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 possibility of high energy synthesis of Ti–Al–C system powder grain refiner by using high voltage electric discharges for treatment of powder mixtures of 75 % Ti + 25 % Al and 85 % Ti + 15 % Al composition in kerosene with subsequent briquetting by spark plasma sintering is shown in present work. It is found out that high voltage electric discharge treatment of powders leads to the increase of dispersity as well as to synthesis of new carbon containing phases during chemical interaction between system components and products of working hydrocarbon liquid destruction. The possibility of controlling this process by changing initial composition of powders, specific treatment energy and spatial distribution of plasma formations by changing electrode system type is shown. It is also shown that changing master alloy synthesis parameters allows controlling inoculation efficiency. Thereby it is possible to achieve surface or volumetric inoculation, so selective increasing of plastic or strength properties of Ni-based cast superalloys becomes possible. Introduction of 0.01 % of synthesized grain refiner during the casting of SM88U (СМ88У) superalloy allows decreasing mean grain size from 1…2 mm to 0.2…0.5 mm. Tensile strength of inoculated superalloy at the temperature of 900˚С was 68 MPa while their stress rupture strength increased by 20 % in average. Composition and properties of inoculated alloys comply with standard technical documentation, which allows their usage for the
production of gas turbines blades.

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.

The possibility of control of efficiency of different factors of high voltage electric discharge (HVED) impact on Ti – Al – С powders system for aimed synthesis of dispersion-hardening components is shown. Nanolaminate-composite Ti₃AlC₂ – TiC with hardness of HV5 = 7 GPa, obtained by consolidation of blend of 85 % Ti + 15 % Al initial composition after HVED with the use of multi-point electrode system has needle structure of Ti₃AlC₂ (a = 0.3068 nm, c = 1.844 nm) with size up to 10 μm, and TiC dispersion-hardening phase (a = c = 4.4331 nm) with particle size no more than 1 μm is situated between grains of Ti₃AlC₂. Dynamic strength of specimens depending on electrode system used during HVED treatment of blend variated in range from 160 to 620 MPa, Young modulus – from 13 to 22 GPa at deformation rate from 600 to 900 s–1. Material has high levels of heat resistance, relative change of mass is no more, than 0.001.

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

Changes of dispersity, form factor and phase composition of powder mixtures of 75% Ti + 25% Al, 50% Ti + 50% Al, and 25% Ti + 75% Al mass compositions after treatment by high voltage electric discharge in kerosene are experimentally studied. Regularities of their dispersion and synthesis of TiC, AlTi₃, AlTi, Al₂Ti, Al₃Ti, double carbide Ti₃AlC, МАХ-phases Ti₃AlC₂ and Ti₂AlC, Lonsdaleite are found.

Peculiarities of titanium carbide obtainment by high voltage electric discharge synthesis (HVED) are considered in present paper. Mathematical and physical modelling of processes that occur during HVED impact on “Ti powder – hydrocarbon liquid” disperse system is performed. HVED creates thermodynamic conditions for pyrolysis of hydrocarbon liquid with formation of solid-phase carbon and gaseous hydrogen and for synthesis of titanium carbide during reaction of carbidization between titanium and carbon particles. Regularities of connection between HVED parameters and changes of dispersity and intensity of titanium carbide formation.

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.

A brief analysis of studies in field of metal-matrix composite (MMC) materials production with use of pulsed-discharge technology (PDT) is performed in present paper. It is shown that high voltage electric discharge (HVED) in liquid allows obtaining homogeneous highly disperse blend of complex chemical composition. Consolidation of blend by method of spark-plasma sintering (SPS) ensures preservation of grain size, which allows achieving high strength characteristics of MMC.