UA104439U - The electrolyte for electrochemical coating alloy cobalt-molybdenum-tungsten - Google Patents

Abstract

The electrolyte for electrochemical coating alloy cobalt-molybdenum-tungsten containing sulfate (II) cobalt tungstate, sodium molybdate, sodium citrate, sodium and potassium diphosphate further in the following component ratio, mol / dm3: Cobalt (II) sulphate (CoSO4∙7H2O) 0,1-0,2 sodium molybdate (Na2MoO4∙2H2O)) 0,04-0,12 sodium tungstate (Na2WO4∙2H2O) 0,06-0,16 sodium citrate (Na3C6H5O7∙5,5H2O) 0,2-0,3 potassium diphosphate (K4P2O7) 0.3-0.7.

Description

A useful model belongs to electroplating, namely the development of an electrolyte for the electrochemical synthesis of functional coatings with alloys of cobalt with refractory metals (tungsten and molybdenum) on a steel or copper base. The purpose of the useful model: the development of a stable electrolyte for the formation of coatings with cobalt-molybdenum-tungsten alloys with a high content of refractory metals (tungsten and molybdenum) and high adhesion to the substrate. The resulting coatings can be applied to parts that work in harsh operating conditions and must have high microhardness, wear and corrosion resistance.

Citrate electrolyte with the addition of ethylenediaminetetraacetic acid (EDTA) is known for the electrochemical deposition of coatings with Co-Mo-M/ |1|Yi alloys. The composition of the electrolyte is shown in Table 1.

Table 1.

The pH value of the solution is maintained in the range of 1-3. The process is carried out at a temperature of 20-35 °C and a cathode current density of 1 to 5 A/dm.

The disadvantages of the above-mentioned electrolyte are low current output (VS), and synthesized coatings are unevenly distributed over the surface and have a dense network of cracks.

The closest in composition, which was chosen as a prototype, is the citrate-ammonia electrolyte for the precipitation of the cobalt-molybdenum-tungsten alloy |2I|, (the composition is shown in Table 2).

Table 2.

The process is carried out at a temperature of 25-30 "C, a current density of 2-8 A/dm7, with constant stirring using cobalt anodes.

The disadvantage of this electrolyte is the danger of ammonia evaporation and the need to purify wastewater and washing water from its compounds, as well as the low concentration of tungstates and molybdates, which leads to rapid impoverishment of the solution in terms of the content of refractory metals and requires frequent adjustment of the solution.

The useful model is based on the task of developing a stable electrolyte for the formation of coatings with cobalt-molybdenum-tungsten alloys with an increased content of tungsten and molybdenum and high adhesion to the substrate, which have high microhardness, wear and corrosion resistance.

The task is solved thanks to the fact that, in addition to alloying compounds (cobalt (I) sulfate, sodium tungstate and sodium molybdate) and sodium citrate, potassium diphosphate is additionally introduced into the electrolyte as a ligand (table 3).

Table C

Cobalt coplanar plates were used as soluble anodes. Solutions were prepared from analytically pure reagents, which were dissolved in a small amount of warm water (30 "C), after which potassium diphosphate was mixed with cobalt (II) sulfate and sodium citrate with sodium tungstate and molybdate. Then everything was mixed and the electrolyte was left for several hours for establishment of an equilibrium state and formation of electroactive complexes.

The high dispersive capacity of the electrolyte ensures the deposition of uniform and light-colored coatings. The alkalinity of the solution increases the stability of the electrolyte, which increases its service life. Thanks to the specified pH interval and the proposed ratio of the concentrations of the components in the electrolyte, citrate, diphosphate and mixed heteronuclear citrate-diphosphate complexes of cobalt with oxometalates (tungstates and molybdates) are formed, which ensure the deposition of fine-crystalline, uniform coatings firmly attached to the base containing refractory components, wt. 90: F(Mo) - 3-44, F(M/) - 2-45.

The proposed electrolyte can be used for the deposition of cobalt-molybdenum-tungsten coatings on steel and copper parts at an electrolyte pH of 8-10, a temperature of 20-60 "С, a current density in the stationary mode of 2-8 A/dm? or a unipolar pulse current with an amplitude of 4- 20 A/dm: with different pulse and pause durations with constant stirring.

Samples made of copper and steel measuring 20x10 mm were used for coating with cobalt-molybdenum-tungsten alloy. Preparation of the surface of the parts before applying the metal coating was carried out by standard methods. Electrochemical deposition was carried out from electrolytes 1-7, the composition of which is given in Table 4.

Table 4 1 Her 2 |of 4 | 516 7 mamubsgNnaO | 006 | 01 | 06 | 05 | (B 06

Example 1

From the Mo 1 electrolyte in the stationary mode at the stomatal density | - 6 A/dm2 coatings containing 77 95 cobalt, 16 95 molybdenum and 7 96 tungsten were obtained. The current yield was 80 95, the deposition rate was 0.9 μm/min.

Example 2

З З of the Mo 5 electrolyte in the pulse mode at the current density | - 12 A/dm? and time parameters of electrolysis (pulse duration 2 ms, pause duration 20 ms), coatings containing 69% cobalt, 22% molybdenum, and 9% tungsten were obtained. Current output - 85 95, deposition rate - 0.5 μm/min.

Information on the composition of the proposed electrolyte, electrolysis modes, and obtained results are given in Table 5.

Table 5

Parameters of electrolysis | Prototype Useful model of coating characteristics sodium citrate 0.25-0.28 cobalt sulfate 0.2 sodium molybdate 0.03-0.07 cobalt sulfate what

The composition of the electrolyte, sodium tungstate 0.06-0.1 sodium molydate U, o 06 4 mol/dm ammonium chloride 0.3 sodium tungstate 0.06-0.16 . sodium citrate 0.2-0.3 sodium sulfate 0.1 potassium phosphate 0.3-0.7 boric acid 0.1 d MO sodium hydroxide to pH 5-6

A/dm

Duration, s: pulse 0.5-103-2-102 pause 2103-5102

Content, 9Uo: cobalt 78.8-83 35-80 35-82 molybdenum 5.6-8.5 2-45 11-35 tungsten 8.7-12.7 10-25 3-44 coatings fine-crystalline bonded to the base

Thus, it is possible to apply high-quality coatings with cobalt-molybdenum-tungsten alloys containing refractory metals, wt. 95: (0(Mo) - 3-44, F(Mu) - 2-45), with a current output of 60-92 95. Coatings are shiny, fine-crystalline, without internal stresses and cracks.

Sources of information: 1. Aeiii5Ki M. IpYanepse oi Sopsiapi Madpeiis Rivia op pe EIesigoderoziiop oi Sobak apa Sobai

APouz / M. Aeiiip5Ki // Ipi. ). Eiesigospet. 5 - 2013. - M. 8. - R. 12192-12204. 2. Utility model patent Mo 81121, Ukraine, IPC C250 3/56 (2006.01) Electrolyte for forming coatings with cobalt-molybdenum-tungsten alloy / Sakhnenko M.D., Vedh M.V.

Zyubanova S.I., Gapon Y.K.; Applicant and owner of the patent NTU "Khpi", publ. 25.06.2013, Bull.

Mo12.

Claims (1)

FORMULA OF USEFUL MODEL Electrolyte for the electrochemical synthesis of cobalt-molybdenum-tungsten alloy coatings, containing cobalt sulfate (I), sodium tungstate, sodium molybdate, sodium citrate, which is distinguished by the fact that potassium diphosphate is additionally introduced into the electrolyte in the following ratio of components, mol /dm: cobalt (II) sulfate (SoBO 7 HO) 01-02 sodium molybdate (Mag"MoO-2H2O) 0.04-0.12 sodium tungstate (MaguO 22) 0.06-0.16 sodium citrate (MazSeNho; :5.5H20) 0.2-0.3 potassium diphosphate (KaRho?) 0.3-0.7. 222 KompyuternaverszhaD Shevvrun 333333 State Intellectual Property Service of Ukraine, str. Vasyl Lypkivskyi, 45, m. Kyiv, MSP, 03680, Ukraine SE "Ukrainian Institute of Intellectual Property", str. Glazunova, 1, m. Kyiv - 42, 01601