StatusThe thesis was presented on the 6 June, 2008
Approved by NCAA on the 18 September, 2008
Abstract– 0.51 Mb / in romanian
1.95 Mb /
In the dissertation work complex studies of electric-spark doping (ESD) under influence of external energy sources are carried out.
There is developed a method for electric-spark doping of metal surfaces at application to the zone under treatment of a magnetic field with the induction of 0-0,1T and at passing of the electric current with the density of 0,5-4,0 A/mm2 and the pulse one with the amplitude of 100-600 A.
There is designed experimental equipment with automated system of the interelectrode space maintaining with a special electrode tool imparting a complex movement to the treating electrode (anode): rotation + vibration + oscillation. A special equipment for the magnetic field application to the zone of electric-spark doping is prepared.
Dependences of mass transfer and intensity of the covering layer formation on the cathode on value and kind of the electric current passing through the electrode volumes as well as on value of induction of the magnetic field applied to the doping zone are found. The greatest transfer of the anode eroded material and correspondingly the cathode mass increase were obtained when the constant current with the density of 1-3 A/mm2 and the pulse one with the amplitude of 200-500 A passed through the cathode and when the magnetic field with the induction of 0,01-0,1T was applied to the ESD zone.
The effect of quasi-polar oscillation of intensity of the anode erosion mass transfer in the spark discharge and structural-phase transformations in the cathode surface layers under the influence of the magnetic field applied to the ESD zone is found. The dependence of intensity of the covering formation on the cathode on magnetic properties of treating electrodes and substrate is revealed. It is shown that other things being equal, at ESD of the substrate of steel St.3 by nickel electrode in the magnetic field, the intensity of the erosion mass transfer in unit time is 3,5-4,0 times higher than at treatment by silver electrode.
In the surface layers of titanium substrate at ESD by nickel anode in the mode of the discharge energy 1,0 J and the induction value 0,07T the material amorphisation effect is found. There is optimized the angle of the treating electrode inclination to the treated surface whereat the greatest transfer of the anode material and the most intense formation of covering on the cathode take place. This angle makes up 8-12 degrees.
In all the cases the magnetic field application to the ESD zone promotes increasing of wear resistance and electric conductivity. Depending on the material nature they may increase within 15-78%.
There is developed a combined method for formation of strengthening coverings by combining of ESD and chemical-thermal treatment in electrolytes into a single technological process allowing significant (2-3 times) increasing of the strengthening zone and hence the resource of obtained coverings.
Results of the studies were used for development of the process of strengthening of titanium pieces and specialized installation for its realization in plants “TOPAZ” and “HIDROTEHNICA”, Kishinev.
The work was carried out in accordance with special-purpose complex programs 01.06.02 F. "Studying of the process of formation of macroscopic inhomogeneous surfaces and development on this basis of methods for control of processes in metals and semiconductors with the purpose to create new technological processes"; 01.08 "To develop new methods of formation and deposition of strengthening coverings and to improve the existing ones" (Decision of the Government of the Republic of Moldova of 14.04.1992) and in accordance with the Program of scientific-research works for 1986-2000 "Development of technology and equipment for strengthening and treatment of metal surfaces by electrophysical methods" (Approved by the Decision of the Government of the RM N 180-d of 15.05.1986).