JP2016196696A - Nitriding treatment apparatus and nitriding treatment method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nitriding treatment apparatus and a nitriding treatment method capable of nitriding easily the inside of a recessed part.SOLUTION: A nitriding treatment apparatus (1) includes a treatment chamber (3) capable of storing a treatment object (21), a plasma generation unit (5) for generating plasma containing high-concentration nitrogen atoms in the treatment chamber, a netlike member (19) comprising a conductive material, and arranged oppositely to the treatment object in the treatment chamber, and a potential application unit (16) for applying a lower potential than a plasma potential to the netlike member and the treatment object.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a nitriding apparatus and a nitriding method.

  Conventionally, nitriding treatment is known in which nitrogen plasma is generated by irradiating an electron beam, and the surface of an object to be treated is nitrided by the nitrogen plasma (see Patent Document 1).

JP 2011-52313 A

  In the technique described in Patent Document 1, when the surface of the processing object has a recess (for example, a hole, a slit, or the like), it is difficult to nitride the inside of the recess. The present invention has been made in view of the above points, and an object thereof is to provide a nitriding apparatus and a nitriding method that easily nitride the inside of a recess.

  The nitriding apparatus of the present invention includes a processing chamber capable of accommodating a processing object, a plasma generating unit that generates plasma containing high-concentration nitrogen atoms in the processing chamber, and an opposing arrangement to the processing object in the processing chamber. A mesh member made of a conductive material; and a potential application unit that applies a potential lower than the plasma potential to the mesh member and the object to be processed. According to the nitriding apparatus of the present invention, even when the object to be processed has a recess, the inside of the recess can be nitrided.

  The nitriding method of the present invention is characterized in that a processing object is nitrided using the above-described nitriding apparatus. According to the nitriding method of the present invention, even when the object to be processed has a recess, the inside of the recess can be nitrided.

2 is an explanatory diagram illustrating a configuration of a nitriding apparatus 1. FIG. 2A, 2B, and 2C are plan views illustrating the configuration of the mesh member 19, respectively. 4 is an explanatory diagram showing a configuration of a small electron beam source 5. FIG. 3 is a perspective view illustrating a configuration of a processing object 21. FIG. It is sectional drawing in the VV cross section in FIG. It is explanatory drawing showing the structure of nitriding processing apparatus R1 in a comparative example.

Embodiments of the present invention will be described with reference to the drawings.
<First Embodiment>
1. Configuration of Nitriding Apparatus 1 The configuration of the nitriding apparatus 1 will be described with reference to FIGS. As shown in FIG. 1, the nitriding apparatus 1 includes a processing chamber 3, a small electron beam source 5, a metal cover 7, a sample table 9, a heater 11, a nitrogen supply pipe 13, and an exhaust pipe. 15 and a potential applying unit 16.

  The processing chamber 3 is a cylindrical container. The small electron beam source 5 generates an electron beam 17 and introduces the electron beam 17 into the processing chamber 3. The detailed configuration of the small electron beam source 5 will be described later. The metal cover 7 is a metal member having a hollow box shape. The metal cover 7 is provided in the processing chamber 3, and more specifically, placed on the sample table 9. The metal cover 7 and the sample table 9 are electrically connected. The upper surface of the metal cover 7 is a metal mesh member 19. As shown in FIG. 2A, the net member 19 has a structure in which metal wires 20 are arranged in a grid pattern at a constant interval. The lower surface of the metal cover 7 is open.

  The metal cover 7 can accommodate the processing object 21 therein. Since the lower surface of the metal cover 7 is open, the processing object 21 accommodated in the metal cover 7 and the sample table 9 come into contact with each other. Therefore, when the processing object 21 is made of a conductive material, the processing object 21 is electrically connected to the metal cover 7 and the sample table 9. The mesh member 19 and the processing object 21 face each other with a predetermined interval.

  The sample table 9 is a metal table provided in the processing chamber 3. The sample stage 9 is applied with a negative potential lower than the plasma potential by the potential application unit 16. As described above, since the metal cover 7 and the processing object 21 are electrically connected to the sample table 9, the metal cover 7 and the processing object 21 are also applied with a negative potential by the potential application unit 16. Is done.

  The heater 11 heats the inside of the processing chamber 3. The nitrogen supply pipe 13 supplies a gas mainly containing nitrogen into the processing chamber 3. The nitrogen supply pipe 13 is provided with a mass flow controller (not shown), and the gas supply amount can be adjusted as appropriate.

  The downstream side of the exhaust pipe 15 is connected to a vacuum pump (not shown). The exhaust pipe 15 is provided with an open / close valve (not shown). By adjusting the opening ratio of the opening / closing valve, the pressure in the processing chamber 3 can be appropriately set.

  Next, the configuration of the small electron beam source 5 will be described with reference to FIG. The small electron beam source 5 includes a housing 25, a cathode 27, a spare anode 29, an anode 31, an acceleration electrode 33, and an argon supply pipe 34.

  The housing 25 is a cylindrical hollow container. The cathode 27, the auxiliary anode 29, the anode 31, and the acceleration electrode 33 are arranged in that order in the housing 25. Hereinafter, a region between the cathode 27 and the anode 31 in the housing 25 is referred to as a discharge region 35. Further, in the discharge region 35, a region between the cathode 27 and the auxiliary anode 29 is a first discharge region 35A, and a region between the auxiliary anode 29 and the anode 31 is a second discharge region 35B. In addition, an area between the anode 31 and the acceleration electrode 33 in the housing 25 is referred to as an acceleration area 37.

  The auxiliary anode 29 has a small hole 29A in the center. The first discharge area 35A and the second discharge area 35B communicate with each other through a small hole 29A. The anode 31 and the acceleration electrode 33 each have a net shape. The argon supply pipe 34 supplies argon gas to the first discharge region 35A.

  The small electron beam source 5 generates the electron beam 17 as follows. First, argon gas is supplied from the argon supply pipe 34 to the first discharge region 35 </ b> A, and direct current discharge is generated between the cathode 27 and the auxiliary anode 29. Thereafter, discharge is transferred between the cathode 27 and the anode 31 to generate a stable argon plasma 39. Only electrons are extracted from the argon plasma 39 by the acceleration voltage in the acceleration region 37 (voltage between the anode 31 and the acceleration electrode 33), and the electron beam 17 is generated. The electron beam 17 passes through the mesh of the acceleration electrode 33 and is introduced into the processing chamber 3. The small electron beam source 5 is an example of a plasma generation unit.

2. Nitriding Method Using Nitriding Apparatus 1 A nitriding method using the nitriding apparatus 1 will be described. A processing object 21 shown in FIGS. 4 and 5 was prepared as a target for nitriding. The material of the processing object 21 is a steel material (SKD61). The processing object 21 includes a bottom plate 43, a pair of side plates 45 and 47, and end members 49 and 51.

  The side plates 45 and 47 are erected on the upper surface of the bottom plate 43 so as to be parallel to each other with an interval of 1 mm in width. The end members 49 and 51 fill both ends of the gap between the side plates 45 and 47. The height of the side plates 45 and 47 is 20 mm.

  The processing object 21 has the recessed part 53 enclosed by the side plates 45 and 47 and the end members 49 and 51 by said structure. The recess 53 opens on the upper surface of the processing object 21 and reaches the bottom plate 43. The recess 53 has a width of 1 mm and a depth of 20 mm.

  This processing object 21 was accommodated in the metal cover 7 of the nitriding apparatus 1. At this time, the bottom plate 43 of the processing object 21 was in contact with the sample stage 9, and the opening of the concave portion 53 was opposed to the mesh member 19.

Next, the nitriding apparatus 1 was operated to generate a plasma 54 containing high-concentration nitrogen atoms in the processing chamber 3 to perform nitriding. The operating conditions at this time were as follows.
Amount of argon gas supplied to the compact electron beam source 5: 40 cc / min
Supply amount of nitrogen gas to the processing chamber 3: 80 cc per minute
Supply amount of hydrogen gas to the processing chamber 3: 5 cc per minute
Gas pressure in the processing chamber 3: 0.2 Pa
Electron beam 17 acceleration voltage: 80V
Current value of electron beam 17: 9.3 A
Plasma potential: 0V
Potential of mesh member 19: -100V
Potential of the processing object 21: −100V
Temperature in the processing chamber 3: 485 ° C.
Nitriding treatment time: 10 hours At this time, it is presumed that nitriding treatment proceeds by the following mechanism. By irradiating the processing chamber 3 with a low-energy electron beam 17 having an acceleration voltage of 80 V with a large current, nitrogen atoms are efficiently generated in the processing chamber 3 and, at the same time, nitrogen plasma is also generated. That is, nitrogen plasma is generated in the processing chamber 3 by the electron beam excitation plasma method.

In the nitrogen plasma, ions of nitrogen atoms (N ⁺ ions) are present at a high concentration. N ⁺ ions in the plasma are accelerated in the direction of the mesh member 19 by the potential difference (−100 V) between the plasma potential and the potential of the mesh member 19, and pass through the mesh member 19. Since the mesh member 19 and the processing object 21 have the same potential, the N ⁺ ions that have passed through the mesh member 19 travel straight toward the processing object 21 without receiving the so-called “edge effect”. At this time, some of the N ⁺ ions are changed to a nitrogen neutral particle (N) beam by a charge exchange reaction. Both the N ⁺ ions and the N beam reach the object to be processed 21 and advance the nitriding process.

Since the N ⁺ ions and the N beam are accelerated in the direction of the processing object 21 due to the above-described potential difference, the N ⁺ ions and the N beam penetrate into the concave portion 53 and proceed with the nitriding process inside.
After completion of the nitriding process, the processing object 21 was taken out from the nitriding apparatus 1 and disassembled for each part. The surface hardness of the portion 43A (see FIG. 5) of the bottom plate 43 facing the recess 53 was measured using a micro hardness meter (Vickers hardness meter). As a result of the measurement, the surface hardness was 1155 Hv. This surface hardness was remarkably improved as compared with 672 Hv which is a value before nitriding.

3. Advantages of the nitriding apparatus 1 (1A) The nitriding apparatus 1 and the nitriding method using the nitriding apparatus 1 advance the nitriding process even in the inside of the recess (for example, the bottom surface, the inner side surface, etc.) to improve the hardness. Can be made.

(1B) The nitriding apparatus 1 generates nitrogen plasma by an electron beam excitation plasma method. As a result, nitrogen plasma suitable for nitriding can be easily generated.
<Comparative example>
As shown in FIG. 6, a nitriding apparatus R1 having a configuration basically similar to that of the nitriding apparatus 1 but partially different is prepared. The nitriding apparatus R1 does not include the metal cover 7 (see FIG. 1), but instead includes an insulating plate 55 made of quartz glass on the sample stage 9. Further, the nitriding apparatus R1 does not include the potential application unit 16.

  Using this nitriding apparatus R1, nitriding was performed on the processing object 21 as follows. First, the processing object 21 was placed on the insulating plate 55. At this time, the processing object 21 and the sample stage 9 are electrically insulated. The processing object 21 is the same as that in the first embodiment, and is placed in a direction in which the bottom plate 43 is in contact with the insulating plate 55.

  Next, the nitriding apparatus R1 was operated to generate plasma containing high-concentration nitrogen atoms in the processing chamber 3 to perform nitriding. The operating conditions at this time are basically the same as those in the first embodiment. However, a negative potential is not applied to the processing object 21. In this comparative example, it is presumed that normal atom nitriding proceeds on the surface of the processing object 21.

After completion of the nitriding process, the processing object 21 was taken out from the nitriding apparatus R1 and disassembled for each part. The surface hardness of the portion 43A of the bottom plate 43 facing the recess 53 was measured using a micro hardness meter (Vickers hardness meter). As a result of the measurement, the surface hardness was 831 Hv. This surface hardness was significantly lower than the measured value after the nitriding treatment in the first embodiment. That is, in this comparative example, the nitridation inside the recess 53 could not be sufficiently advanced.
<Other embodiments>
As mentioned above, although embodiment of this invention was described, this invention can take a various form, without being limited to the said embodiment.

(1) The nitriding apparatus 1 may generate plasma by a microwave excitation plasma method instead of the electron beam excitation plasma method.
(2) As shown in FIG. 2B, the mesh member 19 may be one in which a plurality of through holes 59 are provided in the metal plate 57, or a plurality of slits 63 in the metal plate 61 as shown in FIG. 2C. May be provided.

(3) The gas supplied to the processing chamber 3 may be a gas that does not substantially contain components other than nitrogen.
(4) The potential of the processing object 21 can be set as appropriate within a range lower than the plasma potential. For example, the potential of the processing object 21 may be higher than that of the mesh member 19, or may be lower than that of the mesh member 19.

(5) The material of the mesh member 19 may be a conductive material other than metal (for example, conductive carbon).
(6) The shape of the processing object 21 can be selected as appropriate. For example, the processing object 21 may include a hole (an example of a recess) having a circular or elliptical cross section, or may include a slit (an example of a recess). Moreover, the process target object 21 does not need to be provided with the recessed part.

  (7) The functions of one component in the above embodiment may be distributed as a plurality of components, or the functions of a plurality of components may be integrated into one component. Further, at least a part of the configuration of the above embodiment may be replaced with a known configuration having the same function. Moreover, you may abbreviate | omit a part of structure of the said embodiment. In addition, at least a part of the configuration of the above embodiment may be added to or replaced with the configuration of the other embodiment. In addition, all the aspects included in the technical idea specified only by the wording described in the claim are embodiment of this invention.

  (8) In addition to the above-described nitriding apparatus, the present invention can be realized in various forms such as a system including the nitriding apparatus as a constituent element.

DESCRIPTION OF SYMBOLS 1 ... Nitriding processing apparatus, 3 ... Processing chamber, 5 ... Small electron beam source, 7 ... Metal cover, 9 ... Sample stand, 11 ... Heating heater, 13 ... Nitrogen supply piping, 15 ... Exhaust piping, 16 ... Potential application Unit: 17 ... Electron beam, 19 ... Mesh member, 20 ... Wire rod, 21 ... Object to be processed, 25 ... Housing, 27 ... Cathode, 29 ... Preliminary anode, 29A ... Small hole, 31 ... Anode, 33 ... Accelerating electrode, 34 ... Argon supply pipe, 35 ... Discharge region, 35A ... First discharge region, 35B ... Second discharge region, 37 ... Acceleration region, 39 ... Argon plasma, 43 ... Bottom plate, 45, 47 ... Side plate, 49, 51 ... End 53, recess, 54 ... plasma, 55 ... insulating plate, 57 ... metal plate, 59 ... through hole, 61 ... metal plate, 63 ... slit, R1 ... nitriding apparatus

Claims (5)

A processing chamber capable of accommodating a processing object;
A plasma generating unit for generating a plasma containing a high concentration of nitrogen atoms in the processing chamber;
A net-like member made of a conductive material, disposed opposite to the object to be processed in the processing chamber;
A potential applying unit that applies a potential lower than the potential of the plasma to the mesh member and the processing object;
A nitriding apparatus comprising:   The nitriding apparatus according to claim 1, wherein the plasma generation unit generates the plasma by an electron beam excitation plasma method.   The nitriding apparatus according to claim 1, wherein the plasma generating unit generates the plasma by a microwave excitation plasma method.   A nitriding method, wherein the object to be processed is nitrided using the nitriding apparatus according to any one of claims 1 to 3.   The nitriding method according to claim 4, wherein a region including a bottom surface of the concave portion is nitrided in the surface of the processing object.

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