Seznam abstraktů 2024: SEKCE D - POVRCHOVÉ INŽENÝRSTVÍ

Aircraft fuselage shells made from aluminum are coated to withstand conditions in aviation. The corrosion protection consist mainly of an anodic oxide layer as interface (IF) and a primer as a coating. As the coating can be damaged during the forming process, OEMs such as Airbus restrict the process chain so that the coating may only be applied to the finished formed component. Previous studys with regard to the evolution of coating properties during deformation showed that an incremental bending process known as Deharde Polygon Forming® (DPF®) has the potential to overcome these restrictions. As the IF shows the highest hardness of the coating-interface-substrate (CIS) system combined with a small thickness, it can be assumed that the IF is more endangerd to failure. This paper therefore presents the results of an analysis of the interface before and after deformation. Scaled fuselage shells are incrementally bent by DPF® to induce process-related deformations. Specimens from the initial state and from scaled fuselage shells are investigated by scratch and indentation tests with a Triboindenter TI 950. Due to the low plastic deformations induced by incremental bending with DPF® neither Young’s modulus and hardness nor elastic and plastic behaviour as well as fricition coefficient undergo significant changes. Hence the obtained results imply opportunities for flexibilisation of process chain regarding forming and coating.

The nickel diamond coating NiDi is made up of two materials: electroless nickel (Ni-P) and diamond. Because of the electroless chemical method of deposition, nickel diamond coating covers all surfaces of the work piece with essentially perfect uniformity. A standard coating should contain 20 to 30 % diamond by volume with a thickness of around 20 μm. On wires samples the defects were identified by 3D optical microscopy and by SEM and EDX analysis with electronic scanning microscope. Defects in electroless nickel plating can be divided into two main categories: chemistry problems and deposit problems.

Titanium alloys are characterized by high specific strength, corrosion resistance and good biocompatibility, therefore are widely applied in many industries including medicine as orthopedic or dental implants. However, the low wear resistance and the unfavourable influence of element on human health require the use of additional surface treatment allowing for the production of protective coatings. Good candidate for such obstacles seems to be hard biocompatible titanium nitride surface layer, which is formed with the use of nitriding technique or vapour deposition process (PVD/CVD). Such ceramic layers could effectively protect the human body from diffusion of cancerogenic elements of titanium alloys like aluminum or vanadium. Medical implants are sometimes covered with a layer of hydroxyapatite (HAP), due to its comparable mechanical properties to the bone tissue. Moreover this material promotes bone healing processes, improve the adhesion of medical parts to tissue and limits the occurrence of stress shielding contributing to the implant loosening. The knowledge about the effect of such layers formed on titanium alloys on the stress and strain distribution and deformations is needed.
Based on the microstructural experiments of nitrided affected zone and hydroxyapatite layers produced on titanium alloy available in the literature data, an attempt of modelling of the nitrided titanium coated with HAP coating and numerical analysis with the help Finite Element Method was made. The effect of different parameters of model (layer thickness, mesh size, boundary conditions) on the mechanical behavior under loads was considered.

Surface treatment methods are often necessary to achieve the desired functionality of parts produced by conventional technologies. Plasma electrolyte (ELP) technology has gained popularity in recent times. It is based on the phenomena that occur between the metal surface and the electrolyte under direct voltages exceeding 150 V. The ELP process is characterized not only by its smoothing effect but also by ability to achieve a mirror gloss on surface, with major limited heating of polished surface. The function of tool for reducing the initial roughness is taken over an ionized steam-plasma envelope that surrounds the entire object during the process. The paper presents the results of research into the mechanism being applied when the surface layer of 16MnCrS5 steel after case-hardening is removed using the ELP polishing process. The case-hardened layer required a two-stage treatment using different electrolytes. In each stage, electrolytes with a different chemical composition, concentration, temperatures, and process durations were applied. In the first stage, an electrolyte based on an aqueous solution of ammonium sulphates and chlorides reduced the initial roughness Ra of 0.34 µm more than 50 % within 120 seconds, but a dark coating was detected on surface. In the second stage, an electrolyte based on an aqueous solution of carbonates removed this coating and imparted the surface with a mirror gloss. The final surface roughness Ra reached 0.09 µm. The ELP treatment had a positive effect on the macroscopic character of the steel surface, achieving homogeneity and eliminating traces of grinding tool or other surface macro-unevenness (burrs) that disrupt the surface integrity.

The material in nuclear reactors of the VVER 440 type and their main circulation pipes is exposed to temperatures in the range of 100-300 °C during the operating conditions, but in some nodes can be this range of temperatures exceeded. These temperature conditions are suitable for low-temperature sensitization and the microstructure sensitized in this way may be susceptible to inter-granular corrosion during long-term operation. The material 08CH18N10T that was subjected to observation was obtained precisely from a real operation, where it was exposed to operating conditions for a long time. The microstructure of this material was compared with the microstructure of a new material of the same type that was exposed to operating temperatures in laboratory conditions. The new 08CH18N10T is currently replacing the old one in real operation. The microstructure was evaluated based on the results from optical and transmission electron microscopy and for the identity of the secondary phases was used the selective electron diffraction. The specimens were subjected to a non-destructive corrosion test ASTM A262 method A, on the basis of which a statistical method was used to compare the percentage of attacked grain boundaries of the observed materials.

The boronizing is a thermochemical process in which the boron atoms are introduced into the steel surfaces. This study evaluates the fracture toughness of boride layers developed by powder boronizing of high-chromium steels Sleipner, K 190, Royalloy, Sverker 21 and Sverker 3. The process was carried out at 1323 K, for 10 h, and in solid Durborid powder mixture. First of all, the Vickers microhardness tester was used to generate the microcracks in borides. The load of 2 N was used for indentation. The microhardness of Fe2B phase was ranged between 1551 HV0.2 and 1726 HV0.2. For the FeB phase, the microhardness was ranged between 1974 HV0.2 and 2277 HV0.2. For quantification of the fracture toughness, the Palmqvist method was used, when the values of length of the microcracks that appeared in the corners of the indentations were analyzed. The fracture toughness of the FeB phase was lower compared to the Fe2B phase. The fracture toughness was ranged between 1.98 MPa·m1/2 and 2.58 MPa·m1/2 for the FeB phase and between 3.87 MPa·m1/2 and 4.50 MPa·m1/2 for the Fe2B phase. It was found that the chemical composition of the steel does not have a significant effect on the values of the fracture toughness.

The pack-cementation tcechnique was used to manufacture iron (Fe) silicides on Mirrax steel in this study. In an open atmospheric furnace, pack siliconizing process was performed using silicon oxide (SiO2), Al (as reducer) ammonium chloride (NH4Cl), and alumina (Al2O3) at 850-950 °C with variable deposition periods of 2-4-6 h. Utilizing optical microscopy and scanning electron microscopy-energy dispersive X-ray spectroscopy, the appearance and structure of silicide layers were examined. It was noted that the silicide layers, which were smooth, uniform, and dense and lacked notable porosity, had good bonding with the matrix. By using X-ray diffraction analysis, dominant phase is Fe3Si was determined. From the surface to the matrix, the layer thickness increased with process time and temperature. Additionally, the activation energy for the development of the siliconizing layer is determined. Due to the creation of a layer with a smoother morphology, less porosities and oxygen impurities, and an appropriate thickness silicon layer have been obtained.

This study investigates the microstructure and thermal performance of Cu-Nb microcomposite conductors welded using various techniques, including thermite welding, laser welding, electron beam welding, and pressure welding with a strong magnetic field. The goal was to assess how different welding methods impact the microstructure and temperature distribution of the welded joints. Temperature distribution across all welding methods met the standards for electrical contact joints, ensuring reliable performance. Cu-Nb microcomposite conductors, with their exceptional strength and conductivity, are highly suitable for high-performance magnetic field applications. The findings provide valuable insights for optimizing welding processes, contributing to advancements in welding technology and material science.

During hot forming, the formation of oxide layers when heating ferrous materials such as steels can hardly be prevented. On the one hand, the formation of oxides is beneficial, as certain oxide phases can have a lubricating effect. On the other hand, oxide scale leads to a loss of material and the hard and brittle phases lead to forging defects and die wear. In the numerical simulation of hot forging processes, the formation of oxide scale layers on workpieces is currently not considered, as there is no suitable numerical approach and the material-specific characteristic values are missing. In order to describe the behaviour of oxide scale in finite-element simulations, realistic material data is required. In this work, the basis for the characterisation of oxides shall be established. For this purpose, steel specimens of 1.0503 and 1.0601 were oxidized under controlled conditions, at elevated temperatures. Subsequently, the specimens were examined through a scanning electron microscope (SEM) and the individual oxide scale layers consisting of wustite (FeO), magnetite (Fe3O4) and hematite (Fe2O3) were detected. The specimens were examined using a TriboIndenter to record the mechanical properties such as nanohardness and modulus of elasticity of each oxide scale component on the nanoscale. XPM hardness mappings were used to visualize the phase transitions and porosity of the oxide scale and compared with the microscopy and SEM images. In addition, magnetite spots in the wustite oxide layer could be detected through XPM hardness mapping and SEM examinations.

Influence of various parameters of final machining on stress corrosion cracking of austenitic stainless steel was investigated. Boiling magnesium chloride solution was used as a medium for exposure of samples to find out the susceptibility for corrosion cracking. Residual stresses, the roughness, hardness of the surface layers, feed and cutting speed were the main parameters which were noticed, and their effect was evaluated and compared. The density of cracks on the surface of the machined samples was obtained, as well as the depth of these cracks into the material, while their morphology was also monitored using SEM. Light microscopy was used to monitor the surface after machining (before the corrosion test). Subsequently, the hardness was measured. The machined surface was also analysed using electrochemical methods such as potentiodynamic measurements and electrochemical potentiokinetic reactivation tests for intercrystalline corrosion susceptibility.

Controlling the quality of coatings is a significant objective. The large area parts require the construction of multi-track laser cladding layers, which are influenced by the overlapping conditions. This investigation deals with laser cladding technology, multi-track beads of 42C martensitic stainless steel were coated on FGS600-3A ductile cast iron with different overlap ratios. The percent overlap varied from 20% - 35% - 50% - 65% - 80%, which corresponds to 2.4 mm - 1.95 mm - 1.5 mm - 1.05 mm - 0.6 mm for multi-bead production. The optimum welding parameters were kept constant for production of specimens: laser power 1.3 kW and feed speed 8 mm/s, 3 layers of production were carried out. An experimental approach to investigate the porosity rate, crack and microhardness with variable overlap conditions is presented in this paper. In addition, digital image processing method was also used to calculate the porosity rate in the transverse and longitudinal surface. Vickers method was also employed to measure the hardness from base metal to surface of the coatings. It was found that by reducing the overlap distance, it is possible to drastically reduce the pore formation. The best compromise in terms of porosity was obtained in overlap distance 1.05 mm which corresponds to 65% overlap ratio. The porosity rate was found to decrease in the coating layer by an increase in the degree of up to 1.05 mm overlap distance. For microhardness, there was no correlation between the surface hardness of different overlap values. As the overlap distance decreases, it was possible to obtain higher hardness values at deeper depths. The highest microhardness values in the coating layer were obtained as 550 HV in specimen with 1.05 overlap distance. Experimental results on overlapped cladding layers of stainless steel on mild steel show that it is useful for repairing mold implementation in the automotive sector. This work on varied overlapped cladding layers presents the essential experimental data for an upcoming repair implementation of large parts suitable for industrial mold implementations.

In this paper, carbon-based materials including carbon nanotubes (CNTs) and electroconductive carbon (EC carbon) black were combined with polyurethane resin to produce electromagnetic radiation absorbent paints. Different paint formulations were prepared and characterised to identify the effect of nanocomposite material content and the paint thickness on the electromagnetic shielding effectiveness. The paints were applied to a metallic surface and a mica plastic sheet before conducting the measurements. The electromagnetic shielding effectiveness of the absorbent paints was then measured using vector network analyzer MS2028B according to ASTM D4935-18. The sample with CNTs concentration of 3% and EC carbon concentration of 2.5% had the highest electromagnetic absorbing effectiveness with more than 90% for the electromagnetic waves in the frequency range of 8GHz to 12 GHz.

The subject of the work were composite coatings with a copper matrix and an embedded carbon phase in the form of allotropic varieties of carbon (graphene, carbon nanotubes, diamond). The coatings were produced by electrochemical reduction method on a steel substrate. For comparison purposes, the study also included copper coatings without embedded dispersion phase particles. The paper presents the characteristics of the used carbon. Results of morphology and surface topography (SEM) as well as the structure (XRD) of the produced coatings are presented. Metallographic examinations (cross sections) were used to evaluate the internal structure and measure the microhardness and thickness of the tested materials. The adhesion of the coatings to the substrate was examined by the scratch test method. The test results allowed to determine the influence of the deposition process conditions and the type of incorporated carbon phase on the structure and selected properties of copper matrix composite coatings. The coatings were also tested to assess their solderability. Solderability tests included solder reflow and wettability tests, strength tests of the connections between coatings and solders, and microstructure tests.. Electrochemically deposited copper, due to its very good electrical conductivity, may have great potential for applications on electronic circuit components. However, this metal is characterized by low hardness. The incorporation of carbon phase particles into the copper matrix contributes to the improvement of mechanical properties.

The presented research was financed by the earmarked grants awarded by Łukasiewicz Center, grand contract no 2/Ł-IMP/CŁ/2021. The title project: „New generation thermally conductive layers for electronics and the technology of their production”

In this study, the results obtained in machining Inconel 718 material, one of the nickel-based superalloys, with PVD cutting tools and CVD cutting tools were compared. By comparing TiN and TiCN coatings in the machining of Inconel 718, PVD (Ti,Al)N coating was found to be suitable, and BUE phenomenon and abrasive wear were reduced. By machining Inconel 718 in a dry environment, its super oxidation resistance, chemical stability at high temperatures, high thermal hardness and low thermal conductivity have become the main determinants of tool performance. In a recent study, TiN/AlTiN double-coated coating gave good results. CVD coated tools have higher wear resistance at higher cutting speeds. If the coating material causes a decrease in hardness, this is due to the properties of the coating material. Here, hardness is effective in determining tool life. It is not clear that coated tools are superior to uncoated tools at lower depth of cut when machining Inconel 718. It has been observed that rapid wear occurs as a result of machining at low cutting speeds. In this study, as a result of 8 machining experiments, coated tools were seen to be better, while as a result of 4 machining experiments, coated tools were seen to be worse. However, coated tools gave longer tool life when the depth of cut exceeded 1 mm. Coated tools are generally not useful for nickel- or cobalt-based superalloys, which are high-temperature resistant alloys. However, they were worse only at low depth of cut.