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

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.

The impact of current shape during consolidation of Fe – Ti – C – B system materials on the physio-mechanical properties of obtained specimens is studied in present paper. It is experimentally found that the use of method of decrease of voltage surge on output Schottky diodes of SPS device and the decrease of operation time of overcurrent protection in power circuit of SPS generator allowed changing current harmonic composition which lead to an increase of properties of consolidated Fe – Ti – C – B specimens – porosity decreased from 15.8 to 2.8 %, hardness increased from 50 to 55 HRC, loss of mass during abrasive wear decreased from 2 to 0.5 mass. %, and bending strength increased from 750 to 1500 MPa. It is found out that increase of input power during consolidation from 1.3 to 7.5 kJ/s by changing current harmonic composition leads to an increase of physico-mechanical characteristics of Fe – Ti – C – B system metalmatrix composites. Density of consolidated specimens increased from 75 to 95 %, their hardness increased from 35 to 50 HRC, loss of mass during abrasive wear decreased from 10 to 1 mass. % and their bending strength increased from 400 to 1100 MPa.

The present work is devoted to analysis of relations between the physical, mechanical properties and microstructure of the material produced by spark-plasma sintering (SPS) of bimodal copper powders. The used starting powders were bimodal mixtures of nano- and micro-sized copper powders, including the pre heat treatment of these powders in a hydrogen atmosphere. As a result, it was studied the influence of sintering parameters on the final density, microstructure and mechanical properties of bimodal copper sintered compacts. It was also produced a comparison of physical and mechanical properties of sintered samples obtained by SPS and by hot pressing (HP) from these bimodal copper powders.