KR101511536B1 - Low friction coating and coating method thereof - Google Patents

Abstract

The present invention relates to a low friction coating layer and a method of forming the same, A second Cr layer on the surface of the adhesive layer; And a coating layer composed of at least one layer selected from a DLC coating layer, a metal carbide layer, a metal nitride layer, and a metal carbonitride layer on the surface of the second Cr layer; The present invention relates to a low friction coating layer including a DLC coating layer and the like which have excellent hardness and low friction characteristics and a method for easily forming the low friction coating layer on a base material such as an automobile part.

Description

Low friction coating and coating method < RTI ID = 0.0 >

The present invention relates to a low friction coating layer and a method of forming the same, and more particularly to a low friction coating layer including a DLC coating layer and the like having excellent hardness and low friction characteristics, and a method of easily forming the low friction coating layer on a base material .

The automotive industry is developing various eco-friendly vehicles with the goal of reducing carbon dioxide emissions to 50g / km, which is 35-50% of current levels by 2020. In the case of fuel economy, the Corporate Average Fuel Econmomy), 23.2 km / l (54.5 mpg), to reduce downsizing and improve fuel efficiency.

Downsizing generally means reducing the size of the engine, but it also includes techniques such as reducing the weight of the vehicle body, increasing the efficiency of the transmission, and improving the performance of the engine. This downsizing technique increases the load on the engine components There is a problem that the quality of the parts is deteriorated due to friction and abrasion and the durability life is lowered.

On the other hand, there are components such as camshafts, valve lifts, and valves in the valve train components, which convert rotational motion of the camshafts into upward and downward motion for opening and closing the valves. For example, it is known that when a DLC (Diamond Like Carbon) coating is applied to the camshaft component, the fuel efficiency is improved by about 0.6 to 0.8%.

However, in order to apply the DLC coating, it is necessary to minimize the component surface roughness and surface cleaning. Specifically, the average roughness is reduced through the lapping process (from Ra 0.15 μm or more to Ra 0.08 μm or less) And the foreign matter removal process should be carried out.

That is, when DLC coating is applied to an engine-related part such as a camshaft in order to improve fuel economy, there is a problem that the cost increases excessively due to the above-mentioned additional processes.

In addition, when the conventional DLC coating is applied, there is a problem that the parts that do not generate friction are coated, which is not economical. In addition, parts are charged in PVD (Physical Vapor Deposition) or PACVD (Plasma-Assisted Chemical Vapor Deposition) However, in the case of a large-sized component exceeding the size of the existing coating equipment, it was difficult to implement the DLC coating itself.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above problems and provide a low friction coating layer which is easy to mass-produce with reduced cost and improved coating efficiency, and a method of forming the low friction coating layer on a base material of a component.

According to an aspect of the present invention, there is provided a low friction coating layer comprising: an adhesive layer on a surface of a base material; A second Cr layer on the surface of the adhesive layer; And a coating layer composed of at least one layer selected from a DLC coating layer, a metal carbide layer, a metal nitride layer, and a metal carbonitride layer on the surface of the second Cr layer; And a control unit.

Preferably, the low-friction coating layer further comprises a first Cr layer on the surface of the coating layer, more preferably an Al layer on the surface of the first Cr layer, The surface roughness of the surface in contact with the layer is 0.1 占 퐉 or less.

The coating layer may further comprise a metal carbide layer, a metal nitride layer or a metal carbonitride layer on the surface of the second Cr layer; And a DLC coating layer. It is more preferable that the metal applied to the coating layer is at least one selected from the group consisting of Cr, Zr, Si, Ti, and W.

Meanwhile, the DLC coating layer is preferably a Si-DLC or SiO-DLC coating layer.

The adhesive layer preferably has a shear strength of 20 N or more, more preferably an acrylic structural adhesive.

According to another aspect of the present invention, there is provided a method of forming a low-friction coating layer, comprising: forming a first Cr layer on an Al foil; Forming a coating layer comprising at least one layer selected from a DLC coating layer, a metal carbide layer, a metal nitride layer, and a metal carbonitride layer on the first Cr layer; Forming a second Cr layer on the coating layer; Cutting the Al foil; And bonding the Al foil with an adhesive to bond the second Cr layer to the base material; And a control unit.

The limitation of each configuration is as described above.

The effect of the present invention having the above-described structure can be eliminated by eliminating the additional process such as the hardening treatment of the base material or the roughness improving process accompanied by the conventional DLC coating method.

Further, unlike conventional DLC coatings that are applied to the entire surface of a part to be coated, the present invention enables a coating process to be applied only to necessary parts, thereby enabling a more efficient coating process. When the sliding parts and the counterpart are simultaneously coated, There is an advantage that the low-friction characteristic is doubled as the two excellent materials are rubbed.

In addition, conventionally, there is a problem that it is difficult to coat a large part exceeding the size of a coating equipment, but the present invention has an advantage that it can be applied to a large part regardless of the size of a target part.

1 is a photograph showing a friction portion of a camshaft according to an embodiment of the present invention.
FIG. 2 is a view showing the structure of a low-friction coating layer according to an embodiment of the present invention.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

The lower the roughness of the DLC coating surface, the larger the contact area of the surface during friction, the better the low friction effect of the DLC coating, and the better the low friction property to the counter material contacting with the coating material, the lower friction property is maximized.

Such a DLC coating is applied to automobile parts such as a valve lift. When a low friction coating such as a DLC coating is applied to a sliding portion or a lobe portion of a camshaft, which is a mating member against the valve lift, the valve lifting and camshaft abrasion And durability are improved, and the low friction characteristics that cause fuel economy improvement can be maximized.

In order to apply the DLC coating to the conventional camshaft, the camshaft must be charged into the PVD or PACVD equipment to coat the camshaft. In this case, There is a problem in that coating is performed on the surface of the portion other than the friction portion 100 of the substrate 100, which is inefficient.

In contrast, the present invention has an excellent effect in the performance of the bar coating price that can be applied to only the friction region 100 requiring coating.

A method of forming a low-friction coating layer according to the present invention includes the steps of: forming a first Cr layer on an Al foil; Forming a coating layer comprising at least one layer selected from a DLC coating layer, a metal carbide layer, a metal nitride layer, and a metal carbonitride layer on the first Cr layer; Forming a second Cr layer on the coating layer; Cutting the Al foil; And bonding the Al foil with an adhesive to bond the second Cr layer to the base material; And a control unit.

Conventionally, the surface of the base material is directly coated to form a low friction coating layer on the part. However, in the present invention, after coating the Al foil (including the sheet material and sheet) instead of the base material, To be bonded to the base material.

Therefore, the surface of the base material is not required to be polished, but it is preferable that the surface roughness (Ra) of the Al foil in contact with the first Cr layer is 0.1 μm or less before the coating.

After the Al foil is bonded to the base material, it is preferable to remove the Al foil. The Al foil may be removed by a physical or chemical method, or may be removed by treatment with NaOH.

The reaction formula (1) between NaOH and Al foil is as follows.

_{2Al + 2NaOH + 6H 2 O →} 2Na [Al (OH) 4] + 3H 2 (1)

The forming of the coating layer may include forming a DLC coating layer on the first Cr layer, and then forming a metal carbide layer, a metal nitride layer, or a metal carbonitride layer on the DLC coating layer. The DLC coating layer may include a DLC coating But it is preferable that the metal to be applied to the metal carbide layer, the metal nitride layer and the metal carbonitride layer include at least one selected from Cr, Zr, Si, Ti and W, Si-DLC or Si0- .

In addition, the adhesive serves to bond the coated Al foil and the base material, and it is preferably 20 N or more. A structural adhesive generally used in automobile parts and the like can be used in the art, It is more preferable to use an adhesive.

The present invention uses an Al material and is preferably carried out at a temperature of 150 DEG C or less to prevent material damage due to the low melting property of the Al material.

On the other hand, after the Al foil is removed, the first Cr layer existing on the outermost surface is worn away at an early stage, and the DLC coating layer, the metal carbide layer, the metal nitride layer, and the metal carbonitride layer A coating layer composed of at least one selected layer exhibits a low friction effect.

FIG. 2 is a view showing the structure of a low-friction coating layer according to an embodiment of the present invention, which includes an adhesive layer 20 on the surface of a base material 10; A second Cr layer (30) on the surface of the adhesive layer; And at least one layer selected from a DLC coating layer, a metal carbide layer, a metal nitride layer, and a metal carbonitride layer on the surface of the second Cr layer (30); It is preferable to further include a first Cr layer 50 on the surface of the coating layer 40 and further include an Al layer 60 on the surface of the first Cr layer 50 More preferable.

The coating layer 40 may include a metal carbide layer, a metal nitride layer or a metal carbonitride layer 41 on the surface 30 of the second Cr layer; And a DLC coating layer (42). The limitation of each configuration is as described above.

The thickness of the first and second Cr layers is preferably 0.05 to 2 μm, more preferably about 0.1 μm, and the thickness of the metal carbide layer, the metal nitride layer, or the metal carbonitride layer 41 is The thickness of the DLC coating layer 42 is preferably about 0.1 to 1 μm, more preferably about 0.5 μm, and the thickness of the DLC coating layer 42 is preferably about 1 to 5 μm, more preferably about 2 μm.

Since the coating layer according to the present invention is formed on the Al foil instead of the base material, it is unnecessary to improve the roughness of the coating and it is possible to eliminate the heat treatment such as carburizing and high frequency which is a current hardening treatment process.

However, it is preferable that the surface roughness of the surface of the Al foil, which is in contact with the first Cr layer, is 0.1 μm or less before the coating, so that the roughness improving portion 70 is formed on the surface thereof.

[Example]

Hereinafter, the present invention will be described in more detail with reference to Examples. It is to be understood by those skilled in the art that these embodiments are merely illustrative of the present invention and that the scope of the present invention is not construed as being limited by these embodiments.

(Cr / Si-DLC / WC / Cr) was applied to the PVD coating equipment and the coating was carried out at 150 ° C or lower after improving the roughness of the aluminum foil to a surface roughness (Ra)

Then, the foil was cut in accordance with the parts and then bonded using an acrylic structural bonding agent (H8100). The Al foil was then removed using NaOH.

1. Evaluation of friction wear

The friction coefficient between the coating and the pin was measured by a Pin on Disc friction and wear tester. The test conditions were evaluated under load 10 / 30N, distance 2 / 3km, radius 6mm, linear velocity (100mm / s), oil (GF4). After that, wear resistance and relative aggressiveness were measured by comparing the wear depth of the friction track with the weight of the relative pin material, but it was confirmed that there was no abnormality.

2. Adhesive durability additional test

The adhesive performance of the present invention was further tested using a rocker cover material and a plastic tube material.

Adhesion and effect on O-ring Two items were evaluated by visual and tactile sensation.

1) Evaluation of adhesion

After cutting the cover material to an appropriate size, it was bonded to the hexagonal plane of the tube using an acrylic structural adhesive (H8100).

And after 1 day at room temperature, the adhesive property was evaluated by pulling by hand.

After adhering, the adhesive which had passed for 1 day at room temperature was immersed in commercial diesel engine oil at 150 DEG C for 100 hours, taken out, cooled at room temperature, and pulled by hand to evaluate adhesion.

2) Evaluation of impact on O-ring

The above H8100 was evenly applied to the surface of the O-ring assembled in the tube and left at room temperature for 100 hours.

The state of the neglected O-ring and the normal O-ring were visually and tactile.

3) Results

The H8100 showed stable curing performance even after room temperature curing and high temperature oil immersion. This is a good result as opposed to the easy peeling of existing test adhesives (silicone, polyacrylate, polyurethane, etc.).

In addition, no phenomenon such as softening and cracking was found in the O-ring coated and cured with H8100. The hard surface appears to be due to the hardened mass of the H8100, not the O-ring itself. When the cross section was observed by cutting the O-ring, the inside was not different from the normal O-ring.

As a result, the acrylic structural adhesive can be used for bonding the coating layer and the steel sheet according to the present invention.

Although the present invention has been described in connection with the specific embodiments of the present invention, it is to be understood that the present invention is not limited thereto. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims and their equivalents. Various modifications and variations are possible.

10: base metal
20: Adhesive layer
30: second Cr layer
40: Coating layer
50: First Cr layer
60: Al layer
70: Illumination improvement section
100: Friction zone

Claims (18)

An adhesive layer on the surface of the base material;
A second Cr layer on the surface of the adhesive layer;
A coating layer composed of at least one layer selected from a DLC coating layer, a metal carbide layer, a metal nitride layer and a metal carbonitride layer on the surface of the second Cr layer; And
And a first Cr layer on the surface of the coating layer.
delete The method according to claim 1,
Wherein the low friction coating layer further comprises an Al layer on the surface of the first Cr layer.
The method according to claim 1,
The coating layer comprising a metal carbide layer, a metal nitride layer or a metal carbonitride layer on the surface of the second Cr layer; And a DLC coating layer.
The method of claim 3,
Wherein the Al layer has a surface roughness of not more than 0.1 mu m on a surface in contact with the first Cr layer.
The method according to any one of claims 1, 3, and 4,
Wherein the metal applied to the coating layer is at least one selected from the group consisting of Cr, Zr, Si, Ti and W.
The method according to any one of claims 1, 3, and 4,
Wherein the DLC coating layer is a Si-DLC or SiO-DLC coating layer.
The method according to any one of claims 1, 3, and 4,
Wherein the adhesive layer has a shear strength of 20 N or more.
9. The method of claim 8,
Wherein the adhesive layer is an acrylic structural adhesive.
Forming a first Cr layer on the Al foil;
Forming a coating layer comprising at least one layer selected from a DLC coating layer, a metal carbide layer, a metal nitride layer, and a metal carbonitride layer on the first Cr layer;
Forming a second Cr layer on the coating layer;
Cutting the Al foil, the first Cr layer, the coating layer, and the second Cr layer according to the size of the friction material of the base material; And
Bonding the Al foil with an adhesive to bond the second Cr layer to the base material;
/ RTI > wherein the low friction coating layer is formed on the substrate.
11. The method of claim 10,
Wherein the forming of the low friction coating layer further comprises removing Al foil bonded to the base material.
11. The method of claim 10,
Wherein the forming of the coating layer comprises forming a DLC coating layer on the first Cr layer and then forming a metal carbide layer, a metal nitride layer, or a metal carbonitride layer on the DLC coating layer.
11. The method of claim 10,
Wherein the Al foil has a surface roughness of not more than 0.1 mu m on a surface contacting with the first Cr layer.
12. The method of claim 11,
Wherein the step of removing the Al foil removes the Al foil through NaOH treatment.
13. The method according to any one of claims 10 to 12,
Wherein the metal applied to the coating layer is at least one selected from the group consisting of Cr, Zr, Si, Ti and W.
13. The method according to any one of claims 10 to 12,
Wherein the DLC coating layer is a Si-DLC or SiO-DLC coating layer.
13. The method according to any one of claims 10 to 12,
Wherein the adhesive has a shear strength of 20 N or more.
18. The method of claim 17,
Wherein the adhesive is an acrylic structural adhesive.

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