RU1813812C - Process for applying composite chromium coatings - Google Patents

Abstract

Usage: obtaining electrochemical composite coatings on metal products x. SUMMARY OF THE INVENTION: An ultrafine diamond powder in an amount of 0.5-2.5 g / l is added to a chromium plating electrolyte containing chromium ions and sulfuric acid. The powder is preliminarily irradiated with an electron stream with an absorbed dose of at least 7 Mrad in an oxidizing medium containing at least 2.5 mol of ammonium hydroxide per 1 mol of powder. 4 tab.

Description

with C

The invention relates to electrochemistry and is intended to produce electrochemical composite coatings of non-metallic products,

An object of the invention is to increase the wear resistance of a coating.

This goal is achieved by the fact that in the method for producing composite electroplated coatings, including electrodeposition in an electrolyte containing ions of a deposited metal, acid and ultrafine powder and subsequent heat treatment for 2-2.5 hours, according to the invention, the electrolyte contains ultrafine diamond powder in the amount of 0.5-2.5 g / l of electrolyte, previously irradiated with an electron stream with an absorbed dose of at least 7 Mrad in an oxidizing medium containing at least 2.5 mol of oxidizer per 1 mol

diamond, and heat treatment is carried out at a temperature of 150-200 ° C.

In the known technical solutions there are no features similar to those distinguishing the claimed solution from the prototype. Due to the fact that ultrafine diamond powder is dispersed in the electrolyte, the particles of which are charged with a positive charge when irradiated with an electron flow in an oxidizing medium, coatings produced by electrodeposition have higher wear resistance, because positively charged diamond particles precipitate faster, more uniformly and more firmly in the coating.

The method is carried out as follows. An ultrafine diamond powder with a particle size of less than 0.03 μm is mixed with an oxidizing agent (ammonium hydroxide) in an amount of 2.5; 3.0; 3.5 mol per 1 mol of diamond (i.e. 10.41 g; 12.5 g; 14.58 g of hydroxide

100

-l

with

i2 th

ammonium NHnOH per 1 g of diamond) and is irradiated with a stream of accelerated electrons until a dose of 7 is absorbed; 8; 10 mrad. After that, the diamond powder is dispersed in an amount of 0.5; 1.5: 2.5 g / l in an electrolyte containing 200 g / l of chromic anhydride and 2 g / l of sulfuric acid.

The product, made of steel 20 in the form of a disk with a diameter of 30 mm and a thickness of 1 mm, is subjected to electrodeposition in the obtained electrolyte at a temperature of 55 ± 3 ° C and a current with a specific value of 60 ± 3 A / dm. Then the product is subjected to heat treatment at a temperature of 150; 175; 200 ° C for 2 hours in a thermal furnace of the type SNOL-1,6; 2.5, 1/11-I2.

The study of specific wear resistance of coatings was carried out according to the density-density scheme. A P6M5 tool steel disk was used as a counterbody. Specific wear (weight reduction per unit of abradable surface) was measured at a relative speed of 8 m / s through the BOO m path at a specific pressure of 0.5 kg / cm2. The weight reduction of the samples was determined by weighing on an analytical balance VLA-200-M with an accuracy of 0.0001 g.

The results of studies to determine the optimal amounts of UVD of diamond dispersed in the electrolyte, heat treatment temperature, amount of oxidizing medium and absorbed radiation dose are given in Table 1, respectively; 2; 3; 4.

It can be seen from Table 1 that the optimum amount of dispersed ultrafine diamond powder per 1 liter of electrolyte is 0.5-2.5 g / l. As the amount of diamond UVD (less than 0.5 g / l) in the electrolyte decreases, the specific wear of the coating increases. An increase in the amount of diamond UVD of more than 2.5 g / l does not affect the specific wear of the coating, and the cost of the electrolyte and therefore the coating increases significantly.

Thus, a further increase in the content of diamond UDP in the electrolyte is not economically feasible.

From table 2 it is seen that the amount of oxidizing agent upon irradiation of the UDP of diamond with an electron stream should be at least 2.5 mol per 1 mol of diamond. With less

oxidizing agent the wear resistance of the coating is reduced.

From table 3 it is seen that the optimal absorbed radiation dose by ultrafine diamond powder is at least 7

Mrad. At an absorbed dose of less than 7 Mrad, the specific wear of the coating increases. At a absorbed dose even significantly exceeding 7 Mrad, the specific wear practically does not change.

From Table 4 it can be seen that the optimum heat treatment temperature is 150-200 ° C. At a heat treatment temperature below and above the indicated value, the specific wear of the coating increases, since at a low temperature the coating does not anneal and hydrogen does not subsequently remove from the coating, and at a temperature above 200 ° C diamond particles are graphitized. Both

increases the specific wear of the coating.

Comparative tests of the claimed method and the prototype showed that the specific wear of the coating product obtained by the claimed method is 29

mg / cm, of the coating obtained by the prototype method of 39 mg / cm, i.e. the wear resistance of the claimed galvanic coating is 1.34 times higher than the wear resistance of the coating obtained by the prototype method.

Claims (1)

The claims A method of producing composite chromium coatings, including electrodeposition in an electrolyte containing chromium ions, sulfuric acid and ultrafine powder, and subsequent heat treatment for 2-2.5 hours, characterized in that, in order to increase wear resistance, the powder is irradiated before electrodeposition electrons with absorbed dose of at least. 7 Mrad in a medium containing at least 2.5 mol of ammonium hydroxide per 1 mol of powder, diamond powder in an amount of 0.5-2.5 g / l is taken as an ultrafine powder, and heat treatment is carried out at 150-200 ° C. f ft) l and 11 a 1 table 2 Table 3 Table 4