The dynamics of microdischarges evolution during plasma electrolytic oxidation (PEO) of AMg6 aluminum alloy at anode-cathode mode in alkaline and silicate-alkaline electrolytes was investigated. Experimental studies were carried out using high-speed photography of surface being treated of the alloy synchronized with the registration of the electric current and voltage in the «alloy being treated ‒ electrolyte ‒ counter electrode» system. As a result, the ranges of electrical voltages at which surface being treated is affected by sporadic weak and plural weak, medium, as well as powerful anode microdischarges were identified. The conditions of sporadic cathode microdischarges displaying were determined. Differences in the dynamics of microdischarges evolution during PEO processes in alkaline and silicate-alkaline electrolytes were shown and determined their influence on the thickness, through porosity and microhardness of the formed coatings.

To increase wear resistance, (Zr,Nb)N, ZrN and (Zr,Hf)N coatings with columnar structures and (Zr,Ti)N and (Zr,Nb,Hf)N coatings with nanolayer structures were deposited on an AISI 321 stainless steel substrate. The samples with (Zr,Nb)N and ZrN coatings exhibited the best resistance to failure in the scratch test. The sample with the (Zr,Nb)N coating had the best wear resistance for the first 16,000 s. However, eventually the wear of this sample became notable, and after 20,000 s of testing, the lowest degree of wear was observed in the sample with the (Zr,Nb,Hf)N coating. The wear rate of the uncoated sample was 1.5 times greater than that of the sample with the (Zr,Nb,Hf)N coating. The (Zr,Nb,Hf)N coating also exhibited a low degree of indenter mass loss. The (Zr,Nb,Hf)N and ZrN coatings reduced the coefficient of friction (COF) most (COF of approximately 0.20–0.21, compared to COF = 0.28 for the uncoated sample). Defects (nanocavities) were detected in the interface area between the coatings and the substrate, which in some cases can have a negative effect on the wear resistance of the coating. The (Zr,Nb,Hf)N coating (72.07 at.% Zr, 24.87 at.% Nb and 3.05 at.% Hf) had the best wear resistance and a low friction coefficient.

This study investigated the anticorrosive properties of nitride coatings (V,Zr,Nb)N, VN and (Zr,V)N with a thickness of approximately 3 μm, deposited on a substrate of AISI 321 steel. Experiments were conducted in 3.0 and 0.9% aqueous NaCl solutions. The results indicate that the use of (V,Zr,Nb)N, VN and (Zr,V)N coatings to protect AISI 321 steel in corrosive environments (e.g., chloride-containing solutions) allowed corrosion currents to be reduced by 10–20 times (from 7.0 to 0.29 μA/cm2) for a sample with a (Zr,V)N coating in a 3.0% aqueous NaCl solution, and by 2 times (from 0.36 to 0.18 μA/cm2) for a sample with a (V,Zr,Nb)N coating in a 0.9% aqueous NaCl solution. Based on the distribution of elements on the surface of the samples after holding for 168 h in a 3.0% aqueous NaCl solution at 25 °C, it can be qualitatively concluded that the oxidation intensity of the (Zr,V)N coating was the lowest under this condition, and that the VN coating exhibited the highest oxidation intensity among the considered coatings. Analysis of the structure of the (Zr,V)N coating after holding in a 3.0% aqueous NaCl solution for 168 h at 25 °C shows the presence of nanometre-sized chips, while the analysis of the distribution of elements does not record the presence of anything other than the elements comprising the coating. Based on the distribution of elements on the surface of the VN coating, it can be assumed that the destruction of this coating mainly occurs due to peeling off from the substrate; however, corrosion processes also occur in the VN coating itself. Analysis of the distribution of elements in the surface layers of the (V,Zr,Nb)N coating did not show noticeable signs of oxidation. The destruction of this coating occurs due to fragments peeling off from the substrate, while oxidation processes and substrate corrosion do not have a significant effect on the process of (V,Zr,Nb)N coating destruction.

Investigation of compression plasma flows impact on structure, phase, and elemental composition, as well as mechanical properties of Ti-6Al-4V titanium alloy with ZrN coating was carried out in this work. X-ray diffraction, scanning electron microscopy, energy dispersion X-ray analysis, samples weight measurements, microhardness and tribological tests were used as investigation techniques. The findings showed that plasma impact led to the formation of a composite surface layer based on tita- nium alloy containing inclusions of undissolved ZrN coating. Growth of the absorbed energy density resulted in a decrease of zirconium and nitrogen concentration in the surface layer due to erosion. Formation of solid solutions on the basis of alpha-Ti and beta-Ti was found in the layer analyzed by X-ray diffraction. Presence of nitrogen in a vacuum chamber as plasma generating gas led to the formation of TiN on the surface. Plasma impact resulted in decrease of ZrN/Ti-6Al-4V system microhardness and decrease of friction coefficient (at specific treatment regimes).

The process of manufacturing thin walls using selective laser melting (SLM) from aluminum alloy powder AlSi10Mg was studied. The research aims at specifying a type of lattice structure based on skeletal-triple periodic minimal surface (TPMS) and sheet-TPMS shells. In this regard, the possibility of obtaining well-quality thin walls was studied. The accuracy of manufacturing, surface roughness and porosity of the samples were taken as quality criteria. The dependences of the influence of SLM parameters on the geometric characteristics, roughness, and porosity of thin walls were obtained. The preferential parameters for manufacturing thin-walled aluminum alloy samples have been determined. The microstructure and phase composition of the studied alloy after SLM were studied

The possibility of using plasma electrolytic technologies for surface treatment of 16MnCr5 steel in order to increase its wear resistance is shown. The influence of electrophysical characteristics of plasma electrolytic treatment on structural-phase changes of the surface and its tribological properties is studied. A comparison of anodic and cathodic variants of diffusion saturation, as well as subsequent polishing on the results of surface modification is carried out. The complex effect of surface layers strengthened above 1100 HV, including iron carbide and nitride, martensite and retained austenite, to a depth of up to 250 mu m with the preservation of a viscous core and the formation of a relatively homogeneous surface with reduced roughness on increasing wear resistance has been revealed. The features of tribological behavior of surfaces formed under different electrophysical parameters of processing, mainly related to the difference in surface microrelief, are shown. The correlation of the Kragelsky-Kambolov criterion as a complex assessment of surface roughness with its wear resistance is shown. The influence of changes in sliding speed and friction load on the occurrence and development of leading processes that determine the intensity and nature of destruction of friction surfaces is established.

Investigation of compression plasma flows impact on surface relief of Ti-6Al-4V titanium alloy was carried out in this work. Profilometry, x-ray diffraction, scanning electron microscopy, and sample weight measurements were used as investigation techniques. The findings showed that plasma impact led to the formation of developed surface relief (Ra parameter was changed in the range of 0.7-2.7 μm) due to the action of hydrodynamic instabilities at the melt-plasma border. Increase in the number of pulses resulted in the growth of Ra value. Numerical simulation of surface evolution under plasma impact was carried out on the basis of the model of incompressible fluid potential flow. Simulation data correlated with experimental data set. The hydrodynamic flow of the melt during plasma impact led to another process: surface erosion. Increase in both the absorbed energy density and the number of pulses resulted in erosion intensity increase. Formation of titanium nitride on the surface was observed as a result of the interaction of nitrogen (as a plasma generating gas) with the surface heated under plasma impact. Titanium nitride film prevented the development of the surface relief formed by the action of hydrodynamic instabilities.

The fracture strength was compared in a scratch test of coatings based on the ZrN system with the introduction of Ti, Nb and Hf, which were deposited on a titanium alloy substrate. The coatings were deposited using Controlled Accelerated Arc (CAA-PVD) technology. In coatings that simultaneously include Zr and Ti, a nanolayer structure is formed, while in coatings without Ti, the formation of a monolithic single-layer structure is observed. The comparison was carried out according to two parameters: adhesion strength to the substrate and overall coating strength. The (Zr,Hf)N coating showed better resistance to destruction, but had worse adhesion to the substrate. As a result, although the coating is retained directly in the scribing groove, a large area of delamination and destruction is formed around the groove. The (Ti,Zr,Nb)N coating, with its somewhat lower strength, has a high adhesion to the substrate; no noticeable delamination is observed along the groove boundary. In this paper, not only is the fracture resistance of various coatings deposited on a titanium alloy substrate compared, but the nature of this fracture is also investigated depending on the composition of the coatings.

Investigation of compression plasma flows preliminary impact influence on adhesion of ZrN coating deposited on Ti-6Al-4V titanium alloy was carried out. Profilometry, X-ray diffraction, and scratchtesting were used as investigation techniques. The findings showed that preliminary plasma impact led to the formation of developed surface relief and synthesis of titanium nitride on the surface of the alloy. Plasma processing provided a higher critical force Lc3 during scratch tests, which increases from 44 N (without processing) to 137 N (the density of absorbed energy 26 J/cm2, 6 pulses). With a decrease in the density of absorbed energy and a growth of the number of pulses, there was a tendency of the critical force Lc3 increase, that is mainly associated with the formation of an intermediate layer δ-TiN during plasma impact, the thickness of which increased with a growth of the number of pulses and a decrease in the density of absorbed energy.

The surface adhesion of bacterial cells and the in vivo biocompatibility of a new ceramic–metal composite made of zirconium dioxide and tantalum were evaluated. Within the framework of an in vitro study using the crystal violet staining and colony counting methods, a relatively similar adhesion of Streptococcus oralis to the 3Y-TZP/Ta biocermet (roughness Ra = 0.12 ± 0.04 µm) and Ti-Al6-V4 titanium alloy (Ra = 0.04 ± 0.01 µm) was found. In addition, in an in vivo preliminary study focused on the histological analysis of a series of rods implanted in the jaws of beagle dogs for a six-month period, the absence of any fibrous tissue or inflammatory reaction at the interface between the implanted 3Y-TZP/Ta biocermets and the new bone was found. Thus, it can be concluded that the developed ceramic–metal biocomposite may be a promising new material for use in dentistry.

Renewable energy technologies have been actively developing in the recent decades, primarily due to increasing environmental problems, as well as the rise in price and risk of fossil hydrocarbon reserve depletion. Extensive research has been, and continues to be, carried out to create and improve technologies for extracting energy from environmentally friendly renewable sources at a competitive price. However, it is difficult, if not impossible, to develop new technologies without improving the functional properties of materials. The requirements for products have increased so much that traditional materials often cannot meet them. An effective way to meet this challenge is to develop composites that combine a range of useful properties. Coated materials are one of the promising types of modern composite materials. Such composites combine a relatively soft substrate and an extremely hard, wear- and corrosion-resistant coating. In turn, coatings themselves can have a composite structure that includes functional layers with different characteristics. The coating deposition technologies play an important role in the improvement of renewable energy sources, with the commercial efficiency and reliability of significant importance. There are several coating deposition technologies. In particular, there are physical vapor deposition (PVD), chemical vapor deposition (CVD), and thermal spray coatings. All of the aforementioned methods are used in the production of renewable energy sources to achieve various functions, from traditional device protection to more advanced spectral selectivity, hydrophobicity, and self-cleaning. The PVD methods have significant advantages, including excellent coating adhesion to the substrate (in contrast, for example, to thermal spray coatings and, moreover, traditional painting methods) and a relatively low deposition temperature (compared with the CVD methods). The advantages of the PVD methods also include the excellent quality of the coating deposited, which consists of its high resistance to wear, hardness, and ability to provide chemical passivity and corrosion resistance. Another advantage typical for the PVD methods is the wide possibility of flexible control over the composition and architecture of the coatings deposited.

One of the key factors in manufacturing products by fused deposition molding (FDM) or layer-by-layer printing technology is the material intensity of the product. The task of reducing the amount of material required to manufacture a product without significant loss of mechanical properties is one of the most practically important technological tasks. Material saving in FDM printing of products allows to reduce financial costs and increase the speed of manufacturing of the final product without reducing (or not significantly reducing) the quality properties of the product. In our work it is demonstrated that using Combs filling type and materials of poly lactic acid (PLA) and polyethylene terephthalate glycol (PETG) it is possible to achieve material savings of up to 23% at 50% filling for PLA and 17% at 75% filling for PETG without significant reduction of product strength in comparison with other filling types. Exceptions are PLA samples with 100% fill and Lateral fill. Application of Kruskal-Wallis criterion and Dunn's criterion with Bonferroni multiple comparison correction showed that there were no statistically significant differences within the strength limits of samples made by FDM printing technology from PLA and PETG plastics (p-value = 0.0514), as well as samples with Triangle and Grid filling type (p-value = 1). Based on this result, three groups of samples statistically significantly differing in ultimate strength were identified by methods of hierarchical cluster analysis; in each group (except for group 1, which included samples made of PLA plastic with Lateral filling type and 100% filling), correlation analysis was performed (Spearman correlation was used). The results of the correlation analysis showed a stable average correlation between the percentage of filling, modulus along the secant 0.05-0.2% strain, ultimate strength and strain corresponding to the yield stress. Analysis of the correlation graph showed that the main parameter correlating with all mechanical properties of the specimen is the 0.05-0.2% strain modulus. Based on this conclusion, robust regression equations predicting the 0.05-0.2% strain modulus as a function of the percentage of specimen filling were constructed for the two selected groups. Analysis of the equations showed that in the third group of specimens, the average modulus of 0.05-0.2% strain is more than twice the modulus of 0.05-0.2% strain in the second group. The detected statistical regularities can be explained by the mechanism of strain hardening, the actual value of which depends on the structure of the macrodefect (type of filling), properties and volume of the material (percentage of filling) used in the fabrication of samples using FDM printing technology.

Osseodensification is an innovative surgical instrumentation technique based on additive (non-cutting) drilling using special burs. It is known from the literature, that the osseodensification burs should operate in a clockwise direction to drill holes and in a counterclockwise direction to compact the osteotomy walls. For these purposes, the burs have special design features, like conical contour shape, increased number of helical flutes, and negative rake angle on the peripheral part. However, although other parameters and features of the burs define their overall performance, they are not described sufficiently, and their influence on surgical quality is almost unknown both for clinicians and tool manufacturers. The purpose of the present research is to identify the key design features of burs for osseodensification and their functional relationship with the qualitative indices of the procedure based on an analytical review of research papers and patent documents. It will help to further improve the design of osseodensification burs and thereby enhance the surgical quality and, ultimately, patient satisfaction. Results: The most important design features and parameters of osseodensification burs are identified. Thereon, the structural model of osseodensification bur is first represented as a hypergraph. Based on the analysis of previous research, functional relationships between design parameters of osseodensification burs, osseodensification procedure conditions, and procedure performance data were established and, for the first time, described in the comprehensive form of a hypergraph. Conclusions: This study provides formal models that form the basis of database structure and its control interface, which will be used in the later developed computer-aided design module to create advanced types of burs under consideration. These models will also help to make good experimental designs used in studies aimed at improving the efficiency of the osseodensification procedure.

The (Ti,Y,Al)N coating was deposited at different values of the yttrium cathode arc current (65, 85, 105, and 125 A). With an increase in the arc current from 65 to 105 A, an increase in the Y content in the coating from 30 to 63 at% is observed; however, with a further increase in the arc current to 125 A, the yttrium content practically does not change. This effect can be associated with an increase in the proportion of microparticles in the plasma flow at high values of the arc current. These microparticles do not reach the surface of the substrate, falling on the walls of the chamber. With an increase in the arc current, the dominant shape of the microparticles changes. If at 65 A relatively small (up to 3 mu m) microparticles of a regular spherical shape dominate, then at 85 A a noticeable amount of irregularly shaped microparticles with sizes of 3-5 mu m is observed, and with a further increase in the arc current, large microparticles up to 30 mu m in size are formed. The value of the modulation period of the studied coatings is 42-67 nm. The change in the modulation period lambda depending on the arc current of the yttrium cathode has a character close to linear, increasing with increasing arc current. From the point of view of hardness, scratch test and wear resistance during turning, only coatings deposited at arc currents of 65 and 85 A have prospects for effective operation as a wear-resistant coating.

One of the key factors in the manufacturing of products using fused deposition method (FDM) or layer-by-layer printing technology is the material intensity of the product. The task of reducing the amount of material required to manufacture the product without significant loss in mechanical properties is one of the most practically important. In the presented work it is shown that using the Combs filling type and materials of polylactic acid (PLA) and polyethylene terephthalate glycol (PETG) plastics it is possible to achieve material savings up to 23% at 50% filling (for PLA) and 17% at 25% filling (for PETG) without significant loss in the strength of the product (except for samples made of PLA plastic with 100% filling and Lateral filling type). Application of Kruskell-Wallis test and Dunn's criterion with Bonferroni multiple comparison correction showed that there were no statistically significant differences within the strength limits of samples made by FDM printing technology from PLA and PETG plastics (p-value = 0.0514), as well as samples with Triangle and Grid filling type (p-value = 1). Based on this result, three groups of samples statistically significantly differing in ultimate strength were identified by methods of hierarchical cluster analysis; in each group (except for group 1, which included samples made of PLA plastic with Lateral filling type and 100% filling), correlation analysis was performed (Spearman correlation was used). The results of the correlation analysis showed a stable average correlation between the percentage of filling, modulus along the secant 0.05–0.2% strain, ultimate strength and strain corresponding to the yield strength. Analysis of the correlation graph showed that the main parameter correlating with all mechanical properties of the specimen is the 0.05–0.2% strain modulus. Based on this conclusion, robust regression equations predicting the 0.05–0.2% strain modulus as a function of the percentage of specimen filling were constructed for the two selected groups. Analysis of the equations showed that in the third group of specimens, the average modulus of 0.05–0.2% strain is more than twice the modulus of 0.05–0.2% strain in the second group. The detected statistical regularities can be explained by the mechanism of strain hardening, the actual value of which depends on the type of defect structure and properties of the material used in the manufacture of samples. It is necessary to distinguish between macro and micro defects present in the final product, the structure and distribution of which affects the strain hardening value.

This paper presents research on the effects of the addition of various contents of graphene oxide and sintering temperature on the mechanical, tribological, and electrical characteristics of WC-ZrO2 composites. Wet processing and spark plasma sintering provided dense samples with simultaneous reduction of graphene oxide (rGO) during sintering. The obtained results showed that the best mechanical properties were observed at a sintering temperature of 1700 °C in samples with 0.5 vol.% rGO content; namely, indentation fracture toughness (5.8 ± 0.4 MPa·m1/2) and flexural strength (872 ± 43 MPa) increased by 9% and 24.3% compared with the sample without rGO. In addition to improved mechanical performance, rGO-reinforced composites exhibited lower wear rates and friction coefficients than non-rGO composites, due to the formation of a graphitic lubricating tribolayer on worn surfaces and counterbodies in a friction pair, which provided sufficient lubrication to reduce the coefficient of friction and wear rate. The resulting composites also showed low electrical resistivity, suggesting the possibility of using electrical discharge machining to manufacture ceramic products of complex shapes from them.

A technology has been proposed to increase the hardness and wear resistance of M2 high-speed tool steel by combining low-temperature nitrocarburizing using anodic plasma electrolytic treatment, stepwise heating in plasma electrolysis with a change in the polarity of the workpiece, high-temperature hardening in air and triple tempering release. The structure, phase and elemental composition of the surface layers of high-speed steel after plasma electrolytic treatment with quenching, as well as subsequent tempering, were studied using the methods of x-ray, SEM and EDX analysis. Tribological tests were carried out under dry friction conditions with assessment of the friction coefficient and weight wear, as well as calculation of the microgeometry of the worn surface to assess contact stiffness and determine the wear mechanism. It has been shown that the formation of a structure of highly alloyed martensite with nitride inclusions after nitrocarburizing with quenching and the release of finely dispersed carbides during subsequent tempering leads to hardening of the surface layer to 1090-1100 HV after quenching and to 1350-1380 HV after subsequent tempering. The nitrogen concentration in the surface layer as a result of low-temperature nitrocarburizing reaches up to 13 wt.