Electrospark alloying of titanium and its alloys, the physico-technical perspectives of its electrospark graphitization and corrosion resistance. Part 2
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GITLEVICH, A., MIKHAILOV, Valentin, VERHOTUROV, Anatolii, MIKHAILYUK, Alexei, KONEVTSOV, Leonid, KUDRYASHOV, A., KORNIENKO, L.. Electrospark alloying of titanium and its alloys, the physico-technical perspectives of its electrospark graphitization and corrosion resistance. Part 2. In: Materials Science and Condensed Matter Physics, Ed. 7, 16-19 septembrie 2014, Chișinău. Chișinău, Republica Moldova: Institutul de Fizică Aplicată, 2014, Editia 7, p. 334.
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Materials Science and Condensed Matter Physics
Editia 7, 2014
Conferința "Materials Science and Condensed Matter Physics"
7, Chișinău, Moldova, 16-19 septembrie 2014

Electrospark alloying of titanium and its alloys, the physico-technical perspectives of its electrospark graphitization and corrosion resistance. Part 2


Pag. 334-334

Gitlevich A.1, Mikhailov Valentin1, Verhoturov Anatolii1, Mikhailyuk Alexei1, Konevtsov Leonid2, Kudryashov A.3, Kornienko L.4
 
1 Institute of Applied Physics, Academy of Sciences of Moldova,
2 Institute of Materials Technology, Khabarovsk Research Centre under the Far Eastern branch of the Russian Academy of Sciences ,
3 Moscow State Institute of Steel and Alloys,
4 A.N.Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Science
 
Disponibil în IBN: 23 martie 2019


Rezumat

This report is associated with the work published previously under the same title in the journal “Surface Engineering and Applied Electrochemistry”, 2013, vol. 49, no. 5, pp. 21-44, and its first part is dedicated to the graphite electrospark alloying (ESA) of titanium.  The regularities of electric erosion of the electrode materials and the mass transfer of them from anode to cathode are studied in this report. There is found an effect of a significant erosion of the titanium cathode  at which the mass transfer has the negative sign. The mechanism of this phenomenon is considered from the point of view of the donor and acceptor activity of the interacting materials. It is noted that the appearance of the erosion  of titanium substrate should be taken into account when the workpieces of titanium and its alloys are processed. Alternative methods using ESA are proposed to eliminate this effect. It has been established that the graphite ESA of titanium is accompanied with some phase and structural transformations within the surface layers of the cathode-workpiece; it is possible the formation of carbides, carbonitrides, titanium oxides and saturation of near-surface layers with free graphite ensuring high performance characteristics of the surfaces of titanium workpieces.  Using the process of the graphite ESA of titanium it is simply sufficient to perform some targeted changes of the roughness of surfaces. As graphite  in a free state is an effective solid lubricant material there have been developed some ESA methods to produce (when absent) and increase (when present) free graphite in the surface layers of the titanium  substrate. It is substantiated analytically on the basis of the known thermodynamic calculations and experimental data obtained at interaction of materials in the T-C-N-O system that it is possible  to control the quantity of free graphite in the surface layer of titanium at ESA.  The study of the structure and properties of two-layer coatings on titanium alloy applied by SHS-electrode material (the first layer) and a number of carbon-bearing electrodes on the basis of artificial graphites (the second layer) has shown the efficiency of the secondary electrospark treatment from the point of view of the increase on wear resistance  (more than tenfold), halving of the friction coefficient and decrease in the oxidation rate within the range of tC ~ 400...800.   Under certain conditions and parameters of the graphite ESA of titanium and its alloys there are formed some coating on its surface which have an amorphous or likely structure. Such structures have a high corrosion resistance. The experimental investigations of the coatings produced at the  MPG6 graphite ESA of VT1-0 titanium permitted the increase in its corrosion resistance by almost 3 orders of magnitude in 5 H.H2SO4 at 80 C.  A high corrosion resistance (by 2-5 orders of magnitude) in chloride-alkaline media, in river and sea water, in media at cathode protection (ground) and so on demonstrated the coatings formed on titanium substrates at the nickel ESA (under the conditions of the synthesis of intermetallide Ti2Ni, palladium, as well as the Ti-C-Ni system).  The most important result of these investigations consists in the fact that in this case the electrochemical mechanism of anticorrosion protection has been realized which is the most efficient at the cathode modification being passive when the (Ti) basis is used.