KR19990061520A - Wear-resistant member coated with an amorphous carbon layer - Google Patents

Abstract

The present invention relates to an abrasion resistant member, characterized in that an amorphous carbon layer containing hydrogen is coated on a wear surface, thereby providing excellent wear resistance and friction characteristics.

Description

Wear-proof Parts Coated A Carbon-Layer

The present invention relates to an abrasion-resistant member coated with an amorphous carbon layer. In particular, the amorphous carbon layer is coated with an amorphous carbon layer on a wear surface such as a piston, a piston ring, and a piston liner constituting a piston assembly, thereby providing excellent wear resistance and friction characteristics. It relates to a layer-coated wear resistant member.

In general, wear-resistant members are widely used on rotating surfaces or reciprocating parts of machinery. Pistons, piston rings, or piston liners constituting the piston assembly of an engine are used at high speed while friction with the inner wall of a cylinder in a cylinder of high temperature and high pressure. It is a representative example of the wear-resistant member that serves to generate a rotational force on the crankshaft through the connecting rod by reciprocating motion.

Since the piston assembly is in contact with the combustion gas of high temperature and high pressure during the power stroke, and also frictional movement with the inner wall of the cylinder at high speed, the following conditions are required.

In other words, the mechanical loss must be reduced by reducing friction with the inner wall of the cylinder, and the mechanical properties such as wear resistance should not be degraded even when heated from high temperature combustion gases.

In particular, in the current trend of high engine power, active research is being conducted to improve the airtight action inside the cylinder by increasing the wear resistance of pistons, among which the outer circumferential sliding surface of the piston ring, the inner wall of the liner, the upper part of the piston and A method of increasing the wear resistance of a piston assembly by depositing a diamond film on the side has been proposed.

The method of depositing a diamond film on the piston assembly provides a high temperature wear resistance to the sliding parts of the piston assembly, but has a problem that the quality of the diamond film is very difficult to deposit on the parts.

That is, since the diamond film is to be deposited at a high temperature (800 ℃ or more) has a disadvantage that the material to deposit the diamond film is extremely limited because the base material is affected by a high deposition temperature during deposition, or the mechanical properties change. In particular, a piston part made of an Al-Si-based alloy has difficulty in manufacturing due to the diamond film property. In addition, a relatively large portion of the deposition area, such as a piston has a disadvantage that takes a lot of cost.

In addition, as a result of assembling the piston parts in which the diamond film was deposited, the piston parts in which the diamond film was deposited had increased wear resistance and less wear. However, abnormal wear phenomenon occurred in the cylinder, in which the diamond film was not deposited. This is because the deposited diamond film is a coarse crystalline having a surface roughness of 1 s (Rs; height difference between the highest height and the lowest height of the film; unit μm), thereby grinding the inner wall of the cylinder, which is a relative component.

Therefore, in order to prevent abnormal wear of these counterparts and to use the excellent wear properties of the diamond film, the diamond film must be deposited on the piston and then the diamond film must be mechanically or chemically polished to improve the surface roughness. Since it is hard, it is difficult to apply it to relatively low cost parts such as engine parts because of the high cost of polishing.

Accordingly, the present invention is designed to solve the above problems, and it is an object of the present invention to provide abrasion resistant members having low wear cost while satisfactory wear resistance under conditions of high temperature and high pressure, and which do not cause abnormal wear phenomenon of the counterpart.

The above object can be achieved by forming an amorphous carbon layer on the wear surface of the wear resistant member having a relatively low coating temperature of the film and having a smooth coating surface, which does not require post-processing.

The wear-resistant member according to the present invention having the above configuration is characterized in that the amorphous carbon layer containing hydrogen is coated on the wear surface.

In such a wear resistant member, the amorphous carbon layer preferably contains 0 to 70% of hydrogen.

In addition, the amorphous carbon layer preferably contains 0 to 40% of metal elements such as Si, W, Fe, Ni, Co, Cr, and Mo, since it may further improve wear resistance and friction characteristics.

Hereinafter, the configuration and operation of the present invention will be described in detail by examples.

As described above, the wear-resistant member according to the present invention is characterized in that an amorphous carbon layer containing hydrogen is formed on the wear surface of the wear-resistant member, wherein the wear surface of the wear-resistant member is a piston assembly. In this case, the piston ring refers to a piston cavity, in the case of a piston ring, the outer sliding surface, and in the case of a cylinder liner, the inner wall.

On the other hand, a method of forming a hydrogen-containing carbon layer on the wear surface of the wear-resistant member can be used a general dry coating method, which is chemical vapor phase deposition (CVD) and vacuum deposition (PVD method) Can be mentioned.

The dual CVD method is preferred in terms of manufacturing cost, in which the formation of an amorphous carbon layer on the wear surface of the wear resistant member maintains the carbon source in a vacuum and the wear resistant members such as pistons and piston rings and cylinder liners Blown into the reaction vessel placed in contact with the wear surface to form an amorphous carbon layer.

According to the dry coating method, an amorphous carbon layer may be formed to a thickness of 0.1 to 100 μm on the wear surface of the piston, the piston ring, and the cylinder liner.

In addition, it is preferable that the amorphous carbon layer contains 0 to 70% of hydrogen, and it is preferable to have a hardness of 800 to 12,000 kg / mm ² since it has appropriate wear resistance and friction characteristics. In addition, metal elements such as Si, N, W, Fe, Ni, Co, Cr, and Mo may be included to further improve the wear resistance and friction characteristics of the amorphous carbon layer.

Example 1.

An amorphous carbon layer was deposited on the cylinder liner and the piston ring using an rf-plasma (frequency 250 kHz) chemical vapor deposition (CVD) apparatus while maintaining a bias voltage of 50-1500 V while flowing methane gas into the carbon source.

Thus, the following experiment was carried out to confirm the wear resistance of the cylinder liner and the piston ring in which the amorphous carbon layer was formed on the wear surface.

The piston was equipped with a piston ring in which an amorphous carbon layer was formed on the wear surface, and the engine was operated to perform a severe test for 100 hours. And the conventional chromium piston ring without an amorphous carbon layer was mounted on the piston and tested under the same conditions as described above and compared.

According to the present invention, it was observed that the carbon layer was formed on the wear surface of the wear surface of about 1 μm, and the wear trace of the existing chrome piston ring was about 30 μm, and was observed in the entire piston ring area.

Therefore, in the case of the piston ring formed on the wear surface of the carbon layer, the wear resistance was increased by about 30 times.

Example 2.

The most frequent problem of the piston ring and cylinder liner system is known as adhesion wear.Adhesion wear is caused by local breakdown of the lubrication film at the interface between the piston ring and the cylinder liner. It is the ideal way to prevent abnormal wear. However, since it is practically difficult to supply sufficient lubricating oil to the piston ring and cylinder liner (the lubricating oil burns during combustion, causing pollution), it is important to select a piston material that will not cause abnormal wear when the lubricating film is broken.

Amorphous carbon is a ceramic material with low adhesion to metal, which makes it ideal for piston ring and cylinder liner materials. In order to compare the adhesion resistance characteristics, the piston rings in which amorphous carbon was deposited and the chromium deposited piston rings were compared and tested.

The comparative experiment method is as follows. After cutting the commercially available cylinder liner to an appropriate size, the piston ring was brought into close contact with the inside of the cylinder liner to perform a reciprocating motion. Since it is difficult to reproduce the failure of the lubricating film experimentally, the time for causing the adhesive wear under the condition that the lubricant was not supplied and the load was applied at 50 N was measured.

The criterion to cause adhesion wear was a time point of the friction coefficient is 0.5 or more and the deposition conditions of the amorphous carbon layer was the same as in Example 1.

As a result of the abrasion test, the commercially available chromium-deposited piston ring had an adhesion wear in less than 3 minutes, but in the case of an amorphous carbon-deposited piston ring, the adhesion ring did not occur during the test time of 3 hours.

Even if the lubrication film is locally broken between the piston ring and the cylinder liner in actual engine operation, the piston ring coated with the amorphous carbon layer does not cause adhesion wear until the locally destroyed lubrication film is restored. It can be greatly reduced.

On the other hand, by reducing the friction coefficient between the piston ring and the cylinder liner, the engine output loss due to the friction force can be reduced.

As a result of the abrasion test of the cylinder assembly in which the carbon layer was formed on the wear surface, excellent friction characteristics and wear resistance characteristics were confirmed.

As described above, the wear-resistant member of the present invention has an amorphous carbon layer formed on the wear surface of each component to have excellent wear resistance and friction characteristics.

Claims (3)

A wear resistant member, characterized in that an amorphous carbon layer containing hydrogen is coated on a wear surface. The wear resistant member according to claim 1, wherein the amorphous carbon layer contains 0 to 70% of hydrogen. The piston assembly of claim 1, wherein the amorphous carbon layer contains 0 to 40% of metallic elements such as Si, W, Fe, Ni, Co, Cr, Mo, and the like.