JP6381984B2 - Membrane removal method and membrane removal apparatus - Google Patents

Description

  The present invention relates to a film removal technique for removing a diamond coating or a hard carbon coating formed on the surface of a cemented carbide tool or the like.

  In the case of a cemented carbide tool such as a drill or an end mill, a diamond coating or a hard carbon (DLC / Diamond-Like Carbon) coating is formed on at least the blade portion of the surface for the purpose of improving wear resistance. When these coatings are worn or damaged by the use of tools, the old coating is removed and a new coating is formed again, so that a relatively expensive substrate can be regenerated. Yes.

For example, Patent Document 1 discloses a technique for removing a hard carbon coating film by spraying a hard powder together with air onto a hard carbon coating film formed on the surface of an end mill or the like. .
Patent Document 2 discloses a technique for removing a diamond film or the like coated on the surface of a substrate using oxygen plasma.
JP 2003-200350 A JP2011-162857

Since the technique of Patent Document 1 removes the film by physically colliding the hard powder with the surface of the coating, it is not effective for a substrate having a complicated uneven shape on the surface. There was also a risk of serious damage to the substrate.
On the other hand, in the case of Patent Document 2, since it is a method of removing a carbon-based film using a chemical reaction by oxygen plasma, it is effective even for a base material having complicated irregularities on the surface. Since a high plasma density cannot be realized, there has been a problem that a relatively long time is required for film removal.

  The present invention has been devised to solve the above-described conventional problems, and can remove a diamond coating or a hard carbon coating on a substrate having a complex uneven shape on the surface in an extremely short time. The purpose is to provide a processing technique that can minimize damage to the material.

In order to achieve the above object, a film removal method according to the present invention comprises a substrate having a diamond film or a hard carbon film formed on a surface thereof, which is installed in a vacuum chamber and is cylindrical and has a plurality of through-holes on the surface. inside the hollow cathode but is formed, a step of rotatably arranged, a step of filling a treatment gas containing oxygen into the vacuum chamber, the step of generating oxygen plasma in the vacuum chamber, the substrate While rotating the hollow cathode at a predetermined rotation speed, a negative bias voltage is applied to the hollow cathode and the base material to draw oxygen plasma into the hollow cathode, and a diamond coating or hard carbon on the base surface A step of removing the coating.

The film removal apparatus according to the present invention includes a vacuum chamber, a hollow cathode disposed in the vacuum chamber and having a plurality of through-holes formed on the surface thereof , and a diamond on the surface of the hollow cathode. A rotating jig that rotatably holds a substrate on which a film or a hard carbon film is formed, a gas supply port that supplies a processing gas containing oxygen into the vacuum chamber, and the rotating jig at a predetermined rotation speed. A rotating mechanism for rotating; a pair of RF electrodes disposed in the vacuum chamber; an RF oscillator for generating an oxygen plasma by applying a high-frequency voltage between the RF electrodes; and a negative bias on the substrate and the hollow cathode A bias power source for applying a voltage and attracting oxygen plasma to the hollow cathode side is provided.

In the film removal method according to the present invention, since the surface of the base material is surrounded by the hollow cathode, the oxygen plasma density between the inner surface of the hollow cathode and the surface of the base material becomes extremely high. Efficient film removal processing in a short time is realized.
In addition, since the substrate is rotated in the hollow cathode during the film removal treatment, the film can be removed evenly even when the surface shape of the substrate has complicated irregularities.
As described above, since the film can be uniformly removed in a short time, it is possible to minimize damage to the base material.

  By using the film removal apparatus according to the present invention, the above film removal method can be effectively executed.

  FIG. 1 is a schematic diagram showing the structure of a film removal apparatus 10 according to the present invention, in which a vacuum chamber 12, a hollow cathode 14 disposed therein, a rotating jig 16, a motor 18, and a pair of RFs are shown. Electrodes 20, 20, a gas supply port 22, a pressure sensor 24, and an exhaust port 26 are provided.

The motor 18 is connected to a drive circuit 28 disposed outside the vacuum chamber 12 via a cable.
The RF electrodes 20 and 20 are connected to an RF oscillator 30 disposed outside.
The gas supply port 22 is connected to a gas supply device 32 disposed outside via a pipe.
The pressure sensor 24 is connected to a signal processing circuit 34 disposed outside via a cable.
The exhaust port 26 is connected to a vacuum pump 36 disposed outside via a pipe.

  The hollow cathode 14 is a cylindrical body made of a conductive metal such as stainless steel, and a large number of through holes (gap) 38 are formed on the surface thereof. The diameter of each through hole 38 is set to 2 mm, for example.

On the bottom surface of the vacuum chamber 12, a mounting wall portion 40 is erected vertically.
A through hole 42 is formed near the center of the mounting wall 40.

  A hollow cathode mounting member 44 is formed on one surface of the mounting wall portion 40, and the base end portion of the hollow cathode 14 is fitted into the opening. As a result, the hollow cathode 14 is arranged in parallel with a predetermined distance from the bottom surface of the vacuum chamber 12.

  A rotating jig mounting member 46 is formed on the other surface of the mounting wall 40, and the tip of the rotating jig 16 is rotatably inserted into the through hole 42 of the mounting wall 40 through the opening, and remains as it is. It is introduced into the hollow cathode 14.

A shank 50a of an end mill 50, which is a workpiece, is attached and fixed to the tip of the rotating jig 16.
The blade portion 50b of the end mill 50 is provided with a diamond coating.

A large-diameter pulley 52 is attached and fixed to the rear end portion of the rotating jig 16, and a belt 56 is attached between the small-diameter pulley 54 connected to the output shaft of the motor 18.
As a result, the rotation jig 16 and the end mill 50 rotate while being decelerated by the rotation of the motor 18.

A slip ring 58 is fitted in an intermediate portion of the rotating jig 16.
A bias power supply 60 disposed outside is connected to the slip ring 58 and the hollow cathode 14.

A control device 62 having a CPU and a memory is installed outside the vacuum chamber 12, and the motor drive circuit 28, RF oscillator 30, gas supply device 32, signal processing circuit 34, vacuum pump are provided via a cable. 36, connected to the bias power supply 60.
The control device 62 executes control of each part of the film removal apparatus 10 in accordance with a program stored in the memory.

Hereinafter, a film removal method using the film removal apparatus 10 will be described.
First, the door 64 of the vacuum chamber 12 is opened, and the shank 50a of the end mill 50 is mounted in the recess at the tip of the rotating jig 16.

  Next, the control unit 62 operates the vacuum pump 36 and discharges the air in the vacuum chamber 12 to the outside.

Next, the control unit 62 operates the gas supply device 32 to fill the vacuum chamber 12 with oxygen gas or a mixed gas of oxygen and argon.
At this time, the control unit 62 monitors data output from the signal processing circuit 34 of the pressure sensor 24 and adjusts the pressure in the vacuum chamber 12.

Next, the control unit 62 operates the RF oscillator 30, applies a high frequency voltage between the RF electrodes 20 and 20, and simultaneously applies a negative bias voltage to the rotating jig 16 and the hollow cathode 14 via the bias power source 60. To do.
As a result, oxygen plasma is generated in the vacuum chamber 12, and oxygen radicals and oxygen ions are sucked into the hollow cathode 14 from the respective through holes 38.
Then, the diamond coating formed on the blade portion 50b of the end mill 50 reacts with oxygen radicals and oxygen ions and is chemically removed.

At this time, since the rotating jig 16 and the end mill 50 continue to rotate due to the rotation of the motor 18, the outer periphery of the end mill 50 is uniformly exposed to oxygen ions, and processing unevenness does not occur.
Incidentally, the rotation speed of the rotating jig 16 is set to 5 to 10 times / minute.

Due to the presence of the hollow cathode 14, most of the oxygen plasma in the vacuum chamber 12 is confined in the hollow cathode 14, and both ends thereof are electromagnetically closed, so that the surface of the end mill 50 has a high density. Exposure to oxygen plasma. As a result, extremely efficient processing is possible.
For example, in the case of an end mill 50 to which a diamond coating having a film thickness of 15 μm is applied, film removal is completed in about 2 hours. That is, the film removal rate reaches 7.5 μm / H, and the efficiency is increased by about 10 times compared with the conventional processing method.

FIG. 2 is a graph showing the results of measuring the oxygen plasma density in the hollow cathode 14 during processing. In the meso pressure region (50 to 100 Pa), the electron density is 1 × 10 ¹⁷ m ⁻³ or more, and the ion density is also It can be read that it is in a very high density state of 5 × 10 ¹⁷ m ⁻³ or more.

  FIG. 3 is a graph showing the result of analyzing the nuclide of oxygen plasma generated in the vacuum chamber 12, and shows that OI which is an oxygen radical (activated oxygen atom) is the main nuclide. It is also recognized that the ratio of oxygen molecules (O2) is small and oxygen ions (OH) having a high valence are generated.

  FIG. 4 is a photograph comparing the end mill 50 before the film removal treatment with the end mill 50 after the film removal treatment, and shows that the dark diamond film observed before the film removal treatment is removed cleanly after the treatment. Has been.

  FIG. 5 is an enlarged photograph comparing the surface of the end mill 50 before the film removal treatment and the surface of the end mill 50 after the film removal treatment. Before the film removal treatment, the diamond coating is formed on the “rake face” and the “outer peripheral surface”. As a result of being formed thick (about 12 μm), it can be seen that the “outer edge (cutting edge)” stands up sharply, but the surface of the superalloy substrate is exposed and the outer edge is blunted after film removal. You can see how they are doing.

  FIG. 6 is an enlarged photograph of the surface of the end mill 50 before the film removal treatment and the end mill 50 after the film removal treatment. The diamond crystals existing before the film removal treatment are completely disappeared after the film removal treatment, and the superalloy substrate. The particles are exposed.

FIG. 7 is a table showing the results of measuring the blade diameter reduction before and after the film removal treatment.
When the blade diameter of the base material tool is greatly reduced through the film removal treatment, it is out of tolerance and cannot be reused. Therefore, it is necessary to suppress the reduction amount of the blade diameter due to film removal as much as possible. For this reason, when it is assumed that a plurality of film removal and re-coating operations are repeated, it is desirable that the amount of decrease in the blade diameter in one film removal treatment is suppressed to 10 μm or less.
On the other hand, according to the film removal processing method according to the present invention, the blade diameter reduced by one film removal process is all within about 5 μm.

  In the above description, the cylindrical hollow cathode 14 that covers the entire end mill 50 is illustrated, but a semi-cylindrical hollow cathode that covers the upper half of the end mill 50 can also be used.

  Alternatively, a plurality of cylindrical hollow cathode parts having relatively short dimensions can be prepared, and these can be arranged in a straight line to form a hollow cathode having a required dimension. At this time, it is desirable to provide an oxygen plasma circulation gap of about 2 mm between the hollow cathode components.

  In the above, the example of removing the diamond coating formed on the surface of the cemented carbide tool has been shown, but it goes without saying that the present invention can also be effectively applied to the removal of the hard carbon (DLC) coating. Absent.

It is a schematic diagram which shows the basic structure of the film removal apparatus which concerns on this invention. It is a graph which shows the result of having measured the oxygen plasma density in the hollow cathode at the time of a process. It is a graph which shows the result of having analyzed the nuclide of oxygen plasma generated in the vacuum chamber. It is a photograph comparing the end mill surface before film removal treatment and the end mill surface after film removal treatment. It is an enlarged photograph which compares the surface of the end mill before film removal treatment, and the surface of the end mill after film removal treatment. It is the surface enlarged photograph of the end mill before film removal treatment, and the end mill after film removal treatment. It is a table | surface which shows the result of having measured the blade diameter reduction amount before and behind a film removal process.

10 Film removal equipment
12 Vacuum chamber
14 hollow cathode
16 Rotating jig
18 Motor
20 RF electrodes
22 Gas supply port
24 Pressure sensor
26 Exhaust vent
28 Motor drive circuit
30 RF oscillator
32 Gas supply equipment
34 Pressure sensor signal processing circuit
36 Vacuum pump
38 Through hole
40 Mounting wall
42 Through hole
44 Hollow cathode mounting member
46 Rotating jig mounting member
50 End mill
60 Bias power supply
62 Controller

Claims (2)

The diamond coating or a hard carbon coating formed substrate on the surface, was placed in a vacuum chamber, the interior of the hollow cathode in which a plurality of through-holes on the surface in a cylindrical shape is formed, a step of rotatably arranged ,
Filling the vacuum chamber with a processing gas containing oxygen;
Generating oxygen plasma in the vacuum chamber;
While rotating the base material at a predetermined rotation speed in the hollow cathode, a negative bias voltage is applied to the hollow cathode and the base material to suck oxygen plasma into the hollow cathode, and a diamond coating on the surface of the base material Or removing the hard carbon film;
A film removal method comprising the steps of: A vacuum chamber;
A hollow cathode arranged in the vacuum chamber and having a plurality of through holes formed on the surface thereof ,
In this hollow cathode, a rotating jig that rotatably holds a substrate on which a diamond coating or a hard carbon coating is formed,
A gas supply port for supplying a processing gas containing oxygen into the vacuum chamber;
A rotation mechanism for rotating the rotating jig at a predetermined rotation speed;
A pair of RF electrodes disposed in the vacuum chamber;
An RF oscillator for generating oxygen plasma by applying a high-frequency voltage between the RF electrodes;
A bias power source that applies a negative bias voltage to the substrate and the hollow cathode, and attracts oxygen plasma to the hollow cathode;
A film removal apparatus comprising:

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