RU2231578C1 - Method of electrolytic deposition of iron-vanadium alloy - Google Patents

Abstract

FIELD: methods of electrolytic deposition of solid hard-wearing covers.

SUBSTANCE: the invention presents a method of electrolytic deposition of solid hard-wearing covers, in particular the iron - vanadium covers used for recovery and a reinforcement of surfaces of components. The method provides for deposition of iron - vanadium cover from an electrolyte containing (in g\l): iron chloride - 350-400, metavanadate of an ammonium - 5-30, hydrochloric acid - 1.5-2.0, use of a variable asymmetric current with a coefficient of skewness - 1.2-6 and frequency of the current of 50 Hz at the temperature of electrolyte 30-50°С, an interval of the current cathodic densities of 30-60 А/decimeter. The technical result is an increase of microsolidity, wear resisting property, thickness of covers and speeds of their deposition.

EFFECT: the invention allows to increase of microsolidity, wear resisting property, thickness of covers and speeds of their deposition.

Description

The invention relates to the field of electrolytic deposition of hard wear-resistant coatings, in particular iron-vanadium coatings used to restore and harden the surfaces of parts.

A known method of electrolytic deposition from a chloride electrolyte containing iron (II) chloride 90 g / l, ammonium metavanadate 30 g / l, sodium chloride and water. The coating is deposited at a constant current at a cathodic current density of 5-12 g / l. (Vasko A.T. and Kovach S.K. Electrochemistry of refractory metals. Kiev: Technique, 1983, p. 92). The disadvantage of this method is the high roughness of the resulting coating and its poor adhesion to the metal base.

The prototype is a known method of electrolytic deposition of an iron-vanadium alloy from an electrolyte containing iron (II) chloride 90 g / l, ammonium metavanadate 30 g / l, sodium chloride 80 g / l. The deposition of the coating is carried out in the mode of a pulsed unipolar current at a current density of 300-1300 A / dm ² , the pulse frequency of 0.03-0.07 s (AS No. 1758091 IPC C 25 D 5/18, 3/56. The method of obtaining iron-vanadium coating Auth. OI Akhmerov, BC Kondratyev, AM Kudlai). The disadvantage of this method is the low microhardness and wear resistance of the resulting coating, low deposition rate of the coating.

To increase the microhardness, wear resistance of the resulting coatings, deposition rate and coating thickness, a method for electrolytic deposition of an iron-vanadium alloy from an electrolyte containing, g / l:

Ferric Chloride 350-400

Ammonium Metavanadate 5-30

Hydrochloric acid 1.5-2

The deposition process is conducted on an alternating asymmetric current with a frequency of 50 Hz, starting from an asymmetry coefficient of 1.2 and increasing to 6, a cathode current density of 30-60 A / dm ² , and an electrolyte temperature of 30-50 ° C. The acidity of the electrolyte is pH 0.8-1.2. It is cost effective because deposition occurs at high cathodic current densities and low electrolyte temperatures, which ensures a high deposition rate of coatings. The resulting coatings have high adhesion to the base, high microhardness and wear resistance.

The electrolyte is obtained by combining iron chloride and ammonium metavanadate.

The concentration of ferric chloride is in the range of 300-400 g / l. The lower limit indicates the zone of minimum viscosity. The upper limit indicates the zone of maximum electrical conductivity. (Shvetsov A.N. Fundamentals of the restoration of parts by ostalivanie. Omsk, 1973, p.

The amount of ammonium metavanadate is in the range of 5-30 g / l. Below 5 g / l, the use of ammonium metavanadate is impractical because the resulting hardness coating is close to hard iron coating. Above 30 g / l, the use of ammonium metavanadate leads to the formation of vanadium oxides, which sharply worsens the quality of the coating and reduces the hardness of the coating. The most optimal is the content of ammonium metavanadate 25 g / l. The resulting coating has a microhardness of the order of 8500 MPa.

The content of hydrochloric acid is in the range of 1.5-2.0 g / l. The upper limit is set for economic reasons, the electrodeposition of iron at the cathode occurs with the simultaneous discharge of hydrogen. With an increase in the content of hydrochloric acid, the amount of discharging hydrogen sharply increases and the current efficiency decreases. The lower limit is selected according to the qualitative characteristics of the structures of electrolytic iron. When the content of hydrochloric acid is less than 1.5 g / l, strong alkalization of the cathode layer occurs. The hydroxide formed in the near-cathode layer also turns on the coatings and this worsens their structure.

The temperature range is in the range of 30-50 ° C. The lower limit is limited by the diffusion properties of the electrolyte. The ion motion is slow and the deposition rate of the coating is low. Above 50 ° C, the use of electrolyte is unprofitable from an economic point of view. A qualitative change in the coating does not occur, but the cost of heating the electrolyte increases.

The cathodic current density is in the range of 30-60 A / dm ² . Below 30 A / dm ² the current density is not advisable to use, because The electrolysis process has a low coating deposition rate. At a cathodic current density above 60 A / dm ² , strong dendritic formation occurs and the current efficiency decreases sharply.

The beginning of coating deposition starts from the asymmetry coefficient β = 1.2, which provides a high adhesion of the coating to the base Gst = 300 MPa. If the asymmetry coefficient is lower than 1.2, the deposition process does not occur. In the process of electrodeposition, the asymmetry coefficient is gradually increased to β = 6, which is characterized by a high and stable deposition rate of the coating. A further increase in the asymmetry coefficient is not recommended, because with a further decrease in the anode component, the process switches to a mode close to direct current. Due to the different values of the asymmetry coefficient, it is possible to obtain coatings with various physical and mechanical properties.

Based on the tests performed, the optimal conditions for the electrodeposition method of an iron-vanadium alloy are the conditions described in the example.

The electrolyte consists of the following components in quantity, g / l:

Ferric Chloride 400

Ammonium Metavanadate 25

Hydrochloric acid 1.8

The process of electrolytic deposition of the coating is carried out at a temperature of 40 ° C and a cathodic current density of 50 A / DM ² . Mild steel is the anode. Previously, the part is subjected to degreasing with Viennese lime and anode treatment in a solution of 30% sulfuric acid. The deposition process begins at β = 1.2 and is gradually increased to β = 5 over 3-5 minutes. The coating has Gcc = 300 MPa, microhardness Нμ = 8500 MPa, deposition rate of 0.3 mm / h.

The proposed method has high performance due to the use of alternating asymmetric current. It is cost effective because Coating deposition occurs at a high cathodic current density and has a high coating deposition rate. The coatings obtained by the proposed method have high microhardness and wear resistance, which allows them to be used in the national economy for the restoration and hardening of surfaces of machine parts.

Claims (1)

The method of electrolytic deposition of an alloy of iron-vanadium from an electrolyte containing iron chloride, ammonium metavanadate, hydrochloric acid, characterized in that the deposition is from the electrolyte in the following ratio of components, g / l: Ferric Chloride 350 - 400 Ammonium Metavanadate 5 - 30 Hydrochloric acid 1.5 - 2.0 on alternating asymmetric current with a current asymmetry coefficient of 1.2-6 and a current frequency of 50 Hz at an electrolyte temperature of 30-50 ° C, an interval of cathodic current densities of 30-60 A / dm ² .