Novel chiral palladium complexes containing camphor benzylimine and l-amino acids (proline, tyrosine, serine, isoleucine) as ligands were synthesized and characterized by elemental analysis and by NMR and IR spectroscopies. The antibacterial activity of the new and previously synthesized complexes and reference compounds against the bacteria MRSA, S. aureus, P. aeruginosa, E. coli, and M. vaccae was studied. It was found that the introduction of an amino acid ligand does not contribute to the activity of the mononuclear complex compared to the starting binuclear analogue. The binuclear palladacycle obtained from camphor benzylimine showed the highest activity against the pathogenic strains MRSA and M. vaccae (MIC = 8 mg L−1), which is comparable with that of the clinical antibiotics used for comparison.

The most rational approach in the production of friction units is not to manufacture the entire part from high-quality materials but to apply thin coatings (up to hundreds of micrometers) from expensive materials onto steels already widely used in industry. One such expensive material is Ta. This paper presents the results of a study on the structure of coatings formed by short-pulse laser cladding of Ta, SiC, B4C, and BN powders onto 40Kh steel. The results demonstrate the technical feasibility of producing coatings of such composition using short-pulse laser radiation. Coatings based on the Ta and SiC powder mixture without B4C and BN additions exhibit large pores that connect into channels after cladding, while the chemical elements are distributed uniformly over the surface. In particular, Fe atoms, which were not part of the initial powder mixture, were transferred from the steel substrate, indicating strong adhesion between the coating and the substrate. The addition of B4C and BN powders led to the formation of separate elliptical pores within the coating. The coating with the lowest content of the Ta and SiC powder mixture demonstrated the smoothest surface. Wear resistance tests revealed a positive influence of B4C and BN on the tribological properties of the coating based on Ta and SiC powders. The minimum mass loss values for both the “pin” and “plate” specimens were obtained after testing the coating with the maximum B4C and BN content. Although the TaSiC coating without additives experienced significantly greater mass loss, it was still 1.8 times lower than that of the uncoated 40Kh steel.

Wearless sliding friction in the lack of lubrication remains one of the primary goals of scientific research, as wear greatly reduces the life of mechanical components. While ultralow wear is achievable in sliding friction with proper hydrodynamic lubrication or at microscale normal loads, it remains a significant challenge to overcome wear under high normal loads, high sliding speeds, and in boundary lubrication or dry sliding friction. This paper introduces an approach to significantly mitigate wear in plain bearings operating under boundary lubrication at high normal forces and sliding speeds. The plain bearings were constructed from steel shafts tested against different materials. The surfaces of the steel shafts were alloyed with bismuth oxide using a novel high-energy short-pulse laser treatment. In order to incorporate the bismuth oxide into the surface layers of the steel, MnO2 was utilized as a carrier. Ultralow wear was observed for the Bi-alloyed steel disk sliding against aluminum countersurface at normal loads up to 250 N (similar to 5 MPa) and a sliding speed up to 9 m/s under extreme lack of lubrication. Achieving ultralow coefficient of friction (COF) and ultralow wear depends on eliminating adhesion between sliding surfaces, reducing the mechanical component of friction through diamond burnishing, and ensuring high fatigue endurance. The results of tribological tests demonstrate an exception to the Frenkel-Kontorova-Tomlinson model for wearless friction. The test results for Bi-alloyed steel-aluminum pair offer a new approach for a wide range of applications.

Introduction. During the recrystallization annealing of cold-rolled electrical and automotive steels, the formation of pickups on the surface of furnace rolls presents a significant issue, as they lead to surface damage of the steel strip in the form of indentations. The focus of the present study is the evaluation of this defect. Methods. To this end, a laboratory-based methodology was developed to assess the tendency of furnace rolls to form pickups. The method replicates the contact interaction between the furnace roll and the steel strip under real annealing conditions, taking into account the applied contact pressure, a temperature range of 700–900 °C, the (H2–N2) furnace atmosphere, and a humidity level arising from the presence of oxygen adsorbed on the steel strip. To validate the method’s reliability, a comparative analysis was conducted between pickups formed on the roll surface after industrial operation and those generated under laboratory conditions in the contact zone between steel samples made of roll and strip materials. The analysis employed optical microscopy, X-ray diffraction, and scanning electron microscopy. Results and discussion. The study confirmed that the developed methodology produces pickups on the specimen surfaces with morphology, chemical composition, and phase structure closely resembling those observed on the furnace rolls. A comparative assessment of the pickup formation rate between a typical furnace roll material (EI 283 steel) and a NiCrAlY coating applied by plasma spraying revealed that the pickup formation rate for the EI 283 steel was an order of magnitude higher. The validated methodology can thus be used to evaluate the effectiveness of strategies aimed at mitigating pickup formation on furnace rolls under long-term high-temperature contact conditions.

This study elucidates the dynamic tribo-mechanical response of laser-cladded FeNiCr-B4C metal matrix composite (MMC) coatings on AISI 1040 steel substrate, unraveling the intricate interplay between microstructural features and phase transformations. A multi-faceted approach, employing high-resolution scanning electron microscopy (SEM) and advanced X-ray diffraction/Raman spectroscopy techniques, provided a comprehensive characterization of the coatings’ behavior under mechanical and scratch testing, shedding light on the mechanisms governing their wear resistance. Specifically, microstructural analysis revealed uniform coatings with a columnar structure and controlled defect density, showcasing an average thickness of 250 ± 20 μm and a transition zone of 80 ± 10 μm. X-ray diffraction and Raman spectroscopy confirmed the presence of α-Fe (Im-3m), γ-FeNiCr (Fm-3m), Fe2B (I-42m), and B4C (R-3m) phases, highlighting the successful incorporation of B4C reinforcement. The addition of 5 and 7 wt.% B4C significantly increased microhardness, showing enhancements up to 201% compared to the B4C-free FeNiCr coating and up to 351% relative to the AISI 1040 steel substrate, respectively. Boron carbide addition promoted a synergistic strengthening effect between the in situ formed Fe2B and the retained B4C phases. Furthermore, scratch test analysis clarified improved wear resistance, excellent adhesion, and a tailored hardness gradient. These findings demonstrated that optimized short-pulsed laser cladding, combined with moderate B4C reinforcement, is a promising route for creating robust, high-strength FeNiCr-B4C MMC coatings suitable for demanding engineering applications.

A coating based on a single-phase medium-entropy CrFeNi alloy with a face centered cubic structure has good ductility, relatively high anti-corrosion properties, low cost, but insufficient strength for its widespread use. It is assumed that adding strengthening particles in the form of tungsten carbides and borides to the CrFeNi equiatomic coating will lead to an increase in its mechanical properties. This work studies the influence of tungsten carbide and boride additives on the structure and microhardness of a CrFeNi equiatomic coating. The coatings were formed by layer-by-layer short-pulse laser cladding with preplaced powder on a multifunctional laser installation equipped with a solid-state laser with a lamp pump based on an Nd:YAG crystal. The change in phase composition when adding strengthening particles was detected using X-ray diffraction analysis and transmission electron microscopy (TEM). Both methods confirmed the precipitation of Cr23C6 chromium carbide in the deposited coatings. TEM photographs indicate that the precipitated phase is distributed along the grain boundaries of the -solid solution. The study found that the addition of 6 wt. % WC and 3 wt. % WB increases the level of microhardness of the CrFeNi coating by 26 % (from 340±6 to 430±12 HV 0.025). This occurs due to the presence of Cr23C6, WC particles in the structure and possible microdistortions of the crystal lattice of the -phase as a result of doping with tungsten atoms released during the dissolution of tungsten borides and carbides in the process of high-temperature short-pulse laser heating.

The article presents the results of the implementation of three strategically important programs for the creation of aircraft gas turbine engines of the new generation PD-14, PD-8 and PD-35 for the purpose of solving the issue of ensuring the technological sovereignty of the Russian Federation in civil aircraft engine manufacturing. Considered are developments which are priority for civil rocket engineering, namely: launch vehicle with a reusable returnable first stage and a fully reusable single-stage launch vehicle for vertical take-off and landing made using multilayer composite materials. Provided are new technologies for implementation by short-pulse laser fusion of ceramic coatings based on boron carbide with microhardness up to 43 GPa and bismuth-alloyed surface layers of steel with unique tribotechnical characteristics: excellent wear resistance and ultra-low dry friction coefficient (up to 0.03). To ensure technological sovereignty in metallurgy, presented are Russian innovative technologies for the repair and production of new mold copper plates of continuous casting machines with wear-resistant composite coatings and recovering of the thickness of copper plates by multipass friction stir lap welding.

This work investigates the effect of liquid carburizing at 780°C on the structure, chemical and phase composition, microhardness, and surface roughness of corrosion-resistant austenitic chromium-nickel steel. The depth of the carburized layer has been determined to be about 2 mm. The steel structure at a distance of 0.15 mm from the surface consists of carbon-saturated austenite γ C , α' martensite, and fine Cr 23 C 6 chromium carbides located along austenitic grain boundaries. No carbides are observed in the grain body. There are austenite γ C and chromium Cr 23 C 6 carbides in the structure at a depth from 0.15 to 2 mm. The number and the size of carbides decrease with distance from the steel surface. Carburizing increased the microhardness of the steel surface by a factor of four (from 200 to 800 HV0.025) and the roughness parameter Ra to 1.35 μm.

The surface of the AlSi7Mg alloy was alloyed with CoNiCrW powder using a continuous wave fiber laser with a wavelength of 1.07 μm. The thickness of the alloyed layer is up to 4 mm. Its microstructure is radically different from the microstructure of the AlSi7Mg alloy. The basis of the microstructure of the alloyed layer is an α-solid solution based on aluminum, eutectic α + Si, and (Co,Ni)Al. The strengthening phases are aluminum oxides Al2O3, borides of the CrB type, and chromium carbides of various compositions. The alloyed layer is characterized by an average microhardness of 700 HV, an increased ability to resist elastoplastic deformation, and an increased wear resistance during abrasive wear tests. During wear tests under dry sliding friction conditions on a steel (0.2

The paper determines the effect of frictional treatment of nickel-based coatings of different initial hardness on the degree of their hardening and the depth of the indenter's impact on the surface layer. Frictional treatment was carried out with hemispherical sliding indenters made of finely dispersed cubic boron nitride under a load of 150 N for coating A (wt.%: Cr - 14.8, B - 2.1, Si - 2.9, C - 0.48, Fe - 2.6, Ni - base) and 500 N for coating B (wt.%: Cr - 18.2, B - 3.3, Si - 4.2, C - 0.92, Fe - 2.6, Ni - base). Using instrumental microindentation and optical profilometry, it was shown that the deformation of the softer and more ductile coating A proceeds more significantly: its hardening during frictional treatment reaches 56%, and the indenter impact depth is up to 3.8 mu m, while the corresponding indicators for the harder coating B are 8% and 1.5 mu m. The depth of the indenter impact must be considered if frictional treatment is used as a finishing operation for parts with nickel coatings.

Based on the study of the interaction in the “indenter—steel” contact zone, the choice of process parameters of the frictional treatment with a sliding indenter, namely, indenter material, load, and process medium, was carried out and substantiated for the 12Cr18Ni10Ti austenitic steel. Scanning electron microscopy, energy-dispersive microanalysis, optical profilometry and microhardness measurement are used as methods of investigation. It has been discovered that the choice of the process parameters of frictional treatment with a sliding indenter must be carried out taking into account mass transfer of the steel onto the indenter surface. The combination of significant strain hardening and low surface roughness was employed as a criterion for stating the advantages of using a synthetic diamond indenter and a noncorrosive argon environment over using natural diamond (conventional diamond burnishing), WC–Co hard alloy, and dense boron nitride indenters in the presence of a lubricating and cooling liquid. In the case of a synthetic diamond indenter and a noncorrosive argon environment, microhardness increased from 220 to 590–685 HV0.025, with a surface roughness of Ra = 0.075–0.115 μm. In the other cases, microhardness increased to 515, 635, and 660 HV0.025, with a surface roughness of Ra = 0.060, 0.380, and 0.255 μm, respectively.

The effect of friction-stir processing (FSP) and the subsequent aging treatment on the microstructure, electrical conductivity, and mechanical properties of a Cu-0.3%Cr-0.5%Zr alloy was studied. FSP promoted complex microstructural changes, including significant grain refinement and dissolution of secondary particles within the stir zone and particle coarsening within the heat-affected zone. The particle phenomena resulted in the essential material softening and degradation of electrical conductivity. The subsequent aging treatment provided particle reprecipitation within the stir zone and thus essentially recovered material properties in this area. In the heat-affected zone, however, the recovery effect was less pronounced, thus leading to the characteristic W-shaped profiles of microhardness and electrical conductivity. This result was attributed to the insufficient degree of supersaturation of the solid solution in this microstructural region, which, in turn, promoted the relatively slow precipitation kinetics.

Sorption of pertechnetate on pyrrhotite FenSn+1 (I) and stibnite Sb2S3 (II) from distilled water was evaluated. The distribution coefficients were found to be 185 and 223 cm(3)/g, respectively. The XPS study of the chemical state of (99Tc) absorbed on the surface of pyrrhotite and stibnite from aqueous solution of potassium pertechnetate (KTcO4) was carried out. It was found that Tc(IV) ions are present mostly on the surface of the studied samples, their concentration was 5.7 times higher on the surface of pyrrhotite compared to that on the surface of stibnite. A 13% admixture of Tc(VII) ions on the surface of pyrrhotite was observed.

An innovative technology has been developed and implemented for the restoration and manufacturing of new mold copper plates for continuous casting machines (CCMs) using wear-resistant composite coatings. These copper plates significantly surpass the service life of imported copper plates featuring galvanic coatings, sometimes by up to 20 times. However, the pressing challenge of restoring the copper plates of molds once they have reached the minimum permissible thickness remains unresolved. This study aimed to explore the feasibility of restoring a plate composed of precipitation-hardening Cr–Zr bronze with the same material by employing friction stir lap welding (FSLW). The objectives were to examine the structure, quality, and hardness of the welded joint, alongside investigating the impact of heat treatment (quenching and aging). By utilizing multi-pass FSLW method with a rotating tool crafted from a heat-resistant alloy and overlapping (partially overlapping) successive passes, a welded joint with a thickness of ~5 mm was achieved, devoid of critical continuity flaws (cracks or voids). Within the bronze layer restored through FSW, a softening effect ranging from 85–105 HV1 was observed compared to the initial hardness of the bronze in its hardened and aged state while in service (116–126 HV1). This is attributed to recrystallization and overaging, specifically the coarsening of chromium particles within the Cr–Zr bronze due to the heating of the weld nugget (stir zone) to 600–700 °C. The observed softening effect during FSW can be effectively rectified through heat treatment involving dissolution of the hardening phases followed by aging, resulting in a hardness increase to approximately 120–150 HV1. The process of restoring copper plates to their original thickness via the progressive and environmentally friendly FSW method, followed be the subsequent application of wear-resistant composite coatings, presents the opportunity for an almost infinite operational cycle of molds. This advancement could potentially eradicate the necessity for Russia to rely on importing such molds copper plates.

Equiatomic medium-entropy alloy (MEA) FeNiCr-B4C (0, 1, and 3 wt.% B4C) coatings were deposited onto an AISI 1040 steel substrate using pulsed laser cladding. Based on an SEM microstructural analysis, it was found that the cross-sections of all the obtained specimens were characterized by an average coating thickness of 400 ± 20 μm, a sufficiently narrow (100 ± 20 μm) “coating–substrate” transition zone, and the presence of a small number of defects, including cracks and pores. An XRD analysis showed that the formed coatings consisted of a single face-centered cubic (FCC) γ-phase and the space group Fm-3m, regardless of the B4C content. However, additional TEM analysis of the FeNiCr coating with 3 wt.% B4C revealed a two-phase FCC structure consisting of grains (FCC-1 phase, Fm-3m) up to 1 µm in size and banded interlayers (FCC-2 phase, Fm-3m) between the grains. The grains were clean with a low density of dislocations. Raman spectroscopy confirmed the presence of B4C carbides inside the FeNiCr (1 and 3 wt.% B4C) coatings, as evidenced by detected peaks corresponding to amorphous carbon and peaks indicating the stretching of C-B-C chains. The mechanical characterization of the FeNiCr-B4C coatings specified that additions of 1 and 3 wt.% B4C resulted in a notable increase in microhardness of 16% and 38%, respectively, with a slight decrease in ductility of 4% and 10%, respectively, compared to the B4C-free FeNiCr coating. Thus, the B4C addition can be considered a promising method for strengthening laser-cladded MEA FeNiCr-B4C coatings.

Microhardness and electromagnetic characteristics of corrosion-resistant chromium-nickel (wt. %: 16.80 Cr; 8.44 Ni) austenitic steel subjected to electron beam plasma carburizing at temperatures of 350 and 500°C, frictional treatment with a sliding indenter and combined treatments, including frictional treatment and plasma carburizing have been investigated. It has been found that plasma carburizing increases the microhardness of the steel surface from 200 to 1100 HV0.025. The total hardening depth was 25 microns after carburizing at T = 350°C and 300 microns after carburizing at T = 500°C. Frictional treatment increases the microhardness of the steel to 600 HV0.025 with a total hardening depth of 500 microns. It has been shown that the diffusion-active layer with a dispersed structure formed during preliminary frictional treatment contributes to additional hardening of the steel (up to 1275 HV0.025) during subsequent low-temperature (350°C) carburizing. Combined treatment with carburizing at a temperature of 500 °C increases the microhardness of the steel to 820 HV0.025, and the total hardening depth is 500 microns for both combined treatments. It has also been found that plasma carburizing of the steel leads to a decrease in the eddy-current readings compared to the quenched steel and their growth compared to the steel subjected to frictional treatment, which can be used to develop quality control techniques for such treatments.

Currently, to increase the hardness, strength and wear resistance of thermally non-hardenable austenitic chromium-nickel steels, such methods as frictional treatment with a sliding indenter and liquid carburizing have been used. However, along with an effective increase in mechanical characteristics, the application of these types of treatment may be accompanied by a decrease in the corrosion resistance of austenitic steels. Therefore, it is reasonable to study the influence of frictional treatment and liquid carburizing on the general corrosion resistance of Cr–Ni austenitic steels. In this work, the surface microhardness of the 12Cr18Ni10Ti and AISI 321 steels was determined using the recovered indentation method after electropolishing, mechanical grinding, frictional treatment, and liquid carburizing at a temperature of 780 °C. Using scanning electron microscopy and optical profilometry, the authors studied steel surfaces subjected to the specified types of treatment and determined their roughness. The corrosion resistance of steel was studied by testing for general corrosion using the gravimetric method. When testing for general corrosion, it was found that hardening (up to 710 HV 0.025) frictional treatment leads to an increase in the corrosion rate of the 12Cr18Ni10Ti austenitic steel compared to the electropolished state (from km=0.35 g/(m2·h) to km=0.53–0.54 g/(m2·h)). The corrosion rate of the ground steel is km=0.58 g/(m2∙h), while mechanical grinding does not provide a significant increase in the microhardness of the steel under study (from 220 to 240 HV 0.025). It is shown that the corrosion behavior of 12Cr18Ni10Ti steel subjected to various types of treatment is determined by the following factors: the presence/absence of strain-induced α'-martensite in the structure, the quality of the formed surface and, apparently, the dispersion of the formed structure. Liquid carburizing of the AISI 321 austenitic steel leads simultaneously to an increase in its microhardness to 890 HV 0.025 and a certain increase in corrosion resistance compared to fine mechanical grinding. This is related to the fact that carbon embedding atoms stabilize the electronic structure of iron (austenite and martensite), thereby increasing its corrosion resistance.

Laser cladding is an additive manufacturing process (variety of SLS technology) to form coatings on various types of metal surfaces. THE STUDY GOAL:Evaluate the impact of in-situ B 4 C alloying on the microhardness evolution of composite FeNiCr-B 4 C coatings synthesized by pulsed laser cladding.The 8th Asian Symposium on Advanced Materials (ASAM-8)  Laser cladding combined with in-situ B 4 C alloying process can be considered as a promising method for obtaining strength composite FeNiCr-B 4 C coatings. CONCLUSION

The features of the structure and phase composition of corrosion-resistant austenitic chromium–nickel steel (16.80 wt % Cr, 8.44 wt % Ni) subjected to carburizing in electron beam plasma at temperatures of 350 and 500°C, frictional treatment with a sliding indenter, and a combination of frictional treatment and plasma carburizing have been considered. It has been established that plasma carburizing results in the formation of a modified surface layer consisting of carbon-saturated austenite and carbides (Cr 23 C 6 , Fe 3 C); in this case, the formation of γ C -phase occurs only at a temperature of 350°C. The depth of a modified layer increases with an increase in the carburizing temperature. It has been shown that it is useful to perform combined frictional treatment and plasma carburizing at a carburizing temperature of 350°C, since in this case the deformation-induced structure formed as a result of frictional treatment is preserved, and the precipitated carbides remain highly dispersed. In this case, frictional treatment should provide the formation of the deepest possible diffusion-active layer with a dispersed structure.

Plain bearings, renowned for their versatility and simplicity, are extensively utilized in engineering design across various industries involving moving parts. Lubrication is vital to the functioning of these bearings, yet their usage is inhibited under dynamic load conditions, or at elevated or reduced temperatures due to this dependency on lubrication. This study introduces an innovative method to significantly mitigate friction and wear in plain bearings operating without lubrication. The plain bearings were constructed from steel–bronze pairs, where the steel shafts were alloyed with bismuth oxide via short-pulse laser treatment. MnO 2 was utilized as a carrier to incorporate the bismuth oxide into the surface layers of the steel. Insights from transmission electron microscopy and X-ray photoelectron spectroscopy revealed a highly non-equilibrium state of matter, unattainable through conventional engineering methods. The tribological performance of the modified steel disks was assessed via a block-on-ring sliding test, demonstrating superior wear and friction performance without lubrication, as well as an ultra-low coefficient of friction. Remarkably, the modified friction pairs remained functional after 200 km of linear sliding at a load of 250 N (12.5 MPa) and a sliding speed of 9 m/s. To substantiate the technique’s viability, we tested the performance of an internal combustion engine turbocharger fitted with a modified steel shaft. The turbocharger’s performance validated the long-term effectiveness of the steel–bronze coupling operating without lubrication at 75,000 rpm. The simplicity and resilience of this technique for modifying steel–bronze pairs offer a ground-breaking and promising approach for a wide range of applications.