The Joint Institute of Mechanical Engineering

ZrN and Zr-Si-N coatings were formed using vacuum-arc plasma fluxes deposition system at the substrate bias voltage (UB) ranged from − 50 to − 220 V on HS6-5-2 steel substrates. The structural, mechanical and tribological properties were characterized using x-ray diffraction, atomic force microscopy, scanning electron microscopy, optical microscopy, nanoindentation and ball-on-disk test. The surface roughness parameter Ra of ZrN coatings is lower than Zr-Si-N coatings. Both roughness Ra of Zr-Si-N coatings and the number of surface defects with mainly small dimensions to 1 µm decrease with increasing negative substrate bias voltage. The addition of silicon to ZrN significantly reduces the crystallite size, from about 18.3 nm for ZrN coating to 6.4 nm for Zr-Si-N coating both deposited at the same UB = − 100 V and 7.8 nm for UB = − 150 V. The hardness of Zr-Si-N coatings increases to about 30 GPa with the increase in negative substrate bias voltage (UB = − 220 V). Adhesion of the coatings tested is high, and critical load is above 80 N and reduces with UB increase. Coefficient of friction determined using AFM shows similar trend as surface roughness in microscale.

Introduction. Reliability-critical components of equipment working in contact with high-speed liquid media (for example, turbine blades of hydroelectric power stations, pump impellers, ship propellers) are subjected to one of the types of wear – cavitation erosion. The current study aims to select and scientifically substantiate the type of coating and its structural-phase state for the effective protection of parts from cavitation erosion. Research methods. The study carries out a comparative analysis of differences in the cavitation erosion resistance of characteristic austenitic steels, in the form of bulk material (316L) and coatings (E308L, 60Cr8TiAl), used for protection against cavitation Arc surfacing, i.e. MMA and MIG, is used for depositing the coatings. The tests are carried out on an original installation for evaluating the cavitation resistance of materials with applying ultrasound and the electrical potential difference. Results and Discussion. The results show that the 60Cr8TiAl has a higher resistance to cavitation erosion than that of E308L and 316L by 4 and 10 times, respectively. The structural factors that determine the resistance to cavitation erosion damage are identified to analyze the reasons for the differences in material resistance. Firstly, a strong dependence of the cavitation erosion resistance of austenitic steels on the intensity of the deformation martensitic transformation, developing under the influence of cavitation, is confirmed. This structural transformation contributes to an increase in cavitation resistance of the surface layer. In metastable austenitic steel, a deformation martensite (α′) is formed in the surface layer during the initial test period. This causes an increase in hardness, dissipation of the energy of external action, and the appearance of compressive stresses that prevent the occurrence of microcracks. Subsequently, additional hardening of the previously formed dispersed crystals of α′-martensite occurs. In 60Cr8TiAl, these effects are significantly stronger than that of E308L and 316L due to the higher level of metastability of austenite and formation of carbon deformation martensite.

The finishing accuracy and efficiency of magnetic abrasive finishing (MAF) are mainly depending on magnetic abrasive powders (MAPs). A new kind of core–shell structured carbonyl iron powders (CI-MAPs) with a hard Fe/Al intermetallic shell for magnetic abrasive finishing is successfully synthesized by in-situ alloy-hardening the surface of spherical carbonyl iron powders in this study. The feasibility of such an in-situ alloy-hardening strategy is theoretically designed according to the Fe/Al intermetallic compound formation chemical reaction using the Gibbs free energy principle and the TG-DSC testing, and thus the experimental thermodynamics temperature and time ranges of such chemical reactions are proposed. Experimental results shown that a densely zigzag-like uniform alloy-hardening layer with a thickness of about 11 μm, which are composed of Fe3Al, FeAl, and Fe2Al5 intermetallic compounds, was in-situ chemically synthesized on the surface of the spherical carbonyl Fe powders. The achieved core–shell structured powder is performed to finishing a Zirconium tube experimentally, and the roughness (Ra) of the Zirconium tube is greatly improved from 0.361 μm to 0.085 μm by 3 MAF passes.

Ternary Ni–Co–B alloys with boron content up to 27 at% were electrodeposited from sulfate-chloride electrolyte containing sodium decahydro-closo-decaborate as a boron source, and the effect of the boron content on the structure, morphology, corrosion, mechanical and magnetic properties of the alloy coatings was studied. With increasing the boron content the structure of the alloys is changed from polycrystalline to amorphous-nanocrystalline and then to amorphous, and the surface becomes more smooth and uniform. During prolonged corrosion testing in 3.5% NaCl solution the amorphous alloys with high boron content demonstrate a gradual decrease in the corrosion rate due to the formation of a rather compact film of the corrosion products consisting of nickel-cobalt hydroxides. In addition, the amorphous Ni–Co–B coatings are less susceptible to the pitting corrosion in comparison with polycrystalline and amorphous-crystalline ones. The boron doping of the Ni–Co alloys improves significantly their mechanical properties. Amorphous Ni–Co–B coatings containing 20 at% B and 10 at% Co demonstrate the highest microhardness and wear resistance. At high content of boron and cobalt, the Ni–Co–B alloys are magnetically soft ferromagnetic materials with high magnetic permeability and low coercivity.

Features of the design of operational amplifiers (Op-Amp) on complementary field effect transistors with p-n- junction (junction field-effect transistor, JFET) for operation under the influence of penetrating radiation (PR) and extremely low temperatures up to -197°C are considered. The original circuit of the Op-Amp and the results of its circuit simulation are given.

The results of a study on the technological capabilities of the modification of working profile of the teeth of the gears by nanostructured functionally oriented coating particles formed by the method of cladding by a flexible tool (CFT) and evaluated their impact on the reduction of generated tooth gearing noise. It is established that the efficiency of the technology CFT used for the noise reduction of bevel gear drives of machine tools is largely determined by the rational choice of the donor material composition for the formation of a coating. In some cases, gear teeth made from various materials formed on the working profile can significantly change the general character of the distribution of the frequencies of sound energy reducing the level of noise at one frequency and remaining unchanged or even higher at others. The best results in lower noise level of gearing in the whole spectrum of frequencies provided by the bronze-graphite Br05S20Gr0.5DMO0.5 coating. The decrease in noise at the general level was 2–4 dBA depending on rotation speed and, on a separate spectral component, reaches 6–9 dBA.

We present a comprehensive study of the optimum operating regime in gain-switched Cr:forsterite lasers pumped at kilohertz repetition rates, comparing five crystals of similar quality but different dopant levels. The optimization of the cavity design includes selection of the proper pump fluence to account for excited-state absorption, optimum matching of the pump and laser modes, and consideration of thermal effects. As a result >1-W average output power is demonstrated at 2 kHz. The maximum conversion efficiencies achieved at 1 kHz are 24.2% (slope) and 20% (absolute). Narrow-band operation of this laser is possible with a birefringent filter, which is a prerequisite for efficient frequency doubling to cover the 585-660-nm part of the visible spectral range. Tunable second-harmonic generation in a temperature-tuned noncritical scheme that employs LiB(3)O(5) produces 60 mW of average power near 619 nm with 13.5% conversion efficiency.

The non-isothermal crystallization behaviors of a detonation sprayed Fe-based amorphous coating (AMC) was systematically investigated through differential scanning calorimetry, X-ray diffraction and transmission electron microscopy. The crystallization mechanism of the Fe-based AMC is analyzed and discussed in detail using a combination of the Kissinger-Akahira-Sunose and Ozawa-Flynn-Wall approaches, as well as the local Avrami exponent. The results indicate that the crystallization process of the Fe-based AMC is affected by the non-isothermal heating rate with a significantly higher initial crystallization activation energy (917.7 kJ mol−1) and first peak activation energy (479.6 kJ mol−1), indicating excellent thermal stability. After four stages of amorphous crystallization and phase transformation, the crystallization products of the equilibrium state were primarily composed of 78.5%, 11.3%, and 5.8% (Cr, Fe)23(C, B)6, α-Fe phases, and FeMo2B2 phases, respectively.

The mechanochemically synthesized Cu–20 wt % Al alloys are studied by the X-ray diffraction analysis and scanning electron microscopy. It is shown that, after 20 min of mechanical activation, the single-phase intermetallic compound Cu9Al4 with crystallites ~3 nm in size, low microstrains (~0.03%), and particle size in the range from 0.2–0.4 to 2–4 μm is formed. The morphological characteristics of the solid solution of aluminum in copper, which has been mechanochemically synthesized from the Cu–10 wt % Al alloy, are studied. It is demonstrated that the solid solution is composed of platelike particles 10–50 μm in planar size and 2–10 μm in thickness. The scanning electron and optical microscopy data show that the Cu(Al) solid solution produced by the spark plasma sintering at 700°С are characterized by the low residual porosity (<0.5%). The Vickers hardness is 290 ± 30 HV.

In this paper, we propose a systematic approach to controllably fabricate silver nanoparticles, dendrites and nanovoids on porous template based on silicon and two-step wet process. Geometry of metallic structures was managed by variation of dopant type of silicon, regimes of template formation and deposition of silver. General models of each structure were developed and studied for distribution and strength of electric field arising in them under 473, 633 and 785 nm lasers. Simulation results revealed reasons of variable activity of fabricated structures in surface enhanced Raman spectroscopy, which allowed to define optimal conditions of analysis of target molecules.

This paper shows results of a study on the corrosion behavior of micro-arc oxidation (MAO) coatings sampled from the AlMg6 alloy. The alloy was simultaneously subjected to a corrosive environment and static tensile stress. For comparative purposes, the tests were run for both coated samples and samples without coatings. The research was conducted at a properly prepared stand; the samples were placed in a glass container filled with 3.5% NaCl aqueous solution and stretched. Two levels of tensile stress were accepted for the samples: σ1 = 0.8R0.2 σ2 = R0.2, and the tests were run for two time intervals: t1 = 480 h and t2 = 1000 h. Prolonged stress corrosion tests (lasting up to 1000 h) showed that the samples covered with ceramic coatings demonstrated significantly higher corrosion resistance than the samples without the coatings. Protective properties of the coating could be explained by its structure. Surface pores were insignificant, and their depth was very limited. The porosity level of the main coating layer was 1%. Such a structure of coating and its phase composition provided high protective properties.

Theoretical and experimental research of the “pointlike pole” in magnetic structural analysis and this phenomenon’s instrument implementation are analyzed. It is shown that none of the approaches allows accurate calculation of the induction distribution in matter after pole magnetization. The level of preliminary magnetization that may be attained via pole magnetization without preliminary demagnetization of items is not determined. The strong dependence of test results on the variability of the gap between a sensor and an item in the case of one-way access to the item’s surface remains a significant problem for the method.

This paper discusses the application of fuzzy sets with dynamically alterable membership functions for automotive control systems. The proposed method covers the building of control algorithms based on fuzzy logic with adjustment of the input and output variable descriptions during the control object operation. An application of alterable fuzzy sets is considered by the examples of two variants for the control processes with the different persistence of fuzzy object. In the former case, the wheel slip control in an active safety system is investigated. The second solution is considered for monitoring of tyre/surface friction properties in Intelligent Transportation Systems (ITSs). The simulation results obtained on Virtual Proving Ground (VPG) illustrate theoretical aspects of the presented research work.

The physical-mechanical properties of polycrystals produced on the basis of ultrafine-dispersed diamonds (UDDs) at high static pressures with the use of thermal treatment in vacuum are investigated. The properties of the polycrystals are shown to depend on the sintering conditions and sintering technique, as well as on the modification of the starting powders. With the addition of metals (Co, Ti) to UDD powders, the mechanical strength of compacts increases, their structure improves, and their parameters can be optimized at lower thermobaric treatment temperatures. By studying the products of thermal treatment of UDDs in vacuum, it is established that the compacts and individual particles that form during thermal treatment differ significantly in microhardness.

BACKGROUND: Preceding studies of environmental and occupational risk factors of sarcoidosis yielded inconsistent findings. AIMS: We aimed to ascertain the occupational risk factors for sarcoidosis in a case-control study. METHODS: A total of 237 sarcoidosis patients with a histologically confirmed diagnosis were matched with 474 controls for sex and age (median 49, interquartile range 37; 60 years) recruited from the university hospitals and outpatient centres in Belarus, Kazakhstan and the Russian Federation. Ever and cumulative (considering years and hours per week) exposure to 24 occupational factors were analysed using logistic regression. RESULTS: In the overall sample of 711 subjects, 50% were females and any occupational exposure was more prevalent in cases compared to controls (60% versus 40%, P < 0.001). Current daily smoking as opposed to ex-smoking was associated with the lower risk of the outcome. Adjusted for smoking, age, sex and a few other exposures, ever-exposure to hay in agriculture (odds ratio (OR) 3.64 (95% confidence interval (CI) 1.26; 10.50)), engine exhausts (OR 2.94 (95% CI 1.14; 7.54)) and printing equipment (OR 1.66 (95% 1.03; 2.68)) was associated with sarcoidosis. The effect was also positive for cumulative exposure to hay in agriculture (OR 2.02 (95% CI 1.00; 4.07)), stone dust (OR 1.07 (95% CI 1.01; 1.14)) and engine exhausts (OR 1.18 (95% CI 1.03; 1.38)) and was stronger in never-smokers and subjects 40 years and older. CONCLUSIONS: Widespread occupational exposures may increase the risk of sarcoidosis, but further research is needed to elucidate the complex interplay of environmental and occupational factors in the epidemiology of sarcoidosis.

Abstract— The fatigue behaviour of a Ni‐Cr‐base powder flame‐spray coating on a 0.4% C steel is investigated. Fatigue tests were carried out using mild hour‐glass profile specimens. Cracks were detected and measured using plastic replicas and an image analysis system. Coated specimens showed a slightly lower fatigue endurance than plain specimens under torsion loading, while the opposite was observed for push‐pull loading. Microcracks in coated specimens invariably form at pores. Contrary to the usual case of stage I shear growth for a plain 0.4% C steel in tension or torsion loading, the coated specimens show initial crack growth from pores along directions perpendicular to the maximum tensile stress. The crucial behaviour of short cracks, and their growth rates, relative to the thickness of the coating, are discussed in some detail.

It is believed that materials based on ultrafine (nanoscale) diamond powders can possess high-level physical-mechanical and performance parameters characteristic of a nanocrystalline state. In certain cases, however, conventional methods for compacting ultrafine-dispersed diamonds (UDDs) fail and cannot be used to fabricate materials with desired properties. The difficulties associated with the ultrafine-dispersed state of the initial diamond powders can be surmounted by modifying the chemical and phase composition of the UDD surface. The possible use of UDDs as a catalyst that is conductive to the occurrence of chemical and phase transformations in certain substances at high pressures is analyzed. Sintering UDDs in the region of metastability of diamond makes it possible to produce porous polycrystalline aggregates with large specific surface area and very hard transparent particles.

The use of systematic approaches ensures significant development of the conventional methods of materials science and efficient use of these methods for objects having complex multidimensional structure, including nanostructured materials. The application of wavelet-based multifractal analysis and multidimensional physicochemical analysis for qualitative and quantitative description of material structures, which allows one to detect that differences that cannot be detected using other individual methods, is shown. The system characteristics of material structures are assessed. The self-organization processes in structures are characterized.

The structure of a Zr-2.5% Nb alloy after equal-channel angular pressing (ECAP) at 690–700 K and annealing in the temperature range 670–1070 K is investigated. The structure of the Zr-2.5% Nb alloy deformed by ECAP is an irregular grain-subgrain oriented structure with an enhanced dislocation density, a cross-section of 30–150 nm of oriented structural elements, and an equiaxed-grain (subgrain) size of 50–200 nm. Heating after ECAP in the temperature range 720–770 K for 3–5 h is proposed for the formation of an ultrafine-grained equilibrium structure in the ECAP deformed Zr-2.5% Nb alloy. Heating of the Zr-2.5% Nb alloy after ECAP at 723 K for 5 h leads to the formation of a predominantly equiaxial submicrocrystalline structure with a grain size of 150–500 nm. Equal-channel angular pressing of the Zr-2.5% Nb alloy increases the yield strength to 622 MPa, which is higher than that in the as-delivered undeformed state by a factor of 1.6. In this case, the relative elongation decreases. Heating of the ECAP deformed Zr-2.5% Nb alloy at 723 K for 5 h decreases the yield strength to 504 MPa, but the relative elongation increases to 14%.

The paper presents author's models and method for vehicle planetary transmission, which cover the stages of synthesis, kinematic, quasi-static and dynamic computations, dependability prediction and diagnostics of transmissions in operation process. The obtained data of the synthesis stage (block and kinematic diagrams, gear ratios of transmission mechanisms) are expanded at subsequent design stages with the ultimate goal of forming a complete information model (digital twin), allowing to support transmission design process and predict the behaviour of the transmission in operation. The emphasis is made on the developed original methods solving the most science intensive problems in the transmission life cycle.