BG66882B1 - Nickel coating modified with nano-diamond particles and a method for its production - Google Patents

Abstract

With the method, according to the invention, nickel coatings with thickness from 6 to 15 µm are obtained, modified with nano-diamond particles, on low- to medium-carbon content steel, from a standard acidic nickel electrolyte containing nano-diamond particles with sizes from 1 to 200 nm in an amount of 0.1 to 20 g/l, whereby the nano-diamond particles are added to the standard nickel electrolyte with continuous stirring for 1-1.5 h in the form of a water suspension with concentration from 5 to 200 g/l, activated for 10-60 min through ultrasonic treatment. The electrolyte thus prepared is stirred continuously for 0.5 to 1 hour while at the same time its temperature is raised from 25 to 35° C, after which, at the same temperature and current density of 1 to 5 A/dm2, the nickel coating takes place for a duration of 1 to 25 minutes. The characteristics such as hardness, wear resistance and corrosion resistance of the nickel coating modified with nano-diamond particles are increased by the combination of parameters of the method, according to the invention.

Description

Field of the invention

The invention relates to a nickel coating modified with nanodiamond particles and to a process for its preparation, in particular to low-carbon to medium-carbon steel articles.

BACKGROUND OF THE INVENTION

To improve the wear resistance and lubricity of the drilling machine head, electrochemical or chemical coating based on chromium, nickel, copper, etc. has been proposed. and superabrasive particles such as transition metal carbides, diamonds with nanosizes from 0.1 to 100 nm (1).

Technical essence of the invention

It has surprisingly been found that the hardness, wear resistance and corrosion resistance characteristics of the nickel-modified nickel-plated nickel coating increase with the combination of process parameters according to the invention.

The process according to the invention produces nickel coatings with a thickness of 6 to 15 ppm, modified with nanodiamond particles, on low-carbon to medium-carbon steel, from a standard acidic nickel electrolyte containing nanodiamond particles with a size of 1 to 200 nm in an amount of 0.1 to 20 g / Ι, the nanodiamond particles being added to the standard nickel electrolyte with continuous stirring for 1-1.5 h as an aqueous suspension with a concentration of 5 to 200 g / Ι, activated for 10-60 min by ultrasonic treatment. The electrolyte thus prepared is stirred continuously for 0.5 to 1 hour while at the same time its temperature is raised from 25 to 35 ° C, after which, at the same temperature and current density from 1 to 5 A / dm ² , nickel plating takes place for a time from 1 to 25 hours. min.

The standard nickel acid electrolyte is an aqueous solution of NiSO ₄ and Na ₂ SO ₄ and buffer components NaCl and H ₃ BO ₃ in the following concentrations: NiSO ₄ - 128-135 g / 1, Na ₂ SO ₄ - 60-68 g / 1, NaCl - 15 g / l, H ₃ BO ₃ - 20 g / l as the pH of the solution is maintained in the range 5.5-5.8. In electrodeposition, a nickel metal anode of different shapes is used depending on the shape of the sample (article) prepared for coating. The cathode is the sample itself. The anode and cathode are connected to a current source, and during the process an ammeter measures the strength of the current flowing through the circuit.

By combining the parameters characterizing the method according to the invention, coatings are obtained that meet different requirements depending on the purpose of the coated parts, whose characteristics such as hardness, wear resistance and corrosion resistance are increased.

Microhardness from 2500 to 5000 MPa of the coatings obtained by the method according to the invention is achieved at a concentration of nanodiamond particles from 1 to 5 g / Ι, current density from 3 to 5 A / dm ² , process duration from 15 to 25 min and electrolyte temperature from 25 to 35 ° C;

Wear resistance, measured as weight loss, below 0.1% of the coatings obtained by the method according to the invention is achieved at a concentration of nanodiamond particles of 10 to 20 g / l, current density of 3 to 5 A / dm ² , duration of the process from 15 to 25 minutes and the electrolyte temperature from 25 to 35 ° C;

Corrosion resistance score 7 with a ten-point system (EN ISO 9227 - 2006) of the coatings obtained by the method according to the invention is achieved at a concentration of nanodiamond particles from 1 to 5 g / Ι, current density from 1 to 3 A / dm ² , process duration from 5 to 15 min and electrolyte temperature from 25 to 35 ° С.

It was found that the presence of nanodiamond particles in the nickel electrolyte increases the metal yield and the thickness of the coating layer at the same galvanization parameters and that at a constant concentration of nanodiamond particles in the electrolyte the metal yield and layer thickness increase with increasing current density. and the duration of galvanization. The metal yield and the layer thickness are the highest at nanodiamond particle concentrations in the electrolyte of 5-10 g / Ι (Table 1). The presence of nanodiamond particles in the electrolyte increases

Descriptions of issued patents for inventions № 06.1 / 17.06.2019 microhardness *** of the modified coatings, as well as of the steel matrix, immediately below the deposited nickel layer. The microhardness of the nickel coating at C _ND = 20 g / l is 2712 MPa, and that of the matrix is 2148 MPa at a current density of 3 A / dm ² and a process duration of 15 min. The microhardness of the coating increased by about 45% compared to that of pure nickel coating (C _ND = 0) and that of the matrix by about 25% (Table 2 and Figure 6). The addition of nanodiamond particles to the electrolyte also affects the physical and chemical properties of the resulting coatings. As the concentration of nanodiamond particles in the electrolyte increases to a certain value (5 g / Ι), the wear of the surface decreases, respectively the wear resistance increases, after which the wear of the surface increases (Table 3 and Fig. 8). The same trend is observed in the change of the coefficient of friction (Fig. 9). The corrosion rate * * also depends on the concentration of diamond nanoparticles in the electrolyte, as shown in Tables 4, 5 and FIG. 13. The lowest corrosion rate and respectively the highest corrosion resistance is observed at a concentration of nanodiamond particles of 2 to 5 g / l.

Note:

* - wear resistance is determined under dry friction conditions;

** - corrosion resistance is defined in 3.5 wt. % NaCl solution or in salt spray according to EN ISO 10289;

*** - microhardness is determined by metallographic analysis.

Explanation of the attached figures

Figure 1 - microstructures of nickel plated galvanized alloys with different concentrations of nanodiamond particles, x200:

Figure 1a - at C _ND = 0.1 = 1 A / dm ² , 1 = 15 min;

Figure 16 - at C _ND = 1,1 = 1 A / dm ² , 1 = 15 min;

Figure 1c - at C _ND = 5.1 = 1 A / dm ² , 1 = 15 min;

Figure 1d - at C _ND = 20.1 = 1 A / dm ² , 1 = 15 min.

Figure 2 - microstructures of galvanic coatings of nickel, obtained at different current densities. C _ND = 5 g / 1.1 = 15 min, x 500:

Figure 2a - at 1 = 1 A / dm ² Figure 26 - at 1 = 2 A / dm ² Figure 2c - at 1 = 3 A / dm ²

Figure 3 - microhardness of nickel coating and steel matrix of a sample without nanodiamond particles.

Figure 4 - Microhardness of nickel coating and steel matrix of a sample with nanodiamond particles at a concentration of 1 g / l.

Figure 5 - microhardness of nickel coating and steel matrix of a sample with nanodiamond particles at a concentration of 5 g / l.

Figure 6 - microhardness of the nickel coating and the steel matrix depending on the concentration of ND in the electrolyte.

Figure 7 - schematic view of the device "block ring".

Figure 8 - wear of the samples during friction depending on the concentration of nanodiamond particles in the electrolyte.

Figure 9 - values of the coefficient of friction depending on the concentration of nanodiamond particles in the electrolyte.

Figure 10 - surface topography of a sample obtained from an electrolyte without nanodiamond particles, current density 3 A / dm ² for a time of 15 min.

Figure 11 - surface topography of a sample obtained from an electrolyte with nanodiamond particles at a concentration of 5 g / Ι, current density 3 A / dm ² for a time of 15 min.

Figure 12 - surface topography of a sample obtained from an electrolyte with nanodiamond particles at a concentration of 20 g / Ι, current density 3 A / dm ² for a time of 15 min.

Descriptions of issued patents for inventions № 06.1 / 17.06.2019

Figure 13 - dependence of the corrosion rate on time.

Figure 14 is a multistage shaft with a pure nickel coating and is a nickel coating modified with 5% nanodiamond particles.

Figure 15 - technological scheme.

Detailed description of the invention

The invention is illustrated by the following embodiments.

Example 1 Steel articles are subjected to a preliminary preparation involving degreasing, which is carried out with organic solvents. After removal from the degreasing solvent, the parts are immersed in denatured alcohol at room temperature for about 5 rain. Degreased and washed with alcohol products are air dried.

Degreased and dried products are stained in an aqueous solution of sulfuric acid (H ₂ SO ₄ ) with a concentration of 20 vol. % (V _H2SO4 / V _H2O = 1/4) at a temperature of about 50 ° C until complete removal of the oxide layer. The duration of the staining depends on the degree of oxidation of the surface of the products and is determined for each case, varying about 15 minutes.

After staining, the parts are washed thoroughly with running water, then immersed in denatured alcohol at room temperature for about 5 rain and air dried.

The nickel-plating electrolyte includes crystalline nickel sulphate - (NiSO ₄ .7H ₂ O - 240 g / 1), crystalline sodium sulphate - (Na ₂ SO _4. ЮН ₂ О -150 g / Ι), crystalline sodium chloride - (NaCl -15 g / 1), crystalline boric acid (H ₃ BO ₃ - 20 g / () and aqueous suspension of nanodiamond particles with sizes 1 to 200 nm, pre-activated with an ultrasonic apparatus for 10-60 rain at a concentration of 1 and 20 g / 1. The dry crystalline nickel sulphate in the appropriate amount is dissolved in water, then the remaining components are added sequentially. Mix well, heat the solution and turn green. The solution is clear. Filter if necessary. After the addition of the appropriate amount of nanodiamond particles, the electrolyte is stirred with an electric stirrer for about 1 hour, whereby it acquires a cloudy light brown-green color.

The pre-nickel-plated parts and the "witnesses" are immersed in the electrolyte that should cover them.

The process is controlled by periodically measuring the pH of the solution, which must be maintained in the range of 5.2-5.8; current density varies from 1 to 3 A / dm ² ; the duration of electrolytic nickel plating varies depending on the desired layer thickness and is from 5 to 15, sometimes up to 25 min; the temperature of the nickel electrolyte is 25-30 ° C; the concentration of nanodiamond particles in the electrolyte is from 1 to 20 g / l.

Example 2. The process described in example 1 is carried out in an analogous manner, with the difference that the concentration of nanodiamond particles in the nickel electrolyte is from 1 to 5 g / Ι, the current density is from 3 to 5 A / dm ² , the duration of the process is from 15 to 25 minutes and the electrolyte temperature is from 25 to 35 ° C.

Example 3. The process described in Example 1 was carried out under identical conditions, except that the concentration of nanodiamond particles in the nickel electrolyte was from 10 to 20 g / l.

Example 4. The process described in Example 1 is carried out in an analogous manner, with the difference that the concentration of nanodiamond particles in the nickel electrolyte is from 1 to 5 g / Ι, the current density is from 1 to 3 A / dm ² , the duration of process from 5 to 15 min.

Comparative Example 5 Similarly to Example 1, nickel plating processes were performed under identical conditions, but in the absence of nanodiamond particles in the electrolyte.

All received products are subject to control.

- Coating weight. At each process of electrodeposition in the bath are placed prototypes - "witnesses". It is on them that the weight is determined before and after covering. Weigh the balance on an analytical balance to the nearest ± 1x10 ^-4 g. The difference in weight, Ag, per unit area of the sample is the metal yield, or

Ag '= Agx10 ³ / S [mg / cm ² ]

Descriptions of issued patents for inventions № 06.1 / 17.06.2019

- The thickness of the nickel layer is determined by:

Gravimetric method. The thickness of the coating, 1, is calculated from the yield of metal, Ag, by the formula:

= Ag'xlO / p [pm] where p is the density of the metallic nickel, p = 8.9 g / cm ³ [EN ISO 1461/2002]

Metallographic method based on measuring the thickness of the coating in a cross section with a metallographic microscope. The sample for making the cut is cut by the "witness". The thickness of the layer is measured in 5 points, evenly distributed across the section. The arithmetic mean is taken. The relative error of the method is ± 2%.

To determine the influence of the individual parameters of galvanization on the characteristics and properties of the electrodeposition layer, as well as the influence of the concentration of nanodiamond particles on the characteristics and properties of the modified nickel layer, a number of tests were performed.

Table 1. Influence of process parameters on metal yield and layer thickness

№ on probate Density of current Duration of the process Concentration It's ND electrolyte, Characteristics of the modified Ni layer Dpbni on metal Thickness is » pour - Α / φτι ¹ min g / 1 mgfcin ² pm i 2 of 1 4 ' 5 6 L 1 5 0 0.927 1,042 th most common 2 1 Yu 0 1,865 th most common 2,095 th most common 3 1 15 0 2,218 th most common 2,492 th most common 4 d 5 0 1,750 th most common 1,968 th most common 5 1 10 0 3.0 3374 6 2 15 0 4.14 4,652 th most common 7 3 5 0 2.83 3,183 th most common 8 3 10 0 4.B7 5,473 th most common 9 3 15 0 8.06 9,059 th most common 10 1 5 1 0367 0D13 11 1 10 1 1,905 th most common 2.14 12 1 15 1 2.32 2,604 th most common is 2 5 1 3.5 3,507 th most common 14 2 10 1 2.15 2.15 15 2 15 1 4.ЕО 4,798 th most common 16 3 5 ] 6.04 6-7S n 3 10 1 9.95 IL18 18 3 15 1 7.9 8.89 19 1 5 .5 1.89 2,125 th most common 20 1 10 5 1.93 2,169 th most common 21 1 15 5 2.88 3,233 th most common 22 2 5 5 2.99 3,363 th most common 23 2 10 5 2.96 3346 24 2 15 5 6,056 th most common 6-805 25 3 5 5 2.13 2.39 26 3 10 5 4.94 5.55 27 3 15 5 «31 9.33В

Descriptions of issued patents for inventions № 06.1 / 17.06.2019

28 1 5 ю 1,057 th most common 1.18S 29 1 10 10 2,077 th most common 2,333 th most common 30 1 15 10 2,097 th most common 2356 31 2 5 10 1.87 2J02 32 2 10 10 2.98 3,356 th most common 33 2 15 10 5.19 5-833 34 3 5 10 2.29 3363 35 3 10 10 5.66 6,364 th most common % 3 15 10 7,087 th most common 7,962 th most common 37 1 5 20 1,197 th most common 1,346 th most common ЗЯ 1 10 20 1.22 1333 39 1 15 20 1.95 2.1% 40 2 5 20 1.74 1,953 th most common 41 2 10 20 5,366 th most common 5,796 th most common 42 2 15 20 3.96 4,454 th most common 43 3 5 20 2.19 2,463 th most common 44 3 10 20 4.29 4.Я2 45 3 15 20 7,044 th most common 7,915 th most common 46 3 25 20 10.8 12,149 th most common

Microstructural analysis was performed on all samples and the microhardness was examined. The data obtained are illustrated in Figure 1.

The coating is firmly bonded to the substrate and is visibly homogeneous at a nanodiamond concentration of up to 5 g / Ι. At higher concentrations the coating is torn.

As the current density increases under the same other galvanizing conditions, the thickness of the coatings increases (Fig. 2).

The microhardness of the coatings was determined on microgrinds cut from different samples at a load of 50 g, a duration of 10 s and a loading speed of 10 g / s. The microhardness is determined at points on the surface area and in the steel matrix (Figures 3, 4 and 5).

The results of the microhardness study of samples obtained at different concentrations of nanodiamond particles in the electrolyte are presented in Table 2 and Figure 6. The presence of nanodiamond particles in the electrolyte increases the microhardness of the modified coatings as well as the steel matrix just below the nickel layer. The microhardness of the nickel coating at C _ND = 20 g / l is 2712 MPa, and that of the matrix is 2148 MPa at a current density of 3 A / dm ² and a process duration of 15 min. The microhardness of the coating increased by about 45% compared to that of pure nickel coating (C _ND = 0) and that of the matrix by about 25%.

Table 2. Microhardness of nickel Vickers coatings at current density 3 A / dm ² and process duration 15 min

Obalsts № Cnd, JJ / 1 HV coating, MPa HV matrix, MPa 9 0 1Я72 1728 18 1 2053 1751 27 5 2180 1809 36 10 2357 2051 45 20 2712 _ ^2I4S

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Chemical and mechanical properties of ND-modified nickel coatings

Wear resistance of nanodiamond particle modified coatings.

Nickel coatings and nanodiamond-modified nickel coatings are applied to specially prepared samples according to the requirements of the block ring wear test device (Fig. 7).

During the test, the sample (1) measuring 15 x 5 x 10 mm is mounted in a holder 4 containing a hemispherical insert 3, which ensures correct contact between the sample and the steel ring 2 with a hardness of 55 HRC. The steel ring rotates at a constant speed of 136 rpm. The test surface of the specimen is perpendicular to the direction of loading. The sample is pressed against the ring with a force of 150 N ± 1%.

Mass loss is measured after 500 m of friction. The results are shown in Table 3.

Table 3. Results of measuring the wear of the samples

Cnd 8L 1 A / din ¹ mi ε mi ε Am, ε Πιπ. % AWft. ia 0 3 7.24866 7.24465 0.00401 0-055 0.675 I 3 7.25934 7.2563 0.00304 0.042 0.587 5 2 7.20032 7.19783 0.00249 0.035 0.605 5 Ί 3 7.25879 7/25687 0.00192 0.026 0.586 10 2 7.22569 7.22196 0.00373 0.052 0.702 10 3 7.28432 7.279si 0.0045] 0.062 0.594 20 2 7.23732 7.23452 0.0028 0.039 0.637 20 3 7.237158 7.23452 0.002638 0.036 0.651

It can be seen from Figure 8 that as the concentration of ND in the electrolyte increases to a certain value (5 g / из), the wear of the surface decreases, respectively the wear resistance increases, after which the wear of the surface increases. The same trend is observed in the change of the coefficient of friction (Fig. 9).

Topographic images of the surface of specimens after 500 m of friction are shown in Figures 10, 11 and 12.

The presented images of the surfaces of nickel coatings obtained after dry friction show that there are two mechanisms of wear: adhesive wear and abrasive wear. There is also some smearing of steel ring material on the surface, which implies intensive formation of iron oxides due to adhesive wear.

Corrosion resistance studies

Corrosion resistance was determined in aqueous NaCl solution with a concentration of 3.5 wt. % by the gravimetric method according to EN ISO 10289/2006. The optimal current density 2 A / dm ² and process duration 15 min were selected for galvanization parameters. The change in the corrosion rate over time for pure nickel coating and for coating obtained from an electrolyte with a concentration of nanodiamond particles of 5 g / Ι was studied. The results are presented in Table 4, and in FIG. 11, where Ag 'is the corrosion rate expressed in mg / cm ² h.

Descriptions of issued patents for inventions № 06.1 / 17.06.2019

Table 4. Change of corrosion rate with corrosion time Ag ', mg / cm ² h x 10 ^-3

Time, h 0 4 8 12 16 20 24 30 32 38 ND = 0 0 0 7.6 3.9 4.1 33 036 0.6 03 0.4 ND - 5 g / 1 0 0.2 -0.2 6.4 3.6 2.4 -03 0.1 03 -03

Table 5. Dependence of corrosion rate on ND concentration

Snsh g / 1 Ag, mE / 'cin ¹ I, pin D | ^, mg / crn ² h 0 8.06 5.06 Я.15Х10 ³ 1 8.97 5.97 6.20x10 ’ 5 9.91 632 5.70k IO ⁴

The experiments were performed in a solution of 3.5 wt. % NaCl for 114 h at 37 ° C. The coatings were obtained at a current density of 2 Adm ² and a duration of electrodeposition of -15 min. The galvanization mode described above was chosen on the basis of our preliminary research.

From tables 4, 5 and fig. 13 shows that the corrosion rate depends on the concentration of diamond nanoparticles in the electrolyte.

The lowest corrosion rate and respectively the highest corrosion resistance are observed at a concentration of nanodiamond particles of 2 to 5 g / l.

Conclusions from experimental research

1. The electrodeposited layer of nickel on steel is dense, well formed, visibly homogeneous, with good adhesion to the matrix. The layer thickness varies from 3 to 10 pm depending on the nickel plating conditions.

2. Modified with ND nickel coatings have a greater layer thickness, increased microhardness - about 2 times greater than that of pure nickel coating.

3. Wear resistance is measured under dry friction conditions. Mass wear and coefficient of friction were measured. As the concentration of ND in the electrolyte increases, the wear generally decreases at the same galvanization parameters. At ND concentrations of 1-5 g / Ι the mass wear is about 2 times less than in the pure Ni coating. Wear resistance increases with increasing current density at a constant concentration of ND.

4. The corrosion resistance of modified nickel coatings under constant galvanizing conditions increases with increasing concentration of ND in the electrolyte to a content of about 2 g / Ι, then when increasing C _ND above 5 g / Ι begins to decrease and reaches the values of unmodified coatings. Corrosion resistance decreases with increasing current density at a constant concentration of nanodiamond particles in the electrolyte. The optimal current density is 3 A / dm ² .

The steps of the method for applying a nanodiamond-modified nickel coating to steel articles according to the invention, in their sequence and integrity, are illustrated by a flow chart (Fig. 15), comprising: a bath for degreasing steel parts subject to electrochemical, modified with nanodiamond particles, nickel plating 1; alcohol bath 2; fan for drying degreased and washed products 3; staining bath 4; water bath 5; denatured alcohol bath 6; drying fan 3; a bath with a ready nickel plating solution 9, equipped with a stirrer 10 and connected to a bath with the aqueous solution of the electrolyte 7 and a bath with the activated sol of nanodiamond particles 8; a galvanizing bath 12 equipped with a stirrer 10 and connected to a rectifier 11; water bath 13; a bath for washing with alcohol 14 and a fan 15 for drying the finished products.

Claims (8)

Patent claims A method for producing a nickel-coated nickel-coated nickel coating, characterized in that low-carbon to high-carbon steel products are treated with a standard acidic nickel electrolyte to which aqueous nickel electrolyte is added with continuous stirring for 1-1.5 hours. a suspension of nanodiamond particles with sizes from 1 to 200 nm in an amount of 0.1 to 20 g / Ι, activated for 10-60 min by ultrasonic treatment, and the electrolyte thus prepared is stirred for 0.5 to 1 h as its temperature rises from 25 to 35 ° C, then at the same temperature and current density of 1 to 5 A / dm ² , for a time of 1 to 25 minutes, said coating with a thickness of 6 to 15 pm is achieved. Method according to claim 1, characterized in that the concentration of nanodiamond particles is from 1 to 5 g / l. Method according to claim 1, characterized in that the concentration of nanodiamond particles is from 10 to 20 g / l. Method according to claim 1, characterized in that the concentration of nanodiamond particles is from 1 to 5 g / Ι, and the current density is from 1 to 3 A / dm ² and the process duration is from 5 to 15 minutes. A nickel coating modified with nanodiamond particles obtained by the method according to claim 1. Nickel coating modified with nanodiamond particles obtained by the method according to claim 2. A nickel coating modified with nanodiamond particles obtained by the method according to claim 3. A nickel-coated nickel-plated nickel coating obtained by the method of claim 4.