KR101517788B1 - 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, And a coating layer on the surface of the steel sheet layer; Wherein the coating layer comprises at least one layer selected from the group consisting of a DLC coating layer, a metal carbide layer, a metal nitride layer and a metal carbonitride layer, and includes a low friction coating layer including a DLC coating layer having excellent hardness and low friction characteristics, To an automobile part or the like easily.

Description

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

The present invention relates to a low-friction coating layer and a method for forming the low-friction coating layer. More particularly, the present invention relates to a low-friction coating layer including a DLC coating layer having excellent hardness and low friction characteristics, and a method for easily forming the coating layer.

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 Economy) to 23.2 km / l (54.5 mpg).

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.

To attain the above object, the low friction coating layer of the present invention comprises an adhesive layer on the surface of a base material: a steel sheet layer on the surface of the adhesive layer; And a coating layer on the surface of the steel sheet layer; Wherein the coating layer comprises at least one layer selected from a DLC coating layer, a metal carbide layer, a metal nitride layer, and a metal carbonitride layer.

At this time, it is preferable that the metal applied to the coating layer is at least one selected from Cr, Zr, Si, Ti, and W.

Preferably, the DLC coating layer is a Si-DLC or SiO-DLC coating layer, and the SUS or SPHC steel sheet is preferable. The surface roughness (Ra) of the steel sheet layer is preferably 0.1 m or less.

At this time, the thickness of the steel sheet layer is more preferably 0.05 to 0.2 mm.

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, the method comprising: forming a coating layer on a steel sheet, the coating layer including at least one layer selected from a DLC coating layer, a metal carbide layer, a metal nitride layer and a metal carbonitride layer; Cutting the steel sheet on which the coating layer is formed; And bonding the steel sheet to the base material using an adhesive; 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.

In addition, it can be applied to parts where DLC coating can not be applied due to low melting temperature of plastic materials such as chain guides, and thus it is very useful.

1 is a photograph showing a friction portion of a camshaft according to an embodiment of the present invention.
2 is a view showing the low friction coating layer structure of the present invention.
Fig. 3 is a photograph after evaluation of the frictional wear of the specimen.

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.

The method of forming a low-friction coating layer according to the present invention includes the steps of forming a coating layer on a steel sheet, the coating layer being formed of at least one layer selected from a DLC coating layer, a metal carbide layer, a metal nitride layer, and a metal carbonitride layer; Cutting the steel sheet on which the coating layer is formed; And bonding the steel sheet to the base material using an adhesive; And a control unit.

Conventionally, in order to form a low friction coating layer on a part, a coating layer is formed directly on the surface of the base material. However, in the present invention, a coating layer is first formed on a steel sheet other than the base material, .

At this time, the steel sheet includes all the steels commonly used in the art, but it is preferably SUS or SPHC steel sheet.

In addition, since the coating layer is first formed on the steel sheet, it is preferable that the surface roughness (Ra) is improved to 0.1 μm or less before forming the coating layer on the steel sheet.

The DLC coating layer may include a Si-DLC or Si0-DLC coating as well as a DLC coating. The DLC coating layer may include a metal carbide It is preferable that the metal to be applied to the layer, the metal nitride layer and the metal carbonitride layer is at least one selected from Cr, Zr, Si, Ti and W.

In addition, the adhesive serves to bond the steel sheet and the base material, and preferably has a shear strength of 20 N or more. A structural adhesive commonly used in automobile parts and the like can be used in the art, It is more preferable to use an adhesive. The adhesive needs to have heat resistance of at least 200 DEG C and excellent durability against oil and moisture.

2 is a view showing a low friction coating layer structure of the present invention, in which an adhesive layer 20 on the surface of a base material 10: a steel sheet layer 30 on the surface of the adhesive layer 20; And a coating layer (40) on the surface of the steel sheet layer (30); And the coating layer 40 is formed of at least one layer selected from a DLC coating layer, a metal carbide layer, a metal nitride layer, and a metal carbonitride layer. The limitation of each configuration is as described above.

Since the coating layer according to the present invention is formed on the steel sheet layer instead of the base material, it is unnecessary to improve the roughness of the coating and it is possible to eliminate the current hardening treatment process such as carburizing and high frequency heat treatment. The surface roughness (Ra) of the steel sheet layer bonded to the base material and the bonding layer may be 0.4 μm or less.

However, it is preferable that the roughness improving portion 50 is formed on the surface of the steel sheet layer so that the surface roughness Ra of the steel sheet layer is improved to 0.1 μm or less before forming the coating layer.

[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.

The SUS steel sheet having a thickness of 0.1 mm was improved in surface roughness (Ra) to 0.1 μm or less and then charged into the PVD coating equipment to perform DLC coating, and then the DLC coated steel sheet was cut to the tappet size. The steel sheet and the tappet were bonded and cured using an acrylic structural adhesive to complete the specimen.

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). Thereafter, the abrasion resistance and relative aggressiveness were measured by comparing the wear depth of the friction track with the weight of the counter material pin, but it was confirmed that there was no abnormality (FIG. 3).

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: steel sheet layer
40: Coating layer
50: Illumination improvement section
100: Friction zone

Claims (16)

delete delete delete delete delete delete delete delete Forming a coating layer on the steel sheet, the coating layer comprising at least one layer selected from the group consisting of a DLC coating layer, a metal carbide layer, a metal nitride layer, and a metal carbonitride layer;
Cutting the steel sheet on which the coating layer is formed; And
Bonding the steel sheet to the base material using an adhesive;
Wherein the low-friction coating layer is formed on the substrate.
10. The method of claim 9,
Wherein the metal applied to the coating layer is at least one selected from the group consisting of Cr, Zr, Si, Ti and W.
10. The method of claim 9,
Wherein the DLC coating layer is a Si-DLC or SiO-DLC coating layer.
10. The method of claim 9,
Wherein the steel sheet is an SUS or SPHC steel sheet.
10. The method of claim 9,
Wherein the coating layer is formed on a steel sheet having a surface roughness (Ra) of 0.1 占 퐉 or less.
14. The method of claim 13,
Wherein the steel sheet has a thickness of 0.05 to 0.2 mm.
10. The method of claim 9,
Wherein the adhesive has a shear strength of 20 N or more.
16. The method of claim 15,
Wherein the adhesive is an acrylic structural adhesive.

Images