zone (HAZ), play a critical role in determining joint performance. Accurate prediction of these regions is therefore essential, yet detailed numerical simulations such as Computational Fluid Dynamics (CFD) are often computationally expensive and not practical for rapid assessment.
This work presents a simple data-driven approach to predict weld profiles in AT rail welding. CFD simulations are first performed under varying preheating durations and molten metal temperatures. These simulations focus on a specific welding procedure, the SkV process (German: Schnellschweißverfahren mit kurzer Vorwärmung). This process is used to join 60E1 rails with a weld gap of 25mm. The resulting dataset, comprising key process parameters and corresponding weld profile characteristics, is then used to train a feed-forward artificial neural network based on a multi-layer perceptron architecture.
The developed model demonstrate the capability to accurately reproduce the relationship between process conditions and weld profile formation while significantly reducing computational effort compared to full CFD simulations. Although currently limited to specific conditions, such as preheating duration and molten metal temperature, it establishes a foundation for future work. The framework can be extended by incorporating a broader dataset, including different preheating procedures, rail profiles, etc., enabling more generalised and robust predictions.