KR101003999B1 - A wear-resistant trivalent chromium coating layer with micro-nodules and its manufacturing technique - Google Patents

Abstract

The present invention relates to a wear-resistant trivalent chromium coating layer having irregularities having heat-resistant unevenness formed on the surface thereof and a method for manufacturing the same.

The wear-resistant trivalent chromium coating layer having irregularities according to the present invention has a hemispherical shape and a plurality of irregularities 120 contacting the counterpart are formed, and the diameter of the irregularities 120 is apparent for the friction object to be contacted. It is characterized in that the 0.1 to 50% of the diameter of the contact surface, the unevenness 120 contains 2.0% to 10.0% carbon by weight. According to the present invention configured as described above, there is an advantage that the contact area with the friction object is reduced and wear resistance is improved by preventing the loss of lubricant.

Abrasion Resistance, Coating Layer, Unevenness, Trivalent Chrome

Description

A wear-resistant trivalent chromium coating layer with micro-nodules and its manufacturing technique

1 is a partial longitudinal cross-sectional view schematically showing a state in which the wear-resistant trivalent chromium coating layer having irregularities according to the present invention in contact with the friction object.

Figure 2 is a manufacturing process diagram showing a method for producing a wear-resistant trivalent chromium coating layer having irregularities according to the present invention.

Figure 3 is a manufacturing process diagram showing in detail the heat treatment step one step in the manufacturing method of the wear-resistant trivalent chromium coating layer having irregularities according to the present invention.

Figure 4 is an X-ray diffraction pattern of the coating layer not subjected to the heat treatment step of one step in the manufacturing method of the wear-resistant trivalent chromium coating layer having irregularities according to the present invention.

5 is an X-ray diffraction pattern of the wear-resistant trivalent chromium coating layer having irregularities according to the present invention.

Figure 6 is a scanning electron micrograph of the surface of the coating layer not subjected to the heat treatment step in the method for producing a wear-resistant trivalent chromium coating layer having irregularities according to the present invention.

7 is a scanning electron micrograph showing the surface of the wear-resistant trivalent chromium coating layer having irregularities according to the present invention.

8 is a graph showing a change in the friction coefficient of the wear test results of the coating layer not subjected to the heat treatment step in the manufacturing method of the wear-resistant trivalent chromium coating layer having irregularities according to the present invention.

9 is a graph showing a change in the friction coefficient of the wear-resistant trivalent chromium coating layer having irregularities according to the present invention.

10 is a graph showing a change in the friction coefficient of the coating layer after applying a solid lubricant to the coating layer that has not undergone a heat treatment step in the manufacturing method of the wear-resistant trivalent chromium coating layer having irregularities according to the present invention.

11 is a graph showing the friction coefficient change of the coating layer after applying the solid lubricant to the wear-resistant trivalent chromium coating layer having irregularities according to the present invention.

12 is a scanning electron micrograph after the abrasion test of the wear track formed with the coating layer is not subjected to the heat treatment step in the method for producing a wear-resistant trivalent chromium coating layer having irregularities according to the present invention.

Figure 13 is a graph measuring the wear state of the wear track formed with the coating layer is not subjected to the heat treatment step is a step in the manufacturing method of the wear-resistant trivalent chromium coating layer having irregularities according to the present invention using a carburizing roughness.

FIG. 14 is a scanning electron micrograph of a ball, a friction object of the wear track applied to FIG. 13.

15 is a scanning electron micrograph showing a wear state of a wear track having a wear-resistant trivalent chromium coating layer having irregularities according to the present invention.

FIG. 16 is a graph of a wear state of a wear track having a wear-resistant trivalent chromium coating layer having irregularities according to the present invention, measured using a carburizing roughness. FIG.

FIG. 17 is a scanning electron micrograph of a ball, a friction object of the wear track applied to FIG. 15.

FIG. 18 is a scanning electron micrograph of a ball, a friction object of the wear track applied to FIG. 11.

FIG. 19 is a graph comparing wear volumes of respective balls, which are friction objects of wear tracks applied to FIGS. 4, 5, 10, and 11, respectively.

20 is an appearance photograph of a coating layer having abrasion resistance according to the present invention.

21 is a longitudinal sectional view of FIG. 20;

22 is a graph showing the coefficient of friction behavior of a wear track having a coating layer having abrasion resistance according to the present invention.

Figure 23 is an appearance photograph of the coating layer having abrasion resistance according to the present invention.

FIG. 24 is a scanning electron micrograph showing wear traces of the ball used in the test of FIG. 22.

Explanation of symbols on the main parts of the drawings

100. Coating layer 120. Unevenness

Ad. Apparent contact diameter F. Friction object

Pd. Uneven diameter S100. Coating layer forming step

S200. Coating layer washing step S300. Heat treatment step

S320. Heating process S340. Reduction Process

S360. Heat treatment process W. Coating object

The present invention relates to a wear-resistant trivalent chromium coating layer having irregularities having abrasion resistance by forming heat-treated irregularities on the surface to reduce the contact area with the friction object and to prevent loss of lubricant.

In general, in order to improve wear resistance of molds, tools, automobile parts, and the like, high hardness thin films on the surface have been deposited. In this way, it is possible to extend the life of molds, tools, automobile parts and the like.

However, the surface of the product manufactured by this conventional method is very flat so that the contact surface with the friction object is wide, and the wear particles made during the friction movement harden while being present on the contact surface to damage the friction object or the coating layer.

Furthermore, when the wear particles are placed on the surface of the friction object to cause friction and abrasion, friction increases, and the wear speed increases.

In order to solve this problem, a method for machining the surface coated with a high-hardness thin film is formed so that irregularities are formed.

The unevenness formed in the high hardness thin film was able to solve the problem of increased friction and wear caused by the wear particles by accommodating wear particles generated by the friction with the counterpart so as not to stay between the high hardness thin film and the counterpart. .

However, this method is easy to form irregularities in the case of a good machinability material, there is a problem that the processing of such irregularities is not easy after the coating of a high hardness material.

In addition, in order to form the unevenness by machining is required because excellent machining technology is required to increase the defect rate and thereby increase the manufacturing cost is not preferable.

An object of the present invention for solving the problems described above, the wear-resistant trivalent chromium coating layer having a convex concave and convex to have abrasion resistance by forming a heat-treated concave-convex on the surface to reduce the contact area with the friction object and prevent the loss of lubricant It relates to a method for producing.

Another object of the present invention is to provide a wear-resistant trivalent chromium coating layer having irregularities to improve the wear resistance by adjusting the number of irregularities in contact with the friction object by adjusting the conditions of the heat treatment step.

The wear-resistant trivalent chromium coating layer having irregularities according to the present invention has a hemispherical shape, and a plurality of irregularities contacting the friction object are formed, and the diameter of the irregularities is 0.1 to 50 of the diameter of the apparent contact surface with respect to the friction object to contact. It is characterized by being%.

The unevenness is characterized by having a diameter of less than 50㎛.

The irregularities are characterized in that the lubricant is provided on the outside.

The irregularities are characterized by containing 2.0% to 10.0% of carbon by weight.

The present invention provides a coating layer forming step of forming a coating layer consisting of trivalent chromium on a coating object using a trivalent chromium plating solution, a coating layer washing step of washing the coating layer with an ultrasonic cleaner, and a heat treatment step of heat treating the washed coating layer. In the method for producing a trivalent chromium coating layer having a wear resistance, wherein the heat treatment step, the heating process by charging the coating layer in a heat treatment furnace, heating, a reduction process of reducing the surface of the coating layer in the heat treatment furnace, It characterized in that it comprises a heat treatment process for maintaining the temperature inside the heat treatment furnace.

In the coating layer forming step, the trivalent chromium plating solution is 0.4 to 0.6M of the trivalent chromium compound, 0.8 to 1.2M of the complexing agent to inhibit the polymerization reaction of the trivalent chromium compound in an aqueous solution, and trivalent chromium ion. 0.8 ~ 1.2M conduction aid to increase the electrical conductivity of the agent, 0.8 ~ 1.2M buffer for correcting the hydrogen ion index of the aqueous solution, 8-12 g / l as a polarizing agent for inhibiting trivalent chromium ion oxidation; Organic additives 1 to 4 g / l to increase the gloss of the surface of the coating layer and a reducing agent 10 to 100ppm to increase the adhesion of the coating layer is configured, the reducing agent is characterized in that consisting of an inorganic material or an organic material.

In the coating layer forming step, the temperature of the trivalent chromium plating solution is 30 ℃ to 50 ℃, the hydrogen ion index (pH) is characterized in that 1 to 4.

In the coating layer forming step, the effective current application range is characterized in that 10 to 25A / ㎠.

The reduction process is characterized in that the process of supplying hydrogen (H ₂ ) gas, argon (Ar) gas and SF ₆ gas into the heat treatment furnace.

delete

The heat treatment process is characterized in that for maintaining the internal temperature of the heat treatment furnace at 300 ~ 800 ℃ for 30 to 180 minutes.

According to the present invention configured as described above, there is an advantage that the contact area with the friction object is reduced and wear resistance is improved by preventing the loss of lubricant.

Hereinafter, the configuration of the wear-resistant trivalent chromium coating layer having irregularities according to the present invention will be described with reference to FIG. 1.

Figure 1 is a partial longitudinal cross-sectional view schematically showing a state in which the wear-resistant trivalent chromium coating layer having irregularities according to the present invention in contact with the friction object.

As shown in the drawing, the coating layer 100 is coated on the upper surface of the coating object (W) by wet or dry plating, and the upper surface of the coating layer is formed to be in point contact with the friction object (F).

That is, a plurality of irregularities 120 are formed in an upper portion (a portion in contact with the friction object) of the coating layer. The unevenness serves to reduce the coefficient of friction by a plurality of point contact to the friction object, it is formed integrally with the coating layer.

That is, the coating layer is formed to contain 2% or more and 10.0% or less carbon by weight, and the unevenness is formed to protrude to have a diameter of less than 50㎛.

More specifically, the diameter (Pd) of the concave-convex is a plurality of point contact at the same time at the time of contact, and thus is formed to be in the range of 0.1 to 50% of the apparent contact surface diameter (Ad) for the friction object.

Hereinafter, a method of manufacturing the wear-resistant trivalent chromium coating layer having irregularities configured as described above will be described with reference to FIGS. 2 and 3.

2 is a manufacturing process diagram showing a method of manufacturing a coating layer having a wear resistance according to the present invention, Figure 3 is a manufacturing process diagram showing in detail a heat treatment step that is one step in the manufacturing method of the coating layer having a wear resistance according to the present invention. Is shown.

As shown in these figures, in order to manufacture the coating layer, a coating layer forming step (S100) of first forming a coating layer on a coating object under a trivalent chromium plating solution and conditions having a composition as shown in Table 1 below is performed.

TABLE 1

Chemical No. Capacity (g / l) variable Condition Cr ₂ (SO ₄ ) ₃ 0.5M Current density 25 A / dm ² Formic Acid (HCOOH) 1.0M pH 2 Potassium Chloride (KOH) 1.0M Temperature 30-50 Ammonium Sulfate (NH ₄ Cl) 53.5 (1.0) Delivery time Variable Boric Acid (H ₃ BO ₃ ) 40 (0.65) Anode Graphite Ammonium Bromide (NH ₄ Br) 10 Cathode L.C.Steel (2 * 8cm) PEG # 1500 2 or 0 Stirring Unstirred

In the coating layer forming step (S100), the coating material is formed with a coating layer having a carbon content of 2.0 by coating trivalent chromium for 33 minutes and 12 seconds at 40 ° C., and coating trivalent chromium for 38 minutes and 5 seconds at 50 ° C. Based on Inventive Material 2 with a coating layer of 2.8% content, and Comparative Material coated with Inventive Material 3 and 6-valent chromium with a coating layer having a carbon content of 10.0% by coating trivalent chromium at 60 ° C. for 44 minutes and 16 seconds. Various comparative tests were conducted.

After the coating layer forming step (S100), the coating layer washing step (S200) for washing the coating layer with an ultrasonic cleaner is performed.

Then, the heat treatment step (S300) is followed to heat-treat the coating layer washed in the coating layer washing step (S200).

The heat treatment step (S300) comprises a plurality of processes. That is, the heat treatment step is a heating step (S320) for charging and then heating the coated coating layer in a heat treatment furnace, a reduction process (S340) for reducing the coating layer in the heat treatment furnace, and maintaining the temperature inside the heat treatment furnace It is configured to include a heat treatment process (S360) for heat treatment of the coating layer.

The heating process (S320) is a process of raising the internal temperature to 500 ° C heat treatment, and at the same time the reduction process (S340) is in progress.

More specifically, in the reduction process S340, the surface of the coating layer is reduced by injecting hydrogen (H ₂ ) gas, argon (Ar) gas, and SF ₆ gas into the heat treatment furnace.

delete

Thereafter, the coating layer whose surface is reduced while undergoing the reduction process (S340) is heat treated for 30 to 180 minutes in a heat treatment furnace maintained at 300 to 800 ° C., thereby completing the heat treatment process (S360).

Hereinafter, with reference to the accompanying Figures 4 to 24 will be described the comparative test results of the invention and the comparative material of the present invention.

Figure 4 shows the X-ray diffraction pattern of the coating layer is not subjected to the heat treatment step, which is one step in the method for producing a wear-resistant coating layer according to the present invention, Figure 5 is an X-ray diffraction pattern of the coating layer with abrasion resistance according to the present invention Is shown.

4 and 5 is a model D / Max-2200 X-ray diffractometer manufactured by Rigaku Corporation, using _a CuK _a X-ray and a monocrometer, diffraction angle of 20 to 80 ° and scanning speed of 5 ° / at 36 kV and 29 mA. Tested in min.

As shown in Figure 4, it can be seen that the invention material 1, the invention material 2 and the invention material 3 that is not subjected to the heat treatment step (S300) are all amorphous or nanoparticle phase is formed.

In addition, it can be seen that the crystallization of chromium (Cr) occurred in the inventive material 1, the inventive material 2, and the inventive material 3 having undergone the heat treatment step S300 as shown in FIG. 5.

Looking at the hardness of the invention and the comparative material and the non-inventive material and the comparative material which have undergone the heat treatment step with reference to [Table 2] below,

TABLE 2

division Hardness value before heat treatment (H _v = kg / mm ² ) Hardness value after heat treatment (H _v = kg / mm ² ) Invention 1 705 1,393 Invention 2 864 1,535 Invention 3 935 1,534 Comparative material 797 624

The hardness value of [Table 2] is the measured value using the Vickers hardness tester, the applied load was used 50gf and the load holding time was fixed to 15 seconds.

In addition, the hardness value averaged for the remaining five times except for the minimum and maximum hardness values was recorded by measuring 7 times for each invention and comparative material, and the surface of the plating layer was very rough, so the hardness was measured at the center of the cross section of the coating layer. It was.

The hardness of the invention corresponded to 700 ~ 935 kg / mm ² according to the carbon content and through the heat treatment could achieve a hardness of 1400 ~ 1530 kg / mm ² or more.

For reference, the hardness of the comparative material (hexavalent chromium plating) was about 800 kg / mm ² , and the hardness was lowered to 620 kg / mm ² after the heat treatment. It is believed that softening occurred due to the crystallization of amorphous chromium through heat treatment.

Looking at the surface of the coating layer before the heat treatment with reference to Figure 6, inventive material 1 to invention material 3 nodule was formed.

In the invention materials 1 and 2, the microcracks penetrate the nodule, but in the case of the invention materials 3, the microcracks progress along the boundary of the nodule.

On the other hand, nodule could be observed in the comparative material, and the crack-free area showed a very dense and flat structure.

As shown in FIG. 9, the nodule on the surface of the invention material subjected to the heat treatment step S300 was flattened in the case of Inventive Material 1, and in the case of Inventive Material 2, the shape of the nodule still remained.

On the other hand, the carbon content of Inventive Material 3 was found to be spherical along the nodule. In the case of the comparative material there was little change in the microstructure, but it can be seen that the crack is slightly wider.

Hereinafter, the friction coefficient change is shown in FIGS. 8 and 9 by performing abrasion test on the coating layer before and after the heat treatment step.

Figure 8 is a graph showing a change in the coefficient of friction of the wear test results of the coating layer not subjected to a heat treatment step in the manufacturing method of the wear-resistant coating layer according to the present invention, Figure 9 is a friction of the coating layer having a wear resistance according to the present invention It is a graph showing the change of coefficient.

In the wear test, a chromium layer was formed on the wear track, and a bearing ball (Ø6.35mm, hardness 800 kg / mm ² ) was applied as a friction object of the chromium layer, and the wear track was applied 30,000 times at a rotational speed of 100 g and 200 rpm. Rotated.

The frictional force was measured in real time during the abrasion test to measure the friction coefficient change according to the wear distance. After the wear test, the wear track was measured by using an optical microscope and a-step (Tencor P-11 Model).

Inventive materials 1 to 3 having the coating layer not subjected to the heat treatment as shown in FIG. 8 show high friction coefficient values.

However, in the case of Inventive Materials 1 to 3, the coefficient of friction behavior varied with time, but in the case of the comparative materials, constant coefficients of friction were shown from the beginning.

Inventive materials 1 to 3 having the coating layer subjected to the heat treatment step as shown in FIG. 9 did not significantly reduce the coefficient of friction even after the heat treatment, and in the case of the inventive material 3, the lowest coefficient of friction value was shown. Also, as the wear distance increases, the friction coefficient tends to increase slowly.

On the other hand, in the case of the comparative material, before and after the heat treatment step, the friction coefficient was lowered from 0.8 to 0.5.

10 and 11 show changes in the coefficient of friction measured after the application of the solid lubricant (MoS ₂ ) to the surfaces of the invention and the comparative material and the comparative material and the non-heat treatment step.

First, in the case of the invention material that is not subjected to the heat treatment step as shown in Figure 10, the invention material 3 has a relatively low friction coefficient between 0.2 ~ 0.25 and has a relatively uniform value even if the wear distance increases.

On the other hand, the comparative material had a relatively small decrease in the coefficient of friction from 0.8 to 0.6 even when the solid lubricant was applied, and the coefficient of friction remained constant at 0.6.

In the case of the invention material subjected to the heat treatment step as shown in Fig. 11, Inventive Material 3, the friction coefficient was rapidly reduced to maintain a value of 0.1 or less within the analysis conditions and shows a very constant behavior. On the other hand, in the invention materials 1 to 2, it was difficult to expect a great effect.

This means that in the case of Inventive Material 3, spheroidization occurred along the nodule shape after the heat treatment step, so that the solid lubricant (MoS ₂ ) powder could be stored between the nodules, and the spherical shape could keep the contact amount with the friction object uniformly. can see.

12 to 14 are scanning electron micrographs of wear tracks used in the test of FIG. 10, graphs of changes in depth and width of wear tracks using a probe roughness, and optical micrographs of balls as friction objects of wear tracks. Is shown.

As shown in FIG. 12, all but the invention material 1 showed a non-uniform wear form, and the width of the wear track also appeared non-uniform. This is considered to be because the roughness of the surface is rough and the contact surface is uneven upon contact with the friction object.

However, in the case of the comparative material, even though the surface is relatively flat, the wear tracks appear to be nonuniform, indicating that the wear particles were unevenly distributed between the cracks and the cracks on the surface.

As shown in FIG. 13, the wear of the coating layer occurred in the invention material 1 and the comparative material, but in the invention material 2 and the invention material 3, the wear particles falling from the ball, which is the friction object, were accumulated in the wear track. This is judged to be due to the hardness difference.

That is, the hardness value of the ball friction object is 800Hv, the coating layer hardness of the invention material 1 and the comparative material is 700, 800Hv, while the hardness of the coating layer of the invention material 2 and the invention material is 860, 940Hv.

Therefore, the invention material 1 and the comparative material is abrasion of the coating layer together with the friction object, but in the invention material 2 and the invention material 3, the wear particles are accumulated in the wear track after the wear occurs only in the ball, which is the friction object.

As described above, the invention material 2 and the invention material 3, the hardness of the coating layer is expected to be a lot of wear of the ball is higher than the hardness of the ball friction object, it can be seen that the radius of the wear scar is large as shown in FIG.

However, Invention 1 and Comparative Material showed very contrasting results. It is expected that the wear of the ball was small because the hardness of the invention material 1 and the hardness of the comparative material were smaller than or similar to the hardness of the ball, and the wear of the ball was small.

However, it is peculiar that abrasion traces of the balls with respect to the coating layer of Inventive Material 2 and Inventive Material 3, which have relatively high hardness, occur similarly to the wear traces of the ball with the smallest hardness, such as Inventive Material 1.

It can be assumed that this can be explained by the fact that the wear of the hard material is high when the soft material and the hard material are subjected to the abrasion test.

That is, the wear particles wear the surface of the friction object in the state of being embedded in the surface of the soft material, and in general, since the wear particles undergo a very severe work hardening phenomenon, the hardness is higher than the surface of the coating layer.

Therefore, the cracks present in the coating layer of the comparative material may be accommodated inside the wear particles falling off the friction object to prevent the wear of the ball caused by the wear particles.

15 to 16 are scanning electron micrographs of wear tracks used in the test of FIG. 11, graphs of changes in depth and width of wear tracks using a probe roughness, and optical micrographs of balls as friction objects of wear tracks. Is shown.

15, Inventive Material 2 and Inventive Material 3 are similar to the state of wear before and after the heat treatment step, respectively, but the Inventive Material 1 and the comparative material show a marked difference in the wear state before and after the heat treatment step.

Inventive material 1 has a nonuniform and non-uniform wear track, and the comparative material can find large grains and the grains are arranged in a similar direction along the wear track. Therefore, in the comparative material, there are still many cracks, and the distribution of wear particles between the cracks and the cracks is not uniform.

Looking at Figure 16, it can be seen that the wear depth of the coating layer of the invention material 1 and the invention material 2 was very thin, the invention material 3 was rather high. And, the comparative material can be seen that severe wear occurred.

This is because the hardness of the comparative material was lowered to about 600 Hv after the heat treatment step, and it was not easy to accurately measure the wear depth because the roughness of all surfaces was very high, but the trend could be identified.

Looking at Figure 17, the hardness of the invention was predicted to increase the wear amount of the ball to increase to 1,500Hv, it was confirmed that the radius of the wear scar of the ball is reduced. It is expected that many cracks are generated on the surface of the coating layer when the invention material undergoes a heat treatment step, as described in the previous test results.

Referring to FIG. 18, after applying a solid lubricant to the surface of the coating layer subjected to the heat treatment step, the wear test was performed by analyzing abrasion traces. As a result, wear of the ball, which is the friction object of Inventive Material 3 and the comparative material, was significantly reduced.

In addition, referring to FIG. 19, when comparing the volume of the wear traces of the ball to be rubbed with respect to the coating layer coated with the solid lubricant before and after the heat treatment step, the comparative material has a large variation in whether the heat treatment step is performed and whether the solid lubricant is applied. However, it can be seen that the least wear occurred in the friction object (ball) of the coating layer coated with the solid lubricant after the heat treatment step.

On the other hand, the friction objects of the invention show a high wear rate. In particular, despite the increase in hardness of the invention material after the heat treatment step shows that the wear of the ball is lower than before the heat treatment step.

This is intimately associated with cracks formed on the surface of the invention after heat treatment. That is, if cracks are present on the surface of the coating layer, the wear particles generated during the abrasion test do not accumulate on the contact surface and fall into the cracks, thereby reducing the wear rate by the wear particles.

Inventive material used in the present embodiment was more effective in reducing the wear rate of the friction object to the invention material subjected to the heat treatment step than the reduction of the wear of the ball by the solid lubricant, and friction against the coating layer that is a combination of the heat treatment step and the solid lubricant application The wear of the object was lowered.

In particular, in the case of the invention 3 it was confirmed that the wear rate is sharply lower than the wear rate of the friction object for the comparative material.

Therefore, the characteristics of the microstructure of Inventive Material 3 subjected to the heat treatment step are that the nodule existing on the surface is more developed and spherical, and the solid lubricant is stored between the spherical irregularities due to the presence of a large number of cracks. The continuous supply of solid lubricants allows the wear particles to escape, so the low friction characteristics and the low wear characteristics of the counterparts are satisfied.

In summary, the coating layer coated on Inventive Material 3 was thermally treated at 500 ° C. for 1 hour in a H ₂ , Ar, SF ₆ atmosphere at a volume ratio of 198: 198: 6.5, and then applied with a solid lubricant to stabilize the friction coefficient of 0.1. A value was obtained, and wear by the ball, which is a friction object, did not occur at all.

In addition, when the heat treatment step of the invention material 3 containing 10.0% carbon content, as shown in Fig. 20 and 21, irregularities such as beads are arranged on the upper surface of the coating layer, and the wear track provided with the coating layer is coated with a solid lubricant When the wear test is performed using the ball, as shown in FIG. 22, the friction coefficient has a wear resistance that can be maintained even if the wear track rotates 2 million times.

In addition, as shown in FIGS. 23 and 24, after the 2 million rotational wear test, the friction object (ball) of the invention did not wear, but rather, the wear track portion was found to be higher than the other portions. It is believed that the wear particles falling from the wear object are transferred to the wear track.

In addition, since the wear scar diameter of the ball is 800㎛ and the diameter of the used ball is 6.35mm, the wear volume corresponds to 3.2 × 0 ^-12 m ³ . In terms of wear rate, when the wear test was performed under the same conditions as 4.1 × 0 ^-17 m ³ / Nm, it was found that the wear rate of the friction material for the comparative material was about 1,000 times lower than that of the friction material 3.0 × 10 ^-14 m ³ / Nm. have.

This is a very breakthrough. If the hardness of the coating layer is high, the counterpart material is usually easily worn. However, the test results obtained in the examples of the present invention do not cause wear of the coating layer even if the hardness of the coating layer is increased. Prove that you can significantly lower.

Therefore, when heat-treating the coating layer containing 2.0% to 10.0% of carbon by weight, the hardness is increased by more than 1,500Hv and through the heat treatment to form a bead-like irregularities of less than 50㎛ diameter, the solid lubricant on the surface When the coating is lowered to the friction coefficient to 0.1 level to suppress the wear of the coating layer it is possible to lower the wear of the friction object.

The scope of the present invention is not limited to the above-described embodiments, and many other modifications based on the present invention will be possible to those skilled in the art within the scope of the present invention.

In the wear-resistant trivalent chromium coating layer having irregularities according to the present invention, a large number of irregularities heat-treated on the surface are formed.

Therefore, many unevennesses have a narrow contact area with the friction object, thereby reducing the coefficient of friction.

In addition, since a space capable of storing the lubricant is formed between the plurality of irregularities, the loss of the lubricant is prevented.

In addition, there is an advantage that the wear resistance is maintained for a long time due to the above-described advantages and durability is improved.

Claims (11)

The hemispherical shape has a number of irregularities in contact with the friction object is formed, the diameter of the irregularities wear-resistant trivalent chromium coating layer having irregularities, characterized in that 0.1 to 50% of the diameter of the apparent contact surface for the contact friction object . The wear-resistant trivalent chromium coating layer of claim 1, wherein the unevenness has a diameter of less than 50 µm. The wear-resistant trivalent chromium coating layer of claim 2, wherein a lubricant is provided on an outer side of the uneven surface. The wear-resistant trivalent chromium coating layer of claim 3, wherein the unevenness contains 2.0% to 10.0% of carbon by weight. Wear resistance consisting of a coating layer forming step of forming a coating layer consisting of trivalent chromium on the coating object using a trivalent chromium plating solution, a coating layer washing step of washing the coating layer with an ultrasonic cleaner, and a heat treatment step of heat treating the washed coating layer. In the manufacturing method of the trivalent chromium coating layer, The heat treatment step, A heating process of charging the coating layer to a heat treatment furnace and heating it; A reduction process of reducing the surface of the coating layer in the heat treatment furnace; Method for producing a wear-resistant trivalent chromium coating layer having irregularities, characterized in that it comprises a heat treatment process to maintain the temperature inside the heat treatment furnace. The method of claim 5, wherein the trivalent chromium plating solution in the coating layer forming step, Trivalent chromium compound 0.4 ~ 0.6M, 0.8 to 1.2 M of a complexing agent to inhibit the polymerization reaction of the trivalent chromium compound in an aqueous solution; 0.8 ~ 1.2M conduction aid to increase the electrical conductivity of trivalent chromium ion, 0.8 ~ 1.2M buffer for calibrating the hydrogen ion index of aqueous solution, 8-12 g / l of a polarizing agent which suppresses trivalent chromium ion from oxidizing to divalent, 1 ~ 4 g / l of organic additives to increase the gloss of the plating layer surface, Consists of 10 ~ 100ppm reducing agent to increase the adhesion of the plating layer, The reducing agent is a method for producing a wear-resistant trivalent chromium coating layer having irregularities, characterized in that the inorganic material or an organic material. According to claim 6, In the coating layer forming step, The temperature of the trivalent chromium plating solution is 30 ℃ to 50 ℃, the hydrogen ion index (pH) is 1 to 4, characterized in that the manufacturing method of the wear-resistant trivalent chromium coating layer with irregularities. The method of claim 7, wherein in the coating layer forming step, The effective current application range is 10 to 25A / ㎠ method for producing a wear-resistant trivalent chromium coating layer. The method of claim 5, wherein the reduction process, Method of producing a wear-resistant trivalent chromium coating layer having irregularities, characterized in that the process of supplying hydrogen (H ₂ ) gas, argon (Ar) gas and SF ₆ gas in the heat treatment furnace. delete The method of claim 5, wherein the heat treatment process, Method of producing a wear-resistant trivalent chromium coating layer having irregularities, characterized in that the process of maintaining the internal temperature for 30 to 180 minutes at 300 ~ 800 ℃ the heat treatment.

Images