JP4332636B2 - Discharge surface treatment electrode manufacturing method and discharge surface treatment electrode - Google Patents

Description

  The present invention uses a green compact obtained by compression-molding a metal powder or a metal alloy powder, or a green compact obtained by heat-treating the green compact as an electrode, and pulsed between the electrode and the workpiece in the working fluid or in the air. The discharge surface treatment is to form an electrode material or a film made of a substance obtained by reacting the electrode material with the discharge energy on the surface of the work.

In the conventional discharge surface treatment, a hard material film such as TiC (titanium carbide) is formed using a ceramic powder electrode in order to improve wear resistance of parts and molds.
And as for the manufacturing method of the electrode, after compressing a commercially available powder as it is by the press in air | atmosphere, it heated and manufactured the electrode. (Reference Patent Document 1)
TiC has a stable powder in the air, and it is difficult for the powders to adhere to each other.
Therefore, the fluidity of the powder is high, the surface of the charged powder is easily flattened during pressing, the pressure is uniformly applied to the press surface, and the molded electrode surface has a uniform hardness.

Japanese Patent Laid-Open No. 5-148615 discloses a discharge surface treatment method in which a thick coating layer of several tens of millimeters is formed using WC (tungsten carbide) and Co (cobalt) having an average particle diameter of about 1 μm. (Reference Patent Document 2)
These WC and Co are stable in the atmosphere like TiC, and the fluidity of the powder is high.

Japanese Patent No. 3227454 JP-A-5-148615

The technology for forming a hard ceramic film on the workpiece surface using electrodes such as ceramics and WC can be realized by the above-described conventional technology.
However, in recent years, for example, there has been an increasing demand for forming a metal film having lubricity and corrosion resistance under a high temperature environment by discharge surface treatment.
In addition, for the repair of metal parts and the correction of dimensions, it is required to apply a thick film of metal or alloy by discharge surface treatment.

In order to form a metal or alloy film by discharge surface treatment, the composition / structure of the electrode for forming the film on the workpiece surface is very important. The electrode itself has no hardness distribution on the surface. It has been clarified by experiments of the present inventors that the coating film to be formed becomes non-uniform without treatment.
Therefore, the present invention makes it possible to easily produce an electrode having no distribution of hardness with a powder of a metal or a metal compound when a coating of a metal or a metal compound is formed by the discharge surface treatment, thereby enabling the discharge surface treatment. It aims at establishing the manufacturing method of an electrode.

  The electrode manufacturing method according to the present invention generates a pulsed discharge between a green compact electrode obtained by compression molding a metal powder or a metal compound powder and a work, and the energy of the electrode material or In a discharge surface treatment in which a coating made of a substance in which an electrode material reacts with discharge energy is formed, a step of pulverizing a predetermined electrode material mixed with a solvent, and a mixture of the electrode material and solvent pulverized in this step A step of mixing a wax as a binder, a step of drying and granulating the mixture in an inert gas atmosphere, and a step of forming the green compact electrode using the granulated powder. It is a thing.

  According to the present invention, an electrode having no hardness distribution can be easily manufactured with a powder of a metal or a metal compound, and discharge surface treatment can be performed, and a stable film can be formed by this electrode.

Embodiment 1 FIG.
First, the principle of the discharge surface treatment will be described with reference to FIG.
In the discharge surface treatment described in this embodiment, in order to form a hard thick film, a compacted electrode that is heat-treated after compression molding a metal powder of several μm is used.
Then, a discharge is generated by applying a predetermined voltage in a state where servo is applied to the main shaft so that the electrode (cathode) and the work (anode) do not come into contact with each other in the working fluid (oil).
When the discharge occurs, a part of the electrode is melted and vaporized by the heat of the discharge, and the electrode lump is released by the blast and electrostatic force generated by the discharge and is deposited on the workpiece.
This is the principle of discharge surface treatment using a green compact electrode.

According to the present inventors, it is necessary to use an electrode manufactured from a powder having an average particle size of 3 μm or less in order to form a metal film having lubricity and corrosion resistance under a high temperature environment using this surface treatment. It has become clear.
However, metal and alloy powders having a particle size of 3 μm or less are very sensitive to energy because the ratio of the surface area to the volume of the powder becomes large and the surface becomes activated (easy to oxidize).
Specifically, if oxygen is present in the surroundings, the inside may be oxidized all at once, losing properties as a metal such as conductivity and ductility, or oxidation may explode.
Therefore, powders having an average particle size of 3 μm or less are not distributed on the market, and powders for electrodes for discharge surface treatment of various materials cannot be obtained. Note that the minimum average particle size of generally available powder is about 10 μm.
Therefore, in order to obtain a powder having a particle size of 3 μm or less, a powder having an average particle size of about 10 μm is purchased and pulverized in a liquid such as a solvent to produce a powder having a required particle size.
The reason for grinding in a liquid such as a solvent is to prevent oxidation because the surface is activated as described above simply by grinding.
Moreover, it is for suppressing aggregation of powder and powder.

Next, the electrode manufacturing process in the present embodiment will be described in detail with reference to FIG.
The average particle size of metal powders that are generally distributed is several tens of μm.
These powders are pulverized in volatile alcohol or organic solvent (hereinafter referred to as “solvent”) to a mean particle size of 3 μm or less with a pulverizer such as a bead mill or vibration mill, and the powder and solvent obtained by pulverization are mixed. Get the body. The powder pulverized by these pulverizers is scale-like.
Examples of the solvent include alcohols such as ethanol, propanol, and butanol, and organic solvents such as acetone, toluene, xylene, benzene, and normal hexane.

In order to improve the transmission of the press pressure to the inside of the powder during pressing, the mixture is mixed with wax such as paraffin as a binder in the powder in a weight ratio of about 1% to 10%.
Here, since paraffin has a low polarity, which is a form of charge in a molecule, it is difficult to melt in alcohol or acetone with high polarity.
Therefore, when alcohol or acetone is used as a pulverization solvent, the wax is melted in low-polarity normal hexane or toluene in advance, and the mixture of powder and solvent obtained by pulverization is mixed with normal hexane or toluene in which the wax is melted. Mix.
When normal hexane or toluene is used as a solvent for pulverization, the wax may be mixed as it is with the mixture obtained by pulverization.

Thereafter, the mixture of the powder and the solvent and the mixture of the wax are stirred with a ball mill and sufficiently mixed. In the mixing process using the ball mill, the rotation speed is reduced to several tens of rpm, the moving speed of the ball is lowered, and the ball mill is used for mixing instead of pulverizing the powder.
Next, the mixture is sprayed in an atmosphere in which high-temperature nitrogen is circulated using a drying device generally called a spray dryer, and the solvent is dried.
During this drying, the mixture becomes spherical (granulated powder) due to the internal force (atmospheric gas shear force) generated in the tangential direction of the virtual cut surface of the member and the surface tension of the mixture.
The granulated powder is formed of scaly powder and has a spherical shape.
When granulated using scaly powder, the surface of the powder appears on the surface of the granulated powder, and a smooth granulated powder can be produced (see FIG. 3).
For this reason, a thing with high fluidity | liquidity can be obtained.
The granulated powder is formed by volatilization of all the solvent during pulverization and precipitation of the pulverized powder and wax, and the granulated powder has a size of about 10 μm to 200 μm.
The particle size of the granulated powder can be adjusted by the rotation speed of an atomizer ejected into the drying chamber.
This time, the atomizer was set to 10,000 rpm, and granulated powder of 20 μm to 40 μm could be obtained.
If it is such a magnitude | size, even if it is a metal which is easy to oxidize, it is not oxidized.

Thereafter, the granulated powder of 20 μm to 40 μm is directly molded by a press.
The granulated powder is put into a die and vibration is applied to make the density uniform, and the upper surface of the granulated powder is made parallel to the surface of the press.
Since the spherical granulated powder has high fluidity, it can move by vibration and obtain a uniform density.
When the powder does not move due to vibration, check the parallelism with a level and press mold.
Thereafter, the electrode having conductivity is manufactured by heating in a vacuum furnace or a furnace in a nitrogen atmosphere.
Note that the wax in the electrode is removed during heating.

Next, an example of manufacturing an electrode of stellite (Co alloy) containing Cr (chromium), which is an easily oxidizable metal, will be described.
Co alloy described in the present embodiment is Mo28 wt%, Cr17 wt%, Si3 wt%, remaining Co, or Cr28 wt%, Ni5 wt%, W19 wt%, remaining Co, or Cr25 wt%, Ni10 wt%, W7 wt%, C0. The alloy is made of 5 wt% and the remaining Co, but there are Ni alloy, Fe alloy, and the like.
Ni alloy is Ni52.5wt%, Cr19wt%, Mo3wt%, Nb5.1wt%, Al0.5wt%, Ti0.9wt%, Fe18.5wt%, Mn0.2wt%, Si0.2wt%, C0.04wt, Or they are Ni47wt%, Cr22wt%, Co1.5wt%, Mo9wt%, W0.6wt%, Fe18.5wt%, Mn0.5wt%, Si0.5wt%, C0.07wt%.
The Fe alloy is composed of Ni 32.5 wt%, Cr 21.5 wt%, Fe 46 wt%, Mn 0.8 wt%, Si 0.4 wt%, and C 0.4 wt%.
In addition, Ni as the main component, Ni alloy containing Cr, Fe, Ni as the main component, Ni alloy containing Cr, Mo, Ta, Fe as the main component, Cr, Ni, Mo, (Cb + Ta), Ti, An Fe alloy containing Al may be used.

Generally, the average particle size of the commercially available stellite powder is about 20 μm.
The powder was first pulverized with a vibrating ball mill apparatus made of ball material ZrO ₂ .
In the pulverization, the above stellite powder was put in acetone as a solvent, and pulverized at a frequency of 1200 cpm for about 300 hours to reduce the average particle size to 1.2 μm.

Next, petroleum wax (paraffin) is melted in normal hexane.
It is mixed with the mixture of acetone and stellite powder obtained by the above pulverization and mixed using a ball mill.
Mixing is run at low speed, and stellite and normal hexane (including wax) as well as acetone are thoroughly mixed.

Next, the mixture is sprayed into a drying chamber in which nitrogen as an inert gas is circulated and dried.
The spray dryer used for drying has a rotating disk-shaped atomizer at the upper part of the container, and high-temperature nitrogen is ejected from the periphery in the direction of gravity.
Specifically, the mixture is supplied near the center of the atomizer, and the mixture is sprayed into nitrogen under the influence of centrifugal force.
Immediately after jumping out by this spray, it is thread-like and receives a shearing force from the surrounding gas during the flight.
Also, the liquid tends to become spherical due to surface tension.
A spherical granulated powder can be obtained if the solvent is volatilized when the thread-like mixture is torn off by shearing force and becomes a sphere by surface tension.

And the dried powder falls under the drying chamber of a spray dryer under the influence of gravity, and collects in the accumulation | storage part installed in the lower part.
The state of the granulated powder is shown in FIG.
One scale in the figure is 10 μm, and spherical granulated powder of about 40 μm can be obtained from the figure.

Subsequently, the granulated powder was used to compression-mold the electrode size of 50 × 11 × 5 mm with a press pressure of 70 MPa.
After that, since the wax is mixed, it is necessary to heat the electrode and remove the wax. Therefore, it is kept at 200 ° C. for 30 minutes in a vacuum furnace.
When heated, the wax that has reached the melting point oozes from the electrode to the surface.
Thereafter, when heated to 300 ° C., the exuded wax reaches the boiling point and vaporizes.
Further, the compact was heated in a vacuum furnace at about 700 degrees for about 2 hours to produce a conductive stellite electrode.

FIG. 5 shows the hardness of the surface of the stellite electrode that hits the press surface measured with a dynamic Vickers hardness tester.
In the figure, the horizontal axis represents the position from the electrode end surface, and the vertical axis represents the dynamic hardness obtained from the probe pressing depth.
For reference, when the powder before pressing is not spherical, the fluidity is poor and a uniform density or flat surface cannot be obtained when the powder is charged, resulting in a hardness distribution during pressing.
On the other hand, the electrode using the powder according to the present invention was able to obtain a substantially uniform hardness at any position from the end face of the electrode as shown in the figure.

Next, the results of a deposition processing test using this electrode will be described.
The electric discharge machining conditions were such that the peak current value was ie = 12 A and the discharge duration (discharge pulse width) was about te8 μs.
The state of deposition is shown in FIG.
In the figure, the right shows the result of machining for about 10 minutes near the electrode tip, and the left shows the result of machining for about 10 minutes near the electrode center.
As a result of the deposition, a film having a thickness of about 0.3 mm could be formed.
When spherical granulated powder is not used, the processing time and film thickness vary, but in this embodiment, a stable coating can be obtained at any position on the electrode.
With respect to the coating surface, no discharge concentration or short circuit occurred was observed, stable discharge could be obtained, and the film thickness was uniform over the entire processed surface.

By taking this embodiment as described above, an electrode can be manufactured using a metal such as Cr (chromium), Al (aluminum), or Ti (titanium) that easily oxidizes or an alloy containing them.
This is because powder that is easily oxidized can be dried and granulated without being exposed to oxygen. This is because large granulated powder is difficult to oxidize.
In addition, powders with a particle size of 3 μm or less that are simply pulverized are not spherical and the powder and powder tend to agglomerate, so the fluidity is low, and it is not possible to obtain a uniform plane or density during pressing. Although only an electrode having a uniform pressure and a distribution of pressure was produced, according to the present embodiment, even if the powder is a crushed powder having a low fluidity and having an average particle diameter of 3 μm or less , Granulated powder can be manufactured in a spherical shape with the powder plane being the surface of the granulated powder, and its high fluidity makes the electrode density uniform, and the upper surface of the granulated powder in the mold is parallel to the press surface As a result, an electrode having no hardness distribution can be manufactured.
And with this uniform hardness electrode, it has become possible to obtain a film having the same performance regardless of where the electrode is treated.
Furthermore, since the powder does not come into contact with the air before obtaining the granulated powder, even oxidizable metals that were difficult to manufacture can be manufactured as electrodes for discharge surface treatment, and those coatings can be formed by discharge surface treatment. It was.
In addition, if the powder of the metal containing Cr (chromium), Al (aluminum), Ti (titanium), etc. is compression-molded and made into an electrode, the surface of the electrode is oxidized, but the inside is not so oxidized. Also, oxidation does not progress explosively.

  For example, it is possible to coat Ti, which is light and high in strength and has oxidation resistance at high temperatures, on a jet engine compressor or the like by discharge surface treatment of the green compact.

Embodiment 2. FIG.
Next, an electrode manufacturing process according to the second embodiment will be described with reference to FIG.
As powders of Co, Ni, and Mo (molybdenum) that are difficult to oxidize, powders having a particle size of 3 μm or less are generally distributed.
When manufacturing an electrode using those powders, the powder used as an electrode is thrown into low polarity solvents, such as normal hexane which does not require the grinding | pulverization process of Embodiment 1, and the weight ratio of the amount of powder to 1 to 10 in it. % Wax is melted.
The mixture is stirred with a ball mill so that the powder and wax are sufficiently mixed, and the mixture is dried with a spray dryer and further granulated to about 20 μm to 40 μm.
Thereafter, the granulated powder is directly molded by a press.
The granulated powder is put into a die and vibration is applied to make the density uniform, and the upper surface of the granulated powder is made parallel to the surface of the press.
Since the spherical granulated powder has high fluidity, it can move by vibration and obtain a uniform density.
When the powder does not move due to vibration, check the parallelism with a level and press mold.
Thereafter, the electrode having conductivity is manufactured by heating in a vacuum furnace or a furnace in a nitrogen atmosphere.
Note that the wax in the electrode is removed during heating.

Next, an example of manufacturing the Mo electrode will be described.
Mo powder with an average particle size of 0.7 μm is charged into normal hexane, a wax of about 3% is added by weight ratio of the charged Mo powder, the mixture is thoroughly stirred with a ball mill, and dried with a spray dryer. A mixed granulated powder having an average particle size of about 20 μm to 40 μm is obtained.
Using the powder, it was compression-molded into a shape of electrode size 60 × 60 × 15 mm with a press pressure of 20 MPa.

After that, since the wax is mixed, it is necessary to heat the electrode to remove the wax, and the wax that has reached the melting point by being heated and held at 200 ° C. for 30 minutes in the vacuum furnace will stain the surface from the electrode. Come out.
Thereafter, when heated to 300 ° C., the exuded wax reaches the boiling point and vaporizes.
Further, the compact was heated in a vacuum furnace at about 800 ° C. for about 2 hours to produce a conductive Mo electrode.

Next, the results of a deposition processing test using this electrode will be described.
As shown in FIG. 8, the electric discharge machining conditions are such that the peak current value is ie = 12 A, the discharge duration (discharge pulse width) te is about 8 μs, and the thickness is about 0.3 mm as a result of machining for about 10 minutes. It was possible to form a coating.
When spherical granulated powder is not used, the processing time and film thickness vary, but in this embodiment, a stable coating can be obtained at any position on the electrode.
With respect to the coating surface, no discharge concentration or short circuit occurred was observed, stable discharge could be obtained, and the film thickness was uniform over the entire processed surface.

Embodiment 3 FIG.
Next, the powder material to be mixed in the mixed granulated powder will be described.
In the production of electrodes, conventional discharge surface treatment focuses on the formation of hard coatings, especially the formation of hard coatings at temperatures close to room temperature. In such a technique for forming a film mainly composed of carbide, it is possible to form a dense film uniformly, but the thickness of the film cannot be increased to about several tens of μm or more. There's a problem.
However, according to experiments by the present inventors, it has been found that the coating can be made thicker as a material that does not form carbides or hardly forms carbides is added to the component of the electrode material.
Conventionally, a large proportion of materials that easily form carbides are included. For example, when a material such as Ti is included in an electrode, a chemical reaction is caused by discharge in oil, and the coating is called TiC (titanium carbide). It becomes hard carbide.
As the surface treatment progresses, the material of the workpiece surface changes from steel (when processed into steel) to TiC which is ceramic, and characteristics such as heat conduction and melting point change accordingly.
However, when a material that is not carbonized or hardly carbonized is added to the electrode, the film does not become a carbide, and a phenomenon occurs in which the material that remains in the film as a metal increases.
And, it has been found that the selection of the electrode material has a great significance for thickening the coating.
In this case, it is natural that the hardness, the denseness, and the uniformity are satisfied, and it is a premise for forming a thick film.

As shown in FIG. 9, when a powder obtained by mixing Cr ₃ C _{2 that} is a carbide and Co that is a material that is difficult to form a carbide is compression-molded, and then heated to increase electrode strength, an electrode is manufactured. The ease of forming a thick film changes by changing the amount of Co that is difficult to form carbides.
Specifically, when a film is formed based on the pulse conditions as shown in FIG. 8, the thickness of the film formed on the workpiece varies depending on the weight percentage of Co in the manufactured electrode. When the Co content is low, the film thickness is about 10 μm, and the Co content gradually increases from about 30% by volume. When the Co content exceeds 40% by volume, it becomes easier to form a thick film stably. From the time when the content exceeds 50% by volume, the thickness is increased to nearly 10,000 μm.
In the graph of FIG. 9, it is described that the film thickness increases smoothly from about 30% by volume of Co, but this is an average value obtained by performing a plurality of tests, and actually, If the amount of Co is about 30% by volume, the film may not be thick and even if it is thick, the film is weak, that is, it may be removed if it is rubbed strongly with a metal piece. Yes, not stable.

From another point of view, when a film is formed on the workpiece based on the above-described conditions, it is formed when Co in the electrode is 0%, that is, when Cr ₃ C ₂ is 100% by weight. The thickness of the coat that can be formed is about 10 μm, and the thickness cannot be increased further.
FIG. 10 shows the thickness of the coating film with respect to the processing time when there is no material such as Co that hardly forms carbide in the electrode.
According to FIG. 10, at the beginning of the treatment, the film grows and thickens with time and saturates at some point (about 5 minutes / cm ² ).
After that, the film thickness does not grow for a while, but if the treatment is continued for a certain time (about 20 minutes / cm ² ) or more, the thickness of the film starts to decrease and finally the film height becomes minus, that is, changes to digging. .
However, the film is present even in the dug state, and the thickness itself is about 10 μm, which is almost the same as the state processed in an appropriate time.

That is, by increasing the amount of the material remaining as a metal in the coating, a coating containing a metal component that is not carbide can be formed, and a thick film can be formed stably.
The volume% here is a ratio of a value obtained by dividing the weight of each powder to be mixed by the density of each material, and is a ratio of the volume occupied by the material in the volume of the material of the whole powder.
When the Co content in the electrode was 70% by volume, a thick film having a thickness of about 2 mm could be formed. This film is formed in a processing time of 15 minutes, but if the processing time is increased, a thicker film can be formed.

In this way, by using an electrode containing 40% by volume or more of a material that is difficult to carbonize or not carbonized, such as Co, in the electrode, a thick film can be stably formed on the workpiece surface by discharge surface treatment. .
In the above description, the case where Co is used as a material that hardly forms carbides has been described. However, Ni, Fe, and the like are materials that can obtain similar results, and are suitable for use in the present invention.

The thick film here means a dense structure in which the inside of the tissue (which is a film formed by pulsed discharge, so that the outermost surface has poor surface roughness and does not appear glossy) has a metallic luster. It is a simple film.
Even when there are few materials such as Co that are difficult to form carbides, deposits may rise when the strength of the electrode is reduced.
However, such a deposit is not a dense film, but can be easily removed by rubbing with a metal piece or the like. The deposited layer described in the above-mentioned Patent Document 1 is such a non-dense film and can be easily removed by rubbing with a metal piece or the like.

Next, a specific example of manufacturing a green compact electrode in which a powder obtained by mixing Cr ₃ C _{2 that} is a carbide and Co that is a material that hardly forms a carbide is compression-molded will be described.
FIG. 11 is a cross-sectional view showing the concept of the discharge surface treatment electrode and the manufacturing method thereof.
In the figure, in the space surrounded by the upper punch 2 of the mold, the lower punch 3 of the mold, and the die 4 of the mold, the mixed granulated powder 1 made of Cr ₃ C ₂ (chromium carbide) powder and Co powder is present. Filled.

First, the mixed granulated powder will be described.
Petroleum wax (paraffin) is melted in normal hexane.
Using a ball mill, normal hexane, Co powder, and Cr ₃ C ₂ powder in which wax is dissolved are mixed.
The mixing is performed at a low speed, and Co having a particle diameter of about 4 μm to 6 μm, powder Cr ₃ C ₂ having a particle diameter of about ₃ μm to 6 μm, normal hexane (including wax) and normal hexane are sufficiently mixed.
The material of the base is a _Cr 3 _{C 2,} it is contained Co powder more than 40 vol%.

Next, the mixture is sprayed into a drying chamber in which nitrogen as an inert gas is circulated and dried.
The spray dryer used for drying has a rotating disk-shaped atomizer at the upper part of the container, and high-temperature nitrogen is ejected from the periphery in the direction of gravity.
Specifically, the mixture is supplied near the center of the atomizer, and the mixture is sprayed into nitrogen under the influence of centrifugal force.
Immediately after jumping out by this spray, it is thread-like and receives a shearing force from the surrounding gas during the flight.
Also, the liquid tends to become spherical due to surface tension.
A spherical granulated powder can be obtained if the solvent is volatilized when the thread-like mixture is torn off by shearing force and becomes a sphere by surface tension.

And the dried powder fell under the drying chamber of the spray dryer under the influence of gravity, and a spherical granulated powder of about 40 μm could be obtained in the accumulation part installed in the lower part.
By this method, a mixed granulated powder 1 in which Cr ₃ C _{2 that} is a carbide and Co that is a material that hardly forms a carbide was mixed was manufactured.
Then, the mixed granulated powder 1 is compression molded as shown in FIG. 11 to form a green compact.

The powder used to produce the electrode was compressed at a compression pressing pressure of about 50 MPa, and the heating temperature was changed within the range of 400 ° C to 800 ° C. At the time of pressing, a small amount (2% to 3% by weight) of wax was mixed with the powder to be pressed in order to improve the moldability. The wax is removed on heating.
The heating temperature was increased as the amount of Cr ₃ C ₂ was increased, and the temperature was decreased as the amount of Co was increased.
This is because when the amount of Cr ₃ C ₂ is large, the manufactured electrode tends to become brittle and immediately collapses even when heated at a low temperature, whereas when the amount of Co is large, the strength of the electrode is low even when the heating temperature is low. It was because it was easy to become strong.

In the discharge surface treatment, this green compact becomes the discharge electrode. (See Figure 12)
In order to form a coating film on the workpiece surface with this discharge surface treatment apparatus, the electrode and the workpiece are placed opposite to each other in an oil machining fluid, and a pulse is generated between the electrode and the workpiece from the discharge surface treatment power source in the machining fluid. A discharge of the shape is generated, and a coating film of the electrode material is formed on the workpiece surface by the discharge energy, or a coating film of a substance reacted with the electrode material is formed on the workpiece surface by the discharge energy.
The polarity is negative on the electrode side and positive on the workpiece side. As shown in the figure, an arc column of discharge is generated between the electrode and the workpiece.
The discharge pulse used has a waveform as shown in FIG. 8, and the pulse conditions are as follows: peak current value ie = 10 A, discharge duration (discharge pulse width) te = 64 μs, rest time to = 128 μs, 15 mm × 15 mm area The electrode was processed for 15 minutes to form a film.
By forming a film on the workpiece using the above-described discharge surface treatment apparatus, a thick film can be stably formed on the workpiece surface by the pulse discharge treatment in liquid.

When granulated as in this embodiment, due to the high fluidity, the density of the electrodes is made uniform during pressing and the upper surface of the granulated powder in the mold can be made parallel to the pressing surface, so there is no distribution of hardness. An electrode can be manufactured.
And with this uniform hardness electrode, it has become possible to obtain a film having the same performance regardless of where the electrode is treated.
In this embodiment, the test result under one condition is shown as an example of the discharge condition. However, it is needless to say that the same result can be obtained under other conditions although the thickness of the film is different.
This fact applies not only to this embodiment but also to other embodiments of the present invention.
Hard coatings such as Cr ₃ C ₂ are often used to improve wear resistance.
Abrasion resistance is greatly affected by the hardness distribution and roughness of the coating surface.
If there is a distribution of hardness on the surface of the coating, there will be places that are heavily worn and places that are not worn.
Since the film made of the above-mentioned granulated powder is made of the electrode, a film having the same performance can be formed regardless of which part of the electrode is processed, so that a film having wear resistance can be stably produced.

Embodiment 4 FIG.
In the third embodiment described above, discharge surface treatment is performed using mixed granulated powder in which Cr ₃ C ₂ which is a base carbide contains 40% by volume or more of Co powder which is a material that is not easily carbonized or a material that is not carbonized. In this embodiment, the case of using a mixed granulated powder made of a Ti (titanium) powder that is a metal and a Co powder having a particle diameter of about 4 μm to 6 μm will be described.
Even in this embodiment, it is necessary to contain 40% by volume or more of Co powder that is a material that is not easily carbonized or a material that is not carbonized.
This mixed granulated powder is manufactured in the following steps.

Generally, the average particle size of commercially available Ti powder is about 20 μm.
The powder is first pulverized by a vibrating ball mill apparatus made of a ball material ZrO ₂ .
At the time of pulverization, the Ti powder was placed in normal hexane as a solvent and pulverized at a frequency of 1200 cpm for about 250 hours to reduce the average particle size to 1.2 μm.

Wax is mixed with the mixture of Ti powder, normal hexane, and Co powder obtained by pulverization, and mixed using a ball mill.
The mixing is performed at a low speed, and Ti powder, Co powder, and normal hexane (including wax) are sufficiently mixed.

Next, the mixture is sprayed into a drying chamber in which nitrogen as an inert gas is circulated and dried.
For drying, a spherical granulated powder of about 40 μm could be obtained using a spray dryer as in the third embodiment.
Then, the mixed granulated powder is compression-molded as shown in FIG. 11 to form a green compact.
In the discharge surface treatment, this green compact is used as a discharge electrode.

The powder used to produce the electrode was compressed to have a compression pressing pressure of about 50 MPa, and the heating temperature was changed in the range of 400 ° C to 800 ° C.
Ti and Co are both metals, but the difference is that Ti is an active material, and it is very likely to become TiC (titanium carbide), which is a carbide, in the atmosphere of discharge in oil, which is a working fluid. On the other hand, Co is a material that hardly forms carbides.
Ti is a material that easily oxidizes in the atmosphere.
However, by using mixed granulated powder as in this embodiment, an electrode can be manufactured without being oxidized.
Also in the case of manufacturing an electrode by mixing Ti (titanium) powder and Co (cobalt) powder, Co (cobalt) powder as a material which is not easily carbonized or is not carbonized is contained in the electrode in an amount of 40% by volume or more. By using the electrode, a thick film can be stably formed on the workpiece surface by the discharge surface treatment.

Next, in the same manner as in the third embodiment, the content of Ti powder in the electrode is set to 100% by volume of Ti (titanium) powder, that is, the content of Co powder is changed from the case where Co in the electrode is 0% by volume. The results will be described with reference to the results of examining the state of the film forming step by step.
Here, as the Co powder, a powder having a particle size of about 1 μm to 6 μm was used.

When the electrode material was 100% by volume of Ti, the surface of the coating became TiC at various places on the surface of the coating, and the surface of the coating was rough.
However, as the content of Co, which is difficult to carbonize, is increased, a coating with reduced roughness can be formed. When the Co content in the electrode exceeds 40% by volume, a uniform thick film is formed. It turned out to be easier.
It has been found that it is preferable that the Co content in the electrode exceeds 50% by volume because a uniform thick film can be formed.
This result is almost the same as the result shown in the third embodiment.
This is because Ti contained in the electrode becomes TiC which is a carbide in the atmosphere of discharge in oil as a working fluid, and results are similar to mixing carbide from the beginning. Inferred.
In addition, since TiC has a low thermal conductivity, if a large amount of TiC is formed on the film, it was removed by discharge and the surface was rough. However, the incorporation of Co improves the thermal conductivity of the film. However, it became difficult to remove, and it is considered that a uniform film could be formed.

  In this embodiment, the case where Co (cobalt) is used as a material that is difficult to form the carbide constituting the electrode by mixing with Ti (titanium) powder is taken as an example, but the same applies to Ni, Fe, and the like. It is a material from which results can be obtained and is suitable for use in the present invention.

It is a figure which shows the principle of discharge surface treatment. It is a figure which shows an electrode manufacturing process. 3 is a diagram showing granulated powder in Embodiment 1. FIG. 3 is a diagram showing granulated powder in Embodiment 1. FIG. FIG. 3 is a diagram showing a hardness distribution in the first embodiment. It is a figure which shows the deposition condition at the time of performing discharge surface treatment with the electrode in Embodiment 1. FIG. It is a figure which shows an electrode manufacturing process. It is explanatory drawing of the pulse of the discharge in this Embodiment. It is a figure which shows the film deposition condition by the difference in Co content. The cr ₃ C ₂ powder electrode is a diagram illustrating a processing time and a film thickness of relationship when performing the processing. It is a figure which shows an electrode manufacturing process. It is a whole block diagram of a discharge surface treatment apparatus.

Claims (24)

A substance in which a pulsed discharge is generated between a workpiece and a green compact electrode formed by compression molding a metal powder or metal compound powder, and the electrode material or electrode material reacts with the discharge energy on the workpiece surface. Oite the fabrication method of spark surface modification electrode used for discharge surface treatment for forming a coating film made of,
Mixing a wax as a binder into a mixture comprising an electrode material and a solvent;
Drying and granulating the mixture in an inert gas atmosphere;
Forming the green compact electrode using the granulated powder;
A method for manufacturing an electrode for discharge surface treatment, comprising: A substance in which a pulsed discharge is generated between a workpiece and a green compact electrode formed by compression molding a metal powder or metal compound powder, and the electrode material or electrode material reacts with the discharge energy on the workpiece surface. Oite the fabrication method of spark surface modification electrode used for discharge surface treatment for forming a coating film made of,
Pulverizing a predetermined electrode material in a mixed state with a solvent;
Mixing a wax as a binder with the mixture of the electrode material and solvent pulverized in this step;
Drying and granulating the mixture in an inert gas atmosphere;
Forming the green compact electrode using the granulated powder;
A method for manufacturing an electrode for discharge surface treatment, comprising: 3. The discharge surface treatment electrode according to claim 1, wherein the solvent is an alcohol such as ethanol, propanol, or butanol, or an organic solvent such as acetone, toluene, xylene, benzene, or normal hexane. Production method. As the electrode material, Co alloy or Ni alloy, or the fabrication method of spark surface modification electrode according to claim 1 or 2, characterized in that a Fe alloy. The alloy includes Co as a main component, Co alloy including Cr, Ni, and W, Co as a main component, Co alloy including Mo, Cr, and Si, Ni as a main component, Ni alloy including Cr and Fe, 5. An Ni alloy containing Cr, Mo and Ta as a main component, and an Fe alloy containing Cr, Ni, Mo, (Cd + Ta), Ti and Al as a main component. The manufacturing method of the electrode for discharge surface treatment of description. Co alloy includes Mo 28 wt%, Cr 17 wt%, Si 3 wt%, remaining Co (cobalt), or Cr 28 wt%, Ni 5 wt%, W 19 wt%, remaining Co or Cr (chromium) 25 wt%, Ni (nickel) 10 wt%, W 5. The method for producing an electrode for discharge surface treatment according to claim 4, wherein the alloy is made of (tungsten) 7 wt%, C (carbon) 0.5 wt%, and the remaining Co. The method for producing an electrode for discharge surface treatment according to any one of claims 4 to 6, wherein the alloy material powder is mixed with a metal material which does not form or hardly forms carbides. The method for manufacturing an electrode for discharge surface treatment according to claim 7, wherein the metal material that does not form or hardly forms carbide includes 40% by volume or more. The method for producing an electrode for discharge surface treatment according to claim 1 or 2, wherein an easily oxidized metal such as Cr, Al or Ti is used as the electrode material. 3. The method for producing an electrode for discharge surface treatment according to claim 1, wherein the electrode material contains 40% by volume or more of a metal material that does not form or hardly forms carbide. 4. The method for manufacturing an electrode for discharge surface treatment according to claim 8 or 10, wherein the metal material that does not form carbide or hardly forms carbide is Co, Ni, or Fe. The method for producing an electrode for discharge surface treatment according to any one of claims 1 to 11, wherein the pulverization is refined to an average particle diameter of 3 µm or less. The method for producing an electrode for discharge surface treatment according to any one of claims 1 to 12, wherein the average particle diameter of the electrode material granulated by the granulation step is 10 µm to 200 µm. A substance in which a pulsed discharge is generated between a workpiece and a green compact electrode formed by compression molding a metal powder or metal compound powder, and the electrode material or electrode material reacts with the discharge energy on the workpiece surface. Oite the electrode for discharge surface treatment used for discharge surface treatment for forming a coating film made of,
An electrode for discharge surface treatment, comprising: mixing an electrode powder, a solvent, and a wax; drying and granulating the mixture in an inert gas atmosphere; and molding the granulated powder. As the electrode material, Co alloys or Ni alloys, or spark surface modification electrode according to claim 14, characterized by using a Fe alloy. The alloy includes Co as a main component, Co alloy including Cr, Ni, and W, Co as a main component, Co alloy including Mo, Cr, and Si, Ni as a main component, Ni alloy including Cr and Fe, The Ni alloy containing Cr, Mo and Ta as a main component, and the Fe alloy containing Cr, Ni, Mo, (Cd + Ta), Ti and Al as a main component. The electrode for discharge surface treatment as described. Co alloy includes Mo 28 wt%, Cr 17 wt%, Si 3 wt%, remaining Co (cobalt), or Cr 28 wt%, Ni 5 wt%, W 19 wt%, remaining Co or Cr (chromium) 25 wt%, Ni (nickel) 10 wt%, W The electrode for discharge surface treatment according to claim 16, which is an alloy composed of (tungsten) 7 wt%, C (carbon) 0.5 wt%, and the remaining Co. The electrode for discharge surface treatment according to any one of claims 15 to 17, wherein the alloy material powder is mixed with a metal material which does not form or hardly forms carbides. 19. The method for producing an electrode for discharge surface treatment according to claim 18, wherein the metal material which does not form or hardly forms carbide includes 40% by volume or more. The electrode for discharge surface treatment according to claim 14, wherein an easily oxidized metal such as Cr, Al, Ti or the like is used as an electrode material. The electrode for discharge surface treatment according to claim 14, wherein the electrode material contains 40% by volume or more of a metal material that does not form or hardly forms carbide. The method for manufacturing an electrode for discharge surface treatment according to claim 19 or 21, wherein the metal material that does not form carbide or hardly forms carbide is Co, Ni, or Fe. The electrode for discharge surface treatment according to any one of claims 14 to 23, wherein the electrode powder has a scaly shape. 24. The discharge surface treatment electrode according to claim 14, wherein the granulated electrode material has an average particle diameter of 10 to 200 [mu] m.

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