KR980009510A - Method of forming hard film on various metal surfaces - Google Patents

Abstract

In order to improve the lifetime of materials such as tools, machinery and mold products, a chromium nitride coating is formed on a base material by a reactive ion plating method, wherein nitrogen components in the chemical composition of the chromium nitride coating are made up of three different layers the in the usual hard film of comprising only chromium is a single metal for abrasion resistance improvement relates to forming the hard coating process of various metal surface, and the step of forming a chromium layer on the metal surface to secure adhesion, on the Cr ₂ N coating layer And a step of finally forming a chromium nitride film of CrN only.

Description

Method of forming hard film on various metal surfaces

FIG. 1 is a schematic view of a hard film forming apparatus for explaining the invention; FIG.

DESCRIPTION OF THE REFERENCE NUMERALS

1: vacuum chamber 2: evaporation source

3: ionization electrode 4: filament

5: shutter 6: substrate

7: substrate holder 8: substrate heating device

9: Gas inlet

In order to improve the lifetime of materials such as tools, machinery and mold products, a chromium nitride coating is formed on a base material by a reactive ion plating method, wherein nitrogen components in the chemical composition of the chromium nitride coating are made up of three different layers .

In general, the chromium nitride coating has excellent abrasion resistance and is expected to contribute to the improvement of the service life and quality of the titanium alloy and various tools, and so much research has been conducted.

In particular, there are many cases in which bearings are coated with a chromium nitride coating. When chromium nitride is formed as a coating, there are two phases (CrN and CN ₂ N). When two or more phases are produced in a nitrogen atmosphere, these two phases are present.

From the viewpoint of abrasion resistance, it is known that the coating made of CrN alone is far superior. However, in order to form CrN-only film, it requires very complicated process conditions. When analyzing actual film, most of the two phases are mixed.

This is because the film is coated under the same conditions and because CrN is chemically safe, even if more gas is injected to make CrN, the film is damaged before it becomes CrN, and it is often not usable.

Therefore, the limit of the use of a certain amount of nitrogen gas can not be reached, and therefore Cr ₂ N phase is inevitably present.

The inventors of the present invention have confirmed that it is possible to form a chromium nitride film composed only of CrN by increasing the ionization rate and changing various deposition conditions in forming the chromium nitride film (Japanese Patent Application No. 95-55020 number). In this case, however, the hardness layer supporting the chromium nitride is made of other materials such as TiN and TiC, which inevitably complicates the process.

The invention In this connection that invention to address such issues film consisting of only the Cr ₂ N hardness is paying attention to higher than CrN, but using only a single metal is chromium, the chromium metal, the interface layer using an inert gas as nitrogen gas The present invention is intended to improve the wear resistance and performance of various parts by depositing a Cr ₂ N layer having a high hardness in the intermediate layer and a CrN film only in the final surface layer.

As a method for improving the abrasion resistance of various machines and tools, it is known to spray molybdenum, oxidation treatment, nitriding treatment, hard coating by physical or chemical vapor deposition, and the like.

Among them, reactive ion plating and reactive sputtering are mainly used when physical vapor deposition is used.

Reactive ion plating is a method of evaporating a metal while simultaneously ionizing it to react with a gas to be injected and coating the substrate. Reactive sputtering is a method in which a ball active material is used to remove a substance from a metal plate, .

Titanium compounds such as titanium nitride are mainly used as coating materials, and transition metal compounds are used in many cases. Up to now, a hard coating of a single layer has been produced using such a method to improve wear resistance.

However, when a hard film is directly formed on a substrate of a metal, the adhesion is deteriorated due to the stress of the coating or the like, and thus, the characteristics are deteriorated as a whole.

In addition, various characteristics such as abrasion resistance and adhesiveness are changed depending on the material of the substrate, so that when the substrate is torn or the abrasion resistance is significantly different from the film material, the characteristics of the abrasion-resistant film deteriorate.

SUMMARY OF THE INVENTION Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to solve the above problems. The first aspect is a schematic view of an apparatus for explaining the present invention. An ionization electrode 3 capable of ion plating in the vacuum chamber 1 and a filament 4 are provided in the vacuum chamber 1. The inside of the vacuum chamber 1 is provided with an evaporation source 2, A substrate holder 7, a substrate heating device 8, a shutter 5, a gas inlet 9, and the like.

The evaporation source 2 used an electron gun evaporation source. First, the evaporation source 2 is charged with metal chromium used as a coating material, and the substrate 6 is mounted and then exhausted by using a vacuum pump (not shown).

When the degree of vacuum is less than 10 ^-5 Torr, argon gas is injected to clean the substrate 5, and a negative voltage is applied to the substrate 6 to clean the substrate 6.

The cleaning of the substrate 6 involves removing naturally existing oxide films as well as impurities such as organic substances present in the substrate 6 as a very important step.

If the oxide film is not sufficiently removed, it affects the adhesion and must be cleaned. Cleaning of the substrate 6 is usually 10 ^-2 by applying a negative voltage of 500~1000V the substrate 6 in an argon gas atmosphere of about Torr subjected to induce glow discharge.

In this way, the argon ions present in the discharge region collide with the substrate 6 to remove the oxide film existing on the substrate 6. [

After the substrate 6 is cleaned, the vacuum degree is maintained at 10 ^-5 Torr or lower, and then the chromium film, which is the first adhesion ensuring layer, is produced.

The chromium film can be produced by a conventional vacuum deposition or ion plating method, but an ion plating method is used.

Ion plating of metal chromium was performed by the following method.

First, the evaporation water is ionized by using the ionization electrode 3 and the filament 4 while evaporating chromium.

In the case of gronachrome, argon gas is injected because the ionization does not occur sufficiently by evaporation alone, and the pressure of the argon gas is adjusted to about 2 × 10 ^-4 Torr.

When the discharge is stabilized, a negative voltage may be applied to the substrate 6 and the shutter 5 may be opened to produce a chromium film.

The next step is to make a Cr ₂ N layer so that the nitrogen gas is injected so that the pressure of the nitrogen gas inside the vacuum chamber 1 is (0.5-1) × 10 ^-4 Tor in the state where the chromium evaporates and ionization is continued. When the deposition is performed in this state, a CrN layer is formed on the substrate 6.

The final step is to produce a CrN coating excellent in abrasion resistance.

In this case, the other condition is similar to Cr ₂ N, but it may be manufactured by injecting nitrogen gas at a pressure of (2 to 5) × 10 ^-4 torr and increasing the ionization efficiency.

All these processes consist of a single evaporation.

That is, after the chromium evaporates and ionizes at the same time, the entire process is completed only by controlling the flow rate of the nitrogen gas.

One thing to note in the production of the present invention is the evaporation of chromium. Since chromium is a sublimable substance in vacuum,

Be very careful because it is a foot. The evaporation in the present invention was made in Korean Patent No. 88595.

When the thickness of the chromium film is 0.3 to 1 탆 or less, it does not play a role of securing the adhesion. If the thickness is 1 탆 or more, economical efficiency is deteriorated.

The Cr ₂ N thickness is preferably in the range of 1.5 to ₃ 탆 for the following reasons.

When the thickness of the Cr ₂ N coating is 1.5 탆 or less, abrasion resistance characteristics are not sufficiently exhibited, and when the thickness is 3 탆 or more, economical efficiency is deteriorated.

The nitrogen gas pressure in the final surface layer is preferably (2 to 5) x 10 < ^-4 > Torr because of the following reasons. Due to the pressure of the gas when the 2 × 10 ^-4 Torr or less because it is not a complete and a chromium nitride CrN of different chemical compositions present in the wear-resistant coating film is decreased, the discharge is above at least 5 × 10 ^-4 Torr, such as the coating It is damaged.

In manufacturing the final surface layer, the voltage of the ionization electrode 3 is preferably in the range of 50 to 80 V for the following reasons. When the voltage of the ionization electrode 3 is 50 V or less, ionization does not sufficiently take place, so that complete CrN is not obtained, and chromium nitride having a different chemical composition exists in the film to lower abrasion resistance. The coating is damaged due to an abnormal discharge or the like.

Hereinafter, the present invention will be described in detail with reference to Examples and Table 1.

[Description 1]

An ionization electrode 3 capable of ion plating in a conventional vacuum chamber 1 and a filament 4 were provided to produce a wear-resistant coating consisting of three layers. The vacuum chamber 1 was opened to install the substrate 6, and then an initial discharge was performed to 10 ^-2 Torr using a rotary pump and a Boster pump. Then the oil diffusion pump was evacuated to less than 10 ^-5 Torr. After a desired degree of vacuum was obtained, a glow discharge cleaning was performed for 20 minutes by applying a voltage of about 800 V to the substrate 6 in an argon gas atmosphere in order to remove impurities present on the substrate 6 and clean the substrate 6.

The substrate 6 used in the present invention was a bearing made of a bearing steel and having a diameter of 10 mm. After the substrate cleaning was finished, chromium was formed to a thickness of 0.5 탆 by using an ion plating method.

Ion plating conditions of metal chromium are as follows.

First, for the evaporation of chromium, the power of the entire barbeam was set to 500 W and evaporated.

After the evaporation of chromium was stabilized, the argon gas pressure in the vacuum chamber 1 was adjusted to 2 × 10 ^-4 Torr, and a voltage of 60 V was applied to the ionization electrode 3 while flowing a current of 50 A to the filament 4.

At this time, the current flowing through the ionization electrode 3 was 8 to 10A. When the discharge was stabilized, a voltage of 300 V was applied to the substrate, and then the shutter 5 was opened to deposit for 5 minutes.

Next, in order to form a Cr ₁ N film, the nitrogen gas pressure was adjusted to 8 × 10 ^-5 Torr and the film was deposited for 15 minutes.

At this time, the thickness of the formed Cr ₂ N coating was about 1 탆. Finally, the nitrogen gas pressure was increased to 2.5 x 10 < ^-5 > Torr to form a CrN film, and the film was deposited for 15 minutes. At this time, the thickness of the formed CrN coating was about 1 mu m. Table 1 below shows the inventive and comparative examples, respectively, and the characteristics of abrasion according to the conditions are divided into the interface layer, the intermediate layer and the final surface layer.

The wear test was carried out under both dry and wet conditions using a ring-on-disk abrasion tester.

The wear conditions were adjusted so that the additional load was 0.065 MPa and the rotation speed was 150 mm / s.

The abrasion resistance is divided into three steps, and when it is excellent, it is indicated by?, When it is normal it is marked with?, And when it is bad, it is marked by X.

[Advantage 2]

This is the same as Example 1 except that the final surface layer was produced at a nitrogen gas pressure of 5 × 10 ^-5 torr and an ionization condition of 50 V and 11 A, respectively.

[Practical Example 3]

This is the same as Example 1 except that the final surface layer was manufactured by setting the nitrogen gas pressure to 5 × 10 ^-5 torr and the ionization conditions to 80 V and 15 A, respectively.

[Description 4]

This is the same as Example 1 except that the final surface layer was produced at a nitrogen gas pressure of 3 × 10 ^-5 torr and an ionization condition of 70 V and 14 A, respectively.

[Comparative Example 1]

It is a case in which the film is formed without forming Cr ₁ N coating film of Inventive Example 1 and the intermediate layer.

[Comparative Example 2]

This is the same as Inventive Example 1, except that the chromium film as the interfacial layer is not produced.

[Comparative Example 3]

This is the same as that of Inventive Example 1, except that the CrN film as the final surface layer was not produced.

[Comparative Example 4]

This is the same as Example 1 except that the final surface layer was produced by setting the nitrogen gas pressure to 1 × 10 ^-4 Torr and the ionization conditions to 60 V and 10 A, respectively.

[Comparative Example 5]

This is the same as that of Inventive Example 1, except that the nitrogen gas pressure at the time of manufacturing the final surface layer is 6 × 10 ^-4 Torr.

[Comparative Example 6]

This is the same as that of Inventive Example 1, except that the ionization conditions are 40V and 8A.

[Comparative Example 7]

This is the same as Inventive Example 1, except that the ionization conditions were 100 V and 18 A, respectively.

It can be seen that forming an abrasion-resistant coating by the above-described method largely contributes to improvement of abrasion resistance of a base material having poor abrasion such as a titanium alloy as compared with a conventional method.

Table 1

Claims (1)

A step of forming a chromium coating layer on the metal surface in order to secure adhesion in a normal hard coating made of only chromium which is a single metal for improving abrasion resistance and a step of finally forming a chromium nitride thin film made only of CrN on the Cr ₂ N coating layer And a hard coating layer formed on the surface of the hard coating layer. The method according to claim 1, wherein the chemical composition ratio of the chromium nitride is controlled by the nitrogen gas flow rate. The method according to claim 1, wherein the pressure of the nitrogen gas is (2 to 5) x 10 < 5 > Tor at the time of forming the film of the final surface layer, and the voltage of the ionizing electrode is 80V. ※ Note: It is disclosed by the contents of the first application.