KR20040007378A - Coating systhesized on the parts of motor engines and coating apparatus - Google Patents

Abstract

PURPOSE: A carbon nitride coating layer formed on parts for automobile engine, which can improve the mechanical properties of the engine, resulting in enhanced service life of the engine and reduction in rate of fuel consumption, as well as a coating device therefor having higher synthetic rate are provided. CONSTITUTION: The carbon nitride coating layer formed on parts for automobile engine comprises a carbon nitride layer formed by adding nitrogen to carbon and an intermediate layer selected from a nitride or carbide of transition metals including Cr, Si, W, Ti or CrN, TiN, WC. The carbon nitride coating layer may be controlled to have 15 to 35 GPa of hardness and not more than 0.05 of abrasion rate, at least 50 percentage of reduction of residual stress thereon. The coating device equipped with a vacuum chamber(31) and a vacuum pump(32) is characterized by comprising: two magnetron sources(33,34) in the vacuum chamber(31), any one of which has a carbon target for synthesizing a carbon nitride thin layer; an insulated rotary type jig which can transfer the material to be coated forward the magnetron sources (33,34) and apply direct bias current voltage; and a controlling section for the controlled feeding of N2 and Ar gas.

Description

Coated systhesized on the parts of motor engines and coating apparatus}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the coating of automotive engine parts, and more particularly, to a coating apparatus that realizes carbon nitride (CNx) coating to ensure wear resistance, high lubrication, and high synthesis speed of components for improving the life and fuel economy of an automobile engine. will be.

Automotive engines consist of a variety of mechanical components, including piston rings, tappets, bearings, parking cams and pinions. Until now, most of these automotive engine parts have been improved in mechanical properties by surface treatment such as gas nitriding, carburization, and wet plating. However, with advances in automotive technology, engine power has increased and the adaptation environment for engine components has become more severe. In particular, wet plating, which is most widely applied to automotive engine parts, causes environmental problems and its use is gradually limited.

Accordingly, researches on the application of plasma coatings to automotive parts, which are environmentally friendly and exhibit excellent mechanical properties, have been actively conducted worldwide. Currently, chromium-based antiwear coatings and carbon-based high lubrication coatings are being applied to engine parts, but there is no application in the domestic automotive field. In particular, the carbon-based coating film is expected to be effectively applied to automotive parts due to excellent wear resistance, lubrication characteristics and chemical stability.

However, carbon coatings have many limitations to be applied to automotive engine parts that need to be supplied in large quantities at low cost due to the low synthesis rate of the coating apparatus. Conventionally, carbon coating has been performed by various methods such as chemical vapor deposition (CVD), ion plating, arc evaporation, ion beam sputtering, etc., but the coating apparatus for performing these methods has a relatively low plasma density and ionization rate, generally 20 nm / It has a synthesis rate of min.

Accordingly, the present inventors have completed the present invention by developing a coating apparatus having a high synthesis rate together with a coating having better mechanical properties in the process of studying plasma coating on an automobile engine part.

An object of the present invention is to apply a carbon nitride (CNx) coating in coating automotive engine parts, to provide a coating having better mechanical properties than conventional ones. It is another object of the present invention to provide a coating apparatus that realizes a high synthesis rate.

1 to 3 are conceptual views of coatings according to the invention.

4 is a schematic view of a coating apparatus according to the present invention.

Figure 5 is a cross-sectional photograph of the coating according to the first embodiment.

6 is a cross-sectional photograph of a coating according to a second embodiment.

<Description of the symbols for the main parts of the drawings>

20a, b, c. Coating 21. Coating Material

22. Carbon Nitride Layer 23. Mezzanine

24. Stress Relief Layer 30. Coating device

31.Vacuum box Vacuum pump

33,34. Magnetron One 35. Jig

36. Gas flow rate controller

1 is a conceptual diagram showing the structure of the coating (20a) to be obtained by the present invention. Reference numeral 21 denotes a coating material selected from automotive engine parts, and the coating 20a is synthesized on the coating material 21 and is a carbon nitride (CNx) layer 22 obtained by adding nitrogen to carbon. The coating 20a has a thickness of about 1 to 2 μm, but may be up to several μm in some cases. In addition, the carbon nitride layer 22 is obtained by adding nitrogen to carbon, and has excellent wear resistance and lubrication characteristics as compared with the conventional carbon coating.

2 is a conceptual diagram showing the structure of another coating 20b to be obtained by the present invention. The coating 20b further includes an intermediate layer 23 disposed between the coating material 21 and the carbon nitride layer 22 with respect to the coating 20a described above. The coating 20b has a thickness of about 1 to 2 μm, but may be up to several μm in some cases. The intermediate layer 23 is provided to realize mutual adhesion between the material to be coated 21 and the carbon nitride layer 22, and as a material, transition metal nitrides and carbides such as Cr, Si, W, Ti or CrN, TiN, WC, etc. It is used to choose from.

3 is a conceptual diagram showing the structure of another coating 20c to be obtained by the present invention. The coating 20c is alternately laminated with the stress releasing layer 24 and another carbon nitride layer 22a, b, c ... on the carbon nitride layer 22 with respect to the coating 20b described above. The thickness can be up to several μm. By such a multilayer structure, a coating having a higher adhesion with the to-be-coated material 21 and a low residual stress can be obtained.

4 is a view showing the configuration of a coating apparatus according to a preferred embodiment of the present invention, the carbon nitride coating by the magnetron sputtering method by the coating apparatus 30 is performed. The coating device 30 is:

In the apparatus comprising a vacuum chamber (31) to be coated coating material therein, and a vacuum pump (32) provided outside the vacuum chamber (31) to provide an internal pressure of the vacuum chamber (31);

A magnetron source (33, 34) provided on both sides of the vacuum box (31) facing each other, and equipped with a solid carbon target for synthesis of a carbon nitride (CNx) thin film on one side thereof;

The rotating jig insulated from the vacuum chamber 31 so as to transfer the coated material to the front of the magnetron source (33,34) and apply a DC bias voltage (-) in the interior of the vacuum chamber (31) 35);

It is disposed on the outside of the vacuum box 31 and connected to the inside, it is composed of a gas control unit 36 for supplying a regulated flow rate of N ₂ and Ar gas for the synthesis of the carbon nitride film.

Preferably, a material selected from transition metal nitrides and carbides such as Cr, Si, W, Ti, or CrN, TiN, WC, etc. is targeted to the other side of the magnetron source 33,34 to the adhesion between the carbon nitride film and the coating material. Is mounted.

Referring to the operating principle of the coating device 30 as follows. Magnets are mounted on the cathode on which the material to be coated is mounted to apply a magnetic field in a direction parallel to the target surface to connect electrons, and keep the plasma very close to the target surface by allowing electrons to orbit around it. Let's do it. By this action, the plasma density and the ionization rate are increased, and as a result, the discharge current by the mass produced ions increases and the sputtering speed is improved. Therefore, the collision of electrons on the substrate is reduced and the deposition rate can be improved. In fact, the device can achieve high synthesis rates of over 200nm / min.

First embodiment

5 is a scanning electron micrograph of the carbon nitride coating 20b of FIG. 2 synthesized using the coating apparatus 30 according to the present invention. Process conditions for synthesizing the carbon nitride thin film were as follows.

Ar partial pressure: 3 × 10 ^-3 Torr

N ₂ partial pressure: 0.5 ~ 3 × 10 ^-3 Torr

Magnetron One

Cathode 1: Cr (99.9% or higher purity)

Cathode 2: graphite (99.9% or higher purity)

Current density: 30 W / ㎠

Specimen temperature: about 150 ℃

Specimen bias: DC -200V

Jig Speed: 4 ~ 16 rpm

In FIG. 5, the Cr intermediate layer 23 and the nitrogen carbide layer 22 for the adhesion on the specimen are observed, and the nitrogen content in the carbon nitride thin film synthesized under the same process conditions is 10 to 60% depending on the nitrogen process partial pressure. It has been confirmed that it is synthesized over a wide range.

By controlling the nitrogen content contained in the thin film, the hardness value can be controlled up to 15 ~ 35GPa, and the friction coefficient can be up to 0.05 or less. Therefore, it is possible to synthesize a coating film having mechanical properties corresponding to the purpose of use, and to allow concentration gradient coating to gradually change the nitrogen concentration. In addition, by controlling the rotational speed of the jig 35, it is possible to vary the thickness of each layer (22, 23, 24).

As a result of the application of automotive engine parts coated in this way, the engine friction reduction was greatly improved, and the fuel efficiency reduction effect was also remarkably observed. It also has excellent durability against high temperature deterioration.

The characteristics of the carbon nitride coating film are summarized in comparison with the existing chromium and carbon coating films and are shown in Table 1 below.

Table 1

Carbon Nitride Film (CNx) Chromium-based film (CrN) Carbon film (a-C: H) Hardness (GPa) 15-35 22-25 20-35 Coefficient of friction <0.05 0.35 ~ 0.1 Adhesion (N) > 60 > 60 40-45 Residual Stress (GPa) <2 <1 > 2 Heat resistant and durable Good Great Problem with heat resistance

In Table 1, since the carbon nitride film has various hardness ranges, the application can be made in various ways depending on the purpose of use, and the friction coefficient is superior to other coating films. In addition, since the residual stress can be controlled to 2GPa or less, the force value is also high, and the heat-resistant mill durability is good.

Second embodiment

FIG. 6 is a scanning electron micrograph of the carbon nitride coating 20c having the multilayer structure of FIG. 3 synthesized using the coating apparatus 30 according to the present invention. Process conditions for synthesizing the carbon nitride thin film were as follows.

Ar partial pressure: 3 × 10 ^-3 Torr

N ₂ partial pressure: 0.5 ~ 3 × 10 ^-3 Torr

Magnetron One

Cathode 1: Cr (99.9% or higher purity)

Cathode 2: graphite (99.9% or higher purity)

Current density: 30 W / ㎠

Specimen temperature: about 150 ℃

Specimen bias: DC -200V

Jig Speed: 4 ~ 16 rpm

In FIG. 6, the Cr intermediate layer 23, the nitrogen carbide layers 22, 22a, b, c..., And the Cr stress releasing layer 24 are observed on the coated material 21 for implementing adhesion. The introduction of the stress releasing layer 24 reduced the residual stress of the coating 20c to 1GPa, resulting in an improved adhesion between the specimen and the coating.

The coating according to the invention, the hardness value can be controlled up to 15 ~ 35GPa, the coefficient of friction can be up to 0.05 or less. In addition, the multilayered structure can reduce the residual stress of the coating by 50% or more. Therefore, automotive engines using such coatings have significant effects on life extension and fuel economy.

Claims (6)

A coating synthesized on a coating material selected from automotive engine parts, wherein the coating is carbon nitride (CNx) layer obtained by adding nitrogen to carbon. The method of claim 1, wherein the coating further comprises an intermediate layer disposed between the coating material and the carbon nitride layer, wherein the intermediate layer is a material for achieving mutual adhesion between the coating material and the carbon nitride layer as Cr, Si, W, Ti Or carbon nitride coatings synthesized on automotive engine parts, which are selectively used among transition metal nitrides and carbides such as CrN, TiN, and WC. The method of claim 1 or 2, wherein the coating comprises a stress releasing layer and another carbon nitride layer alternately stacked on the carbon nitride layer, wherein the stress releasing layer is Cr, Si, W, Ti or CrN, A carbon nitride coating synthesized on automotive engine parts characterized by selectively using among transition metal nitrides and carbides such as TiN and WC. An apparatus comprising a vacuum chamber in which a coating treatment of a coating material is performed therein, and a vacuum pump provided outside the vacuum chamber to provide an internal pressure of the vacuum chamber; A magnetron source provided on each of the two sides of the vacuum box facing each other and equipped with a solid carbon target for synthesis of a carbon nitride (CNx) thin film on one side; A rotating jig insulated from the vacuum chamber to transfer the coated material to the front of the magnetron source and apply a DC bias voltage (-) in the vacuum chamber; It is disposed on the outside of the vacuum box and connected to the inside, the coating apparatus, characterized in that made of a gas control unit for regulating supply of the flow rate of N ₂ and Ar gas for the synthesis of the carbon nitride film. The method of claim 4, wherein the other side of the magnetron source is selected from a material selected from transition metal nitrides and carbides, such as Cr, Si, W, Ti or CrN, TiN, WC for the purpose of reducing the adhesion and residual stress of the coating Coating device characterized in that. The method of claim 1, wherein the coating comprises one containing hydrogen in the carbon nitride layer and one not.