A. V. Paustovskii

Optimization of the composition, structure, and properties of electrode materials and electrospark coatings for strengthening and reconditioningof metal surfaces

The structure and phase composition of Ni-Cr-Al alloys doped with Si, Ti, Mn, and Co have been studied. An eutectic three-phase structure was found to be in the doped alloys. Doping with Si and Ti increases the microhardness and wear resistance of the alloys. The highest coefficient of the mass transfer (0.75) during the electrospark alloying is observed for Co-containig alloys. The coatings with the doped alloys have a higher wear resistance than those with the Ni-Cr-Al basic alloy. Steel 45’s heat resistance is increased after the electrospark doping with Si-, Ti-, Mn-, and Co-containing alloys by 4, 4.3, 5.1, and 4.6 times, respectively. The electrode materials have been developed for the electrospark reconditioning of workpieces based on PE8418 (Ni-Ni3B-Cu-Si) with the additions of titanium carbide, chromium carbide, and tungsten carbide, which make it possible to manufacture coatings up to 5-mm thick. The results of the investigation of the erosion properties of B4C-TiB2 alloys manufactured using the method of reactive sintering under hot pressing of B4C-TiO2 powder blends that were used as the electrode materials for the electrospark hardening of titanium surfaces are presented. The tests show that, in the surface layers of the electrode materials, under the impact of the electric discharge, the boron carbide content substantially decreased, while the quantity of titanium borides increased and new phases of TiCxNy, TiO2, and Ti appeared. Only these components are transferred onto the surface of the titanium alloy and form there a protective coating up to 100 μm thick with high hardness (32–43 GPa) and wear resistance. The materials developed are promising for their application as the electrodes in the electrospark alloying of construction steels and titanium alloys.

Modification of the structure and properties of Ni3B-based thick films by the action of laser radiation

The results of studying the influence of pulse laser radiation on the surface morphology and certain electrophysical properties of Ni3B-based thick films produced by screen printing of composite pastes onto a dielectric substrate are presented in this work. The action of nanosecond pulses promotes the size reduction of the conducting phase particles, whereas, under microsecond pulses, the distribution of the conducting phase remains the same on the whole surface. The irradiation with millisecond pulses at energies of E = 0.4–0.6 J results in the surface flowing. The current-voltage characteristics and the dependence of the electrical resistivity on the temperature are presented. Laser processing of the samples in the nano- and microsecond ranges is established to promote the work of resistors, according to the standard and technical conditions, when the I-U linear dependence is realized.

Effect of Pulsed Laser Radiation on the Properties of Resistive Thick Films Based on Nickel and Barium Borides

We have used atomic force microscopy to study the surface morphology of resistive thick films based on powders of nickel and barium borides and a glass binder, treated with laser radiation. We used x-ray phase analysis to study the phase composition of these films. We have observed a change in the surface morphology, the phase composition, and the electrical resistance of the studied films as a function of the laser radiation energy.

Electric-spark coatings on a steel base and contact surface for optimizing the working characteristics of babbitt friction bearings

It is found that the use of transition layers of copper, coated by the electric-spark method in a protective argon atmosphere, improves the heat removal from the contact area and increases the steel bases’ adhesion strength with an antifriction babbitt layer as compared with the traditional technology by 35%. Electric-spark alloying babbitt B83 by indium and stannum allowed us to form running-in coatings without hard inclusions with a thickness of 130 and 100 microns, respectively. New technological solutions allow decreasing the temperature in the friction zone, increasing the thickness of the oil layer, and, as a result, creating a bearing with a better load carrying capability and reliability.

ELECTRODE MATERIALS FOR COMPOSITE AND MULTILAYER ELECTROSPARK-DEPOSITED COATINGS FROM NI-Cr AND WC-Co ALLOYS AND METALS

The layer-by-layer electrospark deposition of Cu, In, Pb, Cd, and Sn group metals and Ti, V, and W metals, as well as their carbides and hardmetals of WC type, onto metallic surfaces is studied. This technique improves the quality and wear resistance of the surface layer compared to coatings without a sublayer. The sintered electrode materials containing 10–30 wt.% of the (Ni–Cr–Si–B)–WC6 alloy allow electrospark coatings with thickness up to 100 μm and microhardness 12.3–14.2 GPa to be formed. The wear resistance and service life of these coatings are substantially higher than of those made of standard hardmetal WC6. Among the Ni–Cr–Al alloys, the best effectiveness in worn-part recovery is shown by the alloy from the ternary eutectic region (50.3 wt.% Ni, 40.2 wt.% Cr, 9.5 wt.% Al), which may provide coating thickness up to 1.0 mm. The novel coating technique and proposed electrode materials increase the resistance of cutting tools and life of equipment parts.

Laser Treatment of Thick Films Based on Powder Composites of Nickel Boride

The thermophysical parameters (coefficients of thermal and temperature conductivity, coefficient of reflection of the laser beam) of resistive thick films (RTF) of powder composites based on Ni3B and glass were determined. Coefficients of thermal conductivity were calculated using the theory of general conductivity for a multicomponent system. The coefficient of diffuse reflection was calculated from the indicatrix of dispersion of the laser radiation. The parameters obtained were used to calculate the dependence of surface temperature of a thick film under the action of pulsed laser radiation on the duration and energy of the impulse and the radius of the laser spot.

Morphology and Hardness of a Steel Surface Layer after Electric-Spark Alloying with TiN ― Ni Alloys

Features of forming a coating surface with electric-spark alloying and TiN ― Ni alloy electrode materials are established. Analysis of coating morphology makes it possible to draw conclusions about the discrete nature of coating structure formation. Features of the interaction of deposited material with the anode due to changes in the phase composition and electrode structure are established.

Electrospark Graphite Alloying of Steel Surfaces: Technology, Properties, and Application

Regularities in the influence of processing time and discharge energy on the thickness, microhardness and roughness of carburized cases during electrospark graphite alloying of steel surfaces are studied and quantitative data on them are obtained. The thickness of the strengthened layer increases with gains in discharge energy and alloying time. Specimens of 40Kh, 38KhMYuA, 40KhN2MYuA, 30Kh13, Armco iron, 12Kh18N10T steels and 20 steel, as well as EGe-4 graphite are studied. The tests were carried out using the following devices: EILV-8А, EILV-9, Elitron-22А, and Elitron-52А, which provide discharge energy in the range from 0.1 to 6.8 J. Experiments show that case depth and microhardness under the same process conditions are differ significantly for various steel grades. Case depth increases with higher initial carbon contents in steel. The greater the discharge energy, the greater this difference is. Wear tests show that the method of nonabrasive ultrasonic finish processing after graphite electrospark alloying is effective, and it allows increases in the wear resistance of specimens by a factor of 7.8 for 40Kh steel and by a factor of 11.5 for 12Kh18N10T steel. Research confirms that the stage electrospark alloying of the surface of a specimen after carbonization with a graphite electrode effectively decreases roughness. Discharge energy is lowered at each stage. The stage graphite electrospark alloying of the 38KhMYuA steel case allowed decreases in the surface roughness from Rа = 11.9–14.0 μm to 0.8–0.9 μm. Industrial tests show that graphite electrospark alloying offers can accomplish a number of practical tasks.

Conductive Composite Materials Based on Thermally Stable Fluorine-Containing Polyamide and Binary Filler

The feasibility of producing “binary filler + polymer matrix” conductive composite film is demonstrated. The mixture of nickel boride and carbon nanofiber at various ratios is chosen as the filler. The film microstructure is studied by SEM. The electrical–physical properties of the films (volt-amps diagrams and the R(T) dependence are determined). It is established that the thermal resistivity constant reverses sign, when the carbon nanofiber is introduced.

Materials for the electrospark strengthening and reconditioning of worn metal surfaces

The aim of this work is the development of technology for obtaining electrode materials from Colmonoy-WC alloys and hard alloys containing TiC, WC, Mo2C, Tin, Co, Cr, Ni, and Al. The phase composition and structure are studied along with the kinetics of mass transfer, hardness, and wear resistance of electrospark coatings made of the manufactured alloys. The methods used were metallography and electron microscopy and X-ray phase and durometric analyses. It was shown that the alloys Colmonoy (Ni-Ni3B–Si–Cu), Colmonoy-10% WC, and Colmonoy-25% WC have a eutectic structure. With an increase in the WC content in the alloys, the structure is found to be an aggregation of the phases of a hard solution based on nickel and tungsten carboborosilicide. At the pulse energy of 7.5 J, the thickness of the coatings formed was 3–4 mm. The wear resistance of the coatings increased with the growth of the WC content in the coatings from 64.5 μm/km for Colmonoy to 18.5 μm/km for the alloy with 70% WC, and the steel wear resistance under those conditions was 160 μm/km. It was established that the structure and composition of the manufactured electrode materials from the hard alloys based on TiC and WC carbides make it possible to produce electrospark coatings with a thickness up to 100 μm and hardness up to 20–24 GPa. The developed materials can be used to harden/recondition worn workpieces made of constructional steels by the electrospark method.