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The main aims of thin biofilm synthesis are to either achieve a new form to promote the transport of drugs in oral delivery systems or as a coating to improve the biocompatibility of the implant's surface. In this study, the Langmuir monolayer technique was employed to obtain films containing Mg-doped hydroxyapatite with 0.5%, 1.0%, and 1.5% Mg(II). The obtained modified HA particles were analysed via the FT-IR, XRD, DLS, and SEM methods. It was shown that the modified hydroxyapatite particles were able to form thin films at the air/water interface. BAM microscopy was employed to characterized the morphology of these films. In the next step, the mixed films were prepared using phospholipid (DPPC) molecules and modified hydroxyapatite particles (HA-Mg(II)). We expected that the presence of phospholipids (DPPC) in thin films improved the biocompatibility of the preparing films, while adding HA-Mg(II) particles will promote antibacterial properties and enhance osteogenesis processes. The films were prepared in two ways: (1) by mixing DPPC and HA-Mg (II) and spreading this solution onto the subphase, or (2) by forming DPPC films, dropping the HA-Mg (II) dispersion onto the phospholipid monolayer. Based on the obtained π-A isotherms, the surface parameters of the achieved thin films were estimated. It was observed that the HA-Mg(II) films can be stabilized with phospholipid molecules, and a more stable structure was obtained from films synthesied via method (2).

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Spot welded joints play a crucial role in the construction of modern automobiles, serving as a vital method for enhancing the structural integrity, strength, and durability of the vehicle body. Taking into account spot welding process in automotive bodies, numerous defects can arise, such as insufficient weld nugget diameter. It may have evident influence on vehicle operation or even contribute to accidents on the road. Hence, there is a need for non-invasive methods that allow to assess the quality of the spot welds without compromising their structural integrity and characteristics. Thus, this study describes a novel method for assessing spot welded joints using ultrasound technology. The usage of ultrasonic surface waves is the main component of the proposed advancement. The study employed ultrasonic transducers operating at a frequency of 10 MHz and a specially designed setup for testing various spot welded samples. The parameters of the spot welding procedure and the size of the weld nugget caused differences in the ultrasonic surface waveforms that were recorded during experiments. One of the indicators of weld quality was the amplitude of the ultrasonic pulse. For low quality spot welds, the amplitude amounted to around 25% of the maximum value when using single-sided transducers. Conversely, for high-quality welds an amplitude of 90% was achieved. Depending on the size of the weld nugget, a larger or smaller amount of wave energy is transferred, which results in a smaller or larger amplitude of the ultrasonic pulse. Comparable results were obtained when employing transducers on both sides of the tested joint, as an amplitude ranging from 13% for inferior welds to 97% for superior ones was observed. This research confirmed the feasibility of employing surface waves to assess the diameter of the weld nugget accurately.

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The surface modification of poly(lactic acid) (PLA) using hydroxyapatite (HAP) particles via Langmuir-Blodgett (LB) and Langmuir-Schaefer (LS) approaches has been reported. The HAP monolayer was characterized at the air/water interface and deposited on three-dimensional (3D) printed poly(lactic acid). The deposition of HAP particles using the LS approach led to a larger surface coverage in comparison to the LB method, which produces a less uniform coating because of the aggregation of the particles. After the transfer of HAP on the PLA surface, the wettability values remained within the desired range. The presence of HAP on the surface of the polymer altered the topography and roughness in the nanoscale, as evidenced by the atomic force microscopy (AFM) images. This effect can be beneficial for the osteointegration of polymeric implants at an early stage, as well as for the reduction of the adherence of the microbial biofilm. Overall, the results suggest that the LS technique could be a promising approach for surface modification of PLA by hydroxyapatite with respective advantages in the biomedical field.

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This paper presents study results of laser processing of W-Cr, WCr/Cr3C2 and Cr3C2 pre-coats applied on steel substrate in the form of paste. For this study, production parameters were selected to obtain the greatest possible durability of final coatings. Laser processing was carried out using a diode laser machine with a rated power of 3 kW. The laser beam scanning speed was constant at 3 m/min, but variable laser beam powers were used: 600 W, 900 W and 1200 W. Multiple laser tracks with 60% overlapping were used. After remelting the pre-coat with a steel substrate, new coatings were obtained. Following the experiment, microstructure, microhardness, wear, corrosion resistance and chemical composition were investigated. It was found that it is possible to produce W-Cr/Cr3C2 coatings through laser processing. These coatings do not have the characteristics of a composite coating; however, increasing the reinforcing phase in the pre-coat positively affects the wear resistance and microhardness. The addition of a reinforcing phase was found to lead to a microhardness of about 750-890 HV01 for 25% and 75% Cr3C2, respectively, in comparison to coating without Cr3C2. The wear resistance of coatings reinforced by chromium carbide improved more than twofold in reference to the W-Cr coating.

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The paper presents study results of Stellite-6/(WC+TiC) coatings produced by laser alloying with varying contents of reinforcing phases (40%wt and 60%wt content of mixture WC+TiC). The coatings were produced on S355 steel using different laser beam power densities: 76 kW/cm2, 115 kW/cm2 and 153 kW/cm2. The coatings obtained were subjected to microhardness measurements, wear resistance tests, chemical composition analysis and microstructure observations using light microscopy and scanning electron microscopy. It was found that both types of coatings were characterized by higher microhardness and wear resistance in comparison to substrate material. The rate of solidification had an impact on the obtained results of the study.

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This paper presents the results of the microstructure, mechanical and physicochemical properties of coatings produced by the remelting of a VC pre-coat applied in the form of a paste on 145Cr6 steel. The remelting process was carried out using a diode laser beam. A laser device with a rated power of 3 kW was used. During these tests, a constant laser beam scanning speed of 3 m/min was used. The variable parameter was the laser beam power. Values of 500 W, 900 W and 1100 W were used. In the first stage of this study, single laser tracks were formed, and basic tests, such as on microstructure, microhardness and chemical composition, were performed. In the second stage of this study, multiple laser tracks were prepared using previously selected parameters. On such specimens, it was possible to test the same traits as for single tracks and, additionally, to perform corrosion and wear resistance tests. It was found that the obtained coatings have different properties than the base material. No primary vanadium carbides were found in the melted zone, but the proposed production method contributed to an increase in microhardness and wear resistance.

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The paper presents the results of studies of microstructure, mechanical and physicochemical properties of surface layers produced by laser modification of the diffusion boron layer on Monel® Alloy 400. The diffusion boron layers were produced at 950 °C for 6 h. The gas-contact method was used in an open retort furnace. The process was carried out in a powder mixture containing B4C carbide as a boron source. The next stage was the modification of the boron layer with a diode laser beam of a nominal power of 3 kW. A constant power of 1400 W of the laser beam was used. The scanning speed was variable (successively 5 m/min, 25 m/min, 50 m/min). In order to determine the best parameters, single tracks were created, after which multiple tracks were prepared using previously selected parameters. It was found that both the diffusion borided layer and the laser modified layer had better properties than the substrate material. Both these processes contributed to an increase in corrosion resistance, hardness and wear resistance. It was also found that laser modification caused a slight deterioration of the properties in comparison with the diffusion borided layer. However, the laser modification process resulted in the production of a much thicker layer.

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In today's developing aircraft and automotive industry, extremely durable and wear-resistant materials, especially in high temperatures, are applied. Due to this practical approach, conventional materials have been superseded by composite materials. In recent years, the application of metal matrix composites has become evident in industry 4.0. A study has been performed to analyze the surface roughness of aluminum matrix composites named Duralcan® during end milling. Two roughness surface parameters have been selected: arithmetical mean roughness value Ra and mean roughness depth Rz regarding the variable cutting speed. Due to the classification of aluminum matrix composites as hard-to-cut materials concerning excessive tool wear, this paper describes the possibility of surface roughness prediction using machine learning algorithms. In order to find the best algorithm, Classification and Regression Tree (CART) and pattern recognition models based on artificial neural networks (ANN) have been compared. By following the obtained models, the experiment shows the effectiveness of roughness prediction based on verification models. Based on experimental research, the authors obtained the coefficient R2 for the CART model 0.91 and the mean square error for the model ANN 0.11.

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Sub-zero treatment of Vanadis 6 steel resulted in a considerable reduction of retained austenite amount, refinement of martensite, enhancement of population density of carbides, and modification of precipitation behaviour. Tempering of sub-zero-treated steel led to a decrease in population density of carbides, to a further reduction of retained austenite, and to precipitation of M3C carbides, while M7C3 carbides precipitated only in the case of conventionally quenched steel. Complementary effects of these microstructural variations resulted in more noble behaviour of sub-zero-treated steel compared to the conventionally room-quenched one, and to clear inhibition of the corrosion rate at the same time.

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The paper presents the results of a study of the microstructure, chemical composition, microhardness and corrosion resistance of Cr-B coatings produced on Vanadis 6 tool steel. In this study, chromium and boron were added to the steel surface using a laser alloying process. The main purpose of the study was to determine the impact of those chemical elements on surface properties. Chromium and boron as well as their mixtures were prepared in various proportions and then were applied on steel substrate in the form of precoat of 100 µm thickness. Depending on the type of precoat used and laser processing parameters, changes in microstructure and properties were observed. Coatings produced using precoat containing chromium and boron mixture were characterized by high microhardness (900 HV0.05-1300 HV0.005) while maintaining good corrosion resistance. It was also found that too low laser beam power contributed to the formation of cracks and porosity.

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In this study, wear properties of Monel 400 after laser alloying with boron are described. Surfaces were prepared by covering them with boron paste layers of two different thicknesses (100 µm and 200 µm) and re-melting using diode laser. Laser beam power density was equal to 178.3 kW/cm2. Two laser beam scanning velocities were chosen for the process: 5 m/min and 50 m/min. Surfaces alloyed with boron were investigated in terms of wear resistance, and the surface of untreated Monel 400 was examined for comparison. Wear tests were performed using counterspecimen made from steel 100Cr6 and water as a lubricant. Both quantitative and qualitative analysis of surfaces after wear test are described in this paper. Additionally, microstructures and properties of obtained laser alloyed surfaces are presented. It was found that the wear resistance increased from four to tens of times, depending on parameters of the laser boriding process. The wear mechanism was mainly adhesive for surfaces alloyed with initial boron layer 100 µm thick and evolves to abrasive with increasing boron content and laser beam scanning velocity. Iron particles detached from counterspecimens were detected on each borided surface after the wear test, and it was found that the harder the surface the less built-ups are present. Moreover, adhered iron particles oxidized during the wear test.

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The paper presents the study results of laser processing of precoat applied on C30 steel. The precoat consisted of powder mixtures with a binder in the form of water glass. Tungsten powder, chromium, and tungsten carbide (WC) were used to produce the precoat. The laser processing was carried out using a Yb:YAG disc laser with a rated power of 1 kW. Constant producing parameters (power of laser beam, 600 W; laser beam scanning rate, 400 mm/min) were applied. Chemical composition of the precoat was a variable parameter in coating production. A mixture consisting of 50% W and 50% Cr as a metal matrix was prepared. Subsequently, WC particles in weight ratios of 25%, 50%, and 75% were added to matrix. As a result, W-Cr metal matrix composite coatings reinforced with WC particles were formed. This study focused on investigation of microstructure, microhardness, phase, and chemical composition as well as corrosion and wear resistance, of the newly formed W-Cr/WC coatings. An instrumented nanoindentation test was also used in this study. As a result of laser beam action, the newly formed coatings had an interesting microstructure and good properties which were improved in comparison to substrate material. It is anticipated that the resulting coatings, depending on the treatment parameters (e.g., W-Cr/WC powder mixture) used, can be successfully applied to metal forming or foundry tools.

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The paper presents study results of laser alloying of CT90 tool steel with an applied pre-coat of boron, molybdenum or a mixture of these elements. Pre-coats were applied on steel substrates in the form of a paste. The aim of the study was to investigate the microstructure, chemical and phase composition, microhardness and corrosion resistance of these newly-formed coatings. The laser alloying process was carried out using a diode laser with a nominal power of 3 kW. In this study a laser beam power of 900 W and a scanning speed of 48 mm/s were used. As a result of the laser beam action, the presence of three areas was observed in cross-sections of specimens: a remelted zone, a heat affected zone and the substrate. The properties of coatings enriched with both molybdenum and boron were better than those of the steel substrate, but only the use of a Mo-B mixture resulted in a significant improvement in microhardness and corrosion resistance.

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In this study, Monel 400 is laser heat treated and laser alloyed with boron using diode laser to obtain adequate remelting and to improve the microhardness Single laser tracks were produced on the surface with three different laser beam scanning velocities: 5, 25, and 75 m/min. In order to enrich Monel 400 with boron surfaces were covered with initial layers of two different thicknesses before the process: 100 µm and 200 µm. In all experiments, laser beam power density was equal to 178 kW/cm2. Produced laser tracks were investigated in areas of microstructure, depth of remelting and microhardness. It was found that remelted zones are mainly composed of dendrites and the more boron is present in the laser track, the dendritic structure more fragmented is. Depth of remelting and microhardness depend not only on the laser beam scanning velocity but also on thickness of the initial boron layer. While microhardness of Monel 400 is equal to approximately 160 HV0.1, microhardness up to 980 HV0.1 was obtained in areas laser alloyed with boron.