RU2422563C1 - Electrolyte for electro-chemical sedimentation of composite chromium coating - Google Patents

Abstract

FIELD: metallurgy. ^ SUBSTANCE: electrolyte contains (g/l): 150-300 of chromium anhydride, 1.5-3 of sulphuric acid, 0.03-0.08 of nano-carbonic material with amount of graphene layers as many, as 30, diameter of fibres from 10 to 60 nm, length not less, than 2 mcm and amount of structured carbon not less, than 95 %. ^ EFFECT: pore-less chromium coating of high micro-hardness and low non-uniformity. ^ 2 cl, 1 ex

Description

The invention relates to the field of electrochemical deposition of metal coatings, in particular chromium, and can be used to obtain a corrosion-resistant, hard, heat- and wear-resistant coating in mechanical engineering, electronics and other industries.

Known chromium electrolyte [1], containing chromic anhydride 150-250 g / l, sulfuric acid 1.5-2.5 g / l, ultrafine silicon particles 3.0-30 g / l and derivatives of phosphorylated tibamides 0.1-1 , 0 g / l. Such an electrolyte allows to obtain coatings to protect products from high temperature oxidation and creep, i.e. with high indicators of heat resistance and heat resistance.

The main disadvantage of this electrolyte is the low microhardness of the resulting coating;

Known electrolyte for applying composite coatings based on chromium

[2] containing chromic anhydride 200-250 g / l, sulfuric acid 2.0-2.5 g / l, the addition of benzoylpyruvoylhydrazinocarbonylmethylpyridinium chloride 0.1-0.5 g / l and particles of the solid phase - dispersed boron nitride particles 8 -20 g / l and calcium fluoride 40-60 g / l. Dispersed particles of boron nitride and calcium fluoride are preferably used in a mass ratio of 1: (3-5). Such an electrolyte provides an increase in the antifriction and ductility of chromium coatings due to the inclusion of particles of solid lubricant in the composition of composite sediments and a decrease in the microhardness of the chromium matrix.

The disadvantages of this electrolyte are:

- a large number of particles of the solid phase, which complicates the preparation and use of the electrolyte and makes it impossible to reinforce it when it is depleted;

- low microhardness of the resulting coating;

- large unevenness of the resulting coating.

These shortcomings have been partially eliminated in the electrolyte for applying chromodiamond coatings [3].

In the electrolyte containing chromic anhydride, sulfuric acid, potassium silicofluoride and barium sulfate, a diamond-containing charge is additionally introduced, which may include ultrafine diamonds in an amount of 40 = 60 wt.%.

This composition is characterized by the following disadvantages:

- low microhardness of the resulting coating;

- large unevenness of the resulting coating.

The technical result of the invention is to obtain non-porous chromium coatings with high microhardness and low unevenness.

The technical result is achieved in that the electrolyte for the electrochemical deposition of a chromium coating containing chromic anhydride, sulfuric acid and water, additionally contains carbon nanomaterial with the number of graphene layers not more than 30, fiber diameter from 10 to 60 nm, length not less than 2 microns and structured carbon not less than 95%, with the following ratio of components, g / l:

Chromic Anhydride - 150-300

Sulfuric acid - 1.5-3

Nanocarbon material - 0.03-0.08.

As a nanocarbon material, the Taunite nanocarbon material purified from the nickel catalyst used for its synthesis was introduced into the electrolyte.

Such an electrolyte is characterized by a minimum amount of components and dispersed additives.

The electrolyte is prepared as follows.

Pre-chromic anhydride is dissolved in distilled water at a temperature of 60-70 ° C. After that, sulfuric acid is added in an amount of 1% by weight of the mass of chromic anhydride. The electrolyte is mixed and run in for the purpose of accumulating Cr ³⁺ ions at a temperature of 45-50 ° C for 12 hours.

After that, a nanocarbon material with a number of graphene layers of no more than 30, a fiber diameter of 10 to 60 nm, a length of at least 2 μm and a quantity of structured carbon of at least 95% is added to the electrolyte solution and the electrolyte is treated on an ultrasonic unit with a frequency of 22 kHz to reduce the size agglomerates from nanocarbon tubes and their more uniform distribution in the electrolyte. As a carbon material, it is preferable to use carbon nanomaterial “Taunit”, a manufacturer of carbon nanomaterial LLC “NanoTechCenter”, Russia, Tambov.

The surface preparation of the parts before plating is carried out by standard methods using known solutions.

Precipitation is carried out at a temperature of 45-60 ° C. Function of changing current: 1.5 minutes, work is carried out on a current of reverse polarity (when the part is the anode), while the anodic current density is 40 A / dm ² , then the direct polarity is turned on (when the part is the cathode) and the current is pushed for 1 minute , the cathodic current density in this case is 150 A / dm ² , then within one minute a smooth transition is made to the cathodic current density of 70 A / dm ² .

Example

The electrochemical deposition of the coating on a previously prepared surface of the base from a steel St3 material is carried out in an electrolyte containing (in g / l):

Chromic Anhydride - 150-300

Sulfuric acid - 1.5-3

Nanocarbon material “Taunit”, purified from nickel catalyst - 0.04.

The process is carried out at a temperature of 50 ° C. Function of changing current: 1.5 minutes, work is carried out at a current of reverse polarity (when the part is an anode), while the anode current density is 40 A / dm ² . Next, the current switches to direct polarity (when the part is a cathode) and the current is pushed for 1 minute, the cathode current density in this case is 150 A / dm ² ; then, within one minute, a smooth transition to a cathodic current density of 70 A / dm ^{2 is} achieved, at which coating is applied for 60 minutes. During this time, a coating with an average thickness of 21 microns is obtained.

The resulting composite coating in terms of "microhardness" exceeds conventional chromium coatings by 1.5-1.6, and chrome-diamond coatings by 1.3-1.4 times.

Information sources

1. RF patent №2126463, IPC C25D 03/04, 15/00 1998

2. RF patent No. 2117080, IPC C25D 3/00, 1998

3. RF patent No. 2107115, IPC C25D 15/00, 1998

Claims (2)

1. An electrolyte for electrochemical deposition of a chromium coating containing chromic anhydride, sulfuric acid and water, characterized in that it further comprises a nanocarbon material with a number of graphene layers of not more than 30, a fiber diameter of 10 to 60 nm, a length of at least 2 microns and an amount structured carbon of at least 95% in the following ratio of components, g / l:
chromic anhydride 150-300 sulphuric acid 1,5-3 nanocarbon material 0.03-0.08 2. The electrolyte according to claim 1, characterized in that, as the nanocarbon material, the nanocarbon material Taunit is introduced into the electrolyte composition, purified from the nickel catalyst used for its synthesis.