Seznam abstraktů 2024: POSTEROVÁ SEKCE D

The paper presents the influence of laser beam on properties of borochromized surface layers produced on C45 steel. Microstructure, phase composition, microhardness as well as fracture toughness of newly formed layers were studied. Analyzd layers were produced using by three methods. First was galvanic-diffusion method, second was galvanic-diffusion method with additional laser modification, and third was galwanic method with additional laser alloying using boron paste. During all processes the thickness of galvanic coatings was 5 µm. For samples where diffusion boronizing was carried, temperature of 950 °C and process time of 4 h was applied. As a result of this process dual-zone microstructure was obtained. On surface continuous zone was observed while on subsurface needle-like iron borides was identified. For the samples where no diffusion boronizing was used, amorphous boron paste was applied to the galvanic chromium coating. In these studies the CO2 laser beam was used for modification processes. Application of laser beam contributed to obtain three microstructural zones: remelted zone, heat affected zone and substrate. In produced layers phases of iron borides and chromium borides were identified. These phases were in accordance with equilibrium diagrams: Fe-B, and Cr-B. An advantageous effect of laser modification on microhardness of borochromized layers was found. Produced layers were compared with diffusion boronized layers. Microhardness profiles showed gradual transition from the remelted zone, through heat affected zone to the substrate. It was found that brittleness of boronized layer decreases after modification with chromium and the laser beam.

This paper presents the results of changes in the structural-phase state and tribological properties of 30CrMnSiA steel after electrolyte-plasma diffusion boriding (EPDB). It is known that electrolyte-plasma treatment is one of the methods of high-speed heating. It is known that electrolyte-plasma treatment is one of the methods of high-speed heating. Compared to traditional heat treatment methods, EPDB is an economically efficient treatment method, which allows to reduce the processing time by 3-4 times. The EPDB process occurs by switching the electric current from the metal anode to the cathode-detail, through the active electrolyte with the formation of a vapor-gas shell (VGS). The surface is saturated with boron elements through diffusion of the elements into the steel surface by evaporation of the saturating component molecules and their diffusion deep into the metal due to high temperatures in the VGS area. Aqueous solution of sodium tetroborate, sodium carbonate and glycerol were used as electrolyte, which are the sources of saturating element. Structural-phase states and tribomechanical properties were investigated using methods of metallographic and X-ray diffraction analysis and tests on tribometer, microhardness meter. According to the results, it was found that the formed borated layer consisting of FeB, Fe2B phases with a thickness of 80 microns provides high strength of the surface layer and contributes to increasing the wear resistance of the product by 1.5-2 times.

This contribution introduces a comprehensive methodology for evaluating cold spray coatings using scratch testing techniques. In contrast to traditional thermal spray coatings, cold spray coatings have not been systematically and thoroughly scratch-tested, leading to a lack of experimental data and evaluation methods. The primary objective of this research is to evaluate the adhesion or cohesion strength of the coating and study the damage mechanism. The methodology focuses on the systematic preparation of testing procedures. Evaluation of individual scratch marks, performed using both light and electron microscopy, forms the basis for refining the testing methodology. This study addresses a gap in the field, offering a straightforward approach for assessing cold spray coatings. The presented methodology is based on standard ISO 27307 where the applicability for cold spray coatings is lacking, especially regarding the evaluation of the crack origin. Inconel 713LC coatings in as sprayed state showed low energetic ductile fracture represented by shallow dimples in specific regions of cracks. The quality of the substrate/coating interface was excellent with the adhesion strength correlating with a normal load of 100 N applied to a scratch test indenter.

The DC-MS magnetron sputtering method is a well-known surface engineering technology and is a very effective technological tool in the processes of producing multi-component coatings. One of the limits of DC magnetron sputtering is the production of metal oxide coatings. Mainly due to the insulating properties of targets made of metal oxides. Currently, the most widely used type of magnetron sputtering, which enables deposotion of metal oxides coating, is High Power Impulse Magnetron Sputtering (HPIMS) and Radio Frequence Magnetron Sputtering (RF-MS). This method is characterized by high power density, high ionization and high plasma density, which enables the production of high-quality multi-component coatings. As part of the presented work, the characteristics of the material and functional properties of MeO coatings produced with the use of DC-MS magnetron sputtering high-power pulsed magnetron sputtering (HPIMS) and radio frequence magnetron sputtering (RF-MS) and were carried out. The mechanical and material properties of the produced coatings were compared. The conducted analysis showed a significant influence of the applied technology on the deposition rate, structure and density of the obtained materials.

Austenitic steel 316L with applied coating was studied to find a suitable material for impeller of main circulation pump at working conditions of small modular lead fast reactor. The chemical compatibility of the materials to the liquid metal environment was evaluated in liquid lead environment containing oxygen to ensure the oxidation while simulating temperature cycling. The operating temperature was controlled to vary between 450 °C and 520 °C, which are the temperatures that can occur in the system. The tests were designed to verify the effect of the different thermal expansion of the steel and the coatings on the corrosion resistance of the system. Austenitic steel 316L was used as a reference material and coatings base on Ti, Al, and W applied by physical vapor deposition were used for corrosion resistance improvement. Microscopical investigation identified oxidation, solution-based attack, and Pb penetration into the material. The damage to the coatings depended on their chemical composition and structure of the coating. However, in general, the application of the coating increased the resistance of the surface to corrosion damage and the thermal cycling did not affect the adhesion of the coating to the steel.

Currently, polymers are a group of future-proof materials, which, in contrast metals, are characterized by low weight and also are easier to obtain and relatively cheap. However, due to their low surface energy, their use is often limited. Due to plasma technology, it is possible to modify the surface properties of polymers in a cost-effective and efficient way. During the last years, low temperature plasma surface functionalization of polymer materials has increasingly earned a high position in a wide range of application fields. This paper present the influence of ion etching technology on modyfication of the surface of polymers. An assessment of the impact of the operating parameters of the ion gun on the hydrophilic properties of polymers was presented. An analysis of the surface morphology, chemical composition and wettability of polymer materials after the activation process was carried out.

The article presents research on the influence of single-mode and multi-mode fiber lasers on the micromachining effects of a diamond-like carbon (DLC) coating surface.
DLC coatings are a form of amorphous carbon, consisting of sp2 bonds characteristic of graphene and sp3 bonds found in diamond. Depending on the proportion of these bonds, DLC coatings exhibit different tribological properties. These coatings are commonly used to reduce wear on parts. It has been proven that the texture applied to the surface of these coatings improves their tribological properties under lubrication conditions.
Using various parameters of the laser process, the changes in the geometric profile of the obtained groove on the coating surface were analyzed. A comprehensive characterization of the obtained effects was carried out, namely microstructure, hardness, wear resistance and adhesion of the layer with the substrate. The experimental results showed significant differences depending on the laser beam parameters, indicating that the properties of the DLC layer can be precisely controlled by adjusting the processing parameters.
The tests were carried out on DLC a-C:H coatings obtained by PVD magnetron sputtering deposition on stainless steel 1.4034.
This research may contribute to the development of a laser surface treatment method to improve wear resistance and durability in applications where DLC layers play a key role, such as in the automotive, tooling, and medical industries.

The corrosion resistance of the aluminum-based coating deposited on Inconel Alloy 625 by CVD method was investigated. Specimens of 625 Alloy in as-received state and coated were exposed to static liquid lead at 520 °C. The aim of work was to compare and evaluate the resistance of the coating in different conditions. Two exposures were studied - low oxygen content 10-8 wt.% for 3500 h and cycling of temperature for 1000 h. The results indicate that coating have good adhesion and could protect the studied alloy from lead corrosion. However, several microscopic anomalies the so-called inner oxidation of alloy under the coating were observed. Corrosion damage was characterized using scanning electron microscopy, which identified the inner oxidation under the coating after the exposure. The coating was intact, uniformly applied, without cracks. Local depletion of Cr and Ni was observed within 4.1 μm for low oxygen content and 4.5 μm for cycling exposure and solution-based attack (SBA) was not observed. Specimens without coating were very damaged and destroyed in both exposures because deep penetration of lead was observed.

AMS 6265 is a low alloy high-strength steel from the Fe-Cr-Ni-Mo system, well-known for its case-hardening ability and high mechanical properties; this steel being the best choice for manufacturing heavy-duty products and parts, whose surface layers are subjected to substantial stresses during operation in the aerospace industry. Mechanical surface treatment (MST) by shot-peening (SP) technique is a practical and cost-effective solution for surface improvement, involving cold locally deforming the near-surface layers and creating residual compressive stresses and strain hardening. The influence of MST/SP duration on the microstructure and mechanical properties of AMS 6265 aerospace steel was investigated in this study. The AMS 6265 steel was subjected to a series of heat and thermochemical treatments (case-hardening treatment) prior to surface modification via SP. The MST was performed using steel shots with a diameter of 0.6 mm, at a working pressure of 3 bar, and applying different values for the peening treatment duration ranging from 300 s to 2100 s. The microstructure evolution during MST/SP processing was investigated by XRD, OM and SEM-BSE techniques, while the mechanical properties by tensile and microhardness testing techniques. The following structural characteristics were analysed: constituent phases, lattice strain, crystallite size, and phase morphology. The mechanical behaviour was assessed through the following properties: microhardness, ultimate tensile strength, yield strength, and elongation to fracture. The obtained results were correlated with the Almen intensity to determine the optimum peening duration and to fine-tune the MST technology for the AMS 6265 heavy-duty aerospace parts.

Acknowledgments
This work was supported by a grant of the Ministry of Research, Innovation and Digitization, CCCDI - UEFISCDI, project number PN-III-P2-2.1-PTE-2021-0195, contract no. 94PTE / 2022, within PNCDI III.

The paper presents the results of research on the production of hybrid layers "nitrided layer + PVD coating", which use ceramic coatings doped with metals. Technological parameters and material testing results of the produced hybrid layers are presented. The method of implementing the technological process of producing hybrid layers on forging dies and molds for extruding aluminum profiles is shown.

Electrical discharge machining is one of the main methods of manufacturing technological equipment used in the foundry industry, plastics processing, plastic working, etc. Important elements determining its quality are, apart from the properties of the materials used, the features imparted in the manufacturing processes. The paper presents a brief study of electro-discharge alloying process of surface with using rod vibrating electrode. It is also economically justified to use EDM (Electrical Discharge Machining) to produce machine parts from materials that are easily machined, but with very complex geometry, and therefore difficult and labor-intensive to produce using conventional methods. Spark discharges are created between the working electrode and the workpiece, the entire process takes place in a working medium with dielectric properties. As a result of the local increase in temperature, melting and partial evaporation of the microvolume of the material occurs. The main factors influencing the formation of the surface layer in the process of its modification are the melting process, diffusion processes, rapid heating and cooling of the material, phase transitions and changes in the structure of the layers adjacent to the crater formation site. In the tested process, the modified surface layer with improved properties reached a thickness of up to 90 micrometers, and the material resolidified on the surface of the workpiece contains about 50% of alloying elements. The geometric structure of the surface resulting from the modification is similar to that obtained by EDM. The distribution of inequality vertices is random. For typical machining conditions, the obtained roughness Sa is approximately 3.5 µm.

Plasma electrolytic oxidation (PEO) technique is a process of surface treatment of light metallic materials such as magnesium alloy, to produce coatings increasing the corrosion resistance. In this work, the effect of direct or alternating current deposition mode on the structure and corrosion behavior of PEO coatings on Mg substrates prepared by powder metallurgy (PM) was studied. It was observed that during the deposition process of PEO coatings, the varying of current mode between alternating current (AC) and direct current (DC) led to significantly different surface modifications and coatings properties. In the case of DC PEO coatings, significantly higher thickness was achieved than in the case of AC PEO coatings. On the other hand, AC PEO coatings achieved smaller pore sizes compared to the DC PEO coatings. Considering the denser and less porous structure of AC PEO coating, significantly better electrochemical properties were observed using potentiodynamic measurements in Hank's solution. Compared to the uncoated PM Mg substrate, there was an order of magnitude decrease in the icorr of PEO-coated Mg substrate. In the case of DC PEO coatings, the icorr value was determined to be 8.3 µA·cm-2, and in the case of AC PEO even 3.4 µA·cm-2.

Magnesium alloys can be used in many fields such as automotive, aerospace, electrical engineering and biomedicine. Their disadvantage is their high reactivity and low corrosion resistance, which limits their widespread use. Corrosion resistance can be increased by the use of corrosion inhibitors, which are preferably selected from widely available and environmentally friendly organic compounds.

In this work, the focus was on malonic acid, which is widely used industrially as a precursor to produce chemicals, acidity regulator or corrosion inhibitor for steel. The aim was to determine whether malonate can serve as a corrosion inhibitor of magnesium alloy AZ31. Corrosion tests were carried out in 0.15 M NaCl at pH 7 with different concentrations of malonic acid using potentiodynamic polarization and immersion tests. Surface characterization was performed by scanning electron microscopy with an enegy dispersive spectrometer and FTIR analysis.

Corrosion tests showed that malonic acid accelerated the corrosion of AZ31 alloy in 0.15 M NaCl, with the highest increase for 0.05 M malonic acid. SEM analysis indicated that the surface of AZ31 alloy was more degraded in the presence of malonic acid. The surface was composed of Mg(OH)2 and adsorption of malonic acid was not demonstrated. Thus, the results showed that the malonic acid has no inhibitory effects for AZ31 alloy in 0.15 M NaCl.

Hot-dip galvanising is one of the most widely used methods for the surface protection of structural steel against corrosion. This article examines the quality and thickness of the Zn coating on low-carbon deep-drawing structural steel Kosmalt E300T welded by the MAG method. The steel meets the conditions for hot-dip galvanising according to the Sandelin diagram with a silicon content lower than the critical concentration of 0.03 wt. %, while the welding wire contains a critical concentration of 0.9 wt. % of silicon. The silicon concentration of 0.9 wt is unsuitable for hot-dip galvanising. On the basis of this fact, according to the assumption derived from the Sandelin diagram, the Zn coating on the weld joint should have a higher thickness along with a different structure compared to the unwelded steel surface. The article assessed the quality of the Zn coating on the weld joint through adhesion tests and tests in a condensation chamber. According to the results of the experimental tests, the Zn coating was formed in a double thickness on the weld joint compared to that of the unwelded steel surface. The Zn coating on the weld joint shows a change in the content of individual phases, good adhesion to the weld joint, and corrosive resistance.

In this study, the nature of boriding mechanism of the steel prestressing strand is evaluated and then the corrosion resistance of the borided steel in hydrochloric acid is assessed (detection of the content of released iron and manganese in the exposure solution). The effect on the bond strength of the treated steel prestressing strand with normal strength concrete is also evaluated (pull-out test). Boriding was carried out in a boron carbide backfill with fluoride activators. In this manuscript are described the first informative results on this topic.