RU2771409C1 - Method for plasma-electrochemical formation of nanostructured chromium coating and device for implementing the method - Google Patents

Abstract

FIELD: electroplating.SUBSTANCE: invention relates to the field of electroplating and can be used in mechanical engineering, instrument making and other fields. The method consists in the fact that at the first stage, galvanic deposition of chromium is carried out, for which the cathode - product is placed in an electrolytic bath with chromium plating electrolyte, then an anode is placed parallel to the cathode, while a capacitive induction filter is connected to the electrical circuit, an electric current of 100-200 A/dm2and voltage 40-60 V, current treatment is carried out to form a chromium layer on the metal surface; at the second stage, exposure to plasma is carried out, for which, when the thickness of the chromium coating reaches 0.5 mcm at the first stage, the voltage of electrochemical deposition of chromium is increased to values ​​of 150-200 V, as a result of which a gas discharge burns in a vapor-air shell, covering the entire surface of the plate, after this, the discharge burning is quenched by reducing the voltage value until the plasma glow visually ceases with bringing the current density to 40 A/dm2, the first and second stages are repeated until the desired coating thickness is obtained. The device includes a bath with an electrolyte, a cathode - a product and an anode; the following are connected to the electrode system: a power supply system, an oscilloscope with the ability to control the shape of the supplied voltage and electric current, additional resistance, a voltmeter, an ammeter, a thermocouple, while the power system consists of a diode bridge, a laboratory autotransformer, and a capacitive induction filter, which is a high-voltage direct current source.EFFECT: obtaining a nanostructured chromium coating.6 cl, 6 ex, 3 dwg

Description

The present invention relates to the production of a nanostructured chromium coating, which can be used in mechanical engineering, instrumentation and other fields of technology.

Further in the text, the applicant gives the terms that are necessary to facilitate an unambiguous understanding of the essence of the claimed materials and to exclude contradictions and / or controversial interpretations when performing an examination on the merits.

Nanostructured coatings are thermal barrier, wear-resistant, corrosion-resistant coatings designed to restore and extend the life of equipment in the oil and gas, aviation, nuclear, machine-building, metallurgical, construction and other industries [https://neftegaz.ru/tech-library/technologii/ 141456-nanostrukturirovannye-pokrytiya/].

A capacitive induction filter is a device for reducing the variable components (ripples) of the rectified voltage, consisting of a choke and capacitive elements - capacitors. The inductor is a conventional coil, characterized by a certain inductance. The smoothing effect of the filter is based on the occurrence of self-induction in the inductor EMF, which prevents a change in the rectified current. Smoothing filters are included between the rectifier and the load to reduce the variable components (ripples) of the rectified voltage.

It provides an adjustable smoothed voltage waveform - a constant voltage that does not drop to zero [https://www.electronicsblog.ru/].

A smoothing filter is a device designed to reduce the ripple of the rectified voltage. Principle of operation: during the action of a half-wave of voltage, the reactive elements (capacitor, inductor) are charged from a source - a diode rectifier, and they are discharged to the load during the absence or low voltage amplitude [https://emkelektron.webnode.com/news/ sglazhivajushchije-filtry/].

The smoothed voltage waveform is a constant voltage that does not drop to zero (Figure 1, bottom graph).

Pulsating voltage form - alternating voltage due to pulsating currents that have a constant direction, but change their value, can be different. Sometimes the value of the current changes from the largest value to the smallest value that is not equal to zero. In other cases, the current decreases to zero. If the DC circuit is interrupted with a certain frequency, then for some periods of time there is no current in the circuit (Fig. 1, top graph) [http://electricalschool.info/].

Electrochemical deposition or galvanic deposition is the process of coating metals with a film obtained as a result of electrolysis of a solution containing ions of necessary impurities, such as chromium, nickel, copper, etc. The equipment for carrying out the process consists of an anode and a cathode immersed in an appropriate electrolyte. The metal is deposited on the cathode

Chrome plating is the process of depositing a layer of chromium from an electrolyte on the surface of a part under the influence of an electric current in the process of electrochemical (galvanic) deposition. A layer of chromium can be applied for decorative purposes, to provide protection against corrosion or to increase the hardness of the surface [Yu.M. Lakhtin, V.P. Leontiev. Materials Science. - M.: Mashinostroenie, 1990].

Chrome plating is a coating obtained during the chromium plating process.

Plasma is a partially or fully ionized gas formed from neutral atoms (or molecules) and charged particles (ions and electrons). In order for a system with charged particles to become a plasma , they need to be located at a minimum distance from each other and interact with each other. Due to the constant movement of particles, plasma becomes an excellent conductor of electric current. And using magnetic fields, you can concentrate it into a jet and control further movement [https://ru.wikipedia.org/wiki/Plasma].

Plasma exposure is a process of low-temperature gas (plasma) processing of materials under the influence of an electric discharge at temperatures from 45 degrees Celsius to 10 ⁵ degrees Kelvin.

A gas discharge is all the phenomena and processes associated with the flow of electric current through a gas.

Chrome plating of steel products is a technological operation in industrial production. Chrome coatings provide products with a beautiful appearance and protect the material from environmental influences, in particular from corrosion, and are also used to restore worn parts. Most often, chromium plating is carried out by the electrochemical method - the metal is deposited in galvanic baths under the influence of an electric current.

The thickness of the galvanic chrome coating is set depending on its purpose and operating conditions. The thickness of the layer designed to restore worn dimensions can reach 500 microns. The protective and decorative layers deposited on parts made of copper and alloys based on it are about 6.0 - 9.0 microns in thickness, and on a nickel sublayer - 0.5 - 1.5 microns. If it is necessary to increase the wear resistance of dies, molds, etc., then the thickness of the chromium layer can vary from 9 to 60 microns.

Electroplated chromium coatings are used [https://magnetline.ru/raznoe/chto-takoe-hromirovannoe-pokrytie.html]:

- in the manufacture of reflectors, mirrors, spotlights, etc., since the coating has high reflective properties that are second only to aluminum and silver, but these properties are more stable due to the good resistance of chromium to oxidation;

- for protective and decorative purposes, since with a sublayer of nickel and copper, the chrome coating perfectly protects steel from corrosion and gives the product an attractive appearance. So, protective and decorative galvanic chromium plating is used to form layers on some parts of cars, appliances, motorcycles, bicycles, etc.;

- to restore dimensions, for example, by building up a chromium layer on the worn surface of heat-treated shafts and bushings, which makes it possible to extend the service life of products and restore their original dimensions;

- to increase the wear resistance of critical parts.

The thickness of the chromium coating depends on the purpose of the products and can be in the range from 5 to 350 microns and more - up to 500 microns.

Thus, hard chrome plating with the smallest thickness variation is required on cylinder rods, piston rings, liners and other cylindrical surfaces.

Electrochemical deposition of metals is usually the most used method both in terms of material costs and the quality of the resulting coatings in comparison, for example, with immersion in molten metal.

However, the electrochemical (galvanic) method is not without drawbacks. These include a decrease in the mechanical characteristics of the product in the process of metal deposition. This especially affects the chromium plating process, since the current efficiency of the metal (W) lies in the range from 8 to 13%, and the rest of the electrical energy is spent on the release of Joule heat (ohmic losses) and mainly on the release of hydrogen.

In addition, the electrochemical chromium plating method does not allow coating with a high degree of smoothness, due to the uneven distribution of chromium. The chromium plating process itself takes a long time, which reduces labor productivity and production efficiency in general.

At the date of filing the application, the issue of increasing the degree of smoothness of the chromium plating surface and reducing the time of the chromium plating process is relevant in the world.

On the surface of chromium coatings (except for "milk") in the process of their application, pores and cracks are formed, which significantly reduce their protective properties. In addition, the chrome-plated part is subjected to additional anodizing in the same electrolyte in which the coating was applied. This is done to expand the pores in the coating. Lubricants enter and retain large pores. At a cathode current density of 40 - 60 A / dm ² and a temperature of 325 - 331 °K, the most developed network of channels and pores on the surface of the chrome-plated part is obtained. Anode treatment is carried out for 10 - 12 minutes [https://magnetline.ru/raznoe/chto-takoe-hromirovannoe-pokrytie.html].

The claimed method provides the possibility of increasing the efficiency of obtaining a nanostructured chromium coating by reducing the time of the electroplating process itself, since the deposition consists of two main processes - electrochemical deposition of chromium and combustion of a gas discharge in a vapor-air shell covering the surface of the product, which proceed alternately. At the same time, the claimed method makes it possible to ensure uniform chromium plating of the product surface, reducing the possibility of crack formation, since the process of plasma-electrochemical chromium plating occurs with continuous alternation of electrochemical action on the product surface, and then plasma exposure. Provided temperature fluctuations within such limits, which allow you to keep the impact of the plasma continuously, alternating with the process of electrochemical chromium plating.

The technical solutions identified by the applicant from the studied prior art, presented below, do not fully solve these problems.

A known method of electrolytic chromium plating which uses an electrolyte according to patent RU No. 2409707 "Chromium plating electrolyte" [1], the essence is a chromium plating electrolyte containing chromium sulphate or potassium chromium alum, sodium oxalate, sodium sulphate, sodium fluoride, aluminum sulphate, characterized in that it additionally contains nanosized particles of zirconium oxide and molybdenum and vanadium compounds in the following ratio of components, g/l: Cr ₂ (SO ₄ ) ₃ ⋅6H ₂ O or KCr(SO ₄ ) ₂ 50-350, Na ₂ C ₂ O ₄ 20- 30, Na ₂ SO ₄ 60-70, NaF 25-30, Al ₂ (SO ₄ ) ₃ ⋅18Н ₂ O 90-110, ZrO ₂ nanoparticles 1-20, sodium or potassium molybdate 3.0-40, sodium vanadate or potassium 0.5-20.

The technical objective of the known invention is the development of a chromium plating electrolyte that provides non-porous, wear-resistant coatings not prone to cracking with high corrosion resistance.

To solve this problem, a chromium plating electrolyte containing chromium sulfate or chromium alum, sodium oxalate, sodium sulfate, sodium fluoride, aluminum sulfate is presented, characterized in that it additionally contains nanosized particles of zirconium oxide, sodium or potassium molybdate and sodium or potassium vanadate in the following component ratio, g/l: Cr ₂ (SO ₄ ) ₃ ⋅6Н ₂ O or KCr(SO ₄ ) ₂ 50-350 Na ₂ C ₂ O ₄ 20-30 Na ₂ SO ₄ 60-70 NaF 25-30 Al ₂ (SO ₄ ) ₃ 18H ₂ O 90-110 ZrO ₂ nanoparticles 1-20 sodium or potassium molybdate 3.0-40 sodium or potassium vanadate 0.5-20. Nanosized particles of ZrO ₂ have a dispersion of 5-250 nm and a specific surface area of 20-200 m ² per 1 g of dry matter. The surface roughness during chromium plating in the proposed electrolyte did not change at thicknesses up to 45 microns, therefore, subsequent grinding of the surface of the steel part was not required. Thus, the well-known technical solution is based on the production of chromium coatings in an electrolyte based on chromic anhydride, sulfuric acid and artificial technical cryolite.

The disadvantage of the known technical solution is that the speed of electrolytic chromium plating (deposition) reaches a value of 2.2 μm/min, it is longer than the claimed technical solution and does not allow uniform chromium plating of the product in a shorter time period. In this regard, the known invention does not ensure the efficiency of the electrolytic chromium plating process, since it requires a large time interval for the chromium plating process of products and at the same time does not allow uniform and high-quality chromium plating of the product.

A known method of electrolytic chromium plating according to patent RU No. 2125125 "Method of electrolytic chromium plating" [2], the essence is a method for obtaining chromium coatings, including chromium plating in an electrolyte based on chromic anhydride, sulfuric acid and trichloroacetic acid, characterized in that chromium plating is carried out at a concentration of chromic anhydride 60-120 g/l, mass ratio of chromic anhydride to sulfuric acid 100:1 and concentration of trichloroacetic acid 0.5-0.9 g/l.

The technical problem of the known invention is to reduce the concentration of chromic anhydride, which reduces the toxicity of the electrolyte. This goal is achieved by the fact that the process of chromium plating in an electrolyte based on chromic anhydride, sulfuric acid and triacetic acid is carried out at a concentration of chromic anhydride 60-120 g/l, the mass ratio of chromic anhydride: sulfuric acid = 100:1 and the interval of change in the concentration of triacetic acid 0.5-0.9 g / l.

The process of chromium plating according to a known method is carried out at current densities of 30-60 A/DM ² temperature 48-60°. The current output of chromium is 12-16%. Coating thickness up to 100-150 microns.

The disadvantages of the known technical solution is that it does not ensure the efficiency of the process of electrolytic chromium plating, as it does not allow for high uniformity of the chromium coating.

A known method of electrolytic chromium plating according to patent RU No. 2125126 "Method of electrolytic chromium plating in a low-concentration electrolyte" [3], the essence is a method of electrolytic chromium plating in an electrolyte containing 70-120 g/l of chromic anhydride, strontium sulfate, a strontium compound selected from the group consisting from oxide, hydroxide, carbonate or chromate, introduced to reduce the solubility of strontium sulfate, and artificial technical cryolite, characterized in that the concentration of the introduced strontium compound is determined from the mass ratio of Sr ₂ + • CrO ₃ = 250 - 270, followed by recalculation to the formula of this connections.

The disadvantages of the known technical solution is that the speed of coating of trivalent chromium and chromium alloys is low and the thickness of the coatings is difficult to increase compared to the claimed technical solution. In addition, the known technical solution does not allow uniform chromium plating of the product surface and, therefore, does not ensure the efficiency of the electrolytic chromium plating process.

The closest in essence to the claimed technical solution, chosen by the applicant as a prototype, is the source "Properties of nanocrystalline Cr coatings prepared by cathode plasma electrolytic deposition from trivalent chromium electrolyte Cheng Quan, Yedong He / Beijing Key Laboratory for Corrosion, Erosion and Surface Technology, University of Science and Technology Beijing, 100083 Beijing, China] [4]. The essence of the prototype is a method for obtaining high-quality Cr coatings with new properties from an electrolyte based on trivalent chromium sulfate using cathode plasma electrochemistry (by electrolytic deposition of cathode plasma). The coating is applied from trivalent chromium sulfite. The chromium plating process is as follows: high purity graphite with bottom holes was used as the anode, a sample prepared by conventional machining of 304 stainless steel with a size of 12 mm (length) x 10 mm (width) x 2 mm was used as the cathode (thickness) after grinding to a grit of 2000 and cleaning in the standard. The distance between the anode and cathode is about 6-8 mm. The sample can be moved either vertically or horizontally or rotated by a three-dimensional drive to enable the chromium plating process for products with large areas and/or different shapes. A thermostatic water bath was used to maintain a constant electrolyte temperature. A vacuum pump was used to recirculate the electrolyte. A stirrer was used for mixing. To prepare the coating, a DC power supply with a wide voltage range was used.

Briefly, the essence of the prototype is that the surface of the product is completely filled with electrolyte, then the voltage is increased using alternating current after a two-half-wave rectification, due to which microarcs appear on the surface of the sample. In the process of electrochemical deposition, the voltage is regulated in small ranges and quenched to zero, while providing the phenomenon of a microarc discharge on the cathode surface from start to finish. Coatings are applied from trivalent chromium sulfate. The coating thickness is estimated at about 30 µm.

The disadvantages of the prototype are:

1 - obtaining a rough, not ideally smooth coating, which significantly reduces its quality, since the electrochemical deposition process is carried out using alternating current after two half-wave rectification, while obtaining a pulsating voltage form, which gives a fluctuation in the voltage value and its decrease to zero. In the prototype, the process of deposition and combustion (melting) occurs simultaneously due to the formation of microarcs that melt the surface of the product and create a nanostructured coating, however, when using alternating current, the effect of microarcs on the surface of the product is point. In this case, a nanostructured, but rough coating is obtained, since the microarcs burn separately on the surface, and since the arc is melting, a large roughness is obtained;

2 - the worst appearance of the product compared to the claimed technical solution due to the visible surface roughness of the coating;

3 - a longer process in comparison with the claimed technical solution, since due to the point effect of microarcs on the surface of the product in the electrolyte, the deposition process takes longer, approximately 2.2 μm / min., which also reduces the efficiency of the prototype for its intended purpose .

The purpose and technical result of the claimed technical solution is to develop a method and device for implementing the method, eliminating the disadvantages of the prototype, namely, allowing to achieve:

1 - reduction of the surface roughness of the coating due to the fact that the discharges do not burn separately on the surface where the coatings are formed, but on the entire surface, since a smoothed voltage is used due to the capacitive induction filter attached to the power source;

2 - improving the appearance of the product, thanks to the proposed method of plasma exposure, according to which uniform nanostructured melting occurs, defects on the surface of the product are eliminated, grains are crushed, and mechanical and electrochemical properties are improved;

3 - reduction of the time of the process of plasma-electrochemical formation of nanostructured chromium coatings due to a continuous process, consisting alternately of electrochemical and plasma effects.

The essence of the claimed technical solution is a method of plasma-electrochemical formation of a nanostructured chromium coating, which consists in the fact that at the first stage, galvanic deposition of chromium is carried out, for which the cathode, which is a chromium-plated product, is placed in an electrolytic bath with a known electrolyte composition, while electrolyte compositions are used , which are used in the production of chromium coatings, then an anode is placed in an electrolytic bath with an electrolyte solution parallel to the cathode, the average current densities are 100-200 A / dm ² and a voltage of 40-60 V, while a capacitive induction filter is connected to the electrical circuit, an electric current up to average current densities of 100-200 A/dm ² , current treatment is carried out to form a chromium layer on the metal surface; at the second stage, exposure to plasma is carried out, for which, when the thickness of the chromium coating reaches 0.5 μm at the first stage, the voltage is increased from the classical values of electrochemical deposition of chromium in A / dm ² and a voltage of 40-60 V to values of 150-200 V, respectively, in As a result, a gas discharge burns in a vapor-air shell, covering the entire surface of the plate, while the capacitive induction filter included in the electrical circuit provides an adjustable smoothed voltage shape to a constant voltage that does not decrease to zero, which ensures the possibility of uniform plasma exposure to the chromium-plated surface, while discharge burning in the form of a plasma shell provides the formation of a nanostructured chromium coating with a high degree of smoothness, then, after the discharge burning, it is quenched by reducing the voltage until the plasma glow visually stops, bringing the current density to 40 A / dm ² , then repeat the first and second stages, until the desired thickness of the nanostructured chromium coating is obtained. The method according to claim 1 , characterized in that the cathode is used in the form of a metal rod, and the anode is in the form of a flat plate of graphite. The method according to claim 1, characterized in that the cathode is used in the form of a flat plate of metal, and the anode is in the form of a flat plate of graphite, a dielectric cover with a round hole is first tightly put on the cathode. A method for plasma-electrochemical formation of a nanostructured chromium coating with jet supply of an electrolyte, placement of a cathode and an anode above the electrolyte, which consists in the fact that at the first stage, galvanic deposition of chromium is carried out , for which an electrolyte of a known composition is placed in the electrolytic bath, which are used to obtain chromium coatings, the electrolyte is kept at average current densities of 100-200 A/dm ² and voltage of 40-60 V; the cathode, made in the form of a plate and representing a chrome-plated product, is fixed horizontally with respect to the electrolytic bath and placed under the anode, made vertically with respect to the electrolytic bath, while the cathode and anode are placed above the electrolyte; an electrolyte dispenser is attached to the anode, an electrolyte supply tube is installed between the electrolyte in the electrolytic bath and the dispenser, a peristaltic pump is attached to the tube, when turned on, the electrolyte circulates from the electrolytic bath through the electrolyte supply tube, then through the dispenser, then through the anode cavity, jet on the chrome-plated product - cathode, then the electrolyte is drained into the electrolytic bath; a capacitive induction filter is included in the electrical circuit, an electric current is connected to average current densities of 100-200 A / dm ² , current treatment is carried out to form a chromium layer of a certain thickness on the metal surface; at the second stage, plasma exposure is carried out, for which, when the chromium coating thickness reaches 0.5 μm at the first stage, the voltage is increased from the classical values of electrochemical chromium deposition to values of 150-200 V, as a result of which a gas discharge burns in a vapor-air shell covering the entire surface plates, while the capacitive induction filter included in the electrical circuit provides an adjustable smoothed voltage shape - a constant voltage that does not decrease to zero, which makes it possible to uniformly influence the plasma on the chrome-plated surface of the product; at the same time, the plasma shell and the burning of the discharge around the anode ensure the formation, under the influence of plasma, of a nanostructured chromium coating with a high degree of smoothness; after that, the combustion of the discharge is extinguished by reducing the magnitude of the voltage until the visual cessation of the glow of the plasma, while the current density is reduced to 40 A/DM ² ; then again the first stage is continuously carried out - the process of electrochemical deposition, then the second stage is continuously carried out, and so alternately - electrochemical and plasma exposure until a given thickness of the nanostructured chromium coating is obtained. A device for implementing the method according to claim 1, including an electrolytic bath with an electrolyte, an electrode system, including a cathode, which is a chromium-plated product, and an anode; the following are connected to the electrode system: an electrical power system, an oscilloscope with the ability to control the shape of the supplied voltage and electric current, additional resistance, a voltmeter with the ability to measure voltage, an ammeter with the ability to measure the discharge electric current, a thermocouple; at the same time, the power supply system consists of a diode bridge - a combination of diodes, a laboratory autotransformer, a smoothing capacitive filter, which are a high-voltage direct current source for creating and maintaining an electric discharge burning with the ability to smoothly control the output voltage in the range from 0 V to 3 kV and the current in the range from 0 A to 10 A. The device according to claim 2, characterized in that the cathode is made in the form of a metal rod, and the anode is made in the form of a flat plate of graphite, while the cathode and anode are parallel to each other and immersed in an electrolyte located in stationary state in an electrolytic bath. The device according to claim 2, characterized in that the cathode is made in the form of a flat plate of metal, and the anode is made in the form of a flat plate of graphite, a tightly fitting dielectric cover with a round hole is put on the cathode, while the cathode and anode are parallel to each other and immersed in an electrolyte that is in a stationary state in an electrolytic bath. A device for implementing the method according to claim 4, including an electrolytic bath with an electrolyte, an electrode system, including a cathode made in the form of a metal plate and representing a chromium-plated product, and an anode made in the form of a hollow graphite plate with the possibility of ensuring electrolyte draining, when this cathode is made horizontally with respect to the electrolytic bath and is located under the anode, made vertically with respect to the electrolytic bath, while the cathode and anode are located above the electrolyte; the following are connected to the electrode system: an electrical power system, an oscilloscope with the ability to control the shape of the supplied voltage and electric current, additional resistance, a voltmeter with the ability to measure voltage, an ammeter with the ability to measure the discharge electric current, a thermocouple; at the same time, the power supply system consists of a diode bridge - a combination of diodes, a laboratory autotransformer, a smoothing capacitive filter, which are a high-voltage direct current source for creating and maintaining an electric discharge burning with the ability to smoothly control the output voltage in the range from 0 V to 3 kV and the current in the range from 0 A to 10 A; the device contains a dispenser, an electrolyte supply tube made between the electrolyte and the dispenser, a peristaltic pump with the possibility of controlled electrolyte supply from the electrolytic bath to the dispenser, then to the anode cavity, then to the cathode and further to the electrolytic bath, while the dispenser is attached to the anode, and a peristaltic pump is attached to the electrolyte supply tube.

The claimed technical solution is illustrated in Fig.1 - Fig. 3.

Figure 1 shows graphs of standard voltage forms:

- smoothed stress form (lower graph);

- pulsating voltage waveform (upper graph).

Figure 2 shows:

2a - general scheme of the installation for the implementation of the claimed method;

2b is a diagram of the power supply system.

Figure 3 shows diagrams of three variants of the claimed device with different versions of electrode systems, where:

3a - the first option,

3b - the second option,

3c - the third option.

Positions in Fig. stand for:

1 - power supply system;

2 - electrolytic bath;

3 - electrode system;

4 - oscilloscope;

5 - additional resistance;

6 - voltmeter (for example, digital universal measuring device MMH-930);

7 - ammeter (for example, digital universal measuring device APPA 109N);

8 - thermocouples;

9, 10, 11, 12 - diodes CL 246 12 -10/8;

13 - capacitive induction filter;

14 - cathode;

15 - anode;

16 - electrolyte;

17 - dielectric plastic cover;

18 - opening of the plastic dispenser;

19 - electrolyte jet;

20 - peristaltic pump;

21 - laboratory autotransformer (for example, regulating type 1M);

22 - tube for electrolyte supply.

Further, the applicant provides a description of the claimed technical solution.

The claimed method can be implemented on the installation shown in Fig. 2(a) having a diagram of the power supply system shown in FIG. 2 (b), using three variants of the device shown in Fig. 3 (a, b, c).

In this case, the common features for 1 and 2 versions of the device are the following.

The device for implementing the claimed method includes an electrolytic bath (2) with an electrolyte (16), an electrode system (3), including a cathode (14), which is a chromium-plated product, and an anode (15). Connected to the electrode system: electrical power systems (1), oscilloscope (4) with the ability to control the shape of the supplied voltage and electric current, additional resistance (5), voltmeter (6) with the ability to measure voltage, ammeter (7) with the ability to measure electric current discharge, thermocouple (8).

At the same time, the power supply system (1) consists of a diode bridge - a combination of diodes (9), (10), (11), (12), a laboratory autotransformer, for example, an adjustable type 1M (21), a smoothing capacitive filter (13), which are a high-voltage direct current source for creating and maintaining the burning of an electric discharge with the ability to smoothly control the output voltage in the range from 0 V to 3 kV and current in the range from 0 A to 10 A.

As a voltmeter (6) use, for example, a digital universal measuring device MMH-930. As an ammeter (7), use, for example, a digital universal measuring device APPA 109N. The relative error in measuring the discharge voltage and current is 0.8%.

Additionally, options 1 and 2 contain the following particular features :

The device according to option 1 with the first type of electrode system (Fig. 2, Fig. 3a):

the cathode (14) is made in the form of a metal rod, for example, stainless steel grade 12X18H9T, and the anode (15) is made in the form of a flat graphite plate,

cathode (14) and anode (15) are located parallel to each other and perpendicular to the electrolytic bath (2),

the cathode (14) and the anode (15) are immersed in the electrolyte (16), which is in a stationary state in the electrolytic bath (2).

The device according to option 2 with the second type of electrode system (Fig. 2, Fig.3b).

the cathode (14) is made in the form of a flat plate of metal, for example, stainless steel grade 12Kh18N9T, and the anode (15) is made in the form of a flat plate of graphite,

a tightly fitting dielectric cover (17) with a round hole is put on the cathode (14),

the cathode (14) and the anode (15) are parallel to each other and are immersed in the electrolyte (16), which is in a stationary state in the electrolytic bath (2).

The applicant explains that the presence of corners at the cathode plate (14) leads to uneven discharge burning at these points and local overheating - melting. To prevent this effect, a tightly fitting dielectric plastic cover (17) is put on the cathode plate (14), leaving an open part of the cathode surface (14) in the form of a circle.

The device according to option 3 with the third type of electrode system (Fig. 2, Fig. 3c) - electrolyte jet supply:

The device for implementing the claimed method according to option 3 includes an electrolytic bath (2) with electrolyte 16, an electrode system (3), including a cathode (14), which is a chrome-plated product made in the form of a flat plate of metal, for example, stainless steel grade 12X18H9T , and an anode (15) made in the form of a hollow graphite plate with the possibility of electrolyte draining, while the cathode (14) is made horizontally with respect to the electrolytic bath (2) and is located under the anode (15), made vertically with respect to the electrolytic bath (2), while the cathode (14) and the anode (15) are located above the electrolyte (16).

The device contains a dispenser (18) with a hole for draining the electrolyte with a diameter of, for example, 2 mm, an electrolyte supply tube (22) made between the electrolyte (16) and the dispenser (18), a peristaltic pump (20) with the possibility of adjustable electrolyte supply (16 ) from the electrolytic bath (16) to the dispenser (18), then to the cavity of the anode (15), then to the cathode (14) and then to the electrolytic bath (2), while the dispenser (18) is attached to the anode (15), and the peristaltic pump (20) is attached to the electrolyte supply tube (22).

Connected to the electrode system: electrical power systems (1), oscilloscope (4) with the ability to control the shape of the supplied voltage and electric current, additional resistance (5), voltmeter (6) with the ability to measure voltage, ammeter (7) with the ability to measure electric current discharge, thermocouple (8).

At the same time, the power supply system (1) consists of a diode bridge - a combination of diodes (9), (10), (11), (12), a laboratory autotransformer, for example, an adjustable type 1M (21), a smoothing capacitive filter (13), which are a high-voltage direct current source for creating and maintaining the burning of an electric discharge with the ability to smoothly control the output voltage in the range from 0 V to 3 kV and current in the range from 0 A to 10 A.

As a voltmeter (6) use, for example, a digital universal measuring device MMH-930. As an ammeter (7), use, for example, a digital universal measuring device APPA 109N. The relative error in measuring the discharge voltage and current is 0.8%.

Further, the applicant describes a method for plasma-electrochemical formation of a nanostructured chromium coating according to the first variant - with an electrolyte in a stationary state in an electrolytic bath, using a cathode in the form of a metal rod and placing the cathode and anode in the electrolyte.

The claimed method as a whole consists of two main stages (processes) that proceed alternately and sequentially:

- at the first stage, electrochemical galvanic deposition of chromium is carried out to obtain a certain thickness of the chromium coating;

- at the second stage, the chromium coating is exposed to plasma , for which, under the influence of an electric discharge, a vapor-air shell is created, while thermal plasma treatment (melting) occurs, as a result of which its nanostructuring occurs. Then the discharge is extinguished.

Next, the first stage of electrochemical deposition is repeated, then the second stage of exposure to plasma is repeated, and so alternately - electrochemical and plasma exposure until a given coating thickness is obtained.

The result is a smooth nanostructured chromium coating in a shorter time compared to the prototype.

The coating thickness varies from 100 to 150 microns.

The microhardness of coatings varies from 900 to 1000 kg/mm ² .

The smoothness of the nanostructured chromium coating, that is, the reduction of the surface roughness of the coating, is achieved due to the fact that at the second stage, the chromium coating is exposed to plasma, that is, under the influence of an electric discharge, a vapor-air shell is created, while thermal plasma treatment (melting) of the coating occurs, as a result of which nanostructuring occurs not locally on the surface of the product where the coating is formed, as in the prototype, but on the entire surface of the product, since the claimed technical solution uses a smoothed voltage by connecting a capacitive induction filter to the power source . The capacitive induction filter provides an adjustable smoothed voltage waveform - a constant voltage that does not drop to zero.

Thus, in the claimed technical solution, the process of plasma-electrochemical chromium plating occurs with a continuous alternation of electrochemical effects on the surface of the product, and then the effects of plasma.

Low-temperature plasma is formed on the cathode (14), which is a chromium-plated product dipped into the electrolyte, while the cathode is made in the form of a metal rod.

The first stage - electrochemical action begins at low voltages, 40-60 V and average current densities of 100-200 A/dm ² .

Then the second stage is carried out - the voltage is increased from the usual values of electrochemical chromium deposition, for example, from 40-60 V, to values of 150-200 V, while the discharge burns (its heat treatment) and the formation of a vapor-air shell.

Under the influence of plasma, a nanostructured chromium coating is formed with a high degree of smoothness of the coating, namely, a roughness of up to 0.5 μm.

Thus, the claimed technical result is achieved - obtaining a nanostructured chromium coating.

At the same time, in the claimed method, a chromium coating with a thickness of 0.5 μm (time is set based on the deposition rate equal to 0.03-0.06 mm/h) is first applied by an electrochemical method, then a 150-200 V discharge burns (its heat treatment) and nanostructuring, then the discharge burning is stopped (extinguished) for 1-2 seconds by reducing the voltage to visual cessation of the plasma glow, for example, 100 V, the current density is reduced to 40 A / dm² (this is necessary to start a new coating cycle), then the process of electrochemical deposition is started again and so alternately provides electrochemical and plasma effects, which ultimately provides a smooth nanostructured coating with a thickness of up to 0.5 μm.

Further, the applicant provides a more detailed explanation of the steps of the claimed method.

The first stage of electrochemical galvanic deposition of chromium.

A metal product in the form of a rod (cathode), for example, made of cast iron, steel, its alloys, is placed in an electrolytic bath with an electrolyte solution, for example, of the composition: Cr ₂ SO ₄ •6H ₂ O - 20 g / l, H ₂ SO ₄ - 40 g / l, NH ₄ COOH - 40-50 g / l, NH ₄ Br - 10 g / l, KCl - 60 g / l, H ₃ BO ₄ -40 g / l, Na ₂ SO ₄ -50 g / l, NH ₄ Cl - 75 g / l at average current densities of 100-200 A / dm ² and a voltage of 40-60 V.

In the chromium plating process, a graphite anode is used, which is placed in an electrolytic bath with an electrolyte solution, a capacitive induction filter is connected to the electrical circuit, an electric current is connected up to average current densities of 100-200 A / dm². Current treatment occurs to form a chromium layer of a certain thickness on the metal surface. The depth of immersion of the chrome-plated parts (cathode) and the anode into the electrolytic bath must be the same, since at different depths thickenings are formed on the edges of the chrome-plated parts, distorting the shape. Chromium layer deposition rate at a current density of 100-200 A/dm² is 0.03-0.06 mm/h. Indicated speed deposition is given as an example.

Specified in the claimed technical solution, the electrolyte has an optimal composition. The standard electrolyte for chromium deposition contains two main components: chromic anhydride and sulfuric acid. The mass ratio between the components should be: chromic anhydride: sulfuric acid = 100: 1. With this ratio, the highest current efficiency is achieved.

The second stage of exposure to plasma.

Then, when the thickness of the chromium coating reaches 0.5 μm at the first stage, the thickness of the chromium coating reaches 0.5 μm (the time is set based on the deposition rate equal to 0.03-0.06 mm/h) increase the voltage from the classical values of electrochemical chromium deposition (for example, 40-60 V) to values, for example, 150-200 V, as a result of which a gas discharge burns in a vapor-air shell covering the entire plate surface. The capacitive induction filter included in the electrical circuit provides an adjustable smoothed voltage shape - a constant voltage that does not decrease to zero, which makes it possible for the plasma to act uniformly on the chrome-plated surface of the product.

At the same time, the vapor-air shell and the combustion of the discharge ensure the formation, under the influence of plasma, of a nanostructured coating with a high degree of smoothness - roughness values up to 0.5 μm.

When exposed to a high temperature, formed as a result of the burning of the discharge, the nanostructuring of the chromium coating obtained during the first stage of electrochemical deposition occurs. After that, the burning of the discharge is stopped (quenched) by reducing the voltage until the visual cessation of the glow of the plasma (up to ~ 100 V), the current density is reduced to 40 A/dm ² . This completes the second stage.

Then again the first stage is continuously carried out - the process of electrochemical deposition, then the second stage is continuously carried out, and so alternately - electrochemical and plasma effects.

Thus, a nanostructured coating with a surface roughness of less than 0.5 µm is obtained.

Thanks to the claimed method of exposure to plasma, a uniform formation of a nanostructured coating occurs during chromium plating, defects on the surface of the product are eliminated, grains are crushed, and mechanical and electrochemical properties are improved. This means that the claimed technical solution is an effective way to obtain high-quality chromium coatings.

The claimed method, implemented on the claimed device, is applicable to all known electrolyte compositions that are used in the production of chromium coatings.

Further, the applicant describes a method for plasma-electrochemical formation of a nanostructured chromium coating according to the second option - with an electrolyte in a stationary state in an electrolytic bath, using a cathode in the form of a metal plate with a dielectric cover having a round hole and placing the cathode and anode in the electrolyte.

The claimed method as a whole consists of two main stages (processes) that proceed alternately and sequentially:

- at the first stage, electrochemical galvanic deposition of chromium is carried out to obtain a certain thickness of the chromium coating;

- at the second stage, the chromium coating is exposed to plasma , for which, under the influence of an electric discharge, a vapor-air shell is created, while thermal plasma treatment (melting) occurs, as a result of which its nanostructuring occurs. Then the discharge is extinguished.

Next, the first stage of electrochemical deposition is repeated, then the second stage of exposure to plasma is repeated, and so alternately - electrochemical and plasma exposure until a given coating thickness is obtained.

The result is a smooth nanostructured chromium coating in a shorter time compared to the prototype.

The coating thickness varies from 100 to 150 microns.

The microhardness of coatings varies from 900 to 1000 kg/mm ² .

The smoothness of the nanostructured chromium coating, that is, the reduction of the surface roughness of the coating, is achieved due to the fact that at the second stage, the chromium coating is exposed to plasma, that is, under the influence of an electric discharge, a vapor-air shell is created, while thermal plasma treatment (melting) of the coating occurs, as a result of which nanostructuring occurs not locally on the surface of the product where the coating is formed, as in the prototype, but on the entire surface of the product, since the claimed technical solution uses a smoothed voltage by connecting a capacitive induction filter to the power source . The capacitive induction filter provides an adjustable smoothed voltage waveform - a constant voltage that does not drop to zero.

Thus, in the claimed technical solution, the process of plasma-electrochemical chromium plating occurs with a continuous alternation of electrochemical effects on the surface of the product, and then the effects of plasma.

Low-temperature plasma is formed on the cathode (14), which is a chromium-plated product dipped into the electrolyte, while the cathode is made in the form of a flat plate of metal, for example, stainless steel grade 12Kh18N9T, while a tightly fitting dielectric is put on the cathode (14). cover (17) with a round hole.

The first stage - electrochemical action begins at low voltages, 40-60 V and average current densities of 100-200 A/dm ² .

Then the second stage is carried out - the voltage is increased from the usual values of electrochemical chromium deposition, for example, from 40-60 V, to values of 150-200 V, while the discharge burns (its heat treatment) and the formation of a vapor-air shell.

Under the influence of plasma, a nanostructured chromium coating is formed with a high degree of smoothness of the coating, namely, a roughness of up to 0.5 μm.

The presence of corners at the cathode plate (14) leads to uneven discharge burning at these points and local overheating - melting. To prevent this effect, a tightly fitting dielectric plastic cover (17) is put on the cathode plate (14), leaving an open part of the cathode surface (14) in the form of a circle.

Thus, the claimed technical result is achieved - obtaining a nanostructured chromium coating.

At the same time, in the claimed method, a chromium coating with a thickness of 0.5 μm (set the time based on the deposition rate equal to 0.03-0.06 mm/h) is first applied by an electrochemical method, then a discharge of 150-200 V burns (its heat treatment) and nanostructuring, then the discharge burning is stopped (extinguished) within 1-2 seconds by reducing the voltage until the plasma glow visually ceases, for example, 100 V, the current density is reduced to 40 A / dm ² (this is necessary to start a new coating cycle) , then again begin the process of electrochemical deposition and so alternately provide electrochemical and plasma effects, which ultimately provides a smooth nanostructured coating with a thickness of up to 0.5 microns.

Further, the applicant provides a more detailed explanation of the steps of the claimed method.

A sequence of actions is carried out according to option 1, characterized in that chrome-plated products (cathode) (14) are used, made in the form of a flat plate of metal, for example, stainless steel grade 12X18H9T, while a tightly fitting dielectric cover is put on the cathode (14) ( 17) with a round hole.

A tightly fitting dielectric plastic case (17), leaving an open part of the cathode (14) surface in the form of, for example, a circle, makes it possible to control the place of discharge burning and, accordingly, prevent melting of the corners at the cathode plate (14).

Further, the applicant describes a method for plasma-electrochemical formation of a nanostructured chromium coating according to the third variant - with jet supply of electrolyte, placement of the cathode and anode above the electrolyte.

The claimed method as a whole consists of two main stages (processes) that proceed alternately and sequentially:

- at the first stage, electrochemical galvanic deposition of chromium is carried out to obtain a certain thickness of the chromium coating;

- at the second stage, the chromium coating is exposed to plasma , for which, under the influence of an electric discharge, a vapor-air shell is created, while thermal plasma treatment (melting) occurs, as a result of which its nanostructuring occurs. Then the discharge is extinguished.

Next, the first stage of electrochemical deposition is repeated, then the second stage of exposure to plasma is repeated, and so alternately - electrochemical and plasma exposure until a given coating thickness is obtained.

The result is a smooth nanostructured chromium coating in a shorter time compared to the prototype.

The coating thickness varies from 100 to 150 microns.

The microhardness of coatings varies from 900 to 1000 kg/mm ² .

The smoothness of the nanostructured chromium coating, that is, the reduction of the surface roughness of the coating, is achieved due to the fact that at the second stage, the chromium coating is exposed to plasma, that is, under the influence of an electric discharge, a vapor-air shell is created, while thermal plasma treatment (melting) of the coating occurs, as a result of which nanostructuring occurs not locally on the surface of the product where the coating is formed, as in the prototype, but on the entire surface of the product, since the claimed technical solution uses a smoothed voltage by connecting a capacitive induction filter to the power source . The capacitive induction filter provides an adjustable smoothed voltage waveform - a constant voltage that does not drop to zero.

Thus, in the claimed technical solution, the process of plasma-electrochemical chromium plating occurs with a continuous alternation of electrochemical effects on the surface of the product, and then the effects of plasma.

Low-temperature plasma is formed on the cathode (14), which is a chrome-plated product located horizontally above the electrolyte (16), at the point where the electrolyte jet falling from the anode cavity (15) onto the cathode (14) falls.

The first stage - electrochemical action begins at low voltages, for example, 40-60 V and average current densities of 100-200 A/dm ² .

Then the second stage is carried out - the voltage is increased from the usual values of electrochemical chromium deposition, for example, from 40-60 V, to values of 150-200 V, while the discharge burns (its heat treatment) and the formation of a vapor-air shell.

Under the influence of plasma, a nanostructured chromium coating is formed with a high degree of smoothness of the coating, namely, a roughness of up to 0.5 μm.

Thus, the claimed technical result is achieved - obtaining a nanostructured chromium coating.

At the same time, in the claimed method, a chromium coating with a thickness of 0.5 μm (time is set based on the deposition rate equal to 0.03-0.06 mm/h) is first applied by an electrochemical method, then a 150-200 V discharge burns (its heat treatment) and nanostructuring, then the discharge burning is stopped (extinguished) for 1-2 seconds by reducing the voltage to visual cessation of the plasma glow, for example, 100 V, the current density is reduced to 40 A / dm² (this is necessary to start a new coating cycle), then the process of electrochemical deposition is started again and so alternately provides electrochemical and plasma effects, which ultimately provides a smooth nanostructured coating with a thickness of up to 0.5 μm.

Further, the applicant provides a more detailed explanation of the steps of the claimed method according to option 3.

The first stage of electrochemical galvanic deposition of chromium.

An electrolyte solution is placed in the electrolytic bath, for example, of the composition: Cr ₂ SO ₄ • 6H ₂ O - 20 g / l, H ₂ SO ₄ - 40 g / l, NH ₄ COOH - 40-50 g / l, NH ₄ Br - 10 g / l, KCl - 60 g / l, H ₃ BO ₄ -40 g / l, Na ₂ SO ₄ -50 g / l, NH ₄ Cl - 75 g / l at average current densities of 100-200 A / dm ² and voltage 40-60 V.

A metal chromium-plated product (cathode), for example, made of cast iron, steel, its alloys, made in the form of a plate, is placed under the anode, made in the form of a hollow graphite plate, and fixed horizontally above the electrolyte.

An electrolyte dispenser is attached to the anode, an electrolyte supply tube is installed between the electrolyte in the electrolytic bath and the dispenser, and a peristaltic pump is attached to the tube. When the peristaltic pump is turned on, the electrolyte circulates from the electrolytic bath through the electrolyte supply tube, then through the dispenser, then through the anode cavity in a jet onto the chrome-plated product (cathode). Next, the electrolyte is drained into the electrolytic bath.

A capacitive induction filter is included in the electrical circuit, an electric current is connected up to average current densities of 100-200 A / dm². Current treatment occurs to form a chromium layer of a certain thickness on the metal surface. Chromium layer deposition rate at a current density of 100-200 A/dm² is 0.03-0.06 mm/h. Indicated speed deposition is given as an example.

Specified in the claimed technical solution, the electrolyte has an optimal composition. The standard electrolyte for chromium deposition contains two main components: chromic anhydride and sulfuric acid. The mass ratio between the components should be: chromic anhydride: sulfuric acid = 100: 1. With this ratio, the highest current efficiency is achieved.

The second stage of exposure to plasma.

Then, when the thickness of the chromium coating reaches 0.5 µm at the first stage (the time is set based on the deposition rate equal to 0.03-0.06 mm/h) increase the voltage from the classical values of electrochemical chromium deposition (for example, 40-60 V) to values, for example, 150-200 V, as a result of which a gas discharge burns in a vapor-air shell covering the entire plate surface. The capacitive induction filter included in the electrical circuit provides an adjustable smoothed voltage shape - a constant voltage that does not decrease to zero, which makes it possible for the plasma to act uniformly on the chrome-plated surface of the product.

In this case, the vapor-air (plasma) shell and the burning of the discharge around the anode ensures the formation, under the influence of plasma, of a nanostructured coating with a high degree of smoothness - roughness values up to 0.5 μm.

When exposed to a high temperature, formed as a result of the burning of the discharge, the nanostructuring of the chromium coating obtained during the first stage of electrochemical deposition occurs. After that, the burning of the discharge is stopped (quenched) by reducing the voltage until the visual cessation of the glow of the plasma (up to ~ 100 V), the current density is reduced to 40 A/dm ² . This completes the second stage.

Then again the first stage is continuously carried out - the process of electrochemical deposition, then the second stage is continuously carried out, and so alternately - electrochemical and plasma effects.

Thus, a nanostructured coating with a surface roughness of less than 0.5 µm is obtained.

Thanks to the claimed method of exposure to plasma, a uniform formation of a nanostructured coating occurs during chromium plating, defects on the surface of the product are eliminated, grains are crushed, and mechanical and electrochemical properties are improved. This means that the claimed technical solution is an effective way to obtain high-quality chromium coatings.

The claimed method, implemented on the claimed device, is applicable to all known electrolyte compositions that are used in the production of chromium coatings.

Further, the applicant provides examples of the implementation of the claimed method on the claimed device.

Example 1. Obtaining a nanostructured chromium coating, for example, at an initial voltage on the electrodes of 40 V and a current density of 100 A/dm ² and when using the first version of the electrode systems.

Take the device according to option 1 (Fig.3a).

Take, for example, a sample of a rod made of stainless steel 12X18H9T, with dimensions of 10 mm * 10 mm * 3 mm and placed in an electrolytic bath containing, for example, an electrolyte of the composition Cr ₂ SO ₄ • 6H ₂ O - 20 g / l, H ₂ SO ₄ - 40 g / l, NH ₄ COOH - 40-50 g / l, NH ₄ Br - 10 g / l, KCl - 60 g / l, H ₃ BO ₄ -40 g / l, Na ₂ SO ₄ - 50 g/l, NH ₄ Cl - 75 g/l. A negative electrode is connected to the plate. At the initial time, a voltage of 40 V and a current density of 100 A / dm ² are applied, they wait 10 seconds, during this time electrochemical deposition of the chromium coating occurs, at 11 seconds the plasma is applied, for which the voltage is sharply increased to values of 150V. At these values, the gas discharge burns in a vapor-air shell covering the entire surface of the plate. At 21 seconds, the discharge burning stops and the process of electrochemical deposition of a chromium coating is restarted at a voltage of 40 V and a current density of 100 A/dm ² . Thus, there is a cyclic electrochemical deposition and exposure to plasma. If we consider the time interval of one cycle, then the electrochemical deposition in the cycle lasts 10 seconds, then the plasma exposure also lasts 10 seconds. The total time of coating formation takes on average 900 seconds. The deposition rate of the chromium layer is 0.03 - 0.06 mm/h.

Under these conditions of formation of a nanostructured coating, the minimum thickness of the resulting coating is 15 μm. Externally, the coating has a silver color.

Example 2. Obtaining a nanostructured chromium coating, for example, at a voltage on the electrodes of 60 V and a current density of 200 A/dm ² and when using the first version of the electrode systems.

Take the device according to option 1 (Fig.3a).

Take, for example, a sample of a rod made of stainless steel 12X18H9T, with dimensions of 10 mm * 10 mm * 3 mm and placed in an electrolytic bath containing, for example, an electrolyte of the composition Cr ₂ SO ₄ • 6H ₂ O - 20 g / l, H ₂ SO ₄ - 40 g / l, NH ₄ COOH - 40-50 g / l, NH ₄ Br - 10 g / l, KCl - 60 g / l, H ₃ BO ₄ -40 g / l, Na ₂ SO ₄ - 50 g/l, NH ₄ Cl - 75 g/l. A negative electrode is connected to the plate. At the initial moment of time, a voltage of 60 V and a current density of 200 A / dm ² are applied, they wait 10 seconds, during which time the electrochemical deposition of the chromium coating occurs, at 11 seconds the plasma is applied, for which the voltage is sharply increased to a value of 200 V. At these values a gas discharge burns in a vapor-air shell covering the entire surface of the plate. At 21 seconds, the discharge burning stops and the process of electrochemical deposition of a chromium coating is restarted at a voltage of 60 V and a current density of 200 A/dm ² . Thus, there is a cyclic electrochemical deposition and exposure to plasma. If we consider the time interval of one cycle, then the electrochemical deposition in the cycle lasts 10 seconds, then the plasma exposure also lasts 10 seconds. The total time of coating formation takes on average 900 seconds. The deposition rate of the chromium layer is 0.03 - 0.06 mm/h.

Under these conditions of formation of a nanostructured coating, the minimum thickness of the resulting coating is 15 μm. Externally, the coating has a silver color.

Example 3. Obtaining a nanostructured chromium coating, for example, at an electrode voltage of 40 V and a current density of 100 A/dm ² and when using the second version of the electrode systems.

Take the device according to option 2 (Fig.3b).

Take, for example, a sample of a flat plate made of stainless steel 12X18H9T, with dimensions of 10 mm * 10 mm * 3 mm, place it in a dielectric case made with a round hole, and place it in an electrolytic bath containing, for example, an electrolyte of the composition Cr ₂ SO ₄ •6H ₂ O - 20 g/l, H ₂ SO ₄ - 40 g/l, NH ₄ COOH - 40-50 g/l, NH ₄ Br - 10 g/l, KCl - 60 g/l, H ₃ BO ₄ -40 g/l, Na ₂ SO ₄ -50 g/l, NH ₄ Cl - 75 g/l. A negative electrode is connected to the plate. At the initial moment of time, a voltage of 40 V and a current density of 100 A / dm ² are applied, they wait 10 seconds, during this time electrochemical deposition of the chromium coating occurs, at 11 seconds the plasma is applied, for which the voltage is sharply increased to a value of 150 V. At these values a gas discharge burns in a vapor-air shell covering the entire surface of the plate. At 21 seconds, the discharge burning stops and the process of electrochemical deposition of a chromium coating is restarted at a voltage of 40 V and a current density of 100 A/dm ² . Thus, there is a cyclic electrochemical deposition and exposure to plasma. If we consider the time interval of one cycle, then the electrochemical deposition in the cycle lasts 10 seconds, then the plasma exposure also lasts 10 seconds. The total time of coating formation takes on average 900 seconds. The deposition rate of the chromium layer is 0.03 - 0.06 mm/h.

Under these conditions of formation of a nanostructured coating, the minimum thickness of the resulting coating is 15 μm. Externally, the coating has a silver color.

Example 4 Obtaining a nanostructured chromium coating, for example, at an electrode voltage of 60 V and a current density of 200 A/dm ² and when using the second version of the electrode systems.

Take the device according to option 2 (Fig.3b).

Take, for example, a sample of a flat plate made of stainless steel 12X18H9T, with dimensions of 10 mm * 10 mm * 3 mm, place it in a dielectric case made with a round hole, and place it in an electrolytic bath containing, for example, an electrolyte of the composition Cr ₂ SO ₄ •6H ₂ O - 20 g/l, H ₂ SO ₄ - 40 g/l, NH ₄ COOH - 40-50 g/l, NH ₄ Br - 10 g/l, KCl - 60 g/l, H ₃ BO ₄ -40 g/l, Na ₂ SO ₄ -50 g/l, NH ₄ Cl - 75 g/l. A negative electrode is connected to the plate. At the initial moment of time, a voltage of 60 V and a current density of 200 A / dm ² are applied, they wait 10 seconds, during this time electrochemical deposition of the chromium coating occurs, at 11 seconds the plasma is applied, for which the voltage is sharply increased to values of 200 V. At these values a gas discharge burns in a vapor-air shell covering the entire surface of the plate. At 21 seconds, the discharge burning stops and the process of electrochemical deposition of a chromium coating is restarted at a voltage of 60 V and a current density of 200 A/dm ² . Thus, there is a cyclic electrochemical deposition and exposure to plasma. If we consider the time interval of one cycle, then the electrochemical deposition in the cycle lasts 10 seconds, then the plasma exposure also lasts 10 seconds. The total time of coating formation takes on average 900 seconds. The deposition rate of the chromium layer is 0.03 - 0.06 mm/h.

Under these conditions of formation of a nanostructured coating, the minimum thickness of the resulting coating is 15 μm. Externally, the coating has a silver color.

Example 5. Obtaining a nanostructured chromium coating, for example, at an electrode voltage of 40 V and a current density of 100 A/dm ² and when using the third version of the electrode systems.

Take the device according to option 3 (Fig.3c).

As a cathode (14) take, for example, a sample of a flat plate made of stainless steel 12X18H9T, dimensions 10 mm * 10 mm * 3 mm, placed horizontally, under the anode (15), placed vertically. With a peristaltic pump through the electrolyte supply tube, then through a plastic dispenser (18) an electrolyte is supplied into the anode cavity (15), for example, the composition Cr₂SO₄•6H₂O - 20 g/l, H₂SO₄ - 40 g/l, NH₄COOH - 40-50 g/l, NH₄Br - 10 g/l, KCl - 60 g/l, H₃BO₄ -40 g/l, Na₂SO₄ -50 g/l, NH₄Cl - 75 g/l. The anode (15) in this case is a hollow plate made of graphite, inside which the electrolyte (2) drains through the hole of the plastic dispenser (18) with a diameter of, for example, 2 mm, onto the cathode (14), and then draining it (electrolyte) into the electrolytic bath (2).

At the initial moment of time, a voltage of 40 V and a current density of 100 A / dm ² are applied, they wait 10 seconds, during this time electrochemical deposition of the chromium coating occurs, at 11 seconds the plasma is applied, for which the voltage is sharply increased to a value of 150 V. At this value a gas discharge burns in a vapor-air shell covering the entire surface of the plate. At 21 seconds, the discharge burning stops and the process of electrochemical deposition of a chromium coating is restarted at a voltage of 40 V and a current density of 100 A/dm ² . Thus, cyclic electrochemical deposition and exposure to plasma occur. If we consider the time interval of one cycle, then the electrochemical deposition in the cycle lasts 10 seconds, and the plasma exposure also lasts 10 seconds. The total time of coating formation takes on average 900 seconds. The deposition rate of the chromium layer is 0.03 - 0.06 mm/h.

Under these conditions of formation of a nanostructured coating, the minimum thickness of the resulting coating is 30 μm. Externally, the coating has a silver color.

Example 6. Obtaining a nanostructured chromium coating, for example, at a voltage on the electrodes of 60 V and a current density of 200 A/dm ² and when using the third version of the electrode systems.

Take the device according to option 3 (Fig.3c).

As a cathode (14) take, for example, a sample of a flat plate made of stainless steel 12X18H9T, dimensions 10 mm * 10 mm * 3 mm, placed horizontally, under the anode (15), placed vertically. With a peristaltic pump through the electrolyte supply tube, then through a plastic dispenser (18) an electrolyte is supplied into the anode cavity (15), for example, the composition Cr₂SO₄•6H₂O - 20 g/l, H₂SO₄ - 40 g/l, NH₄COOH - 40-50 g/l, NH₄Br - 10 g/l, KCl - 60 g/l, H₃BO₄ -40 g/l, Na₂SO₄ -50 g/l, NH₄Cl - 75 g/l. The anode (15) in this case is a hollow plate made of graphite, inside which the electrolyte (2) drains through the hole of the plastic dispenser (18) with a diameter of, for example, 2 mm onto the cathode (14), and then draining it (electrolyte) into the electrolytic bath (2).

At the initial moment of time, a voltage of 60 V and a current density of 200 A / dm ² are applied, they wait 10 seconds, during this time electrochemical deposition of the chromium coating occurs, at 11 seconds the plasma is applied, for which the voltage is sharply increased to a value of 200 V. At this value a gas discharge burns in a vapor-air shell covering the entire surface of the plate. At 21 seconds, the discharge burning stops and the process of electrochemical deposition of a chromium coating is restarted at a voltage of 60 V and a current density of 200 A/dm ² . Thus, cyclic electrochemical deposition and exposure to plasma occur. If we consider the time interval of one cycle, then the electrochemical deposition in the cycle lasts 10 seconds, and the plasma exposure also lasts 10 seconds. The total time of coating formation takes on average 900 seconds. The deposition rate of the chromium layer is 0.03 - 0.06 mm/h.

Under these conditions of formation of a nanostructured coating, the minimum thickness of the resulting coating is 30 μm. Externally, the coating has a silver color.

Thus, from the above, we can conclude that the applicant has achieved the set goals and the claimed technical result , namely, a method and device for its implementation have been developed, eliminating the disadvantages of the prototype, namely, allowing to achieve a chromium layer deposition rate of 0.03 - 0, 06 mm/h. At the same time, it has been achieved:

1 - reduction of the surface roughness of the coating due to the fact that the discharges do not burn separately on the surface where the coatings are formed, but on the entire surface, since a smoothed voltage is used due to the capacitive induction filter attached to the power source; The surface roughness was measured with a model 283 profilometer according to GOST 19300-86.

2 - improving the appearance of the product, thanks to the proposed method of plasma exposure, according to which uniform nanostructured melting occurs, defects on the surface of the product are eliminated, grains are crushed, and mechanical and electrochemical properties are improved;

3 - reduction of the time of the process of plasma-electrochemical formation of nanostructured chromium coatings due to a continuous process consisting of two stages: at the first stage, a coating is applied by an electrochemical method, then a discharge burns, that is, plasma is applied, and the surface of the product is heat treated. When exposed to temperature, nanostructuring occurs, the discharge is extinguished, then the process of electrochemical deposition begins again, and so alternately from electrochemical and plasma effects, and thus a smooth nanostructured coating of the product is obtained in a shorter time, compared with the prototype, up to values of 0.03-0, 06 mm/h.

The claimed technical solution complies with the "novelty" patentability condition for inventions, since the set of features given in the independent claim of the invention has not been identified from the prior art studied by the applicant.

The claimed technical solution complies with the "inventive step" patentability condition for inventions, since the totality of the features listed in the independent claim and the totality of the technical results obtained have not been identified from the prior art studied by the applicant.

The claimed technical solution complies with the "industrial applicability" patentability condition for inventions, since the claimed technical solution can be implemented in industry through the use of materials, equipment and technologies known from the prior art.

Information sources

1. Patent 2409707 class. From 25 D 15/00. Electrolyte of chromium plating / Zhirnov Alexander Dmitrievich. - Application No. 2009139784/02, 2009.10.28, Appl. 2009.10.28, publ. 2011.01.20.

2. Patent 2125125 class. From 25 D 3/04. The method of electrochemical chromium plating / Malinin Vladimir Fedorovich - Application No. 97121625/02, 1997.12.24, Appl. 1997.12.24, publ. 1999.01.20.

3. Patent 2125126 class. From 25 D 3/04. The method of electrochemical chromium plating in a low-concentration electrolyte / Malinin Vladimir Fedorovich - Application No. 98102322/02, 1998.01.27, Appl. 1998.01.27, published 1999.01.20.

4. Properties of nanocrystalline Cr coatings prepared by cathode plasma electrolytic deposition from trivalent chromium electrolyte Cheng Quan, Yedong He / Beijing Key Laboratory for Corrosion, Erosion and Surface Technology, University of Science and Technology Beijing, 100083 Beijing, China.

Claims (8)

1. The method of plasma-electrochemical formation of a nanostructured chromium coating, which consists in the fact that at the first stage, galvanic deposition of chromium is carried out, for which the cathode, which is a chromium-plated product, is placed in an electrolytic bath with chromium plating electrolyte, then an anode is placed in an electrolytic bath with an electrolyte solution parallel to the cathode, while a capacitive induction filter is connected to the electrical circuit, an electric current is supplied 100-200 A / dm ² at a voltage of 40-60 V, current treatment is carried out to form a chromium layer on the metal surface; at the second stage, exposure to plasma is carried out, for which, when the thickness of the chromium coating reaches 0.5 μm at the first stage, the voltage of electrochemical deposition of chromium is increased to values of 150-200 V, as a result of which a gas discharge burns in a vapor-air shell, covering the entire surface of the plate, at At the same time, the capacitive induction filter included in the electrical circuit provides an adjustable smoothed voltage shape to a constant voltage that does not decrease to zero, which makes it possible for the plasma to act uniformly on the chromium-plated surface, while the discharge burning in the form of a plasma shell ensures the formation of a nanostructured chromium coating, then after that, combustion the discharge is quenched by reducing the voltage value until the plasma glow visually ceases to bring the current density to 40 A/dm ² , then the first and second stages are repeated until the desired thickness of the nanostructured chromium coating is obtained. 2. The method according to claim 1, characterized in that the cathode is used in the form of a metal rod, and the anode is in the form of a flat graphite plate. 3. The method according to claim 1, characterized in that the cathode is used in the form of a flat plate of metal, and the anode is in the form of a flat plate of graphite, a dielectric cover with a round hole is first tightly put on the cathode. 4. Device for plasma-electrochemical formation of nanostructured chromium coating, including an electrolytic bath with an electrolyte, an electrode system, including a cathode, which is a chromium-plated product, and an anode; the following are connected to the electrode system: an electrical power system, an oscilloscope with the ability to control the shape of the supplied voltage and electric current, additional resistance, a voltmeter with the ability to measure voltage, an ammeter with the ability to measure the discharge electric current, a thermocouple; at the same time, the power supply system consists of a diode bridge - a combination of diodes, a laboratory autotransformer, a capacitive induction filter, which is a high-voltage direct current source for creating and maintaining electric discharge burning with the ability to smoothly control the output voltage in the range from 0 V to 3 kV and the current in the range from 0 A to 10 A. 5. The device according to claim 4, characterized in that the cathode is made in the form of a metal rod, and the anode is made in the form of a flat graphite plate, while the cathode and anode are parallel to each other and immersed in an electrolyte that is in a stationary state in an electrolytic bath . 6. The device according to claim 4, characterized in that the cathode is made in the form of a flat plate of metal, and the anode is made in the form of a flat plate of graphite, a tightly fitting dielectric cover with a round hole is put on the cathode, while the cathode and anode are parallel to each other friend and immersed in an electrolyte that is in a stationary state in an electrolytic bath.

Images