JPS5928640B2 - Composite chrome plating method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a composite chromium plating method. It is being put into practical use to achieve this goal.

By applying dispersion plating, which uses dispersion materials such as highly hard oxides, carbides, and nitrides, and self-lubricating molybdenum disulfide and Teflon, it is extremely hard and wear-resistant. The present invention relates to a composite chromium plating method that further improves the quality of chromium plating, which has excellent oxidation resistance and high-temperature oxidation resistance. Conventionally, chrome plating has been commonly used as an inner surface plating for automobile engine cylinders to improve wear resistance. On the other hand, by dispersing SiC (silicon carbide) as a dispersant during Ni plating, wear resistance comparable to that of chrome plating can be obtained. Since they are extremely economically advantageous, various types of them have been developed.

Therefore, research has begun in order to economically improve the properties of conventional chrome plating by dispersing a dispersant during plating in the chrome plating method. However, the plating method that uses a surge-end type chromium plating bath composed of chromic anhydride and sulfuric acid, which is generally popular as a chromium plating method, is
, the deposition potential is higher than that of plating with Zn, etc., and moreover, C
During r (chromium) precipitation, a large amount of hydrogen is released, and as a result, the dispersion material, which is a fine powder, escapes from the surface of the plated material, and almost no eutectoid occurs, resulting in eutectoid formation. Even if it was added, the amount was extremely small, and as a result, the effect of enhancing wear resistance etc. could not be expected at all.

In addition, as a different method, heat-resistant metal powder such as Mo (molybdenum), Ta (tantalum), W (tungsten), etc. is dispersed in a tightening bath using Tarom as a matrix.
Cr-W, Cr-MO by heat treatment at 0'C
, a dispersion-strengthened alloy plating method that can obtain dispersion-strengthened alloy plating of Cr-Ta, and a dispersion-strengthened plating method that eutectoidizes highly hard fine powders of Zr2B (zirconium borate) and TiO2 (titanium oxide) have been reported. has been done. However, in any of the plating methods, it has not been possible to perform plating at a practical speed, economically, and evenly eutectoidally dispersing the dispersing material. For example, to give an example using the dispersion plating method, in the case of dispersion plating of Cr-Zr2B, Z
R2B grain size of 20 to 40 μm was used, and the current density was 2.7 A/d.

However, in that case, the precipitation rate of Cr-Zr,B is 0.2
The speed is extremely slow at μm/h, which is hardly a speed that can be put to practical use.Moreover, although the dispersion of the dispersant is effective when the fine particles are uniformly eutectoid, the normal method uses relatively coarse particles. It is possible to eutectoid the dispersion materials. Therefore, in view of the above-mentioned drawbacks, the present invention aims to improve the conventional extremely low precipitation rate of dispersion material, and to achieve uniform dispersion plating at the rate of chromium plating that has conventionally been practically used. It is something.

The details of the composite plating method according to the present invention will be explained below.

The present inventor conducted a detailed study on the relationship between dispersion material eutectoid and current density using the Hull cell test method when performing dispersion plating using a surge-end type chromium plating bath, and found that 2 to 4A A large amount of dispersed material can be easily eutectoid in the current density range of /d, but hardly any eutectoid of the dispersed material can be obtained in the current density range of 10 to 50A/d, which is carried out in normal chrome plating. We were able to obtain this knowledge.

In other words, since a low current of around 2 A/d is advantageous for eutectoiding the dispersion material during chrome plating, the dispersion material for enhancing the wear resistance, lubricity and oxidation resistance of plating is It has been found that the dispersion material can be dispersed and eutectoid during chromium plating by setting the current density range for dispersion and eutectoid fixation to around 2 A/d. In order to make this chrome plating possible at normal electrodeposition speeds, further research and consideration revealed that a dispersant for enhancing the wear resistance, lubricity, and oxidation resistance of the plating was uniformly dispersed. In the electrolytic bath of chromium, the dispersion material is dispersed in chromium plating on the cathode, and eutectoid is fixed.2! Current in both the first current density range of Hy/d ~ 4A/DTrI and the second current density range of 10Vdm ~ 50A/d where chromium plating is performed at a normal electrodeposition speed. By performing dispersion plating by performing complex electrolysis using pulsed electrolysis, which repeatedly electrolyzes using density, dispersion plating that disperses the dispersion material during chrome plating, and the dispersion plating that can be performed at a normal electrodeposition speed. It became possible to do it at As a result, the dispersion and eutectoid dispersion of the dispersion material, which has excellent wear resistance, lubricity, and oxidation resistance, into the chromium plating has resulted in a 2Vd gold plate with significantly less hydrogen gas generation.
Composite electrolysis can be easily carried out under the conditions of the first current density range of 4 A/d Go, followed by complex electrolysis in the current density range of 10 A/d Go to 50 Vdm1, followed by chromium plating at normal electrodeposition speed. If this is done, chromium is embedded between the dispersed and eutectoid materials, and the dispersion material enhances wear resistance, lubricity, and oxidation resistance at the conventional chromium plating speed. You can get Tarom Meteki based on your time.

Further, as a result of experiments and research, it has been found that the above-mentioned composite electrolysis has a first current density range that disperses and eutectoidally fixes the dispersion material, and a second current that enables chromium plating at a normal electrodeposition speed. It has been found that the same effect as the above-mentioned pulsed electrolysis can be obtained by superimposed electrolysis in which electrolysis in the density region is carried out one after the other. Specific examples of the composite chromium plating method according to the present invention are shown below.

Example 1 Chromium electrolytic bath composition was chromic anhydride 250g/1,H
2S04 (sulfuric acid) 2.59/l was used, and S was used as a dispersant.
IC (silicon carbide) 0.2 μm (particle size) 509/
1, and the bath temperature is maintained at 45° C. to uniformly disperse the SiC in the bath by mechanical stirring.

On the other hand, as electrodes, the cathode is a steel plate (dimensions 20 mm x 20 x 3 mm) and the anode is two lead tin (5%) alloy plates (dimensions 50 m71 L x 507! L7! L x 10 mm). current density 3A/d, period width 50
Composite chromium plating was performed by pulse electrolysis at a current density of 30 msec, a cycle width of 50 msec, and a cycle width of 50 msec for 60 minutes. As a result, the chromium plating obtained under these conditions was analyzed to contain 5 wt % of SlC, and hardness measurement revealed that it had a high hardness of Hvl2OO.

Furthermore, when chromium plating is carried out using the bath and apparatus of the above example under the conditions of normal (DC electrolysis 30A/d, 60 minutes), the hardness of the chrome plating obtained is H.
It was v9OO.

Then, for the composite chromium plating of Cr-SiC and the normal tarom plating described later, a wear resistance test with SK5l material was conducted at a load of 32.5 KV and a friction speed of 1.43 m/Se.
When the test was carried out using lubricating oil under the condition of 8000 m of Cl wear distance, the surface roughness after the test was Cr-SiC
Composite chrome plating is 0.1 μm, and normal chrome plating is 0.5 μm.One thing is that the Cr-SiC composite chrome plating has a finer surface roughness than the chrome plating described below. There was found.

Also, when we measured the hardness of the wear marks after this test, we found that Cr
-SiC composite chrome plating is Hv7OOI chrome plating is Hv3OO, Cr-! SiC composite chromium plating, that is, plating by the composite chromium plating method according to the present invention, yielded significantly better results in terms of wear resistance and hardness than ordinary chrome plating. Example 2 The composition of an electrolytic bath for chromium was as follows: To 2.09/l of chromic anhydride 2009/11 sulfuric acid, 1009/l of Al2O3 (aluminum oxide) 0.5 μm (particle size) powder was added as a dispersant, and the bath temperature was set to 2009/l. ℃ and mixed the Al2O3 uniformly into the bath by mechanical stirring. I'll let you.

On the other hand, as an electrode, the cathode is a mild steel plate (dimensions 20mm x 20mm).
Dwarf x 3m0, lead-tin (5%) alloy plate as anode (dimension 5
Using two sheets of 0U x 50mm x 10m0, current density 3A/Dm゛ for the cathode, period width 20msec, current density 20
Composite chromium plating was carried out by pulse electrolysis under the conditions of A/D Go and a cycle width of 20 msec for 30 minutes. As a result, analysis revealed that the tarom plating obtained under these conditions contained 7 wt % of Al2O3, and hardness measurement revealed a hardness of HllOO.

Furthermore, when chromium plating is carried out using the bath and apparatus of the above embodiment under the conditions of normal DC electrolysis at 20 A/d for 30 minutes, the hardness of the chromium plating obtained is Hv.
It was soft at 6OO.

An attempt was made to analyze Al2O3 in this chromium plating, but no Al2O3 was detected. Example 3
Tarom's electrolytic bath composition uses chromic anhydride 1509/l, sulfuric acid 1.59/l, MOS2 (molybdenum disulfide) 1 μm (particle size) powder is mixed in at 60 g/l as a dispersing agent, and the bath temperature is 30°C. The MOS2 is kept uniformly dispersed in the bath by mechanical stirring.

On the other hand, as an electrode, the cathode is a mild steel plate (dimensions: 30 cm x 50 m).
m
For the cathode, current density is 3 A/d, period width is 40 mse.
c1 current density 30A/d, period width 20msec 30
Composite chromium plating was carried out by pulse electrolysis under conditions of 1 minute. As a result, the chromium plating obtained under these conditions was analyzed to contain 5 wt% of MOS2, and when the hardness was measured, the hardness of the chrome plating itself was Hv7OO. When tested using an abrasion tester, it was found that the wear resistance was significantly improved compared to ordinary chrome plating, and the self-lubricating effect of MOS2, which has been known in the past, was confirmed. Furthermore, when chromium plating was performed using the bath and apparatus of the above example under the conditions of normal DC electrolysis at 20 A/d for 30 minutes, the hardness of the chromium plating itself was Hv7OO. However, when the content of MOS2 in tarom plating was analyzed, it could not be confirmed at all.

Example 4 The composition of the chromium electrolytic bath was chromic anhydride 2509//, sulfuric acid 2.59/', and SlCO. 6μm
(particle size) powder was mixed in at 1009/l, and the bath temperature was set at 30°C.
Hold the vibrating barrel (amplitude 4.0, frequency 180)
0 cpm) and stir.

On the other hand, as an electrode, the cathode is a mild steel plate (dimensions 100 mm x 5
0mm x 5mm), two lead-tin (5%) alloy plates (dimensions 150771m x 150mm x 2077!m) were used as anodes, and a current density of 4A/d, 70m was applied to the cathode.
Composite chromium plating was performed by pulse electrolysis under conditions of 120A/d, 70msec for 60 minutes.
As a result, analysis revealed that the chromium plating obtained under these conditions contained 10 wt % of SiC, and hardness measurement showed that it had a high hardness of Hvl2OO.

Furthermore, when tarom plating is carried out using the bath and apparatus of the above embodiment under the conditions of normal DC electrolysis at 20 A/d for 60 minutes, the hardness of the chrome plating obtained is Hv6.
As a result of analysis, no SiC was found in the chromium plating at OO.

Example 5 Chromium electrolytic bath composition is chromic anhydride 250
9/l, sulfuric acid 2.59/l, and SlC as a dispersing agent.
1009/l of 2 μm (particle size) was added, mechanically stirred and suspended, the bath temperature was maintained at 40°C, and the cathode was made of a steel plate (
The dimensions are 50 mm x 20 m TL x 3 m0, and as an anode,
An insulating plate (58 m) of lead-tin (5%) alloy with a diameter of 10 mm
A total of 9 pieces, 3 x 11 x 3 x 11 x x 58 m0, and
A current density of 2A/D7T for each of the 9 alloys was used, with evenly spaced widths of 7m1IL between them.
A constant current of 2 is applied, and a current density of 2
A current of 0 A/d was applied to the nine alloys in order with a period width of 50 m.
Chromium plating was performed by performing superimposed electrolysis for 30 minutes in which electrolysis was repeated at sec.

The eutectoid amount of SiC in the resulting chromium plating was 3 wt(f).

Therefore, we used the same electrode as in 2 above, the composition of the chromium electrolytic bath was 2509/l of chromic anhydride, 2.59/l of sulfuric acid, the bath temperature was 40°C, and A as a dispersion material mixed into the electrolytic bath.
12O32μm (particle size) powder and TLC (titanium carbide)
3 μm (particle size) was mechanically suspended in each electrolytic bath at 1009/l, the superposition electrolysis was performed on each, and the state of the chromium plating was examined.
The state of chromium plating when electrolyzed in suspension bath 3 has a hardness of Hvl2OO and an eutectoid amount of Al2O3 of 3wt%.
And, for the TiC suspension bath, the hardness is 1500
, the eutectoid amount of TiC was 4wt#).

Therefore, superimposed electrolysis, in which electrolysis in the two current density regions is sequentially carried out, provides similar effects as compared to the pulsed electrolysis.

As mentioned above, the composite chromium plating according to the present invention is achieved by performing composite plating in the current density range in a bath in which the above-mentioned dispersion material is uniformly dispersed. By improving the low precipitation rate of dispersion material and making it possible to perform dispersion plating at a speed conventionally used in practical use, the quality of chrome plating can be further improved.
It can be used in a wider range of fields than ever before, and has excellent effects such as significantly improving plating life.

Claims (1)

[Claims] 1. In a chromium electrolytic bath in which a dispersant for enhancing wear resistance, lubricity and oxidation resistance of plating is uniformly dispersed,
dispersing the dispersion material in chromium plating for the cathode;
A first current density range of 2A/dm^2 to 4A/dm^2 for eutectoid fixation, and a second current density range of 10A/dm^2 to 50A/dm^2 for chromium plating at a normal electrodeposition rate. A composite chromium plating method characterized in that dispersion plating is performed by performing composite electrolysis using pulsed electrolysis, which is repeated electrolysis using current densities in both current density regions. 2. The composite chromium plating method according to claim 1, which uses superimposed electrolysis in which electrolysis in a first current density region and a second current density region are sequentially performed as composite electrolysis.