No 1 (2023)

The electrochemical behavior of tungsten and the VNZHK alloy (wt. %: W 90; Ni 7.2; Fe 1.8; Co 1) in solutions of (0.5—1.5 M) ammonium carbonate was investigated by linear voltammetry in a potentiodynamic mode. An increase in the maximum anodic density of the oxidation current of tungsten and the VNZHK alloy was revealed with an increase in the ammonium carbonate concentration. The process of electrochemical dissolution of the VNZHK alloy waste in a 1.0 M solution of ammonium carbonate was investigated by galvanostatic electrolysis, as well as electrolysis under the action of a sinusoidal alternating current of industrial frequency. The advantage of alternating use of direct and alternating currents is justified. It has been established that during the processing of the VNZHK alloy waste under the alternating action of direct and alternating currents, the transition of tungsten from the alloy to an ammonium carbonate solution is accompanied by the concentration of the iron subgroupmetals in the microdisperse sludge of electrolysis. A basic technological scheme for the tungsten extraction from the heavy tungsten alloys waste with the production of ammonium paravolframate as the final product is proposed.

The possibility of increasing the filling degree of open pores with aluminum melt during the impregnation of carbon-graphite material by applying metal-galvanic film coatings to its surface is investigated. Two types of electroplating coatings are used - nickel and combined coating consisting of copper and cadmium layers. Impregnation of the coated samples was carried out using autoclave-free technology in a special impregnation chamber.  It is shown, that metal-galvanic coatings contribute to a lighter flow of aluminum melt into the pore cavity, providing a full-fledged impregnation of carbon-graphite material with a matrix alloy at reduced temperature (≤ 900°C) and pressure (3-5MPa). 

Numerical simulation of unsteady processes during laser butt welding of a plate made of porous titanium and a monolithic (non-porous) titanium plate is performed. The influence of the laser beam position relative to the welded surfaces on the quality of the resulting joint and the geometric seam characteristics is considered. The calculated welded joints parameters of porous and monolithic plates are in satisfactory agreement with the physical experiments results.

The technological influence effectiveness of plasma flows on the treated surface of 30HGSA steel during electric arc vacuum ion-plasma (EVIP) treatment was evaluated by measuring the surface relief, volt-ampere characteristics, the values of the surface potential, as well as using short-term corrosion tests to experimentally determine the chemical activity of the surface. It is established that when treated with an independent gas discharge with an increase in the reference voltage, the surface cleaning efficiency increases, however, the distortion of the relief and the  energy state heterogeneity of the surface increase. It is shown that when processing using the "Plugus" module, high cleaning efficiency and activation are achieved
surfaces with a moderate level of relief distortion and a more uniform energy
state of the surface. As a result, a reproducibility higher level of the service properties of coatings is provided.

The results of studies of the structural-phase state of copper and tin mixture powders (12-20 wt.% Sn), formed during high-energy mechanical processing in a planetary ball mill, are presented. The effects of mechanochemical synthesis of composites during sintering and formation of the structure of sintered bronzes are considered. The relationship between the tin content and the formation of grain-boundary segregations and their influence on the properties of materials is shown. Thus, an increase in the concentration of tin contributes to the acceleration of grain-boundary interactions, a decrease in the rate of bulk diffusion, followed by the formation of supersaturated bulk and grain-boundary solid solutions. For the composition of the mixture with a tin content of 18-20 wt.% during mechanochemical synthesis, grain-boundary supersaturation with tin is achieved by more than 2 times, which contributes to dispersion strengthening of sintered materials based on them and provides microhardness within 2.1-3.0 GPa in a temperature range of 20-800 °С.

The paper demonstrates a technique that combines the use of artificial intelligence and the finite element method to analyze the production process of the liner – the seamless part of composite overwrapped pressure vessels obtained by tube forming. Instead of expensive physical experiments, computer simulation was used, which made it possible to quickly obtain "big data", including the main technological parameters of tube forming process, some metal flow features and the tendency for defects to appear. The processing of the data array was carried out in MATLAB using neural networks and a genetic algorithm for the multi-objective optimization problem. As a result, the influence of technological parameters on the formation of the liner geometry was determined, and the optimal variant of their manufacture was proposed, which is of practical interest to companies producing metal-composite cylinders.