JPH09192937A - Surface treating method by submerged electric discharge - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a deposited layer having strong adhesive force on the front surface of an iron steel, a cemented alloy, or the like by using a material in which the powder containing metal halide compound powder is formed as a discharge electrode, and generating electric discharge between the electrode and a work piece in liquid in which carbon exists. SOLUTION: A submerged electric discharge deposited front surface by a TiH2 powder electrode is composed of Ti and TiC and bonded to a cemented alloy front surface of a base material without containing any oxide. In the reaction with the base material surface in electric discharge, since the temperature of the cemented front surface instantaneously reaches the boiling point of the material, the deposited Ti and TiC can be diffused and fused to the base material side. The component composition from the boundary surface to the base material to the front surface of the deposited layer is Ti and TiC, and the boundary surface and the front surface are bonded without containing any oxide. This Ti component of the topmost front surface part of the deposited layer is oxidized in the air into TiO2 , however, the inside is Ti with activity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for depositing and coating a material having extremely high wear resistance or corrosion resistance on a metal material or a conductive ceramic material on the basis of a high degree of adhesion. The present invention relates to a surface treatment technology that gives the above-mentioned characteristics excellent to tools or machine parts.

[0002]

2. Description of the Related Art A technique for depositing and coating the surface of a metal material or the like by in-liquid discharge to provide corrosion resistance and wear resistance has already been patented and publicly known by us.
The outline of those known technologies is as follows. (1) The WC and Co powders are mixed and compression-molded in an electrode to perform in-liquid discharge. In this method, once the deposition processing is performed, another electrode (for example, a copper electrode or a graphite electrode) is used to perform remelting electric discharge processing to obtain higher hardness and high adhesion. (2) High-temperature chemical reaction occurs with carbon generated by thermal decomposition of the working fluid such as titanium (hereinafter Ti), and Ti is TiC.
(Titanium carbide), which is an extremely high-hardness substance, is a discharge surface treatment method in liquid for deposition coating. At this time, a metal that can serve as a binder, such as Co (cobalt), is added to the compression molding material.

The prior art will be described below with reference to FIG. Using the mixed powder compact electrode of WC-Co (tungsten carbide-cobalt), the material to be treated (base material S5
0C) is subjected to electric discharge machining in a liquid to be deposited (primary machining). Next, remelting processing (secondary processing) is performed using an electrode that does not wear so much, such as a copper electrode. In the as-deposited primary processing, the hardness of the structure was about Hv = 1410, and there were many cavities, but the remelting processing of the secondary processing eliminated the cavities in the coating layer, and the hardness also improved to Hv = 1750. ing. (Fig. 2)

These methods deposit well on steel materials on the basis of a high degree of adhesion, and have the same composition of WC + Co or TiC.
The hardness is about 50% higher than that of + Co sintered cemented carbide. For example, the hardness of a normal cemented carbide tool of WC70 and Co30 is Hv = 850 to 950, but on the surface of the cemented carbide of the same composition as the electric discharge machined, Hv = 1710 after the completion of secondary machining.

However, according to the conventional method, it is difficult to form a coating layer having a strong adhesive force on the surface of a sintered material such as a cemented carbide bite, and the adhesion strength of the coating layer is also increased. There are large variations.

The reason why the prior art often deposits a coating layer on the surface of steel, but the coating layer cannot be firmly deposited on the surface of cemented carbide will be described. These phenomena will be described here for Ti, since deposited coatings with Ti and mixtures thereof are the main subject of this invention.

Ti has a melting point of 1800 ° C. and a boiling point of 300.
It is a metal of 0 ° C or higher. In the air at room temperature,
It is chemically stable because it is covered with a thin and dense oxide film (Ti-O ₂ ). This is similar to aluminum covered with a dense oxide film Al ₂ O ₃ . So Ti
The following phenomenon occurs when this powder is compression-molded and used as an electric discharge machining electrode (hereinafter referred to as a green compact electrode). When electric discharge occurs between the electrode surface and the surface to be treated, the discharge point becomes the boiling point of the material, and at the same time, the working fluid (in this case, mineral oil) causes vaporization pyrolysis explosion, and The substance disperses. The scattered substances impinge on the surface to be processed of the work piece of the opposite electrode, and about 50% of them are usually deposited.

Although Ti forms a thin oxide film in air, electric discharge occurs. The reason for this is that this oxide film is very thin and easily causes dielectric breakdown. Electric discharge occurs due to dielectric breakdown. If the voltage is increased or the distance between the electrodes is shortened, the potential gradient (V / cm) generated between the electrodes is increased, and the electric discharge is caused to cause electric discharge. Is. This can be understood from the fact that the high-voltage power transmission line causes corona discharge, or tunnel current flows in the case of a thin oxide film. However, in order to increase the potential gradient in this way, if the distance between the electrodes is reduced, a discharge occurs and the molten metal rises due to the discharge pressure, and the electrode is separated from the other electrode before it is separated from the electrode matrix or the object matrix. If it comes into contact with a contact, a discharge stop state called a short circuit between electrodes occurs. In short, an unstable phenomenon of electric discharge machining can occur.
We have already experienced that the electric discharge machining of the Ti electrode and the Ti powder compact electrode is unstable.

During the process of this Ti bombardment and during the time it accumulates on the surface to be treated and the surface is covered by the next bombardment, the carbon produced by the decomposition of the processing oil and the high-temperature titanium chemically react. Occurs, and part of it becomes TiC. In this case, if the material to be treated is likely to form an alloy with Ti, such as steel, and the melting point is relatively lower than that of cemented carbide (for example, in steel, the melting point is 1560 ° C. and the boiling point is 2500 ° C.) When it collides, it often melts into the base material or is deposited by adhering to it.

If the electrode polarity and discharge electric conditions are changed by the same electrode or another electrode with respect to the once-deposited material and the secondary processing is performed, the cavities generated by the first deposition are crushed by remelting, and the density of As described in the previous application, high deposition coating can be achieved.
Just in case, the layer deposited at the beginning in Figure 2 (primary processing)
And the micrograph of the structure by secondary processing are shown.

However, the material to be treated is cemented carbide (WC +
For Co, WC + Co + TiC sintered alloys), etc.,
If the above Ti powder is compression molded, even if it is deposited, it is very easy to peel off and hardly deposits. To understand this, it is better to infer from the welding phenomenon of metallic materials. Steel can be arc welded. Arc welding is impossible for cemented carbide alloy comrades. Also, arc welding of cemented carbide and steel is impossible. However, even in the arc welding of steel, if the material surface is oxidized, the welding cannot be performed. Therefore, it is common knowledge to use an anti-oxidation flux for the welding rod and the welding wire. Further, even in the case of aluminum, which has a low melting point, arc welding is difficult in a normal state. The reason is that a dense film of thin aluminum oxide is constantly generated and covered on the surface of aluminum in the air, and it is possible to weld by breaking it with something like ultrasonic vibration. It has been known.

From the above welding phenomenon, the reason why the powder compact electrode of Ti does not deposit even on the surface of the cemented carbide by impact will be explained. The surface of Ti powder is a thin oxide film (TiO
_Since it is covered with ₂ ), it is considered that this hinders the bond between the deposited layer and the base metal. That is, the smaller the particle size of the Ti powder, the larger the surface area ratio relative to the volume, and therefore the larger the ratio of the oxide powder to the surface. This is similar to the case where the oxidized surface in welding or the amount of attached oxide is significantly increased. This is shown below.

The ratio between the surface area and the volume of the granules will be calculated. (1) the volume of the case where the particle body is assumed to be a sphere surface area S = π · d ² grain body ^{V = π · d 3/6} ( where d is the diameter of the granules) surface area to volume ratio S / V = 6 / d (2) Assuming that the particles are cubes Surface area S = 6 · d ² Volume of particles V = d ³ (where d is the length of one side) Ratio of surface area to volume S / V = 6 / D From the above consideration, it can be seen that the smaller the granules, the greater the surface area ratio. From this, when the surface is densely covered with an oxide film or the like, the smaller the particles, the more affected by the oxide film. It is also considered that the high melting point of cemented carbide makes welding and joining difficult. This is because if the melting point is high, it becomes difficult for the weld fusion portion to flow. On the other hand, in steel, the weld fusion portion is likely to flow.

Considering that the surface oxide layer inhibits fusion due to deposition, the effect of oxides on the compression-molded powder is large, and the smaller the particle size, the greater the effect. Compared with this, since the solid Ti metal titanium electrode occupies a small proportion on the surface of the oxide layer, coating with the metal Ti electrode is not efficient but is possible. Ti solid electrodes deposit fairly well. Further, a Ti electrode or the like that is sintered or pre-sintered in a vacuum furnace or the like is also deposited quite well. However, Ti solid electrode is also Ti
The amount of deposition (thickness) of the sintered electrode is also small, and the adhesion is
It does not reach iH ₂ . That is, the inhibiting factor of the oxide is
It is thought that it remains.

[0015]

As is clear from the above description, in the conventional surface treatment method using electric discharge machining, in the case of an electrode in which powder of Ti or the like is compression-molded, the surface is closely covered. The presence of the oxide film (TiO ₂ ) prevents the powder metal that composes the electrode from depositing on the surface to be processed or fusing with the mating metal even if oxygen is separated during discharge. Conceivable. Furthermore, since the thermal decomposition temperature of TiO ₂ is extremely high (1800 ° C.), when the electrode body scatters due to the discharge pressure, the TiO ₂ remains as it is and is often impinged on the surface to be treated. Not only that, but because the gap between the discharges is narrowed (since discharges are less likely to occur due to the oxide film), short-circuiting during machining increases, which deteriorates the machining surface and hinders machining efficiency. It is believed that

The present invention has been made in order to solve the above-mentioned problems, and even for a sintered cemented carbide or the like,
It accumulates well, its adhesion is strong, and
It is intended to provide a surface treatment method by electric discharge machining, in which a short circuit hardly occurs in machining, the machining efficiency is high, and the finished surface roughness is also beautiful.

[0017]

According to a first aspect of the present invention, there is provided a surface treatment method by submerged discharge, wherein a powder containing a metal hydrogen compound powder is molded as a discharge electrode, and the above electrode is used in a liquid containing carbon. A discharge is generated between the workpiece and the workpiece to form a surface layer containing the compound of the metal on the surface of the workpiece.

In the surface treatment method by submerged discharge of the second invention, a powder obtained by molding a powder containing a metal hydrogen compound powder is used as a discharge electrode, and in a liquid in which a polymer material which thermally decomposes to generate carbon exists. Then, a discharge is generated between the electrode and the workpiece to form a surface layer containing the compound of the metal on the surface of the workpiece.

The surface treatment method by submerged discharge of the third invention is the method according to the first invention or the second invention,
A transition metal is used as the metal contained in the electrode as a hydrogen compound.

In the surface treatment method by submerged discharge of the fourth aspect of the present invention, a metal hydrogen compound powder is mixed with another metal, a carbide, a nitride or a boride powder to be molded and used as an electrode for submerged discharge. A discharge is generated between the electrode and the workpiece in a liquid containing carbon to form a surface layer containing a high hardness compound on the surface of the workpiece.

In the surface treatment method by submerged discharge of the fifth invention, a powder obtained by mixing powder of a metal hydrogen compound with powder of another metal, carbide, nitride or boride is used as an electrode for submerged discharge. In order to form a surface layer containing a high hardness compound on the surface of the workpiece by causing an electric discharge between the electrode and the workpiece in a liquid containing a polymer material that thermally decomposes to generate carbon. It was done.

A surface treatment method by submerged discharge according to a sixth aspect of the invention is the method according to the second aspect or the fifth aspect,
A mineral oil or vegetable oil is used as the polymer material that thermally decomposes to generate carbon.

A surface treatment method by submerged discharge of a seventh invention is the method according to any one of the first to sixth inventions, wherein one or more powders of zircon, vanadium, niobium, tantalum or the like are added to the electrode material. This is molded and used as an electrode, and an electric discharge is generated between the electrode and the work to form a high toughness surface layer on the surface of the work.

The surface treatment method by submerged electric discharge of the eighth invention is the method according to any one of the first to seventh inventions, in which a metal powder of the same kind as that of the workpiece is added and used as an electrode. Electric discharge is generated between the electrode and the workpiece to improve the surface properties of the workpiece.

In the surface treatment method by submerged electric discharge of the ninth invention, after the surface layer is formed on the surface of the workpiece by any one of the first to seventh inventions, the secondary processing is performed by using the non-consumable electrode. It is carried out to improve the physical properties of the surface layer.

According to a tenth aspect of the present invention, there is provided a surface treatment method by submerged discharge in which the non-consumable electrode is made of graphite, copper, tungsten, silver tungsten, copper tungsten, or tungsten carbide. Is.

An eleventh aspect of the present invention is the surface treatment method by submerged electric discharge according to any one of the first to tenth aspects, wherein a non-ferrous metal is used as the work piece.

A surface treatment method by submerged discharge according to the twelfth invention is the method according to any one of the first to tenth inventions, wherein a superalloy is used for the work piece.

[0029]

BEST MODE FOR CARRYING OUT THE INVENTION

First Embodiment of the Invention The characteristic effects of using TiH ₂ as a compression-molded electrode will be described.
Hydrogen starts desorbing from TiH _{2 at} a temperature of 300 ° C. or higher. It is considered that the surface at the discharge point is at the boiling point of the material during the time from the start to the end of discharge (usually 0.1 μs to 1000 μs), so TiH ₂ is completely decomposed. At that time, Ti and decomposed hydrogen exhibit a very strong chemical reaction. That is, a hydride such as TiH ₂ is an unstable compound and causes a highly active reaction even if common knowledge of chemical changes is taken. That is, when nascent hydrogen hits the surface to be treated, an oxide film or the like existing on the surface (the surface of cemented carbide, steel, etc., whether dense or not, has oxides etc.) Has the action of removing (cleaning).

Ti does not contain any oxide,
Since it hits the surface to be treated while maintaining its activity, it can be deposited with high adhesion. Moreover, since TiH ₂ is essentially a brittle substance, it is refined by the occurrence of electric discharge,
It is considered that the particle size becomes smaller than the original particle size of H ₂ . Therefore, when processed under the same electrical conditions, a better finished surface roughness can be obtained than with the conventional WC-Co green compact. Conventionally, 6 to 12 μmRmax has been obtained as compared with 30 to 40 μmRmax.

Moreover, the initial state of the surface to be treated is the metallic material to be treated which has been cleaned with nascent hydrogen.
Once the treated part goes around the surface and is coated with Ti or TiC, the next step is Ti or Ti.
It becomes the surface of C (due to the combination with carbon by oil decomposition), but it means that there are no particles covered with Ti such as TiO ₂ as in the conventional case. Therefore, the subsequent coating is also a deposited layer with extremely high adhesion. For this reason, it has been found that it exhibits extremely high adhesion even to cemented carbide, and also exhibits epoch-making wear resistance that has not been obtained in the past even in the wear test.

Although it is impossible to weld cemented carbide by ordinary arc welding, in electric discharge machining, the electric discharge point reaches the boiling point of the material, and moreover, the energy density is several hundreds compared to arc welding. Since it is twice as high, it is considered that it adheres if it is cleaned as described above.

[0033]

【Example】

Embodiment 1 FIG. A powder of TiH _{2 having} a particle size of 10 μs or less is compression-molded under the following conditions. Diameter: 15 mm, load: 11.4 tons (about 6500 kg / cm
² ), thickness: about 5 mm This is bonded to a copper rod with a conductive adhesive and used as an electric discharge machining electrode. Processing is based on primary processing only. The material to be treated and cemented carbide (WC + TiC + Co: GTi30 Mitsubishi Material) were subjected to electrical discharge machining under the following conditions to form a deposited layer on the surface. (1) Machining condition, hardness, finished surface roughness, wear test result 1) Machining condition: discharge current Ip = 3.5 A, pulse width τp = 32 μs, machining time = 2 minutes, powder compact electrode polarity (−) 2 ) Hardness, surface roughness: Vickers hardness Hv = 600 to 900 (measurement pressure 10
g), Deposition layer thickness 13μm, Finished surface roughness 10μm R _Z 3) Wear test (Okoshi type pin disk method) Results: Atmosphere, pin shape φ7.98mm (0.5c
m ² ) Pressing force 0.5 Kgf, pressing pressure 1 Kgf / cm ² friction speed 1 m / s, disk material SKH-3, wear amount 0 mg was obtained in 25 km of wear test run.

For comparison of the wear test results, the wear amount of the cemented carbide material is shown below. Abrasion amount of cemented carbide (GTi30) whose surface is ground: 2.1 mg Discharge coating surface with titanium metal electrode: 0.7 to 1.5 mg TiN + Ti ₂ N (film thickness 2 μm) Ion mixing surface: 1.5 mg ( Note) (It is considered that the resolution of wear measurement is 0.1 mg.) The above results are shown in Fig. 3. Hardness Hv = 6 obtained here
Although 0 to 900 is only a hardened steel or a tempered steel, its wear resistance is extremely high. Although the hardness of the cemented carbide of the base material is as high as Hv = 1500 to 1800,
Cemented carbides whose surface has just been ground will wear as much as 2.1 mg, as the above results show.

(2) Consideration for remarkable improvement in wear resistance 1) Since the wear resistance is high despite the low hardness, no clear analysis has been made so far. However, the inventors think as follows. The surface of the in-liquid discharge deposition by the TiH ₂ powder electrode is Ti
And TiC, and is in close contact with the surface of the cemented carbide of the base material without containing any oxide. The reaction with the surface of the base material at the time of discharge can instantaneously reach the boiling point of the material on the cemented carbide surface, so that the deposited Ti and TiC can diffuse and fuse to the base material side to some extent. From the interface with the base material to the surface of the deposited layer (in this case, about 13 μm)
The composition of is also Ti and TiC, and they are in close contact without containing any oxide. This Ti component is oxidized in the air at the uppermost surface portion of the deposited layer to become TiO ₂ , but the inside remains as active Ti.

Therefore, when a wear test is carried out, when the uppermost surface portion is worn and removed when it comes into contact with the disk material (SK-3), the disk material is fused and removed to the Ti deposition layer side, and the surface to be treated is removed. It is thought that they will be attached to and transferred to. Since TiC originally exists on the surface to be treated, it is considered that the disk material (SK-3) having the slightly soft Ti surface adhered and transferred protects it.

2) In consideration of the above, it is necessary to state the adhesiveness of the electroplating surface and the logical difference from the decomposed hydrogen of the working fluid due to electric discharge. Electroplating also deposits plated metal on the cathode. In that case, the cathode surface should be cleaned by hydrogen in the nascent stage due to the decomposition of the plating aqueous solution, but the adhesion of the plating is not high.
Rather, it is known that hydrogen embrittlement makes the base material and the plating surface brittle. This may be because the surface of the plating may be cleaned by plating, but the plating metal cannot be fused and diffused into the base material because it is not at high temperature and high pressure.

3) Further, when the processing oil is decomposed by electric discharge machining, it is divided into carbon and hydrogen, and a large amount of carbon is deposited on the anode side, so that hydrogen is bombarded on the cathode for cleaning. That is to say. This effect cannot be ignored. It is true that when a WC + Co green compact is deposited on the surface of steel, a deposited layer with extremely high adhesion is obtained. However, even if it was attempted to be deposited on the surface of the cemented carbide, high adhesion could not be obtained. In addition, even if an attempt was made to deposit on a steel material by simply using a titanium powder compact electrode, it was not possible to find a condition for good deposition.
From such experimental results, it was impossible to deposit hydrogen on the cemented carbide with hydrogen decomposed by in-liquid discharge,
It is considered that even though the surface is covered with an oxide film like titanium powder, the reducing action is impossible.

Embodiment 2 FIG. Next, the experimental results using the TiH ₂ green compact electrode when changing the electrical discharge conditions are shown. Processing is based on primary processing only. (1) When the electrode polarity is changed The powder compacting conditions for TiH ₂ are the same as in Example 1) 1) Powder compact electrode polarity (−) Discharge current Ip = 10 A, pulse width τp = 32 μs Processing time = 5 minutes When the hardness of the surface to be treated Hv = 670-900 (measurement pressure 10
g) 2) Polarity of green compact electrode (+) Same as above Electrical hardness Hardness of treated surface Hv = 1450 to 1550 (measurement pressure 1
0g) From the above 1) and 2), hardness changes depending on the polarity.

(2) When the discharge current is increased and the pulse width is made extremely small: discharge current Ip = 45 A, pulse width τp = 0.5 μs, processing time = 2 minutes, powder compact electrode polarity (−) surface to be treated Hardness Hv = 2000-3000 (measurement pressure 1
0g) Hardness of treated surface Hv = 1300-2000 (measurement pressure 5
0g) Deposition thickness 2μm, Finished surface roughness 6μm Rz The hardness is large when the measured load is small, and it becomes a little soft when the load is large, which means that the surface is hard and the inside tends to be a little soft. This means that it forms a slope. This is said to be strong against thermal expansion and impact in practical use.

(3) From the results of (1) and (2) above, the surface was made extremely hard and softened as it entered the inside.
As a means for significantly increasing the inclination, first, the above (1)
There is a processing step under the condition 1) and then the condition 2). Alternatively, there is a method of changing the electrode polarity to (+) (-).

Embodiment 3 FIG. The experimental result of the electric discharge surface treatment to the steel material by the powder compact electrode of TiH ₂ is shown. (1) Using a TiH ₂ powder compact electrode, a steel material (SK-3) was subjected to electric discharge surface treatment (primary processing only) under the same conditions as in Example 1. Discharge current Ip = 3.5 A, pulse width τp = 32 μs Processing time = 5 minutes Hardness Hv of the surface to be treated Hv = 900 to 1000 (measurement pressure 10
g) Deposition thickness 47 μm, wear amount 0 mg as a result of wear test (2) Example 3 above. Under the conditions of (1) of No.
3) shows the results of secondary processing using a graphite electrode after the processing. Secondary processing conditions are discharge current Ip = 3.5A, pulse width τp = 4 μs, processing time = 5 minutes, polarity of graphite electrode (−), hardness of surface to be processed Hv = 1600 to 1750. It can be seen that the hardness has increased remarkably. The hardness of the copper electrode subjected to the secondary processing similarly increased.

The reason for this is that in the state where new Ti or TiC is not deposited by the secondary processing, C generated by decomposition of the processing oil is combined with residual Ti in the coating layer to form Ti in the coating layer.
This is because the proportion of C increases.

Embodiment 2 of the Invention An example using a powder compact electrode in which TiH ₂ is mixed with another metal, carbide, nitride, or boride will be shown. In order to further expand the above-mentioned excellent properties of TiH ₂ , (1) a metal that can become a carbide by a discharge in liquid (eg, T
a, Nb, V, Zr) (2) Carbide (Example: TiC, TaC, NbC, VC, B
C, B ₄ C) (3) Nitride (Example: TiN, hBN, CBN) (4) Boride (Example: TiB ₂ , boric acid H ₂ BO ₃ , borax Na ₂ B ₄ O ₇ · 10H ₂ O) (5) Many experiments were carried out in which yttria (Y ₂ O ₃ ) was mixed with TiH ₂ to form a powder compact electrode. As a typical example among them, a mixture of TiB ₂
A mixture of TiN and a mixture of TiB ₂ and TiN are shown.

Even when only the primary processing is performed, the hardness is higher than that of the cemented carbide, but when the secondary processing is performed with a graphite electrode or the like (electrodes such as copper and tungsten may be used), the hardness is further improved and the surface is diamond. 1/2 (Hv5 equivalent to CBN
000) or more), and it has been found that it has an inclination that the inside becomes soft.

Embodiment 4 FIG. Electrode material: TiH ₂ + TiB ₂ (7: 3 weight ratio) 1) The pressing conditions of the green compact are the same as in Example 1, and only the primary processing is performed Electrical conditions: Ip = 5.5A, τp = When 32 μs and processing time = 5 minutes, hardness: Hv = 1850 to 2500 (load 10 g), thickness: 24 to 28 μm and hardness: Hv = 1650 to 2500 (load 50 g) were obtained. As a result of performing a wear test on this in the same manner as in Example 1, the amount of wear on the treated surface was 0 mg. Further, the rake surface and the front flank of the carbide tool (Mitsubishi Material UTi20) were each subjected to the above-mentioned discharge treatment for 2 minutes, and a cutting test by a lathe was performed to examine the adaptability to a cutting tool. As a result, under the following cutting conditions, the life was 1.9 times longer than that of the case where no discharge treatment was performed.

Electrical conditions: Ip = 8A, τp = 8μ
s, machining time = 5 minutes, the life was 2.8 times longer than that of the case where no electric discharge treatment was performed under the following cutting conditions. Cutting conditions: Work material S45C, Depth of cut 0.5 mm, Feed 0.3 mm / rev, Cutting speed 160 m / min Dry cutting Life judgment: Wear width of front flank at cutting distance 7 km (generally indicated as VB)

2) After the above-mentioned primary processing, the graphite electrode was processed for 5 minutes under the following electrical conditions: Electrical conditions: Ip = 3.5 A, τp = 4 μs, processing time =
5 minutes Hardness: Hv = 2100 to 5100 (load 10g), green compact electrode (-) Hv = 1500 to 3000 (load 50g), thickness 32 to
36 μm hardness Hv = 5000 is 100 for diamond
It is second only to 00 and equal to 5000 of CBN. In this case as well, the surface is extremely hard and shows a gradient hardness distribution that gradually becomes softer as it enters the inside, and is extremely useful because it has both surface hardness and toughness.

Embodiment 5 FIG. Electrode material: TiH ₂ + TiN (7: 3 weight ratio) 1) Primary processing conditions: Electric conditions: Ip = 5.5 A, τp = 32 μs, processing time = 5 minutes Hardness: Hv = 1050 to 1800 (load 10 g), electrode (-) when the primary processing only, but not as TiB ₂ mixed which has high hardness next to when mixed with TiB _2. 2) After the above-mentioned primary processing, the hardness when the secondary processing is performed with the graphite electrode is about Hv = 1700 to 2300.

Embodiment 6 FIG. Electrode material: TiH ₂ + TiB ₂ + TiN (2: 1: 1) 1) Hardness by primary processing only Processing conditions are the same as in Example 1 Processing time = 5 minutes Hardness Hv = 2000 to 2300 (load 10 g) Thickness 12 -18 μm 2) When the secondary processing is performed with a graphite electrode Processing conditions are the same as in Example 1 Processing time = 5 minutes Hardness Hv = 2550-6050 (load 10 g) Thickness 14-18 μm Measured load is high and 50 gr Then, since Hv is reduced to about 1800, it is clear that this also has a gradient.

Third Embodiment of the Invention The above-described embodiments are intended to improve wear resistance. In the primary processing of the TiH ₂ green compact, it is considered that the adhesion is remarkably strong even if the hardness is not so high, but the result is that the abrasion resistance is high. Further, when TiB ₂ or the like is added, the hardness is high and the wear resistance is high. When the hardness is too high and brittle fracture is likely, it is effective to add Nb, Ta, NbC, TaC or the like in order to impart toughness. (This is the knowledge known to carbide tools)

Ta, Nb and V were added to TiH ₂ in an amount of about 10%, and the processing was carried out under the same conditions as in Example 1. The results are Ta, N
Although the hardness does not increase to Hv = 600 to 700 for b and 900 for V, the toughness is considered to be improved because the surface is less likely to be chipped even when hit with a hammer or the like. The thickness is 10 to 20 μm after being processed for 5 minutes, and is deposited in a stable processed state.

Nb, TaC, VC, etc. are also effective in cutting tools for improving toughness against interrupted cutting, so in this experiment, addition was made at a weight ratio of about 10%. As a result, Hv = 900 to 1050, which is not so high, but after 5 minutes processing, 20 μm or more and 30 μm
It is deposited in a stable state with a certain thickness and is tough against impacts.

Fourth Embodiment of the Invention As mentioned above, T
It has been clarified that a surface deposited layer having a higher hardness can be obtained by adding iB ₂ alone or TiB ₂ or TiN based on iH ₂ . The reason why TiH ₂ adheres to the material to be treated is, as described above in the section of the embodiment of the invention, that the decomposed Ti is caused by the reducing action of the deposited surface by nascent hydrogen ions generated when the hydride is decomposed. This is because it is extremely activated. It is also considered that the effective contact area with the base material increases because Ti becomes finer when electric discharge occurs. Further, since the fine structure of Ti makes the deposited structure finer, the finished surface roughness tends to be fine.

Extending this principle, metal hydrides can be used for surface treatment. The hydrides considered to be usable for the surface treatment are as follows. ZrH ₂ , VH, VH ₂ , NbH, TaH, FeTi
_{H 2, LaNi 5 H 6,} TiMnH 2, NaBH 4 among this describes ZrH ₂ as Example 6 so experiments were conducted as an example. Zr has excellent heat resistance and corrosion resistance,
It is also used in nuclear reactors as a thermal neutron moderator. Used for cutting tools, bearings, heat engine heat resistant wear parts, pump parts, etc.

Example 7. ZrH ₂ powder was made into a green compact under the same conditions as in Example 1 (compressing pressure 6,500 kg / cm ² ),
For steel SK-3, Ip = 5.5 A, τp = 32 μs
Processed in, and deposits well in an extremely stable processing state. Although the thickness is 8 to 10 μm and the hardness Hv is 660 to 690 after processing for 5 minutes and the hardness is not so high, this alone shows high wear resistance. When high hardness is required, the hardness is increased by performing secondary processing with a graphite electrode or the like. 2
The electrical conditions for the next processing are Ip = 3.5A, τp
= 4 μs, hardness Hv = due to the graphite electrode (-)
1350-2000-2350 are obtained.

Fifth Embodiment of the Invention . The surface of aluminum, zinc, or steel (particularly mild steel) does not need to be so high in hardness, but a surface having high wear resistance may be required. For example, in the case of aluminum, the wear resistant part of the aluminum engine, in the case of zinc, the mold made of zinc, the surface of machine parts made of mild steel is not so hard, and you want to add wear resistance. There is. In such a case, when TiH ₂ powder and metal powder requiring surface treatment are mixed and used, a surface coating having high adhesion and hardness higher than that of the base material is formed. As a specific example, an example of a powder compact electrode of TiH ₂ + Al on aluminum will be described.

Embodiment 8 FIG. An aluminum die casting material containing 11% of the material to be treated, a powder electrode having a weight ratio of TiH ₂ to Al of 3: 7 is used. Current Ip = 5 A, τp = 32 μs
When the hardness is about Hv = 400 to 600, the hardness reaches about Hv = 1400 at the surface layer when Ip = 20 A and τp = 260 μs. Similar results are obtained by treating zinc with this electrode composition.

Sixth Embodiment of the Invention Some non-ferrous metals are called superalloys (superalloys), and this material is also subject to discharge surface treatment technology. That is, Ti and 6% A
The material of 14% V has a tensile strength of about 100 kg / mm ² and a Vickers hardness Hv of about 260. Surface treatment was performed with a ZrH ₂ powder compact electrode, and the area was 1.7 cm ^2.
Process with Ip = 5.5A, τp = 32μs,
The hardness Hv = 660 to 690 and the thickness 10 μm are obtained.
Hv = 135 when secondary processing is performed with a graphite electrode.
About 0 to 2000 is obtained. This processing is Ni-A
The same result was obtained by discharge coating the 1-Ti-Nb-Ta alloy.

In the present invention as described above, the material to be treated (the substance that generates an electric discharge facing the electrode) is steel or special steel,
Cemented carbide, cermet, aluminum and its alloys, zinc and its alloys, copper and copper alloys, and super heat-resistant alloys (also called superalloys) containing Ni, Co, etc. as the main components are targeted. So-called non-ferrous materials and non-ferrous alloys are also applicable.

[0061]

As described above, Ti, Zr, V, Nb, T
forming a metal such as a or a hydride as a green compact,
By performing in-liquid discharge, it is possible to form a deposition layer having a thickness of several μm to several tens of μm, which has a strong adhesive force, on the surface of steel, cemented carbide or the like. This deposited layer has extremely good wear resistance. In addition, the finished surface roughness is better than that of the other example (WC + Co) performed under the same electrical conditions, and is 1/2 to 1/3.
It becomes the roughness of. In addition, in order to increase hardness in the above hydride, TiB ₂ , TiN, TiC, TaC,
The hardness can be further increased by mixing NbC, VC and the like. The toughness is improved by adding Ta, Nb, and V metals to the green compact component. When secondary processing is performed with a graphite electrode or a copper electrode, the hardness increases from 50% or more to about twice.

[Brief description of the drawings]

FIG. 1 is an example of a green compact of a mixture of WC + Co used as an electrode.
It is a figure which shows the principle which performs secondary processing and secondary processing.

FIG. 2 is a micrograph of a cross section of a treatment layer of a material to be treated after primary processing and secondary processing when a green compact is used for an electrode.

FIG. 3 is a diagram showing a comparison of wear test results.

[Explanation of symbols]

 1 electrode, 2 base materials

 ─────────────────────────────────────────────────── --- Continuation of the front page (72) Inventor Nagao Saito 12-12, 9-12 Iwanaridai, Kasugai City, Aichi Prefecture (72) Inventor Naotake Mohri 661-51 Yakuji Ishizaka, Tenpaku-ku, Nagoya (72) Inventor Hirohisa Sunada Sanyoso, Mizuho-ku, Nagoya City, 3-44, Sanmeiso 10 (72) Inventor Takuji Maji 2-3-3, Marunouchi, Chiyoda-ku, Tokyo Sanryo Electric Co., Ltd. (72) Akihiro Goto Marunouchi, Chiyoda-ku, Tokyo 2-3-2 Sanryo Electric Co., Ltd.

Claims (12)

[Claims] 1. A powder obtained by molding a powder containing a metal hydrogen compound powder is used as a discharge electrode, and an electric discharge is generated between the electrode and a workpiece in a liquid containing carbon to form a discharge on the surface of the workpiece. A surface treatment method by in-liquid discharge, which comprises forming a surface layer containing the compound of the above metal. 2. Electric discharge is generated between the electrode and a workpiece in a liquid containing a polymer material which is thermally decomposed to generate carbon, by using a powder formed of a powder containing a metal hydrogen compound powder as an electric discharge electrode. And forming a surface layer containing the compound of the metal on the surface of the object to be processed. 3. The surface treatment method by submerged discharge according to claim 1 or 2, wherein the metal contained in the electrode as a hydrogen compound is a transition metal. 4. A metal hydrogen compound powder mixed with another metal, a carbide, a nitride, or a boride powder, which is molded, is used as an electrode for in-liquid discharge, and is used as an electrode for the in-liquid discharge. A method of surface treatment by in-liquid discharge, characterized in that an electric discharge is generated between workpieces to form a surface layer containing a compound of high hardness on the surface of the workpiece. 5. A polymer material, which is formed by mixing powder of a metal hydrogen compound with powder of another metal, carbide, nitride or boride, and is used as an electrode for in-liquid discharge to thermally decompose to generate carbon. A surface treatment method by in-liquid discharge, characterized in that an electric discharge is generated between the electrode and a workpiece in an existing liquid to form a surface layer containing a compound of high hardness on the surface of the workpiece. 6. The surface treatment method by submerged discharge according to claim 2 or 5, wherein the polymer material that thermally decomposes to produce carbon is a mineral oil or vegetable oil. Surface treatment method by medium discharge. 7. The method of surface treatment by submerged discharge according to claim 1, wherein a zircon, vanadium, niobium or tantalum powder is added to the electrode material in one kind or in a composite form. A surface treatment method by in-liquid discharge, which is used as an electrode to generate an electric discharge between the electrode and a work to form a surface layer with high toughness on the surface of the work. 8. The method for surface treatment by submerged discharge according to claim 1, wherein a metal powder of the same kind as that of the workpiece is added and used as an electrode, and the electrode and the workpiece are processed. A surface treatment method by in-liquid discharge, characterized in that a discharge is generated between the two to improve the properties of the surface of the workpiece. 9. The surface treatment method according to claim 1, wherein a surface layer is formed on the surface of the workpiece, and then the secondary processing is performed using a non-consumable electrode. A surface treatment method by electric discharge in a liquid, which is characterized by improving physical properties of a layer. 10. The method for surface treatment by submerged discharge according to claim 9, wherein the non-consumable electrode is any one of graphite, copper, tungsten, silver tungsten, copper tungsten, and tungsten carbide. Surface treatment method. 11. The surface treatment method by submerged discharge according to claim 1, wherein the workpiece is a non-ferrous metal. 12. The surface treatment method by submerged discharge according to claim 1, wherein the work piece is a superalloy.