SU1723206A1 - Deposition of composite coats by electroplating - Google Patents

Abstract

This invention relates to the electrodeposition of composite coatings. The purpose of the invention is to increase the wear resistance of coatings. The method of applying composite electrolytic coatings involves the implementation of a process in a flow-through electrolyte by applying an additional direct current to the direct current, which is passed along the surface to be coated in the direction of electrolyte movement. The use of a flow-through electrolyte and additional direct current makes it possible to regulate the content of non-conductive particles in the coating, as well as increase the deposition rate and reduce the roughness of the coatings. 3 dw., 3 tab.

Description

The invention relates to electrochemical coating and can be used in the application of composite coatings in the aviation, chemical, petroleum industries, as well as in the repair of parts.

There is a method of electroplating in which a constant magnetic field is applied along the deposition surface, which is created by passing a direct current through the cathode.

The main disadvantage of the known method of coating is low wear resistance due to the absence of electric current passing through the surface to be coated.

The closest in technical essence and the achieved result to the proposed -. Capable is an electrolytic chrome plating method in which pulsed is applied to a direct current.

Although the known method of coating makes it possible to increase the current efficiency and the deposition rate, however, it has the following disadvantages: reduced wear resistance of coatings, especially on nickel and copper matrices; high roughness of the surface being coated; technical difficulties in coating in hard to reach places.

The purpose of the invention is to increase the wear resistance of coatings.

The goal is achieved by the fact that in the electrolytic method of applying composite coatings from an electrolyte with solid particles, when an additional current is applied to a constant coating process, the flowing constant electrolyte is passed through the

cl

with

v | GOBO O O

the surface of the part in the direction of movement of the electrolyte.

When an additional current flows through the surface to be coated in the interelectrode space, a circular magnetic field is formed, which affects the dissociated ions moving in the electrolyte. In this case, the Lorentz Rl force will act on the electrolyte cations, determined by the equation

RL q NLL / e-Slna, (1)

where q is the charge of the electrolyte cation;

L / E is the average speed of electrolyte movement in the interelectrode space (MEP);

H is the intensity of the magnetic field in the MEP;

a is the angle between the velocity and intensity vectors H; in our example, a is 90 ° nSina 1.

The intensity of the magnetic field generated by the additional current is determined by the expression

H

.ЯР

where I is the additional current flowing over the surface being coated;

g - the radius of the coated part surface.

Under the action of the Lorentz force, electrolyte cations receive additional acceleration when moving toward the surface being coated. At the same time, they carry away non-conducting particles in the electrolyte, which constitutes the second phase. As a result of the passage of additional current over the surface being coated on the part, a more dense precipitate is formed with a low surface roughness, which significantly increases the wear resistance of the coating.

1 shows a device for carrying out the method, a central longitudinal section; in fig. 2 is a view A of FIG. one; in fig. 3 is a graph of the dependence and wear resistance of coatings deposited on various matrices on the additional current density, where curve I is for a chrome plating; II - for a copper coating with molybdenum disulfide when the electrolyte moves in the direction of the additional current; III - the same, when the electrolyte moves in the opposite direction; IV - for the nickel matrix and molybdenum disulfide when the electrolyte moves in the direction of the additional current; V - the same, when the electrolyte moves in the opposite direction.

A device for carrying out the proposed method of applying a composition

The coating contains a mandrel 1, a current-bearing water 2, 3, insulating rings 4, 5, 6, a washer 7, a nut 8, a workpiece 9, a detachable anode 10, sealing rings

5 11, Brush holders 12-14, copper-graphite brushes 15, technological current source 16, additional 17 current source, centrifugal pump 18, electric motor 19, coupling 20, electrolyte bath 21, pipes 10, 23.

The mandrel 1 is a shaft with a collar and a threaded portion. A mandrel 1 is installed in the spindle of the cathode head and is driven from it in rotation. Insulating rings 4, 5, 6 are coated on part 9 of the cylindrical surface of the mandrel 1. Current surfaces of the current 2 2 are mounted on the outer surfaces of the rings 5, 6, which are external

The 20 surfaces are in contact with the copper-graphite brushes 15 located in the brush holders 13, 14 connected to the additional current source 16. We cover item 9 with washer 7 and

25, the nut 8 is pressed against the end surfaces of the current leads 2, 3.

The negative bus of the process current source 17 through copper-graphite brushes 15 located in the brush holder 30, the mandrel 1 is connected to the part 9 to be coated, and the positive bus is connected to the anode 10. The anode 10 is installed with respect to the part 9 with a gap S chosen from technological considerations.

35 The centrifugal pump 18 is driven into rotation by the electric motor 19 through the coupling 20 and connected via a conduit 22 to an anode channel 10. The withdrawal conduit of the anode 10 is connected by means of a conduit 23 to a bath 21 filled with electrolyte.

The proposed method of applying composite coatings is carried out as follows.

45 The part to be coated 9 is mounted on the mandrel 1 and secured by means of a current supply 2, washers 7, nuts 8. The detachable anode 10 is installed relative to the part 9c with a gap S. After the part is installed

50 9 and anode 10, part 9 is rotated at an angular velocity (Wk, selected by their process variables).

In the gap S using a centrifugal pump 18, driven in rotation from

55 motor 19, through the pipe 22 from the bath 21 serves the electrolyte. In the interelectrode space, the electrolyte moves in the axial direction and through the pipe 23 is drained into the bath 21. The electrolyte, circulating in the interelectrode gap S, contains non-conducting particles of the composite coating and forms a suspension. After the suspension circulation system is turned on, the operating voltage is applied to the workpiece 9 and the anode 10 from the source of process current 17. At the same time, the technological current through the negative bus, copper-graphite brushes 15, the outer surface of the collar of the mandrel 1 is supplied to the part to be coated 9, and to the anode 10 through the positive bus of the source 17. After switching on the current source 17, an additional current source 16 is turned on. When you turn on this source, additional current flows through the surface to be coated. The density of the additional current j is determined by the expression

where m is the thickness of the layer through which the additional current 1 flows.

Current | impose a constant technological current and pass in the direction of the electrolyte. The electrolyte flows into the MEP with the speed L / e. By varying the density of the additional current j, it is possible to adjust the percentage of particles of the second phase in the coating, reduce the roughness of the part surface being coated, and thereby increase the wear resistance of the coating.

The invention is illustrated by examples, which are summarized in table. 1-3.

An analysis of coating examples shows the following.

When applying chromium coatings, the proposed method provides an increase in the rate of coating application by 11%; increase in wear resistance of coatings by 9.8%.

. When applying composite coatings based on copper and molybdenum disulfide, the speed of coating is increased by an average of 35% and wear resistance by 24%.

When applying composite coatings based on nickel and molybdenum disulfide, the coating speed increases by an average of 33% and wear resistance by 26%.

An analysis of the test results shows that the proposed method of applying composite coatings is most advantageous when applying copper and nickel composite coatings.

Thus, passing an additional current over the surface to be coated of the part, as compared with the prototype, provides an increase in wear resistance by an average of 25% and a reduction in roughness by a factor of 1.5.

The movement of the electrolyte in the direction of the movement of the additional current makes it possible to increase the wear resistance of the coatings by 2.8-3.3% compared with the movement of the electrolyte in the opposite direction.

It has been found that the additional current density has the greatest effect on wear resistance. The dependence of the wear resistance on the additional current density is shown in FIG. 3, which shows that the additional current affects the wear resistance at a current density of 320 kD / m2. Since the current density is directly proportional to the voltage U applied to the metal layer to which the coating is applied, the dependence of wear resistance on Voltage is similar to current density. This is seen from

equations

i U - lh

J o w

where j is the additional current density;

U is the auxiliary voltage; K is the electrical conductivity of the matrix material;

or is the length of the matrix layer through which the electric current flows.

Since the values of Eq and A do not change during deposition of the coating, equation (4) can be transformed as

J - CU -; (5)

Therefore, the dependences of the speed of coating, wear resistance on the density and voltage of the additional current will be the same and differ only in

scale.

Formulas of the Invention An electrolytic method of applying composite electrolyte coatings with solid particles, in which an additional current is applied to a direct current, characterized in that, in order to improve the wear resistance of the coatings, the process is carried out in a flow-through electrolyte.

the current is passed along the surface to be coated in the direction of the electrolyte.

Table 1

Wear resistance of coatings

IM / P1

during the movement of the electrolyte "the direction of the transmission of additional current

 direction opposite to the transmission;: current

bea flow electrolyte

Main current density

Additional current density, kA / m1

Deposition rate, 10 m / s

Electrolyte movement speed, and / s

The content of molybdenum disulfide in the coating, nes:

The same, ob.t Evenness, nor / 4t

when the electrolyte is moving. in the direction of passing additional current

when the electrolyte moves in the opposite direction

0,0088 0,0091

0.097

Tables

12.0

0.27

The composition of the electrolyte, g / l:

Nickel sulfate (NiS04)

Ammonium chloride

Sodium nitrate (NaN03)

Boric acid molybdenum disulfide Deposition conditions:

Density of the main current, kA / m2

Additional current density, kA / m2

Electrolyte movement speed, m / s

Deposition rate

The content of molybdenum disulfide in the coating, wt%,:

The same, about 0%

Wear resistance of coatings, mm3 / h:

when the electrolyte moves in the direction of passing additional current

in the opposite direction of passing additional current

Surface roughness,

Table3

0.14

6.7

Dendrites are observed.

Type A

SO 200 300 WO 500 600 700 BOO Density of additional current., KA / pg 0U2.3

Claims (1)

Claim The electrolytic method of applying composite coatings of an electrolyte with solid particles, in which an additional current is applied to the direct current, characterized in that, in order to increase the wear resistance of the coatings, the process is carried out in a flowing electrolyte, and an additional direct current is passed along the surface to be coated in the direction of movement of the electrolyte. Table Τ Indicators Coating Method Proposal · I Prototype being I well The composition of the electrolyte "g / l: Chromic anhydride 370 370 Sulfuric acid 1.8 1.8 Sodium hydroxide fifty fifty Sugar 1.5 1,5 Sodium lauryl sulfate 4 4 Deposition Conditions: The density of the main one · sq. "KA / m ^a 9.6 7.8 Density of longitudinal current, kA / m ’ 720 fifty The speed of electrolyte "m / s 1.9 -6 0.042: Deposition Speed »10 m / s 0,038 Ieanostability of coatings, IM ’/ H! when the electrolyte moves in the direction of transmission of additional current 0.0088 in the direction "opposite to current transmission 0.0091 without flowing electrolyte • 0,097 Table 2 Indicators Coating Method Proposed According to the prototype The composition of the electrolyte, g / l> 250 Copper sulfate (Cu ₂ SO ₄ ) 250 250 Sulfuric acid fifty fifty fifty Bromic acid (H ^ BrO ^) 2 2 2 Molybdenum disulfide M> s _e 20 20 20 Precipitation conditions1 The density of the main current, kA / m * 12.5 12.0 0.27 Additional current density, kA / m ^a 650 700 fifty Deposition rate, 10 ** m / s 0.3 0.27 0.19 The speed of the electrolyte, m / s 1.9 1.9 - The content of molybdenum disulfide in the coating, wt. "X: 3.9 3.8 2.1 The same thing 14.7 14.3 10.3 Wear resistance, mm ’/ h: 1.12 when electrolyte is moving in the direction of transmission 0.88 additional current 0.89 when electrolyte is moving IN opposite direction nom passing additional current 0.92 0.91 - Surface roughness, 10 * and 3.1 2,5 4.2 There are dendrites Table 3 Indicators Coating Method Proposed According to the prototype The composition of the electrolyte, g / l: Nickel sulfate (NiS0 ₄ ) 190 190 Ammonium chloride 3 3 Sodium nitrate (NaN0 ₃ ) 2.2 2.2 Boric acid M 1Λ Molybdenum disulfide 20 20 ; Deposition Conditions: The density of the main current, kA / m ² 1.27 0.31 Additional current density, kA / m ² 800 Electric speed lit, m / s 2.2 - Deposition rate oh s4 0.21 Molybde- disulfide content on the cover, May L: 4.8 1.98 ' The same, about <,% 18.7 9.7 Wear resistance of coatings, mm ³ / h: 0.14 when the electrolyte moves in the direction of transmission of additional current 0.11 in the opposite direction of passing additional current 0.105 > Surface roughness, 10 ^bm 2.2 6.7 Watch Xia dendrites L ---- h \ X_ _____ g Type A ------------- / 7 Figure 2. CM ι o Additional current density ^ kA / m ² FigZ