JPH07268606A - Hard coating film resistant to oxidation and wear - Google Patents

Abstract

PURPOSE:To improve the resistance of the coating film to wear and oxidation by forming the laminated coating film of TiN and TiAlN on the surface of the steel material for tools and dies or on the surface of a sintered hard alloy. CONSTITUTION:The laminated coating film of first to fourth layers is formed from the surface being in fromcontact with a metallic material toward the outer surface. The first and third layers are formed TiN and the second and fourth layers from TiAlN, and the Al content of the TiAlN is controlled to 40-60mol%. The thickness ratio of the first layer is controlled to 10-15%, that of the second layer to 65-80%, that of the third layer to 5-10% and that of the fourth layer to 5-10%. Although the film forming method is not specified, ion plating is preferably used since >=2 kinds of coating films are formed in the same device, and a highly adhesive coating film effective in improving the wear resistance can be formed.

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 of metal tools and the like.

[0002]

2. Description of the Related Art It is known to coat the surface of steel materials such as tools and molds or cemented carbide materials with a TiN film by an ion plating method or the like in order to improve the wear resistance of the materials. . However, metal nitrides such as TiN are easily oxidized at a high temperature, and the resulting brittle oxide layer has a drawback that the wear resistance is significantly deteriorated. A TiAlN film has been proposed as a film that has improved the problem of oxidation of TiN. For example, W. of Leibold Heraeus. D. Research by Munts et al. (J. Va
c. Sci. Tecnol. , A4, 2717 (198
6)) and the like report that TiAlN has excellent oxidation resistance.

However, although the TiAlN film has improved oxidation resistance due to the addition of Al, the hardness of the film increases as the amount of Al increases, but the toughness decreases, and when applied to a tool or the like. There is a problem that performance is deteriorated due to the latter drawback. According to the research conducted by the present inventors, Ti
Since the AlN film essentially adds Al as a kind of defect in the TiN film, the hardness of the film increases due to the introduction of defects, but the toughness of the film deteriorates and the mechanical properties are inferior to those of TiN. Was there.

Such a decrease in toughness due to the addition of Al becomes remarkable in the region where the amount of Al in the TiAlN film exceeds 10% in terms of mol% of the metal component. A TiAlN coating film having an Al content of 10% or less exhibits mechanical properties similar to those of TiN, but the addition of such a low concentration of Al causes little effect on oxidation resistance. In order to compensate for the contradictory phenomena of reduction in toughness and improvement in oxidation resistance due to the addition of Al, a film having a structure in which the 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, an object of the present invention is to provide a hard coating having both the wear resistance and the oxidation resistance of a metal tool.

[0006]

In order to achieve the above object, the present invention provides a laminated coating formed on a metal material from the closest part to the surface from the first layer to the fourth layer.
The first and third layers are TiN, the second and fourth layers are TiAl
N, Al accounts for 40 to 65% mol% in the TiAlN, and the thickness ratio of each layer in the laminated coating film is 10 to 15% for the first layer, 65 to 80% for the second layer, 3 layers are 5 to 1
0%, and the fourth layer is 5% to 10%.

[0007]

The steel-based metallic material used in the present invention includes, for example, steel-based metallic materials and cemented carbides. Examples of the steel-based metal material include structural steel, spring steel, bearing steel, tool steel, stainless steel, and the like, and cemented carbide is used, for example, in cutting tools such as indexable inserts, drills, and end mills. WC with Co as a binder
Examples include sintered cemented carbide.

In the four-layer film of the present invention formed on these metallic materials, TiN is formed as the first layer, and a TiAlN layer having Al of 40 to 65 mol% is formed as the second layer, and further thereon. TiN is formed as the third layer, and a TiAlN layer of 40 to 65 mol% is again formed as the outermost layer in the fourth layer. The thickness ratio of each layer in the laminated coating is 10% to 15% of the first layer. %, Second layer 65% to 80%, third layer 5% to
It is necessary to be 10% and the fourth layer 5% to 10%.

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

Generally, when forming a film 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 types of evaporation sources, metal Ti and metal Al, but a Ti-Al alloy is used instead of the pure metal. Is also 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. The reactive gas is introduced into the reaction vessel, ionized in the same manner as the above metal ions, a negative bias voltage is applied to the metal material, and the composition ratio of Ti and Al is controlled by the above method. By changing the film formation time of TiAlN and TiAlN, the ratio of the film thickness is controlled to form the laminated coating 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, up to 65% of the metal component Al is mol%. It has the same B1 type crystal structure as TiN, and when the Al concentration exceeds 65%, the crystal structure changes,
The toughness of the laminated coating is extremely reduced, 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 coating 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.
It is preferably at least mol%.

Further, 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.
Compared to iN, the film hardness increases and the wear resistance improves, but on the other hand, the toughness decreases, and TiAlN alone is inferior in mechanical properties to TiN. Therefore, in the laminated coating structure of the present invention, the first layer of TiN improves the adhesion with the metal material and improves the toughness. By the action of the first layer, the TiAlN of the second layer exerts the function as a hard film and the function as an oxidation resistant film without impairing the toughness. Further, the third layer of TiN and the fourth layer of TiAlN are thinly laminated to increase the impact resistance of the film surface and to improve the mechanical properties of the film.

At this time, the thickness ratio of each layer in the laminated coating is 10% to 15% for the first layer and 65% to 80% for the second layer.
%, The third layer 5% to 10%, and the fourth layer 5% to 10%. The thickness of the laminated coating is usually 2 to 5 μm when it is used for a tool, but if the thickness is 4 μm,
m, TiN of the first layer is about 0.6 μm, TiAlN of the second layer is 3 μm, and the third and fourth layers are about 0.4 μm.
m or less. When the ratio of the thickness of TiN of the first layer is less than 10%, that is, when the ratio of the thickness of TiAlN of the second layer is more than 80%, the brittle surface of TiAlN is emphasized, which is not preferable. On the contrary, when the thickness ratio of the first layer exceeds 15%, that is, when the thickness ratio of the TiAlN layer is less than 65%, mechanical properties and oxidation resistance properties of the high hardness film are not sufficient, which is inconvenient. .

The ratio of the thickness of the third layer to the thickness of the fourth layer is 5%.
If it is less than 10% or more than 10%, the thin film is formed and the function of improving impact resistance is impaired.

[0018]

【Example】

(Example 1) A 6 mmφ high speed steel (SKH51) drill was used as a metal material. TiN and TiAlN
The coating was formed using a cathode arc discharge type ion plating device. As the evaporation source in the ion plating, a Ti target and T having an Al concentration of 50 mol% were used.
An i-Al alloy target was used.

The drill of the metal material base material is ultrasonically cleaned in an organic solvent, set in a predetermined position in the ion plating apparatus, and the inside of the reaction vessel is evacuated to 2 × 10 ^-5 Torr. Apply a bias voltage of 1000V,
Arc discharge was generated from the Ti cathode. The arc discharge current at this time was 70A. While monitoring the substrate surface temperature with an infrared radiation thermometer, arc discharge was continued for about 2 minutes to vaporize and ionize Ti, and the substrate surface was sputter cleaned. An increase in the surface temperature of the drill was recognized up to an arc discharge width of up to 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 70A. 1 arc discharge
The first layer of TiN was deposited for 5 minutes.

Next, in order to coat the TiAlN layer of the second 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 is 70A
Met. The arc discharge was continued for 60 minutes to apply a TiAlN film.

Next, arc discharge was applied to the Ti cathode for 5 minutes,
Subsequently, an arc discharge was similarly generated on the Ti-Al cathode for 5 minutes to form a third layer of TiN and a fourth layer of TiAlN.

The four-layer film produced as described above has a total thickness of about 4 μm, and the ratio of the thickness of each layer is as follows: first layer: second layer
Layer: Third layer: Fourth layer = 15: 75: 5: 5.

A cutting test was conducted on the drill having the four-layer coating. The cutting test uses SCM44 as the work material.
0C, the rotation speed is 1500 rpm, and the feed speed is 0.15 mm / rev. Was cut to a depth of 20 mm, and the number of holes until cutting became impossible was evaluated. Example 1
It was possible to cut 315 times.

(Embodiment 2) Using a drill similar to that of Embodiment 1, the ratio of the thickness of each layer is the same as that of the first layer: the second layer:
Third layer: Fourth layer = 10: 70: 10: 10 to form a four-layer film. The number of times of cutting with this drill was 270 times.

(Embodiment 3) A drill similar to that of Embodiment 1 is used, and the thickness ratio of each layer is set in the same manner as in the first layer: second layer:
Third layer: Fourth layer = 10: 80: 5: 5 to form a four-layer film. The number of times of cutting with this drill was 285 times.

(Embodiment 4) A drill similar to that of Embodiment 1 is used, and the thickness ratio of each layer is set in the same manner as in the first layer: second layer:
Third layer: Fourth layer = 15: 70: 10: 5 to form a four-layer film. The number of times of cutting with this drill was 260 times.

(Embodiment 5) A drill similar to that of Embodiment 1 is used, and the ratio of the thickness of each layer is the same as the first layer: the second layer:
Third layer: Fourth layer = 15: 70: 5: 10 to form a four-layer film. The number of cuts with this drill was 275.

(Embodiment 6) A drill similar to that of Embodiment 1 is used, and the thickness ratio of each layer is set in the same manner as in the first layer: second layer:
Third layer: Fourth layer = 15: 60: 10: 10 to form a four-layer film. The number of cuttings with this drill was 290.

(Embodiment 7) A drill similar to that of Embodiment 1 is used, and a Ti-Al cathode is replaced with an alloy target having an Al concentration of 70% and a mole ratio of 70%. 1st layer: 2nd layer: 3rd layer: 4th layer = 15: 7:
A 4-layer film of 5: 5: 5 was formed. The number of times of cutting with this drill was 191 times.

(Embodiment 8) A drill similar to that of Embodiment 1 is used, and the thickness ratio of each layer is the first in the same manner as in Embodiment 7.
Layer: Second layer: Third layer: Fourth layer = 10: 70: 10: 10
Was formed into a four-layer film. The number of cuts with this drill is 1
It was 95 times.

(Embodiment 9) A drill similar to that of Embodiment 1 is used, and the thickness ratio of each layer is the first in the same manner as that of Embodiment 7.
Layer: Second layer: Third layer: Fourth layer = A four-layer film having a thickness of 10: 80: 5: 5 was formed. The number of cuttings with this drill is 206
It was once.

(Embodiment 10) A drill similar to that in Embodiment 1 is used, and the thickness ratio of each layer is the first in the same manner as in Embodiment 7.
Layer: second layer: third layer: fourth layer = 15: 70: 10: 5 to form a four-layer film. The number of cuttings with this drill is 18
It was 0 times.

(Embodiment 11) A drill similar to that in Embodiment 1 is used, and the thickness ratio of each layer is the first in the same manner as in Embodiment 7.
Layer: Second layer: Third layer: Fourth layer = 15: 70: 5: 10 A four-layer film was formed. The number of cuttings with this drill is 21
It was three times.

(Embodiment 12) A drill similar to that of Embodiment 1 is used, and the thickness ratio of each layer is the first in the same manner as in Embodiment 7.
Layer: Second layer: Third layer: Fourth layer = 15: 60: 10: 10
Was formed into a four-layer film. The number of cuts with this drill is 1
It was 87 times.

(Comparative Example 1) The same drill as in Example 1 was used, and the ratio of the thickness of each layer was the same as the first layer: the second layer:
Third layer: Fourth layer = 50: 30: 10: 10 to form a four-layer film. The number of times of cutting with this drill was 90 times.

(Comparative Example 2) A drill similar to that in Example 1 was used, and the thickness ratio of each layer was the first in the same manner as in Example 7.
Layer: Second layer: Third layer: Fourth layer = 50: 30: 10: 10
Was formed into a four-layer film. The number of cuts with this drill is 6
It was 5 times.

(Comparative Example 3) The same drill as in Example 1 was used to form TiN for 20 minutes and TiAlN for 50 minutes without forming the third and fourth layers by the same method.
A TiN two-layer film was formed. First layer: Second layer = 30: 70
Was formed into a two-layer film. The number of cuts with this drill is 3
It was 5 times.

(Comparative Example 4) The same drill as in Example 1 was used to form the third layer and the fourth layer in the same manner as in Example 7 without depositing TiN for 20 minutes and TiAlN for 50 minutes. Then
A TiAlN / TiN two-layer film was formed. A two-layer film in which the first layer: the second layer = 30: 70 was formed. The number of times of cutting with this drill was 14.

Here, in order to confirm the Al concentration of the TiAlN film in Examples 1 to 6 and Comparative Examples 1 and 3,
A composition analysis by EPMA showed that the metal component A
The l concentration was between 40 and 45 mol%.

Further, in order to confirm the Al concentration of the TiAlN film in Examples 7 to 12 and Comparative Examples 2 and 4,
A composition analysis by EPMA showed that the metal component A
The l concentration was between 60 and 65 mol%.

[0041]

As described above, according to the present invention,
Oxidation resistance can be imparted without lowering the toughness of the laminated coating, and the characteristics of the metal tool or the like can be significantly improved.

Claims (1)

[Claims] 1. A laminated coating formed from a first layer to a fourth layer on a metal material from the closest portion to the surface,
The first and third layers are TiN, the second and fourth layers are TiAl
N, and 40 to 65 mol% of Al in the TiAlN
And the thickness ratio of each layer in the laminated coating is 1 for the first layer.
0-15%, 2nd layer 65-80%, 3rd layer 5-10
%, The fourth layer is composed of 5 to 10%, an oxidation resistant and wear resistant hard coating.