JPH0427294B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a method for treating the surface of a member by glow discharge, and is aimed at uniformly distributing a reactive gas on the surface of a workpiece to obtain a treated layer with less unevenness. This invention relates to an ionic surface treatment method that allows for.

[Background of the invention]

2. Description of the Related Art A surface treatment method using glow discharge, which is a type of surface treatment technique for members such as metal members, has recently been attracting attention. A typical example is ion nitriding (Masanobu Fukazawa: Metal materials;
Vol.15, No.7, p43-46).

As shown in Fig. 2, in the ion nitriding method, a workpiece 2 to be treated is held by a hanging device 3 in a sealed container 1 whose pressure is reduced to at least 10 ^-1 Torr or less, and the sealed container 1 is used as an anode (the container is used as a cathode). ), a voltage is applied from the DC power supply 4 using the member 2 to be treated as a cathode, and a glow discharge is generated while introducing the gas substance necessary for processing into the sealed container 1 from the supply port 19. This is to harden the surface of the processing member 2.
Such a sealed container 1 has a water-cooled structure to prevent various devices and parts from being overheated due to heating by glow discharge.

When performing ion nitriding treatment, the vacuum pump 6 is operated to reduce the pressure inside the sealed container 1 to at least 10 ^-1 Torr, while hydrogen and nitrogen gas, or ammonia gas (NH ₃ ), etc. are sealed from the gas supply port 19. It is introduced into the container 1 and maintained at a pressure of 0.1 to 10 Torr, and a voltage of 300 to 1500 V is applied from the DC power source 4 between the anode terminal 7 and the cathode terminal 8 to generate glow discharge. In addition, in Figure 2, 1
2 is a gas cylinder, 10 is an optical pyrometer, and 11 is a vacuum gauge.

On the other hand, recently, CVD methods have been actively developed as surface treatments using glow discharge. this
CVD methods are used, for example, to coat metal surfaces with TiC. In this TiC coating, the workpiece is held in a sealed container 1.
After reducing the pressure to 10 ^-1 Torr, processing gases of TiCl ₄ and C ₂ H ₂ are supplied together with a carrier gas (Ar + 5% H ₂ ) into a sealed container to coat the surface of the workpiece with TiC.

FIG. 3 is an explanatory diagram showing an example of a conventional CVD apparatus, in which a member to be processed 2 is held in a sealed container 1, the member to be processed 2 is used as a cathode, and the sealed container 1 itself is used as an anode. Then, the pressure inside the sealed container 1 is reduced via a vacuum pump (not shown), and the carrier gas 12a is
(Ar+H ₂ ) is passed into the container 14 containing TiCl ₄ to vaporize the TiCl ₄ and introduced into the sealed container 1 together with the Ar+H ₂ gas 12b. On the other hand, C ₂ H ₂ source 12c
Then, C ₂ H ₂ is introduced into the sealed container 1 and a voltage is applied by the power source 4 to generate glow discharge, thereby coating the surface of the member 2 to be treated with TiC.

At this time, the member 2 to be processed is heated by the glow discharge energy generated on the surface, so no external heat source is required. Therefore, the temperature of the member to be processed changes depending on the ratio of the surface area to the volume of the member to be processed. On the other hand, in order to form a uniform coating layer, it is necessary to make the glow discharge generated on the surface of the object to be treated uniform. However, traditional
In the CVD method, uniform glow discharge can be generated when the shape of the workpiece is relatively simple, but when the workpiece has a complex shape, ions can be generated at different relative distances from the anode. A disadvantage is that the impact energy and the ionization density of the processing gas vary, making it impossible to achieve uniform surface treatment. This is due to the varying coating speeds due to variations in the concentration of atoms trapped on the surface of the workpiece. Therefore, it is almost impossible to form a film on the surface of the concave portion of a workpiece having large irregularities.

In particular, in glow discharge surface treatments such as carburizing, boring, etc., or CVD methods that require a high temperature range of 700 to 1200°C, the discharge voltage becomes high, resulting in uneven discharge and temperature differences, which can cause damage to the treated product. There is a problem in that there is a strong tendency that uniform surface treatment cannot be performed. As a solution, there are, for example, a method of performing ion treatment in a conventional vacuum heat treatment furnace, or a method of performing ion treatment while applying high frequency heating from the outside. However, in the former case, the object to be processed is heated by a heater such as carbon fiber, which requires a high output heating power source and requires less heating by ions, compared to conventional processing using only ions. As a result, the amount of ions reaching the surface of the product to be treated is also reduced. Therefore, the structure of the device is complicated, the control is complicated, the overall energy consumption is large, and the concentration of atoms involved in the cleaning action of ions and the processing of atoms captured on the surface is also reduced. In the latter case, heating is performed by induced current caused by high frequency, so if many parts are installed in the furnace, the heating temperature of each individual part will differ depending on the distance from the high frequency coil, and the former Similarly, controlling the output of the power supply becomes complicated. In addition, a large amount of energy is required for the treatment, and there are drawbacks in terms of ion cleaning effect and control of surface ion concentration.

On the other hand, in addition to the cathode that is the workpiece, an auxiliary electrode is provided near the workpiece, and by using this auxiliary electrode as the cathode and the workpiece as the anode, the temperature of the surface of the workpiece near the auxiliary electrode can be reduced. Controlling processing methods are also being used. However, these methods required a heating power source in addition to a glow discharge power source, and the apparatus was complicated. Therefore, the inventor first arranged a plurality of cathodes at a constant interval apart from the cathode, which is the object to be processed, on the outer periphery of the object to be processed and inside a vacuum container. By controlling the gas pressure, spacing, power output, etc. during ion treatment, glow discharge is also generated at this cathode, creating a hollow cathode discharge with high ionization density, which allows the surface of the workpiece to be treated. revealed that it can be heated or held at high temperatures (patent no.
No. 1254821). Such processing can be carried out by installing a hollow cathode jig 5 for forming a hollow cathode discharge in the conventional apparatus shown in FIG. 2, as shown in FIG. 4, according to the purpose.

In all of these treatments, it is important to control the plasma gas pressure of glow discharge. Gas pressure in the conventional ion nitriding equipment shown in Figures 2 and 4 is controlled by adjusting a variable leak valve or by measuring gas pressure with a vacuum gauge and opening and closing a solenoid valve, etc. Ta. In addition, since the gas outlet was fixedly installed in a part of the upper part of the furnace body, there were no major problems with nitriding treatment due to the diffusion of nitrogen, etc., but when performing carburizing etc. at a high treatment temperature, , non-uniformity of the hardened layer was observed depending on the location. This is because the gas concentration is non-uniform depending on the position. Traditionally, a stirring fan has been used as a means to obtain a uniform distribution of processing gas, or the processing pressure is 0.1~
Since the pressure is 10Torr, it is very difficult to move the gas by rotating the fan.

Therefore, the present inventor first attempted to solve the above problem by intermittently or continuously changing the position of the gas outlet above the reduced pressure vessel when introducing the processing gas (Japanese Patent Laid-Open No. 58 −9974). As a result, the effect was remarkable in carburizing treatments, etc., in which elements are diffused from the surface of the treated product. However, in CVD that forms a film on the surface to be treated, it is difficult to efficiently supply the introduced treatment gas such as halogen gas into the hollow cathode discharge region.
Unreacted process gas adsorbs to the walls of the furnace body and when the furnace body is opened, it comes into contact with the air and absorbs moisture, and these substances release gas during the next process, creating gases that are harmful to the process. There was a problem that uniform processing could not be performed due to the atmosphere.

[Purpose of the invention]

An object of the present invention is to provide an ionic surface treatment method that is suitable for surface treatment of objects to be treated, particularly for CVD film formation and carburizing treatment that require high temperatures, and that is capable of uniformly and efficiently forming a single or multiple surface treatment layers. is to provide.

[Summary of the invention]

In the present invention, an article to be treated is used as a cathode in a reduced pressure atmosphere containing a gaseous substance, an auxiliary electrode connected to the cathode is disposed opposite to and in the vicinity of the article to be treated, and the ionic surface is surface-treated by glow discharge. In the processing method, while moving a gas supply pipe having a gas outlet in a space between the object to be processed and the auxiliary electrode between the object to be processed and the auxiliary electrode or the opposing auxiliary electrodes,
By supplying the gaseous substance into the space from the gas outlet of the gas supply pipe, the gaseous substance is uniformly and efficiently supplied into the high ionization density discharge region to effectively perform glow discharge treatment. It is.

[Embodiments of the Invention] The ionic surface treatment method using glow discharge, which is the premise of the present invention, achieves surface hardening, lubricating effect, and
It imparts functions such as corrosion resistance and fatigue resistance to the surface of the treated product. At this time, in order to provide these functions without adversely affecting the mechanical and chemical properties of the processed material, the amount, depth, thickness, etc. of atoms to be diffused and precipitated must be adjusted appropriately. It is important to control. Factors that control these include treatment temperature time and surface temperature during reaction. In other words, these control factors are the main factors that influence the atomic diffusion rate, the critical amount of solid solution, the crystal structure and formation rate of precipitates, etc.

First, the treatment temperature is generally in the range of 400 to 700℃ when surface hardening steel with nitrogen, 700 to 1100℃ in case of surface hardening by carburizing, and 800 to 1200℃ in case of ferrous treatment. ℃, in the case of sulfurization treatment to obtain surface lubrication using sulfur, the temperature is 150 to 600℃, while in the case of film formation by CVD, it varies depending on the atoms to be coated on the surface, but in general
Most temperatures range from 500 to 1200℃. As described above, it is necessary to select an appropriate temperature depending on the atoms to be diffused or precipitated and the type of product to be treated.

In the ion surface treatment method, a method using an external heat source can also be used to efficiently raise the surface temperature of the object to be treated or to partially heat it to an appropriate temperature. In the method of the present invention, an auxiliary electrode having approximately the same potential as the workpiece member serving as the cathode,
gas pressure, which is arranged at a predetermined distance from the surface of the object to be treated and connected to the cathode, and introduced into the space formed by the object to be treated and the auxiliary electrode during ion treatment;
The composition is controlled and the treatment is performed using high ionization density discharge.

Here, heat absorption from the processed item is heat exchange of glow discharge energy, radiant heat from the processed item or auxiliary electrode, etc., and heat loss due to heat release is radiant heat,
These include convection of the process gas, heat conduction from the electrode (outflow from the electrode cooling water), etc. Among these factors, radiant heat between the auxiliary cathode and the workpiece can be used to heat the required part of the workpiece to a predetermined temperature. This makes the cathode spacing constant,
By setting the introduced gas pressure to a predetermined value and causing interaction between two negative glows, a discharge with a higher ionization density than one negative glow discharge section is generated to perform heating and heat retention. .

Note that, in the high ionization density discharge, when two negative glow discharges are brought close to each other at a certain distance, interaction occurs between the negative glows, and the ionization density becomes higher than that of other glow discharge parts. In this region of interaction, the discharge current becomes high. in this case,
The ion density of the gas in the space between the workpiece and the auxiliary electrode is also increased. Therefore, on the surface of the object to be treated, surface reactions with active atoms also become active, promoting diffusion or precipitation. In order to make this diffusion and precipitation phenomenon more effective, the distance from the surface of the workpiece to the auxiliary electrode, the gap between the auxiliary cathodes, the material, shape, area, gas pressure, and method of introducing the processing gas must be adjusted appropriately. Control is important.

First, the distance from the surface of the workpiece to the auxiliary electrode or the spacing within the auxiliary cathode varies depending on the gas pressure, but the negative glow generated between the workpiece and the auxiliary electrode interacts in some way, resulting in a high ionization density discharge. If this does not occur, the desired effect will not occur.
This is because the width of the negative glow varies depending on the gas composition and gas pressure, which strongly influences high ionization density discharge. Furthermore, the auxiliary electrode and negative glow discharge area, which are closely related to these, must also be considered. Therefore, in general ionic surface treatment, if this distance is less than 0.5 mm, the reaction of the processing gas to the object to be treated tends to be inhibited, while if the distance is more than 50 mm, the interaction between the glows may be affected. This weakens the heating effect of radiant heat from the auxiliary electrode to the workpiece, and also causes heat loss to the auxiliary electrode, resulting in a loss of energy.

Next, the gas pressure naturally has an appropriate value once the gas composition and the purpose of surface treatment are determined. For example, if the gas composition and the distance between the workpiece and the auxiliary electrode are kept constant, changing the gas pressure will cause a high ionization density discharge in a certain range, the current density of the discharge will increase, and the The temperature of the processed product also increases and reaches its maximum temperature. If the gas pressure is not appropriate, it tends to lower the temperature of the processed product.

Processing temperature is thus influenced by gas pressure and gas composition. The appropriate gas pressure is preferably in the range of 0.01 to 10 Torr in terms of absolute vacuum.

Next, the surface concentration, which is one of the important factors in the surface treatment reaction, is introduced, and the gas pressure of the treatment gas,
It depends on the gas composition and gas distribution. In order to form a surface treatment layer using high ionization density discharge, it is necessary to consider the method of introducing the treatment gas. The processing gas introduced into the closed container is diffused by suction from a vacuum pump, convection of the furnace temperature, gravity, and the like. In the conventional ion nitriding processing apparatus shown in FIG. 2, the processing gas is supplied from the gas supply port 19 fixed to the upper part of the sealed container 1, so the gas pressure and mixture vary depending on the spatial position within the sealed container 1. The partial pressure of some gases fluctuates. In particular, fluctuations in the gas partial pressure of substances involved in the reaction greatly affect the formation of the surface treatment layer.

This will be explained using the case of TiC coating CVD as an example. CVD involves a reaction between a gaseous substance of a metal compound and a gaseous substance (reactive gas) that reacts with the gaseous substance to form a reactant, and coats the surface of the processed object with the reaction product. This reactant is supplied from the atmospheric gas. For example, in TiC coating, TiCl ₄ as a gaseous substance of a metal compound is dispersed in H ₂ as a carrier gas, and CH ₄ is dispersed as a gaseous substance (reactant gas) that reacts with the gaseous substance of the metal compound to form a reactant. When forming TiC by changing the partial pressure (composition) of TiCl ₄ and CH ₄ , depending on the ratio of partial pressures (composition),
Films of TiC+Ti, _{TiXC1 -X} , and TiC+C are formed. Therefore, in order to form a TiC film having a stoichiometry in which X of Ti _X C _1-X is 0.5, it is necessary to accurately control the partial pressure (composition) of TiCl ₄ and CH ₄ . This partial pressure is controlled by controlling the vaporization temperature and pressure of TiCl ₄ , the flow rate of H ₂ as a carrier gas, and the flow rate of CH ₄ as a reaction gas. This flow rate can be easily controlled by using a mass flow meter or the like. However, even if the flow rate is maintained accurately and the partial pressure is controlled in this way, the partial pressure (composition) of the TiCl ₄ and CH ₄ processing gases will vary depending on the position of the processed product when introduced into the furnace. There are different things. This tends to fluctuate due to the flow caused by the diffusion of the processing gas, the suction of the evacuation device, and the convection of the furnace temperature. Furthermore, TiCl ₄ , which is a gaseous metal compound, is consumed by thermal decomposition or adsorption to the cooled furnace wall, resulting in a change in the supplied partial pressure. As a result, TiC is not formed at all on the surface of the workpiece, or even if TiC is formed, it is difficult to uniformly form TiC having the desired stoichiometry on a plurality of workpieces at different positions. For this reason, it is necessary to control the gas partial pressure so as to reduce fluctuations. In other words, the partial pressure of the gaseous substance of the metal compound is extremely low, in other words, a very small amount of gas is supplied, and this very small amount of gas is passed through the gap between the auxiliary electrode and the processed item to the processed item. It is necessary to uniformly distribute the new gaseous substance on the surface. Further, it is necessary that the gaseous substances and reactants do not remain in this gap and are immediately attached to the surface of the object to be treated.

Therefore, in order to uniformly form a film with the target composition, a reactive gas adjusted to an appropriate equivalence ratio is supplied through a gas supply pipe to the object to be treated and the auxiliary electrode, or to the space between the auxiliary electrodes, resulting in highly ionized In addition to generating a dense glow discharge to cause the reactive gas to react,
It is necessary to uniformly distribute the reactive gas so that the composition of the coating is homogeneous and uniform. For this purpose, the reactive gas supply pipes and/or the article to be treated are moved. For example, the reactive gas supply pipe is rotated or reciprocated to change its position intermittently or continuously. Similarly, when moving both the article to be treated and the reaction gas supply pipe, the article to be treated is also moved relatively.

Embodiments of the present invention will be described below based on the drawings. FIG. 1 shows an example of a surface treatment apparatus used to carry out the present invention, and in the figure, 1
1 is a furnace body, and an upper lid and a lower lid are fixed to the upper and lower openings of a hollow cylindrical body through packing, so that the furnace body is in a sealed state. Reference numeral 2 denotes an article to be processed that serves as a cathode, and is held by a rotating holding member 3 connected to a rotating cathode terminal 8 . The other end of this rotating cathode terminal 8 is connected to the cathode of the power source 4 by a rotating power supply mechanism 9. Further, the rotation holding member 3 is adapted to be rotated by a rotary electric motor 21. Inner and outer cylindrical auxiliary electrodes 5 are located near the workpiece 2.
a and 5b, one end of which is connected to the cathode side. On the other hand, one end of the furnace body 1 is connected to an anode 7 of a power source 4.

The reactive gas supply means has the following configuration. The flow rate of the carrier gas 12a is controlled by the flow rate control system 13, and the TiCl ₄ is vaporized through the container 15 containing TiCl ₄ , and the reaction gas 1 is
2b is controlled in flow rate by a flow rate control system 13, and both of these gases are introduced into a gas supply pipe 17 in the furnace body 1 via a gas rotating supply structure 16 insulated from the cathode and anode by an insulating seat 18. Gas supply pipe 1
7 is installed in a space near the workpiece 2 and the auxiliary electrodes 5a, 5b. The gas supply pipe 17 rotates as the rotary gas supply mechanism 16 receives rotational motion from the rotary conductor 21 .

Examples of detailed configurations of the workpiece 2, auxiliary electrodes 5a, 5b, and gas supply pipe 17 are shown in FIGS. 5, 6, and 7.

FIG. 5 shows an electrode structure in which cylindrical auxiliary electrodes 5a and 5b are arranged facing each other while sandwiching the workpiece 2, and a circular orbit between the workpiece 2 and the auxiliary electrodes 5a and 5b. It is a perspective view showing an example where gas supply pipe 17 is arranged so that it may be located. In the figure, the cylindrical auxiliary electrodes 5a and 5b have an inner circumferential surface of the auxiliary electrode 5a and an outer circumferential surface of the auxiliary electrode 5b facing each other in a concentric circle, and a pin-shaped workpiece 2 is placed on the concentric circle in between. Further, a plurality of branched gas supply pipes 17 are disposed on a concentric circle between the inner circumferential surface of the auxiliary electrode 5a and the article 2 to be treated, and between the outer circumferential surface of the auxiliary electrode 5b and the article 2 to be treated. Workpiece 2 and auxiliary electrodes 5a, 5
One end of b is connected to the cathode of the power source. Processing gas is supplied to the gas supply pipe 17 by a mechanism shown in FIG. Note that the gas supply pipe 17 is provided with a plurality of gas ejection ports 22 , and the processing gas is ejected toward the workpiece 2 .

FIG. 6 shows an electrode structure in which disc-shaped auxiliary electrodes 5a and 5b are opposed to each other, a workpiece to be processed is connected to the auxiliary electrodes, and a gas supply pipe 17 is arranged between the disc-shaped auxiliary electrodes. This is an example of a supply structure. In the figure, two disc-shaped auxiliary electrodes 5a and 5b are placed parallel to each other and facing each other with a constant gap. The object to be processed 2 is placed on one or both surfaces of the opposing planes of these auxiliary electrodes. A plurality of radially branched gas supply pipes 17 are arranged in the space between the article to be processed 2 and the auxiliary electrodes 5a and 5b arranged in this way, and the gas supply pipe 17 is configured to supply the gas shown in FIG. Rotates by a rotation supply mechanism. This plurality of branched gas supply pipes 17 have a plurality of gas jet ports 2.
2 is provided. Note that the article to be processed 2 is connected to the cathode of the power source by being placed on an auxiliary electrode. Further, one end of the plurality of auxiliary electrodes 5a, 5b is connected to the cathode of the power source, and depending on the case, the plurality of auxiliary electrodes 5a, 5b may rotate relative to each other, or the plurality of auxiliary electrodes 5a, 5b may
Either one of them rotates, or moreover, a plurality of auxiliary electrodes 5a and 5b rotate simultaneously.

FIG. 7 shows an example in which flat plate-shaped auxiliary electrodes 5a and 5b are opposed to each other, a workpiece 2 is placed on the auxiliary electrodes, and a gas supply pipe 17 is arranged in the space between the flat plate-shaped auxiliary electrodes 5a and 5b. FIG. In the figure,
The flat plate-shaped workpiece 2 has flat plate-shaped auxiliary electrodes 5a, 5.
It is connected to the cathode of the power source by being installed on one or both opposing sides of b. The gas supply pipe 17 reciprocates over a range greater than the processing range of the workpiece 2 installed on the flat plate-shaped auxiliary electrode, and ejects reactive gas from a plurality of gas ejection ports 22 provided therein. On the other hand, the flat plate-shaped auxiliary electrodes 5a and 5b also reciprocate relative to each other, singly, or simultaneously, as described above.

In this way, while moving the gas supply pipe 17, the processing gas is ejected from the gas outlet 22 onto the article 2 to be treated, and more preferably the article 2 to be treated, or the auxiliary electrode 5 on which the article 2 is installed, and further By performing the treatment by rotating or reciprocating the opposing auxiliary electrodes 5, the treated layer can be made uniform. Furthermore, by supplying the reactive gas only between the auxiliary electrodes or between the auxiliary electrode and the workpiece, the supplied reactive gas reacts quickly in this space to form a treatment layer on the surface of the workpiece. Therefore, efficient processing is possible, and there is also the advantage that there is less diffusion of unreacted gas into the furnace.

Here, in order to make the thickness of the film formed on the object to be processed uniform, it is preferable to control the distribution state of the reaction gas. The distribution state of the reaction gas changes depending on the size and distribution of a plurality of gas jet ports provided in the single or plural branched gas supply pipe 17.

Control of the distribution state of the reactant gas will be explained by taking as an example a configuration in which a workpiece to be treated and a gas supply pipe are disposed between disk-shaped auxiliary electrodes as shown in FIG.
FIG. 8 shows the distribution range of the reaction gas obtained in each of the four gas supply pipes 17 when a plurality of gas jet ports having the same diameter are arranged at the same intervals in each of the four gas supply pipes. FIG. 9 shows the relationship between the position in the longitudinal direction of the gas supply pipe in FIG. 8, the amount of reactant gas, and the thickness of the coating. As shown in FIGS. 8 and 9, when the spacing and size of the gas jet ports are the same, when the reaction gas is supplied from the center, the position of the center is higher than that of the tip of the gas supply pipe. The distribution is such that a larger amount of reactant gas is supplied at the position. As a result, the thickness of the formed coating on the processed object is thin at the tip of the gas supply pipe and thick at the center, making it difficult to obtain a uniform distribution over a wide range within the auxiliary electrode. It is. Therefore, in order to achieve a uniform distribution of coating thickness, it is necessary to have the reactive gas distribution range as shown in Figure 10 using the same electrode structure and gas supply system as in Figure 8. . FIG. 11 shows the relationship between the longitudinal position of the gas supply pipe in FIG. 10, the amount of reactant gas, and the thickness of the coating. Figures 10 and 11
As shown in the figure, by increasing the amount of reactive gas at the tip of the gas supply pipe compared to the center, the distribution range of the reactive gas is made wider at the tip.
As a result, the thickness of the formed coating on the processed object is uniform at both the tip and center of the gas supply pipe, making it possible to obtain a uniform distribution over a wide range within the auxiliary electrode. Become.

In order to increase the amount of reactant gas at the tip of the gas supply pipe and reduce it at the center, it is preferable to control the distribution state and/or size of the plurality of gas jet ports. For example, in FIG. 12a, the size of the plurality of gas nozzles 22 is kept constant, and the distribution state is controlled by changing the interval between each gas nozzle, and as the tip of the gas supply pipe approaches, the gas nozzle The distribution is such that the spacing becomes dense and becomes sparse towards the center. In addition, in FIG. 13a, the intervals between the plurality of gas jet ports 22 are constant, and the diameter of each gas jet port is varied.
The diameter of the ejection port increases toward the tip of the gas supply pipe, and decreases toward the center. By configuring the gas outlet as described above, as shown in FIGS. 12b and 13b, the amount of reactant gas supplied increases toward the tip of the gas supply pipe, and the product to be treated increases. It is possible to perform treatment with a uniform coating thickness on the inner and outer circumferential sides of the auxiliary electrode. Note that the same effect can be obtained even if both the size and interval of the gas ejection ports are changed.

The above explanation regarding the gas outlet 22 uses opposing disk-shaped auxiliary electrodes as shown in FIG.
Gas is supplied by gas supply pipes installed radially from the center, but other auxiliary electrode structures,
For example, in the case of a cylindrical or parallel plate shape as shown in FIGS. 5 and 7, gas jet ports are arranged above and below each auxiliary electrode so that the same reaction gas distribution range as above is obtained. This allows the coating to be processed to have a uniform thickness.

Hereinafter, specific examples of the present invention will be described.

<Example 1> Carburization and subsequent TiC coating were performed using the processing apparatus shown in FIG. 1 and the configuration of the auxiliary electrode and gas supply means shown in FIG. The material to be processed is JIS standard SKD61 hot die steel 61.
I used a pin for an aluminum die-cast mold (diameter 12 mm, stepped, height 120 mm). The auxiliary electrodes 5a and 5b in Fig. 5 have a height of 150 mm, the inner diameter of the auxiliary electrode 5a is 340 mm, and the outer diameter of the auxiliary electrode 5b is 250 mm.
Both were made of mild steel with a thickness of 5 mm. At a position with a diameter of 295 mm, which is the middle between the inner diameter of the auxiliary electrode 5a and the outer diameter of the auxiliary electrode 5b, 25 pins of the workpiece 2 were placed at intervals of 24 mm. A total of 12 gas supply pipes 17 were provided, two each at an angle divided into six equal parts in the pin spaces of the auxiliary electrodes 5a, 5b and the workpiece 2. This gas supply pipe has a large number of gas jet ports 22 each having a diameter of 1.0 mm in a range of 130 mm at the end.

The inside of the furnace body 1 is vacuumed 5× by the vacuum pump 6.
The pressure is reduced to 10 ^-3 Torr or less, H ₂ gas is introduced in that state, and a DC voltage of 400 to 900 V is applied to generate a discharge with high ionization density between the workpiece 2 and the auxiliary electrodes 5a and 5b. After holding the temperature at 1020° C. for 5 mm, CH ₄ gas was introduced and the temperature was maintained at 2.5 Torr, thereby performing carburization for 5 minutes as a pretreatment before TiC coating. After carburizing, the gas in the container 15 is then
TiCl ₄ was vaporized with H ₂ of the carrier gas 12a, mixed and supplied, and TiC coating treatment was performed at 1020° C. for 50 minutes. In addition, when supplying processing gas,
The gas supply pipe 17 was continuously rotated at a rotation speed of 17 rpm. In addition, the workpiece 2 and the auxiliary electrode 5
A and 5b were also rotated at 5.0 rpm in a direction relative to the gas supply pipe 17 for treatment.

The treatment was also carried out by the conventional method shown in FIG. 4 using the same steps as above.

As a result, according to the example of the present invention, the TiC coating was uniformly formed in the range of 10 to 12 μm,
The chemical composition ratio of Ti and C was close to 1. Therefore, it is clear that the processing gases were uniformly distributed and that the partial pressures of each gas were also uniform.

On the other hand, in the conventional method, a uniform TiC film was not formed, and the film that was formed was a black soot-like soft layer containing a lot of carbon. Therefore, it can be seen that either the processing gas effective for forming a TiC film was not supplied to the surface to be treated, or even if it was supplied, the distribution of each gas changed and TiC of the desired composition was not formed. . In addition, unreacted TiCl ₄ and reaction products adhere to the entire surface of the furnace wall, and react with moisture in the air, turning the furnace wall into a sticky hygroscopic substance, which becomes 5×10 ^-3 in the next pressure reduction process. The time taken to exhaust Torr has become extremely long. On the other hand, there were fewer deposits on the furnace wall after the treatment according to the embodiment of the present invention, unlike the conventional method, and the effect of efficient film formation in the high ionization density discharge region was clearly confirmed. Ta.

<Example 2> Using the processing apparatus shown in Fig. 1 and the configuration of the auxiliary electrode and gas supply means shown in Fig. 6,
Carburizing treatment was performed. (CVD was not performed.) As the member to be treated, a plate-shaped part made of chromium molybdenum steel of JIS standard SCM415 and processed into a size of 20 x 20 x 5 mm was used. As the disk-shaped auxiliary electrode shown in FIG. 6, a heat-resistant steel disk with an outer diameter of 360 mm, an inner diameter of 180 mm, and a plate thickness of 5 mm was used. Fifty pieces of the processed article 2 were dispersed on the disk-shaped auxiliary electrode located on the lower side, and were installed with a distance of 17 mm from the upper disk-shaped auxiliary electrode. The processing gas supply pipes 17 are adjusted to have a height midway between the upper disc-shaped auxiliary electrode and the workpiece 2 and are arranged in a radial manner. be done. The gas supply pipe 17 has a gas outlet 22.
A plurality of electrodes with a diameter of 1.5 mm are provided within a 60 mm area excluding the inner and outer 15 mm of the disk-shaped auxiliary electrode.

During the treatment, the inside of the furnace body 1 is evacuated to 5×10 ^-2 Torr or less using the vacuum pump 6, and the temperature is maintained in that state.
H ₂ gas is introduced and a DC voltage of 400 to 900 V is applied to generate a glow discharge with high ionization density between the workpiece 2 including the lower auxiliary electrode and the upper disc-shaped auxiliary electrode. , soaked and heated at 1040℃ for 5 minutes,
Then _CH4 gas was introduced and maintained at 4 Torr to 1040
Carburizing treatment was carried out at ℃ for 15 min. After carburizing, only H ₂ gas was heated and maintained at 1040°C, and diffusion treatment was performed for 170 min. Processed product 2 processed in this way
The hardness (H _V ) was measured to determine the depth of hardening. Based on the results, we observed the carbon diffusion situation. The effective hardening depth was defined as H _V 550 or more.

FIG. 14 is a diagram showing the effective hardening depth after carburizing. The length of the vertical line indicates the range of variation. As is clear from the figure, in the present invention, 5 min
Target effective hardening depth for carburizing and 170min diffusion treatment
The error is around 0.1mm compared to 1.5mm. On the other hand, when using the conventional method, a carburized layer is not formed, or even if it is formed, a carburized layer with a surface carbon concentration above a certain value indicating the effective hardening depth is not formed, or when the carburized layer reaches the target value of 1.5 mm. Layers may be formed and the range of variation tends to be very wide. In other words, with the method of the present invention, a nearly uniform carburized layer can be obtained over the entire product being treated, whereas with the conventional method, there are many variations between the products being treated, making it difficult to obtain a stable and uniform carburized layer. I found out something.

Factors that affect the above-mentioned variations in effective hardening depth include the processing temperature and the carbon concentration on the surface of the workpiece when the processing time is constant. Although it is possible to maintain the processing temperature almost uniformly in the conventional method, the surface carbon concentration is distributed throughout the introduced CH ₄ gas furnace, so it depends on the location of the object to be processed, or between the auxiliary electrode and the object. Since _the amount of CH ₄ gas supplied between
The gas partial pressure becomes low and the effective cure depth varies. In contrast, according to the method of the present invention, the processing gas is uniformly supplied to the discharge region at high density and with little variation in gas partial pressure, so the gas partial pressure and gas density at the surface of the workpiece are improved. The process becomes uniform over the entire object to be processed, allowing for processing with little variation.

〔Effect of the invention〕

In the conventional method, gaseous substances that contribute to the reaction are diffused throughout the reduced pressure container, and the treatment is performed by glow discharge on the surface of the processed object while causing fluctuations in the partial pressure of the processing gas. Since the gaseous substances that contribute to the reaction are uniformly distributed and supplied to the space between the auxiliary electrode and the auxiliary electrode, the gaseous substances are immediately reacted in the glow discharge region of high ionization density, and the processed objects are uniformly and efficiently treated. Not only can a surface treatment be performed on the surface of the container, but also unreacted gas is less likely to diffuse into the container, and unreacted gas can be prevented from adhering to the container wall. The present invention includes a single or multiple surface treatment layer on the whole or part of the surface of the article to be treated,
For example, it can be effectively used for surface treatment to form a surface diffusion layer or a surface coating layer, and is particularly effective for surface treatment in a high temperature range.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram showing an example of a surface treatment apparatus used to carry out the present invention, Fig. 2 is an explanatory diagram showing an example of an apparatus used in the conventional ion nitriding process, and Fig. 3 is an explanatory diagram showing an example of the apparatus used in the conventional ion nitriding process. FIG. 4 is an explanatory diagram showing an example of a conventional processing apparatus for conductive members. FIGS. 5, 6, and 7 are diagrams showing an electrode structure and gas supply means used in the method of the present invention. Figure 8 is a diagram showing the gas distribution range when the size and spacing of the gas outlets are uniform, Figure 9 is a diagram showing the gas amount and coating thickness in the case of Figure 8. FIG. 10 is a diagram showing the preferred gas distribution range, FIG. 11 is a diagram showing the gas amount and film thickness in the case of FIG. A diagram showing the changed gas supply pipes, the gas amount and coating thickness in that case,
Figures 13a and 13b are diagrams showing gas supply pipes with different gas outlet sizes, the gas amount and film thickness in that case, and Figure 14 is a diagram showing the effective hardening depth of carburizing treatment. . 1...Furnace body, 2...Product to be processed, 4...DC power supply, 5
a, 5b... Auxiliary electrode, 6... Vacuum exhaust system, 7... Anode terminal, 8... Rotating cathode terminal, 11... Vacuum measuring probe, 1
2a, 12b...carrier and reaction gas, 13...
Gas flow rate control system, 15...Metal halide storage container, 16...Gas rotation supply mechanism, 17...Gas supply pipe, 21...Electric motor, 22...Gas jet port.

Claims (1)

[Claims] 1. An article to be treated is set as a cathode in a reduced pressure container, an auxiliary electrode connected to the cathode is disposed opposite to and near the article to be treated, and a gas substance is supplied into the container. In an ion surface treatment method in which a treatment layer is formed on the surface of a workpiece under glow discharge with high ionization density, a gas supply pipe having a gas outlet located in a space between the workpiece and an auxiliary electrode is treated. An ion surface treatment method characterized by supplying a gas substance into the space from a gas outlet of a gas supply pipe while moving the substance relative to the product and the auxiliary electrode. 2. The ion surface treatment method according to claim 1, wherein the gas supply pipe has a plurality of gas jet ports, the diameter of which increases as it approaches the tip. 3. The ion surface treatment method according to claim 1, wherein the gas supply pipe has a plurality of gas ejection ports that are spaced closer to the tip.