E. I. Zamulaeva

Specific features of formation of nanostructured electrospark protective coatings on the OT4-1 titanium alloy with the use of electrode materials of the TiC-Ti3AlC2 system disperse-strengthened by nanoparticles

The effect of nanodispersed additives of ZrO2, Al2O3, NbC, W, WC, and WC-Co into the composition of the TiC-Ti3AlC2 electrode on the kinetics of formation of coatings by electrospark doping (ESD) on the titanium alloy of the OT4-1 grade on varying the duration of pulsed discharges in a wide range is investigated. The structure, phase composition, properties (continuity, thickness, microhardness, friction coefficient, wear resistance, and heat resistance) are investigated. The optimum energy mode of the ESD treatment of the OT4-1 titanium alloys by new electrode materials is determined. It is found that the introduction of a nanodispersed component is favorable to an increase in continuity and the microhardness of electrospark coatings and a substantial increase in wear resistance and heat resistance of titanium alloys.

Influence of production parameters of sintering on the structure and properties of VK5 hard alloy made of tungsten carbide SHS powder

The features of sintering of the WC-Co hard alloy of the VK5 brand using the feedstock of tungsten carbide powder fabricated by self-propagating high-temperature synthesis (SHS) are investigated. It is established that the physicochemical processes occurring when sintering hard alloys are similar to sintering processes of standard alloys made of traditional tungsten carbide powders. The hard alloy produced in this study possesses high hardness, strength, and crack resistance, which are characteristic of quasi-nanocrystalline materials.

Features of formation and the structure, composition, and properties of electrospark coatings on the ZhS6U nickel alloy with the use of the KhTN-61 SHS-Ts alloy

Features of the mass transfer of a KhTN-61 SHS-Ts electrode material onto a substrate of a ZhS6U nickel alloy with a variation in frequency (1000–1400 Hz) and time (25–70 µs) of pulsed discharges was studied. A complex of studies of the structure, composition, and properties of the formed coatings was carried out. The optimum frequency-energetic mode of the treatment (E = 0.30 J, f = 1000 Hz, and τ = 50 µs), which was characterized by a high rate of coating at a satisfactory degree of the roughness of the surface layer, is found. As a result of electrospark alloying (ESA) at the optimum energetic parameters, 40-µm-thick coatings with a uniformity of 95% and a microhardness of 5.2 GPa form on the surface of the nickel alloy. The ESA treatment of a ZhS6U nickel alloy with the use of KhTN-61 SHS-Ts electrode material allows us to enhance its wear resistance (by more than a factor of 10), hardness (by a factor of 2), and heat resistance, as well as to decrease (by a factor of 5) the friction coefficient.

Formation processes, structure, and properties of spark coatings of armco iron obtained with the use of nanostructured and microstructured WC-Co electrodes

Nanostructured and microstructured electrode materials of the composition 92%WC-8%Co were used for deposition of spark coatings on Armco iron upon variation in the energy of pulsed discharges in the range from 0.01 to 1.2 J. Physicochemical processes on contact surfaces are considered during operation by both types of electrode pairs, namely, in the forming coating of the cathode substrate and in the secondary structure of the anode electrode. It is found that the main phases in coatings are the amorphous phase and tungsten semicarbide W2C. In the case of a nanostructured electrode, an increase in the energy mode above a certain threshold value leads to an increase in the fraction of crystalline phases and to the formation of a structure consisting of submicron W2C/WC grains surrounded by an amorphous binder. With the use of a microstructured electrode, the fraction of the amorphous phase in coatings prevails in all energy modes. The use of nanostructured electrodes in the technology of spark treatment of substrates made from Armco iron is expedient only at a pulse energy of <0.23 J.

Composite SHS materials based on titanium carbide and nikelide doped with a refractory component

This study is devoted to the synthesis and investigation of composite ceramic materials based on titanium carbide and nickelide with the use of the effect of dispersion strengthening by force of the dedicated alloying of reactionary mixtures with a nanodispersed refractory component. The influence of nanodispersed particles on the main combustion parameters in conditions of quasi-isostatic compression is shown. The phase composition and the structure of compact synthesis products, in which the main phase components are TiC and the TixNiy intermetallic compound, are investigated. It is established that doping with a nanocomponent does not vary the phase composition qualitatively but leads to a substantial modification of the structure of the materials, at which the average grain size of the main refractory component decreases by a factor of 1.5–3.5. In addition, a similar effect is observed with a decrease in the TiC concentration in the composition of the samples. Complex investigations into the physicomechanical properties and heat resistance of fabricated materials are performed. The effect of the positive influence of refractory nanoparticles on such characteristics of alloys as hardness, strength, Young modulus, and durability to high-temperature oxidation are shown.

Formation of protective coatings on steel Kh12MF by the force of the sequential electric spark treatment by boride and carbon-containing electrodes

Coatings on steel Kh12MF are fabricated by the force of electric-spark treatment by the TiB2-20% NiAl electrode and carbon-containing materials. Kinetics of their formation, the phase composition, mechanical and tribological properties, roughness, and durability to high-temperature oxidation are investigated. When depositing the coating using the TiB2-20% NiAl electrode, the effect of a disproportionate increase in the substrate erosion, which is observed with an increase in the energy of a single pulse and leads to lowering the content of boride phases in the coating is discovered. The subsequent electric-spark treatment of the boride coating using an electrode made of fine-grain dense graphite led to a noticeable improvement of tribological properties of the coating having no noticeable effect on its durability to high-temperature oxidation. In the case of applying an electrode made of the silicicated composition material, the coating durability to high-temperature oxidation increased substantially, but no improvement of tribological properties was observed.

New Multifunctional FGM Coatings Produced Using ESA and TRESS Methods

The influence of nanodispersed complex additives (ZrO2, Al2O3, W, WC, WC-Co, NbC, Si3N4) to SHS electrode materials on the mass transfer, structure and properties of electrospark coatings has been considered dependent on variation of the energy regimes of processing. The influence of the pulse discharge energy on the structure, composition, and properties of TRESS coatings has been studied. The optimum energy regimes of depositing high-quality multifunctional graded ESA and TRESS coatings have been found. It has been shown that introduction of nanodispersed complexes into electrode materials promotes improvement of the properties of ESA coatings.