Key Engineering Materials Vol. 910

Abstract: The work intends to study the microstructure, chemical and phase composition and homogeneity of chemical elements distribution in the Co-Cr-Fe-Mn-Ni high-entropy alloy produced via wire-arc additive manufacturing technology. The study has revealed three structure types in the alloy: (1) a smooth shagreen-type structure (an orange peel), which turns into a stripe-like structure (2) in some areas, and a grain structure (3) to appear as lengthy thin layers with the width of 50-80 μm and an average grain size of 12.5 μm, the most probable size of grains is detected to be in the range from 10 to 15 μm, a preferred number of such grains is 31%. The chemical composition of the produced alloy is assessed using X-ray microspectroscopy. The elements identified rank in descending order of concentration: Fe (38.88 wt. %), Co (26.08 wt. %), Ni (17.34 wt. %), Cr (14.33 wt. %), Mn (3.37 wt. %). The mapping of the alloy structure demonstrates the homogeneous and uniform distribution of chemical elements.

Abstract: In this work, the insulating properties of nitride coatings against the hydrogen penetration into semi-finished or finished products made of VT6 titanium alloy during hydrogenation annealing have been studied. It has been established that an increase of the duration of titanium nitride deposition for more than 30 minutes leads to the formation of pores and cracks in the coating and, as a consequence, to a decrease in the «protective» properties of such coating. It is shown that during linear gradient structure creation, the nitride coating effectively “protects” alloy from penetration of up to 0.5 wt%. of hydrogen.

Abstract: The paper describes the process of obtaining a high-density ceramic material based on magnesium aluminate spinel - material, which feature-wise will be lighter by mass of the used bullet-proof glass, and less resource-proof compared to modern ceramic armored. The sintering was carried out in a vacuum using a modifying gallium oxide additive to intensify the process. The effect of the additive concentration on the phase formation in the magnesium aluminate spinel-oxide gallium system, as well as the density and ceramics light transmission, is considered.

Abstract: The effect of Pb small additives on the microstructure and phase composition of palladium-based diffusion membrane-filters was studied in this work. In the present study, we comprehensively investigated the lead-containing palladium alloy by X-ray diffraction using synchrotron radiation and high-resolution scanning electron microscopy. The predisposition of the alloy to the formation of a conditionally homogeneous nanodisperse substructure with small values of micro-deformations is established. The stable preservation of the phase composition during a single hydrogenation is revealed.

Abstract: The authors investigated the effect of ultrasonic cavitation on the surface of St3, 20, 45 steels. It was found that cavitation causes a change in the structure and properties of the surface layer of the samples. A refinement of the grain and an increase in the microhardness of the surface layer similar for the investigated materials were revealed. The dependences of dynamics of the increase in microhardness under the action of ultrasound were given, which show that there was a steady state, characterized by an indicator of relative microhardness of 1.3...1.5. The results of changes in the parameters of roughness and sub-roughness were given. Studies showed that cavitation erosion leads to an increase in altitude and step parameters of the surface microgeometry. The research results can be used for development and creation of ultrasonic technological processes carried out in liquid media.

Abstract: In this paper, the algorithm for strength analysis of diaphragms made of elastomers is described, and the strength analysis of the diaphragm made of polyurethane "Vitur" T-1413-85 is carried out. The results obtained showed that the description of the material behavior using the Moony-Rivlin model (5 parameters) gives the greatest accuracy. A comparison of the results of modeling the stress-strain state of the diaphragm and the experimental studies carried out to determine the displacements confirmed the adequacy of the chosen model (average correlation coefficient between numerical simulation and experiment R² = 0.98) for both studied diaphragm thicknesses. The conducted evaluation of the diaphragm resource according to the criteria of fatigue failure showed the correctness of the selected models of durability.

Abstract: This paper presents the results of the studies on the effect of the surface tension of the intrapore liquid on the specific surface (S_BET) and pore volume (V_BJH) of hydrated aluminium oxide (HAO) obtained by treating aluminum potassium alum with ammonia. It has been found that replacing of water, the surface tension of which at the drying temperature is 57.87 mN/m, to acetone (13.19 mN/m) allows to increase both S_BET and V_BJH nearly 4 times. There are obtained equations, which connect specific surface area and specific pore volume of synthesized samples HAO with surface tension of intrapore area. It is found that in the initial presence of water in the aluminum hydroxide pores, the average pore diameter of the dried product is 3÷4 nm. Treatment of the synthesized sample with acetone increases the average pore diameter of the dried product to 5÷10 nm.

Abstract: In this work, studies have been conducted on the treatment of ultrahigh molecular weight polyethylene (UHMWPE), which is one of the structural materials used in the endoprostheses, with atmospheric pressure plasma in high-purity argon and helium. For this purpose, an installation consisting of a high-voltage pulsed generator, voltage and current measuring devices and a reaction quartz chamber with electrodes, in which UHMWPE samples were placed, was developed and constructed. It is shown that processing under certain conditions in Ar plasma and He at atmospheric pressure leads to the appearance of terminal double bonds in the structure of the processed polyethylene, as evidenced by the appearance of a peak of 880 cm^-1, in the attenuated total reflection IR spectrum. This peak is observed both for samples treated in helium and argon plasma. The formation of such bonds is a consequence of the generation of active radicals in the UHMWPE surface layer under plasma treatment, which, during recombination, also form intermolecular crosslinking, thereby increasing the strength characteristics of the material as a whole. The modification of the surface of the treated samples begins within the first minute of processing and reaches its peak values 10-20 minutes after treatment in plasma.

Abstract: The article investigates influence of large plastic deformations created in the Bridgman anvils on the mechanical properties and microstructure of metastable alloys of the iron-chromium-nickel system of the austenitic-martensitic class. It is found that the application of deformation in the Bridgman anvils with a true logarithmic deformation e = 6-7 leads to formation of the α-phase (deformation martensite) with significantly higher mechanical properties compared to martensite formed during deformation by linear rolling. The authors reveal the differences in the microstructure of the alloy after deformation in the Bridgman anvils and deformation by rolling, which explain the discovered effect.

Abstract: The diagrams of isothermal transformation based on kinetic curves R = (τ) for retained austenite in high-strength alloy low-carbon at overcooling have been built. It is shown that the temperature of quenching influences the stability at overcooling and resistance to isothermal transformation of austenite at sub-zero temperatures.