JPH0718416A - Oxidation and wear resistant hard coating film - Google Patents

Abstract

PURPOSE:To enhance wear and oxidation resistance and to improve the characteristics of a tool, etc., by imparting a two-layered structure to a TiN layer and a TiAlN layer formed on a steel type metallic material and specifying the thickness percentage of the TiAlN layer. CONSTITUTION:This hard coating film is a coating film having a two-layered structure formed on a steel type metallic material or a cemented carbide and composed of a TiN layer and a TiAlN layer contg. 40-60mol% Al formed on the TiN layer. The thickness percentage of the TiAlN layer in the two- layered coating film is regulated to 5-50%.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hard coating having excellent wear resistance, and more particularly to a hard coating having improved wear resistance and oxidation resistance for improving the characteristics of tools and the like.

[0002]

2. Description of the Related Art It is known to coat the surface of steel or cemented carbide material such as tools and molds with a titanium nitride film by an ion plating method or the like in order to improve the wear resistance of the material. There is. However, titanium nitride and other metal nitrides are easily oxidized at high temperatures, and the resulting brittle oxide layer has a drawback that wear resistance is significantly deteriorated. A TiAlN film has been proposed as a film that solves the problem of titanium nitride oxidation. For example, W. of Leibold Heraeus. D. In the study by Munts et al. (J. Vac Sci. Tecnol., A4, 2717 (1986)),
TiAlN is reported to have excellent oxidation resistance.

However, although the TiAlN film has improved oxidation resistance due to the addition of Al, the mechanical properties of the film deteriorate as the amount of Al increases, and when applied to a tool or the like, the latter causes the drawback. There is a problem of reduced performance. According to the research conducted by the present inventors, since the TiAlN film essentially adds aluminum as a kind of defect in the titanium nitride film, the toughness of the film deteriorates and the mechanical properties are inferior to those of titanium nitride. ing.

The deterioration of mechanical properties due to the addition of aluminum becomes remarkable in a region where the amount of aluminum in the TiAlN film exceeds 10% in terms of mol% of metal component. A TiAlN coating film having an aluminum content of 10% or less exhibits mechanical properties similar to those of TiN, but the addition of such a low concentration of Al shows almost no effect of oxidation resistance. In order to compensate for the contradictory phenomena of deterioration of mechanical properties and improvement of oxidation resistance due to the addition of Al, a film having a structure in which Al concentration is continuously changed has been proposed. For example, Japanese Patent Application Laid-Open No. 2-170965 proposes a film having a structure with a sloping concentration, in which the Al concentration increases toward the surface and the highest Al concentration is obtained on the outermost surface.

[0005]

However, even the above-mentioned coating film having a graded Al concentration does not have sufficient mechanical properties.
When applied to tools, etc., no great effect has been obtained.

Therefore, it is an object of the present invention to provide a hard coating having both wear resistance and oxidation resistance.

[0007]

In order to achieve the above object, the present invention provides a TiN layer formed on a steel-based metallic material or a cemented carbide, and an Al mole% of 40 on the TiN layer.
% Or more and 60% or less of the TiAlN layer is formed, the ratio of the thickness of the TiAlN layer to the two-layer coating is 5% or more and 50% or less, oxidation resistance It provides an abradable hard coating.

[0008]

The steel-based metal material used in the method of the present invention includes structural steel, spring steel, bearing steel, tool steel, stainless steel and the like. Also, cemented carbide is a cemented carbide chip,
Cemented carbide used for cutting tools such as drills and end mills.

The Ti of the present invention formed on these substrates
In the AlN / TiN two-layer film, it is necessary that the Al concentration of the TiAlN layer is 40% or more and 60% or less and the ratio of the film thickness thereof is 5% or more and 50% or less.

The coating film of the present invention may be produced by a known method such as an ion plating method, a CVD method or a sputtering method, but two or more units of metal ions can be simultaneously supplied and two or more kinds of coating films can be produced. It is most desirable to use the ion plating method, which allows the film to be formed in the same apparatus and allows the production of a film exhibiting a strong adhesive force effective for improving the wear resistance. Therefore, here, the formation of the coating film by the ion plating method will be described below as an example.

Generally, when a film is formed by an ion plating method, a metal source is evaporated and the evaporated metal is ionized and supplied to a substrate. When the coating structure of the present invention is produced by the ion plating method, it is necessary to use two kinds of evaporation sources of titanium metal and aluminum metal, but a Ti-Al alloy is used instead of the pure metal. Good. Vapors of Ti and Al can be supplied at a target ratio by using the evaporation sources of these pure metals or alloys having different compositions either individually or simultaneously.

The method of ionizing the metal is not particularly limited,
A known method provided in the ion plating device is adopted. That is, the evaporation of the metal may be resistance heating, electron gun heating, or the like, and the evaporated metal may be ionized by known arc discharge, glow discharge, high-frequency discharge, or the like.

The reactive gas used in the ion plating method is a reactive gas for producing a nitride,
A mixed gas with nitrogen or ammonia, a mixed gas thereof, or another kind of gas including these is used. Introducing the reactive gas into the reaction vessel, ionizing in the same manner as the above metal ions, applying a negative bias voltage to the substrate, controlling the composition ratio of Ti and Al by the above method,
Further, by changing the film forming time of TiN and TiAlN, the film thickness ratio is controlled to form the film of the present invention.

TiN is a substance having a B1 type crystal structure, but in TiAlN which is a substitutional solid solution in which a part of Ti in TiN is substituted with Al, the mol% of Al is 60%.
Until then, it has the same B1 type crystal structure as TiN. When the Al concentration exceeds 60%, the crystal structure changes, and the toughness of the coating extremely decreases, which is not preferable.

When TiAlN is exposed to an oxidizing atmosphere, a solid solution of Al forms an oxide layer on the surface of the film, which serves as a protective layer. Therefore, cutting tools have a function of preventing oxidative deterioration of the coating due to heat generated by wear.
Since this characteristic increases as the Al concentration increases, the Al concentration is 40% in order to provide sufficient oxidation resistance.
% Or more is preferable.

Although TiAlN has the same crystal structure as TiN, when Ti and Al having a different atomic diameter are substituted and solid-solved, a kind of defect is introduced.
The mechanical properties are inferior to those of iN. Therefore, in the film structure of the present invention, by forming a two-layer film with TiN, the toughness of the film can be improved by TiN of the first layer and the oxidation resistance can be improved by TiAlN of the surface layer.

At this time, the ratio of the film thickness of TiAlN must be 5% or more and 50% or less of the whole. TiAl
When the film thickness ratio of N is thinner than 5%, the mechanical properties can be sufficiently achieved by TiN which is the first layer.
If the layer is worn away during use, the oxidation resistance is impaired and the object of the present invention cannot be achieved. Also, the film thickness ratio is 5
When it is higher than 0%, the toughness of TiAlN appears to be low, and the mechanical properties of the coating deteriorate, which is not preferable.

[0018]

The preferred embodiments of the present invention will be described below.

(Example 1) 6 mmφ high speed steel (SKH
51) drill was used as a substrate. TiN and T
The iAlN coating was formed by a cathode arc discharge type ion plating device. As the evaporation source in the ion plating, a titanium target and a Ti—Al alloy target with an Al concentration of 50% by mol% were used.

After ultrasonically cleaning the drill of the base material in an organic solvent, setting it at a predetermined position in the ion plating apparatus, and evacuating the inside of the reaction vessel to 2 × 10 ^-5 Torr, the substrate was subjected to -1000V. Applying bias voltage, Ti
Arc discharge was generated from the cathode. The arc discharge current at this time was 90A. While monitoring the substrate surface temperature with an infrared radiation thermometer, continue arc discharge for about 2 minutes,
Ti was evaporated and ionized, and the substrate surface was sputter cleaned. During the arc discharge, a rise in the drill surface temperature was recognized up to a maximum of 500 ° C. Next, nitrogen gas was introduced as a reaction gas, a bias voltage of -400 V was applied to the substrate while maintaining the pressure at 3.0 × 10 ^-2 Torr, and arc discharge was generated from the Ti cathode. The arc discharge current at this time was 90A. 6 arc discharge
Continued for 5 minutes.

Next, in order to coat the TiAlN layer, the arc discharge of the Ti cathode was stopped, and the arc discharge was generated in the Ti-Al cathode without changing the nitrogen gas pressure and the bias voltage. The arc discharge current at this time was 90A. The arc discharge was continued for 5 minutes to apply the TiAlN film.

The two-layer film produced as described above had a total film thickness of about 3 μm and a TiAlN film thickness ratio of 7.5%.

A cutting test was carried out on this two-layer drill. In the cutting test, SCM440C was used as a specific cutting material, the rotation speed was 1500 rpm, and the feed rate was 0.15 mm.
/ Rev. Was cut to a depth of 20 mm, and the number of holes until cutting became impossible was evaluated. The drill of Example 1 was capable of cutting 320 times.

Example 2 Using the same drill as in Example 1, TiN was added for 60 minutes and TiAlN was added for 10 minutes in the same manner.
A film was formed for a minute to form a TiAlN / TiN2 layer film. The total film thickness of the obtained film was about 3 μm, and the ratio of the TiAlN film thickness was 15%. The number of times of cutting with this drill was 243.

Example 3 Using the same drill as in Example 1, TiN was added for 50 minutes and TiAlN was added for 20 minutes by the same method.
A film was formed for a minute to form a TiAlN / TiN2 layer film. The total film thickness of the obtained film was about 3 μm, and the ratio of the TiAlN film thickness was 30%. The number of times of cutting with this drill was 130 times.

Example 4 Using the same drill as in Example 1, TiN was added for 40 minutes and TiAlN was added for 30 minutes in the same manner.
A film was formed for a minute to form a TiAlN / TiN2 layer film. The total film thickness of the obtained film was about 3 μm, and the ratio of the TiAlN film thickness was 45%. The number of times of cutting with this drill was 199 times.

Comparative Example 1 Using the same drill as in Example 1, TiN was added for 30 minutes and TiAlN was added for 40 minutes in the same manner.
A film was formed for a minute to form a TiAlN / TiN2 layer film. The total film thickness of the obtained coating film was about 3 μm, and the ratio of the TiAlN film thickness was 55%. The number of times of cutting with this drill was 37 times.

(Comparative Example 2) Using the same drill as in Example 1, TiN was added for 20 minutes and TiAlN was added for 50 minutes in the same manner.
A film was formed for a minute to form a TiAlN / TiN2 layer film. The total film thickness of the obtained coating film was about 3 μm and the ratio of the TiAlN film thickness was 70%. The number of times of cutting with this drill was 40 times.

Comparative Example 3 Using the same drill as in Example 1, TiN was added for 10 minutes and TiAlN was added for 60 minutes in the same manner.
A film was formed for a minute to form a TiAlN / TiN2 layer film. The total film thickness of the obtained coating film was about 3 μm, and the ratio of the TiAlN film thickness was 85%. The number of times of cutting with this drill was 22 times.

Comparative Example 4 Using the same drill as in Example 1, TiAlN alone was formed into a film by the same method for 70 minutes.
The film thickness of the obtained TiAlN drill was about 3 μm.
This drill was cut 4 times.

Here, Examples 1 to 4 and Comparative Examples 1 to 4
In order to confirm the Al concentration of the TiAlN film in
When the composition was analyzed by MA, the Al concentration was 40% to 45% in mol%.

[0032]

As described above, according to the present invention,
By making TiN and TiAlN into two layers and setting the ratio of the TiAlN film thickness to 5% or more and 50% or less, it is possible to impart oxidation resistance without lowering the toughness of the coating, and to improve the characteristics of tools and the like. It can be greatly improved.

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[Procedure amendment]

[Submission date] September 14, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0023

[Correction method] Change

[Correction content]

A cutting test was carried out on this two-layer drill. In the cutting test, SCM440C was used as the work material, the rotation speed was 1500 rpm, and the feed rate was 0.15 mm.
/ Rev. Was cut to a depth of 20 mm, and the number of holes until cutting became impossible was evaluated. The drill of Example 1 was capable of cutting 320 times.

Claims (1)

[Claims] 1. A TiN layer formed on a steel-based metallic material or a cemented carbide, and a mole% of Al of 40 on the TiN layer.
% To 60% of the TiAlN layer is formed, the TiAlN layer in the two-layer film has a thickness ratio of 5% to 50%. Abrasion resistant hard coating.