The paper presents the results obtained when studying the adsorption and structural peculiarities of aluminum nitride nanopowder interaction with water, particularly the morphology and  phase composition of oxidation products. Powder surface areas and porosities are calculated. The peculiarities of the adsorption  isotherms of the investigated samples are analyzed before and after interaction with water in terms of their correspondence to a  certain type according to the recommendation of the International  Union for Pure and Applied Chemistry (IUPAC), as well as to a  certain porosity type, which is necessary for the understanding of  their further application. The mechanism of aluminum nitride powder and water interaction is discussed. It is shown that aluminum nitride interacts with water by the ion-adsorption mechanism that  leads to the formation of porous agglomerates consisting of needle and platelet shaped aluminum oxyhydroxide nanoplates  connected by contacts with pores 55 Å in diameter. Specific surface  area increases from 48 to 115 m2/g. It is also found that phase  composition changes as a result of AlN nanopowder interaction with aqueous environment, and interaction products are represented by AlO(OH) and Al(OH)3 phases.

The effectiveness of the technique for automatic dosed mould filling with fine ferromagnetic powders without natural fluidity is experimentally proved in the paper. In order to obtain steady  powder fluidity, disperse medium in the hopper of the considered device is affected by variable 50 Hz gradient magnetic  field with vertical induction lines and higher gradient in the area of stimulated fluidity formation and constant magnetic field with  horizontal induction lines. At certain magnetic fields parameters, disperse medium passes to a dynamically steady  suspended state thus forming a magnetic fluidized bed, and powder  flows into a dispenser. The paper provides the results obtained in  experimental studies of constant magnetic field induction and  variable magnetic field gradient influence on the mass flowrate of  barium ferrite powders with an average particle size dav of 1 μm and strontium ferrite powders with dav = 1, 9 and 50 μm through a 2  mm hole. Presented experimental dependencies show that for dav =  1 μm barium and strontium ferrite powders the speeds of powder  transportation to the dispenser reach their maximum values at a  constant magnetic field induction of 15,7 mT and a variable  magnetic field induction gradient of 593 mT/m and are equal to 96,9 and 181,1 mg/s, respectively. According to experimental data, the  minimal relative mass error of dav = 1 μm strontium ferrite powder  flowed in the dispenser is observed at electromagnetic effect modes  providing maximal disperse material fluidity and equals to 2,1–2,3 %.

This paper provides experimental data on ZrB2–CrB composite production by SHS compaction. Thermodynamic data were used to  calculate adiabatic flame temperatures of the Zr–Cr–B system and  compositions of equilibrium synthesis products and to determine optimum conditions for SHS composite production. It was  shown that equilibrium products of combustion synthesis are ZrB2  and CrB refractory compounds that ensure high thermodynamic  stability of SHS composites. They are used as a dispersed phase  (ZrB2) and a ceramic binder (CrB). As the binder content increases  from 25 to 64 wt.%, the adiabatic combustion temperature decreases from 3320 to 2350 K. A solid dispersed  phase (ZrB2) and a molten binder (CrB) are formed at these  conditions. It was identified that SHS composites with a residual  porosity less than 1% can be produced due to molten binder  formation. The effect of reaction mixture composition on the phase  composition, microstructure, physical and mechanical properties of  SHS composites was studied. It was found that the residual porosity  of SHS composites is ~1 % at the 30–50 wt.% CrB content. Vickers  hardness is 31,3 to 42,6 GPa, and flexural strength is 480 to 610  MPa. It was shown that physical and mechanical properties depend  on the residual porosity of SHS composites. The obtained ZrB2– 30CrB SHS composite was used to make cutting inserts and conduct  tests for high-strength hardened steel machining. The test results  proved that ZrB2–30CrB ceramic inserts feature high wear resistance when machining ShKh15 chromium bearing steel with a hardness of 61–65 HRC.

The in-situ synthesis of the Ti2AlNb-based intermetallic alloy using selective laser melting of powder materials was studied. The object of research is the Ti–22Al–25Nb alloy (at.%), the main phase of which is the Ti2AlNb intermetallic compound with an ordered orthorhombic lattice (O phase). The Ti–22Al–25Nb alloy has good mechanical properties at room and elevated temperatures, low specific weight, and is considered as a promising material for aerospace industry applications. Experiments used a mechanical mixture of pure titanium, aluminum and niobium powders in a ratio required for Ti–22Al–25Nb alloy synthesis. Selective laser melting as an additive technology is the most promising way for additive layer manufacturing of parts. This technology allows manufacturing complex-shaped items based on CAD model data. Selective laser melting was used to make compact samples for investigations. Their microstructure, density, phase composition and microhardness were studied. In addition, the effect of heat treatment homogenization at 1250 °C for 2,5 h and then aging at 900 °C for 24 h on the microstructure and chemical homogeneity of samples were studied. It was shown that the compact material obtained by selective laser melting contains unmelted niobium particles. Homogenization annealing makes it possible to dissolve these particles completely in the alloy. As a result, the material microstructure consists of B2 phase grains of different sizes and needle-like precipitates of the orthorhombic phase.

Friction cladding as one of the simplest methods of surface modification with simultaneous coating application was used for surface nanostructuring. Intensive plastic deformation using a rotating wire brush (RWB) was performed during friction cladding. Brush fibers had an impulse-friction effect on the work surface with simultaneous coating application. Normalized steel samples (diameter 45 mm, width 10 mm) made of Grade 45 steel were tested for wear resistance. A copper-containing coating was applied at a circular grinder. Samples treated by various operating modes were tested at the SMC-2 friction machine using a disk-to-disk friction drive scheme. The tests showed that samples with a copper coating (C1) and a brass coating (B63) feature 2–10 times higher wear resistance in comparison than reference ones depending on the treatment mode. Samples with a brass coating (coating thickness 10–15 μm) applied in 6 passes with 2 mm interference (RWB feed on the work piece) at a sliding speed of 25 m/s demonstrated the highest strength. Smooth specimens (four series, a total of 60 pieces) made of 20CN steel were tested according to GOST 25502-82 «Fatigue Test Methods» to study the effect of friction cladding modes on endurance. Test results showed that the most effective way is surface plastic deformation with brass coating application. The endurance limit increase factor was Kυ = 1,41. It was found that steel mechanical properties (σв, σт, δ10) are not affected by coating application using friction cladding. Copper coating applied on coupling rods and plungers in hydraulic systems ensured 1,4–3,0 times longer service life, and up to 6 times longer life when applied on wave gear teeth in edge version.

The paper studies performance reproduction stability for protective coatings formed by microarc oxidation (MAO) when processing the  group of workpieces. Ceramic-like MAO coatings exhibit high  resistance to wear, corrosion, shock temperature impact while featuring high adhesive strength. At the same time, an  essential indicator of any technological process is the stability of its  results. In general, most research findings published in the MAO field disregard the analysis of stability of obtained results and fail to study the effect that technological factors have on this parameter. This  paper is the first one that provides experimental reproduction  stability estimates for the key characteristics (thickness, through  porosity and microhardness) of MAO coatings formed while  processing  the group of workpieces and for electrolyte exhaustion  effect on the values of these characteristics. The studies allow for a  conclusion that the stability of these MAO coating indicators depends  largely on electrolyte exhaustion and the time of microarc  oxidation process. It is noted that values of these characteristics can  significantly differ for coatings formed simultaneously on workpieces in the same group, and the stability of coating characteristics  (thickness, through porosity and microhardness) increases with an increase in MAO processing time. The results also prove the  assumption about changes in the characteristics of coatings formed when processing the group of workpieces are due to unevenly  distributed electric current density between these workpieces and resulting unequal electricity amount flowed in the galvanic circuit,  that determines the formation of the coating substrate.

Nanosized titanium dioxide allows solving complex engineering problems. One of such tasks is the creation of materials and coatings that reduce the likelihood of nosocomial infections on the surface of  orthopedic structures including implant systems. The paper presents  the results of the Raman spectroscopy, X-ray diffraction analysis and  scanning electron microscopy of anatase ceramic coatings deposited  by sol-gel technology on a sintered material based on a nanosized  titanium dioxide powder (rutile modification). The resulting coating  has a complex layered structure, which is almost completely  represented by titanium dioxide in the anatase phase according to  the Raman spectroscopy data. The simultaneous existence of both  phases in the coating was recorded. The identification of rutile on  diffractograms seems to be due to the fact that modified peak  intensity rutile is mainly formed during the first stages of coating application on the polycrystalline rutile surface. The fact that non-stoichiometric phases also present in the diffractograms suggests  that coating phase composition is not the same in thickness and is  represented by a gradual layerwise transition from rutile to anatase.  The coating thickness is 60 ± 15 μm. The coating is represented by  lamellar blocks of various sizes. The thickness of a single plate in the  coating is 60–80 nm. The developed technique makes it possible to apply the anatase coating not only on samples of titanium dioxide  ceramics but also on the surface of titanium implants with the preliminary formation of a titanium dioxide layer in the form of rutile  on the metal surface. Experiments on the study of  antibacterial properties and morphological characteristics of bone  tissue in contact with the implant were carried out at the  Department of Prosthetic Dentistry at the PSMU.

The study covers the growth kinetics of the coating formed on VT6 titanium alloy by plasma electrolytic oxidation (PEO) at a specified  current density of 10 А/dm2 in the alkali aqueous solution containing 40 g/l of NaAlO2. Coatings with varied thicknesses (30, 80 μm) formed on VT6 titanium alloy was tested for wear resistance by the «pin-on-disc» test using the Hightemperature tribometer and WYKO  NT1100В optical surface profiler. Relationships between phase  coating composition and PEO process duration, as well as wear  resistance are determined. The mechanisms of coating thickness  growth that explain its kinetic features are suggested. The  mechanisms are as follows: 1) migration and diffusion of metal  cations towards the outer phase boundary on sections adjacent to  microdischarges; 2) thermochemical transformation of deposited  ions or polyanions, in particular, tetrahydroxyaluminate; 3) high-temperature oxidation of the metal substrate at the bottom of coating pores where plasma anode microdischarges occurred. The  considered equivalent scheme of the anodic component of the  alternating current at titanium alloy PEO allows us to understand the causes of a significant decrease in the initial coating growth rate at VT6 alloy PEO without anodic voltage reduction. The peculiarity of this scheme is the presence of rheostats since the flow resistance of alternate current components depends largely on the PEO process time. It is shown that the presence of a high-temperature modification (α-Al2O3) in the TiAl2O5 spinel coating makes it possible to increase VT6 alloy wear resistance by almost 6 times when the coating thickness is ~80 μm.

Oxidation resistance of detonation sprayed coatings obtained from FeAlCr/Al2O3 powder produced by the method of mechanically assisted self-propagating high-temperature synthesis  (MASHS) using aluminothermic reactions has been investigated. The powder has a sufficiently homogeneous composite structure  consisting of chromium-alloyed ordered B2–FeAl and fine inclusions of α-Cr2O3 and α-Al2O3. Detonation coatings sprayed on  a stainless steel substrate have a typical layered coating structure  without cracks or spalling. The coating thickness is 250–300 μm,  microhardness is 5,9–6,1 GPa. Coatings of a synthesized powder  mainly inherit its structure and phase composition although some  aluminum and chromium oxidation takes place when spraying. The features of cyclic and isothermal oxidation of the obtained  coatings in air within a temperature range of 900–1000 °C have  been studied. The oxidation resistance of synthesized powder detonation coatings after 48 h of oxidation in air at 950 °C is close to that of coatings obtained from FeAl–FexAly powder with an  aluminum content of 45 wt.%. At the same time, the coefficient of  linear  thermal expansion of FeAlCr/Al2O3 coatings is closer to that  of the substrate, and their creep resistance is higher as compared  with the substrate due to the presence of fine inclusions of refractory oxides. α-Cr, Cr2O3 and a lot of fine alumina inclusions present in the synthesized powder and formed when spraying are supposed to  accelerate the protective film formation while suppressing the nucleation and growth of hematite at early oxidation stages at  temperatures up to 950 °C.