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Journal of Physical Studies 24(3), Article 3501 [8 pages] (2020)
DOI: https://doi.org/10.30970/jps.24.3501 CREATION OF NANOSTRUCTURAL CARBIDE COATINGS ON MATERIAL SURFACES USING PRODUCTS OF REFRACTORY WIRE ELECTROEXPLOSION
L. Z. Boguslavsky
Institute of Pulse Processes and Technologies, NAS of Ukraine,
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A series of electric explosions of single wires and bunches of copper, titanium and tungsten in propane-butane was carried out and the respective time dependencies of voltage and current were analyzed. The products of the exploded refractory metals and their chemical compounds with carbon, deposited in the form of coating on a structural surface, were investigated by means of optical and scanning electron microscopy and X-ray diffractometry. The process of resistive heating of Cu is characterized by a sharp, and, most importantly, monotonous increase in voltage to a peak value while the voltage curves of Ti and W are characterized by the formation of a flat plateau followed by a peak of overvoltage slightly lower than the one for Cu. These features are due to the difference of the resistivity and the temperature coefficients of resistance in the liquid state for refractory conductors and high-conductive Cu, which can absorb during resistive heating 1.5-2 times more energy accumulated by the condenser than Ti and W. Relatively thick bunches of tested metals (twisted wires 0.3 mm in diameter) explode with the energy deposition that does not exceed the sublimation energy, and form liquid metal microdrops and agglomerated spherical particles less than 100 nm in size. The presence of the electric arc may be due to the heterogeneous heating of the cross section of thick bunches, as compared to a single wire, and the development of electroemission from the surface of the refractory conductors. The study of the obtained coatings shows that an increase in the energy input into Ti and W during the resistive heating, which can be realized either by changing the parameters of the electric circuit, or by the electro explosion of conductors insulated with dielectric varnish, is conducive to the formation of different carbides, in particular, stabilized high temperature carbide phases, to reducing the amount of pure metal in the coating, reducing the average particle sizes of destroyed conductors and to smoothing the surface relief of the coating. The calculated mass balance of the system reveals that the weight of the coating increases in proportion to the number of electroexplosions, despite the fact that a certain quantity of destroyed electric wires does not participate in the formation of the coating and falls to the bottom of the reactor as powder. The mass growth of the coatings composed of the Ti and W destruction products is determined by the sublimation energy and the density ratio of pure metals and carbide phases provided the same modes of wire electroexplosion and the uniform geometry of conductors.
Key words: electric explosion of the conductor, refractory metals, precipitated energy, sublimation energy, carbides, coatings.
