JP2590349B2 - Wear-resistant coating method - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a method for coating a surface of a milling tool or the like with a wear-resistant film, and more particularly to a method for preventing deterioration of a substrate and formation of a decarburized layer. The present invention relates to a method for efficiently coating a wear-resistant film having excellent adhesion to a base material.

[Prior art] Nitride such as Ti, on the surface of high speed tool steel or carbide tool steel
There is known a technique for forming a wear-resistant film made of carbide and carbonitride to further enhance wear resistance and the like. There are chemical vapor deposition (CVD) and physical vapor deposition (PVD) methods for forming such abrasion-resistant films. Of these, the CVD method uses abrasion-resistant film Ti (for this type of application). Other metals applicable to the group IVa, Va, VIa of the periodic table, or
B TiCl _4, Si, there are Al, etc., as hereinafter represented simply Ti) source
900 to 1 for film formation to utilize gas thermal decomposition
Requires high temperature treatment of 100 ° C. Therefore, when the CVD method is adopted, an abrasion-resistant film with excellent adhesion to the substrate can be formed, but the base material is also heated to a high temperature at the same time, and the extremely fragile decarburized layer on the base material surface (For example, W ₃ Co ₃ C) is generated, so it is not particularly applicable to milling tools. Further, since the base material is softened or thermally deformed by the high-temperature treatment, there is a problem particularly in application to precision tools.

In contrast, the PVD method enabled the formation of a wear-resistant film under relatively low temperature conditions, and the P
This is a holo cathode (HCD) type ion plating which is one of the VD methods.

However, in the above-mentioned HCD type ion plating, since the deposited metal is melted and evaporated in the crucible, the installation position of the evaporation source is restricted. As a result, the method of coating a substrate having a complicated shape was a coating method with low productivity.

[Problems to be Solved by the Invention] Studies have been conducted for the purpose of eliminating the disadvantages of the HCD type ion plating, and various improved ion plating methods have been proposed. One of them is a cathode arc type ion plating, which attracts attention as a method for efficiently coating a substrate having a complicated shape. That is, in the cathode arc ion plating method, a negative voltage is applied to a metal (target) to be evaporated, the metal is evaporated by an arc discharge between the target and the vacuum chamber, and collision of electrons due to the arc discharge is performed. After forming a plasma state of the target metal by ionizing in the above, a film is formed on the substrate to which a negative bias voltage is applied, and since the arc spot moves rapidly on the target, a molten pool is not formed, It is as if a metal vapor and even ions are generated from the target without going through a molten state. Accordingly, the position of the target is not limited, and the target can be vapor-deposited from all directions. The number of targets and the type of metal are not limited, and a single or plural same or different targets can be used as the cathode electrode. Further, since the evaporation method is used in a large current region of several tens of A or more, the ionization efficiency of the evaporated particles is high, so that not only the film formation rate is high but also the film thickness can be increased.

However, the cathode arc type ion plating is not a well-established method in terms of film forming conditions and the like, and has a problem in adhesion and the like. That is, in the cathodic arc ion plating method, it is necessary to increase the absolute value of the negative bias voltage applied to the base material in order to increase the adhesion of the film to the base material. As a result, the collision speed with the base material increases, and the conversion of kinetic energy to heat energy increases. As a result, the temperature of the base material instantly rises to 800 ° C. or more, which causes a problem that the base material is deteriorated. As shown in FIG. 1, if the pressure of the reactive gas atmosphere is reduced, the temperature of the substrate is reduced even with the same bias voltage. In this case, the balance between the metal ions and the gas ions (stoichiome) is reduced.
try), resulting in the inability to obtain films of stoichiometric composition.

The present invention has been made in view of such circumstances, and it has been proposed to provide a wear-resistant film having excellent adhesion while preventing a rise in the temperature of the substrate, which causes deterioration of the substrate and generation of a decarburized layer. It is an object of the present invention to provide a method capable of efficiently forming.

Means for Solving the Problems According to the method of the present invention which has attained the above object, a cathode arc in which a negative voltage is applied to a target metal to be evaporated to cause an arc discharge to form a plasma of the target metal. When coating a wear-resistant film on a substrate by a reactive ion plating method,
While heating to 00 ° C, the pressure of the reactive gas atmosphere is 10 ^-2 to
The gist of the present invention is that the substrate is maintained at 10 ^-3 Torr and a negative voltage of 300 V or less is applied to the substrate.

[Operation] In the present invention, when performing ion plating by the cathode arc method, the reactive gas atmosphere pressure is set to a relatively high pressure of 10 ^-2 to 10 ^-3 Torr. Despite the high ion rate despite arc discharge under high gas pressure, metal ion plasma occurs over a wide area, making it easy to deposit on substrates with complicated shapes and sufficient for large area substrates. A film can be formed. Further, since the presence balance of gas ions and metal ions is maintained, a wear-resistant film having a desired film composition can be obtained.

On the other hand, the bias voltage applied to the substrate is a negative voltage of 300 V or less, preferably a bias voltage of -50 to -100 V, thereby preventing the temperature of the substrate from rising due to kinetic energy of ions. As a result, it is possible to prevent the deterioration of the substrate strength and the formation of the decarburized layer due to the increase in the substrate temperature.

By adopting the above conditions, the features of cathodic arc ion plating, which is one of the PVD methods (film formation on a substrate with a complicated shape, prevention of temperature rise of the substrate, etc.) can be exhibited. However, it has not been able to solve the problem of the film adhesion to the substrate, which is a disadvantage of the PVD method when compared with the PVD method. Therefore, in the present invention, as another main requirement, the substrate is heated to 400 to 600 ° C., thereby increasing the adhesion. In other words, problems such as deterioration of substrate strength and generation of a decarburized layer when forming a film on a substrate made of high-speed tool steel or carbide tool steel occur when the substrate temperature is increased to about 800 ° C. or more. Below this, the above problem does not occur. On the other hand, by employing the gas pressure condition and the substrate bias voltage condition, the substrate temperature does not increase due to ion collision. Therefore, even if the base material is heated to 400 to 600 ° C., the base material temperature does not become too high, and at the above temperature, the deterioration of the base material strength and the formation of a decarburized layer do not occur. Then, since the substrate is placed under moderately high temperature conditions, diffusion of the coating material is promoted, and a wear-resistant coating film having high adhesion can be obtained. In addition, the reactivity between metal ions and gas ions on the substrate is increased, and a high-density wear-resistant coating film can be obtained.

Although the base material composition of the present invention is as described above, there is no particular limitation on the type of the wear-resistant film formed by the method of the present invention, and Ti and other IVa group, Va group, VIa group. And nitrides, carbides, carbonitrides, and the like of metals such as B, Si, and Al. In this case, the target (cathode electrode)
As it may be adopted the general procedure of reactive ion plating method for introducing into the device an N ₂ and hydrocarbon gas such as a reactive gas together disposing the metal or an alloy thereof.

[Example] Example 1 A carbide drill was attached to a substrate holder of a cathode arc type ion plating apparatus having a Ti cathode electrode. The apparatus is provided with a heater capable of raising the temperature of the substrate to 700 ° C., a substrate rotating mechanism for uniformizing the state of coating the wear-resistant film, and the like.

At the time of film formation, the atmosphere gas was released while heating the inside of the apparatus, the pressure was reduced to 1 × 10 ⁻⁵ Torr, and the temperature of the base material was raised to 430 ° C. Thereafter, the substrate surface was cleaned by ion sputtering. Then, while maintaining the substrate at the same temperature, a bias voltage of −50 V was applied to the substrate, high-purity N ₂ gas was introduced into the apparatus to 7 × 10 ⁻³ Torr, and Ti arc discharge was started to start the operation. A TiN film was coated on the material surface.

Example 2 A TiCN-TiN composite layer film was coated in the same manner as in Example 1 except that the reactive gas introduction operation was changed. That is, the first
In the stage, a mixed gas of N ₂ and CH ₄ is introduced to
Then, in the second stage, only N ₂ was introduced to form a TiN film on the TiCN layer.

Comparative Examples 1 to 3 For comparison, when the substrate was not heated (Comparative Example 1), when a bias voltage of -400 V was applied to the substrate (Comparative Example 2), the reactive gas atmosphere pressure during film formation Is 5 ×
In the case of 10 ^-4 Torr (Comparative Example 3), a TiN film was formed in the same manner as in Example 1 except for the other conditions.

Cutting tests were performed on the wear-resistant film-coated carbide drills (diameter 6 ^mmφ ) obtained in Examples 1 and 2 and Comparative Examples 1 to 3, and the results shown in Table 1 were obtained. However, S50C material was used as a work material.

In Examples 1 and 2, since the base material bias voltage was reduced, the kinetic energy of ions was suppressed, conversion to thermal energy was reduced, and a rise in the temperature of the base material was prevented. In addition, the adhesion between the substrate and the film was improved by heating the substrate, and excellent abrasion resistance was obtained.

On the other hand, in Comparative Example 1, the film was peeled off because the substrate was not heated. In Comparative Example 2, the substrate temperature rose to 800 ° C. or higher because the absolute value of the substrate bias negative voltage was too large,
Chipping occurred due to the deterioration of the base material. In Comparative Example 3, since the gas pressure was too low as 5 × 10 ⁻⁴ Torr, the film composition was not appropriate and a brittle TiN film was formed, and as a result, the film was peeled.

[Effects of the Invention] The present invention is configured as described above, and a hard film having excellent adhesion and abrasion resistance can be formed while utilizing the features of the cathodic arc ion plating method. Further, by employing the cathode arc method, a film could be efficiently formed even on a substrate having a complicated shape.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the substrate bias voltage and the substrate surface temperature.

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Yasuyuki Yamada 4-8-1 Tsutsujigaoka, Tarumizu-ku, Kobe-shi, Hyogo (72) Inventor Yusuke Tanaka 947-1 Okubo-cho, Okubo-cho, Akashi-shi, Hyogo (72) Inventor Kazutoshi Shimogori 8-4-35 Nishimaiko, Tarumi-ku, Kobe City, Hyogo Prefecture (56) References JP-A-52-149277 (JP, A) JP-A-53-80379 (JP, A) JP-A-52-10871 ( JP, A) Surface and Coaitugs Technology 29 (1986) 275-290

Claims (1)

(57) [Claims] An abrasion-resistant film is formed on a substrate by a cathode arc reactive ion plating method in which a negative voltage is applied to a target metal to be vaporized to cause an arc discharge to form a plasma of the target metal. In coating, the substrate is heated to 400 to 600 ° C., and the reactive gas atmosphere pressure is maintained at 10 ⁻² to 10 ⁻³ Torr, and a negative voltage of 300 V or less is applied to the substrate. Wear-resistant film coating method.