International Scientific Journals
of Scientific Technical Union of Mechanical Engineering "Industry 4.0"

A novel two-stage approach for obtaining wear-resistant multifunctional powder composites based on metal powders with highmodulus Ti–TiC system fillers is proposed. The method combines high-voltage electric discharge (HVED) treatment and spark plasma sintering (SPS), offering a promising alternative to conventional techniques for producing Al–Ti–C system composites. This approach enables the development of a unified route for material synthesis using high-energy-density processing. HVED treatment prevents oxidation of metal particles, reduces contamination by tool materials, and initiates the synthesis of additional dispersed strengthening phases. For example, HVED treatment of titanium powder in a hydrocarbon liquid promotes the in situ formation of titanium carbide (TiC) particles.
The present work investigates the influence of adding Ti–TiC powder—synthesized via HVED in ethanol under reverse polarity mode with a specific energy input of 20 MJ/kg—on the structure, phase composition, and properties of Al–Ti–C metal matrix composites (MMCs). It was shown that the addition of 2 wt% of Ti–TiC powder synthesized via HVED in ethanol to aluminum powder results in an MMC with an electrical resistivity of 0.5 Ω·mm²/m and a hardness of 31 HRB. However, the heat resistance of this composite is 2.5 times lower than that of consolidated pure aluminum powder. Increasing the Ti–TiC content to 10 wt% leads to the formation of a wear-resistant Al–Ti–C composite, whose structure includes Al, Ti, TiC, the intermetallic compound Al₃ Ti, MAX phases Ti₂ AlC and Ti₃ AlC₂ , and free carbon. For the MMC sample with the addition of 10% Ti–TiC, the mass gain per cycle during the heat resistance test is 0.23%/cycle, whereas for samples made from consolidated Al powder it is 0.18%/cycle, indicating that their heat resistance is approximately the same. The wear resistance of this composite is more than three times higher than that of the consolidated base aluminum powder, with wear rates of 0.003 g/km and 0.010 g/km, respectively. This material also demonstrates a hardness of 43 HRB and relatively low electrical resistivity at the level of 0.3 Ω·mm²/m.

Studies of the impact of high voltage electric discharge (HVED) treatment on the dispersion and phase composition of 87,5 % Al + 12,5 % Cu powder system were performed. It was shown that HVED treatment in ethanol with specific treatment energy of 5 MJ/kg leads to the decrease of mean diameter of treated powder from 15 to 11 μm, and the increase of specific treatment energy to 20 MJ/kg leads to the decrease of mean diameter of treated powder from 15 to 6 μm. X-ray diffraction analysis shows that CuAl2 and Al4C3 are synthesized in all considered treatment regimes, and the quantity of these phases depend on the specific treatment energy.
The use of “three point – plane” electrode system instead of “point – plane” during HVED treatment of 87,5 % Al + 12,5 % Cu powder system in ethanol leads to the increase of quantity of synthesized Al4C3 and CuAl2 phases with the slight decrease in the dispersion efficiency.
Up to 35% of particles in powder mixture, treated by HVED in ethanol with the use of “three point – plane” electrode system, have diameter close to the diameter of the initial powder mixture.
It is shown that the preparation of powders with an initial composition of 87.5% Al + 12.5% Cu using HVED treatment in kerosene or ethanol with subsequent consolidation by SPS method allows obtaining metal-matrix composites of the Al – Cu – C system with increased indicators of hardness, electrical conductivity and wear resistance.

The impact of industrial frequency (50 Hz) current with the voltage of U = 10 V while using the Field Activated Pressure Assisted Synthesis (FAPAS) method as well as the impact of superposition of direct and alternating (with 10 kHz frequency) currents with the voltage of U = 2 V while using Spark Plasms Sintering (SPS) method on the phase composition, structure and properties of Ti-Al-C system metal-matrix composites, consolidated from the powder mixtures, prepared by high voltage electric discharge, is experimentally studied. It is shown, that using SPS and FAPAS methods allows synthesis of materials, dispersion-strengthened by phases of TiC and Al4C3 carbides and Ti3AlC2 MAX-phase. It is found out, that using FAPAS method allows obtainment of Ti-Al-C system composites with higher values of density, hardness and wear-resistance, than those of materials obtained by SPS due to more homogeneous structure. Such a differences can be explained by the fact that high frequency (10 kHz) current component promotes movement of disperse phase inside the matrix, which leads to the agglomeration of strengthening particles as well as to increase of obtained composite porosity up to ~ 8 %.

The features of the structure formation of Al-Cu and Al-Cu-C materials under conditions of spark-plasma sintering under conditions of superposition of a direct and pulsating current at a temperature of 600ºC and a mechanical pressure of 60 MPa are studied. The obtained Al-Cu-C system materials with hardness from 400 to 1000 MPa, porosity from 3 to 1% are recommended for use as slip contacts, and also as antifriction materials in friction pairs either in dry (carbon-containing composites) or wet friction (composites not containing carbon).

The functional parameters of lead magnesium niobate PbMg1/3Nb2/3O3 (PMN) and materials based on it make it possible their use as elements of precision motion devices. Nevertheless, it is necessary to increase the time stability of these parameters. Here, the ceramic (1-x)PMN-xPbTiO3 (PMN-PT) was sintered by the spark plasma sintering method (SPS), which, in contrast to traditional sintering methods, allowed to reduce the sintering time and temperature and to obtain fine-grained ceramics with high and stable piezoelectric parameters. The preparation technology of ferro-piezoceramic material PСR-1 needs to be improved, in particular, it is necessary to increase the density of its ceramics. It is shown that the use of ultrasound as an additional influence on the process of mechanically activating of the initial powders on different equipment affects the density, piezo- and dielectric properties of mechanically activated PСR-1 ceramics and allows increasing its density by 10% and at the same time to low its sintering temperature.

The possibility of synthesizing the Ti3AlC2 and Ti2AlC MAX phases by SPS (spark-plasma sintering) consolidation of the charge obtained as a result of mechanoactivation and a charge obtained by HVED (high-voltage electric discharge) of processing titanium and aluminum powders in kerosene has been experimentally studied. The influence of the charge activation method on phase formation and physical properties of consolidated materials is shown.

Theoretical and experimental data on the impact of heating rate during spark-plasma sintering on densification kinetics, grain size and capillary pressure in powder compacts, based on Fe, are given. It is found out, that an increase of heating rate in range from 10 °C/s to 20 °C/s leads to acceleration of process of obtainment of non-porous compacts and decrease of structure grain size.

A complex approach to obtainment of titanium carbide hard metals, which consists of utilization of high density energy flows of high voltage electric discharges (HVED) for dispersion and activation of particles of powders mixture of 80 % Ti + 20 % Fe composition and synthesis of carbide phase and subsequent consolidation of obtained powders mixture by high density electric current with spark plasma sintering (SPS) method. Connection between specific cyclic energy of treatment of “kerosene – Ti + Fe powders mixture” disperse system and changes of dispersity, shape and phase composition of powders and physical and mechanical properties (hydrostatic density, hardness, thermal conductivity, wear resistance, dynamic strength) of materials consolidated from them is found. Tungstenless titanium carbide hard metals, which have high specific values of strength and wear resistance, hardness of which is higher than 82 HRA, and thermal conductivity of such materials is insignificantly lower than thermal conductivity of VK6 alloy, were obtained

Investigated was the spark plasma sintering (SPS) of β-SiAlON/0–30 wt % BN ceramic composites. The raw materials (β- Si₅AlON₇ and BN powders) were prepared by infiltration-mediated combustion synthesis (CS). Experimentally established were the following process parameters for SPS of composites with high relative density (>95 %) and flexural strength of 250–300 MPa: (a) heating rate 50 deg/min, (b) maximum temperature 1650–1750°C, (c) and holding time 5 min.

The purpose of this paper was to study the regularities of formation of ultrafine structure in alumina by magnetic pulse compaction (MPC) and spark plasma sintering, and the producing of nanostructured compacts having high density and microhardness. The combined application of two technologies magnetic pulse compaction and spark plasma sintering in the practice of compacting powders is very rare and unique. We have studied the microstructures of consolidated alumina samples. The anomalous zones present in volume of magnetic pulse compacted and spark plasma sintered samples of both types α and δ phases of alumina. The microstructure of the fracture surface between anomalous zones depends on the phase state of the particles of the initial powder. MPC of δ-alumina leads to a more uniform distribution of anomalous zones along diameter compact after SPS. MPC of α-alumina leads to an increase of the microhardness on the surface of compacts.

Prospects for creation of plasma electric discharge technology for production of dispersion-hardened by nanoparticles composite materials are considered. Physical modelling of plasma formations distribution in discharge camera is performed. The regularities of the electric discharge processing parameters influence on dispersity, phase composition and electrical resistivity of obtained powders are studied. The regime for spark plasma sintering of processes powders is theoretically and experimentally justified.

Review of pulses discharge technologies (PDT), in which pulses electric discharge in liquid is utilized, is given. PDT of processing and obtainment of new materials allows to impact both changes of geometrical size and the structure of objects in order to give it certain mechanical and physical properties. They are used in oil production, instrumentation, mechanical engineering, metallurgy, chemical industry, mining complex, and other.