Alexander A. Burkov

Investigation of WC-Co Electrospark Coatings with Various Carbon Contents

Electrospark deposition was employed to clad WC-10%Co, W/C1.6-10%Co, and W/C0.5-10%Co hard alloys on steel 1035, and the tribological properties of the coatings obtained were examined. The influence of the W/C ratio in the electrode materials on the decarburization of tungsten carbide was studied. It is shown that the degree of tungsten carbide degradation can be reduced by increasing the concentration of carbon in the WC-Co electrode materials, and also that the WC decarburization reaction is reversible on annealing. Coatings deposited using new electrode materials with an excess of carbon (W/C0.5) and/or tungsten (W/C1.6) have increased microhardness and improved frictional characteristics compared with the conventional coating.

Formation of electrospark coatings of the VK8 hard alloy with the Al2O3 additive

The results of studying the formation of coatings by electrospark alloying with the use of an electrode material based on the VK8 tungsten-containing alloy with the addition of an aluminum oxide nanopowder are presented. It is shown that introducing Al2O3 into the hard alloy promotes an increase in the mass transfer coefficient, microhardness, and wear resistance of the formed coatings. The duration of electric discharges exerts a significant effect on the phase composition of the alloyed layer.

Optical characteristics of particles produced using electroerosion dispersion of titanium in hydrogen peroxide

Titanium oxide particles are produced using electric-discharge dispersion of titanium in aqueous solution of hydrogen peroxide. Electron vacuum microscopy, X-ray diffraction, and diffuse reflection spectroscopy are used to study the morphology, composition, and optical characteristics of the erosion particles. It has been demonstrated that the particles consist of titanium and titanium oxides with different valences. The edge of the optical absorption is located in the UV spectral range. The band gap is 3.35 eV for indirect transitions and 3.87 eV for direct allowed transitions. The band gap decreases due to the relatively long heating in air at a temperature of 480–550°C, so that powder oxide compositions can be obtained, the optical characteristics of which are similar to optical characteristics of anatase. The erosion products are completely oxidized to rutile after annealing in air at a temperature of 1000°C.

The use of titanium aluminides to form electric-spark coatings

Titanium aluminides (TiAl3, TiAl, Ti3Al) fabricated by powder metallurgy were used as alloying electrodes for the formation of electric-spark coatings. Intermetallic coatings were deposited on steel substrates in argon or nitrogen. The microstructure and composition of fabricated coatings were investigated by scanning electron microscopy, X-ray structural analysis, and electron probe microanalysis. It is established that initial Ti–Al intermetallic phases are present in fabricated coatings; however, the ratio between Ti and Al concentrations is shifted to aluminum compared with the stoichiometric one. When depositing titanium aluminide in the nitrogen medium, titanium nitride is additionally formed in surface layers. Thermal and tribotechnical tests showed that the Ti3Al coating deposited in nitrogen possesses high wear resistance and heat resistance.

Hydrothermal synthesis of TiO2/WO3 compositions and their photocatalytic activity

Photocatalytic activity, optical properties, thermal stability, phase patterns and morphology of nano-size ТiО2/WO3 compositions obtained from organic precursors through hydrothermal synthesis have been studied. It has been shown that doping of anatase nanoparticles with tungsten W+6 results in particle diameter reduction from 35 to 10 nm; decrease in width of the band gap from 3.15 eV to 2.91 eV and increase in temperature of phase transition of anatase to rutile up to 980оС. Catalytic activity of ТiО2/WO3 (4 mol.%) composition under photochemical methylene blue (MB) oxidation by simulated solar light exceeds that of undoped anatase (obtained in the same way) 6-fold.

Tungsten Carbide Decarburization by Electrical Discharges

Electrospark deposition (ESD) was employed to clad WC-10%Co hard alloy on steel 1035 and the tribological properties of the coatings obtained were examined. The influence of the duration and frequency of discharges, the nature of the environment, and the carbon concentration in the electrode materials on the decarburization of tungsten carbide was studied. It is shown that the degree of tungsten carbide degradation can be reduced by decreasing the discharge frequency and increasing the concentration of carbon in the WC-Co electrode materials and also that the WC decarburization reaction is reversible on annealing.