JP2001138141A - Method for surface coating treatment using submerged discharge and consumable electrode used therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for forming a coating layer of excellent surface property of material to be treated only with an only single discharge treatment process using a consumable electrode by changing and controlling an input in a surface treatment method for reforming the surface of the material to be treated by submerged discharge. SOLUTION: In this method, the surface of a conductive material to be treated is coated by submerged pulse discharge between the consumable electrode and the conductive material to be treated. The consumable electrode is formed of a compact of mixed powder composed of compounds having high melting points of elements of the group IVa, Va or VIa in the periodic table and iron-based metal as a binder metal. The treatment method includes the following processes: supplying a current by using the consumable electrode as a negative electrode; transferring and coating the composition of the consumable electrode on the surface of the material to be treated by increasing the input of discharge in an initial stage of the discharge; and smoothing a coated surface by decreasing the input of the discharge without changing a discharging polarity in a terminal stage of the discharge.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a consumable electrode used for modifying the surface of a material to be treated by electric discharge, and a surface treatment method using the same.

[0002]

2. Description of the Related Art With respect to the conventional technology for treating a metal surface by electric discharge, another alloy or cermet is applied to the metal surface by using an electric discharge machining technique, and the properties of this surface coating layer are used to make the surface of the metal surface. Methods for modifying properties are known. These methods, in particular, provide wear resistance, corrosion resistance,
Oxidation resistance and heat resistance can be imparted, and attention has been paid.

[0003] For example, Japanese Patent Application Laid-Open No. 5-148615 discloses a process of depositing another metal, alloy or cermet on the surface of a metal base material, and melting the deposited layer by pulsed discharge to form a dense coating. A surface treatment method comprising a step of forming a layer is disclosed. In this example, a mixture of a metal or an alloy and a nonmetallic material such as a carbide or a nitride is selected as the coating material. In order to apply these materials on the surface of the base material in advance, the materials are deposited on the surface of the base material using a discharge deposition method.

Japanese Patent Laid-Open Publication No. Hei 8-300227 discloses a method in which powder such as carbide or nitride is compression-molded, calcined at a sintering temperature or lower to form an electrode, and the surface of the base material is subjected to electrical discharge machining. I have. This surface treatment method by electric discharge machining is the first method.
In this method, the electrode material is deposited on the surface of the base material by the electric discharge machining process, the polarity and heat input of the electrode are changed, and the surface hardness is increased by electric discharge in the second electric discharge machining process.

Further, Japanese Patent Application Laid-Open No. 9-19829 discloses that
An electrode is formed from refractory metals such as W, Ti, V, and Nb, which are active in the carbonization reaction, by compression molding and temporary sintering, and the electrode is discharged between the base material and a carbon-decomposing liquid. A technique is disclosed in which an electrode material is fused onto a base material surface while simultaneously forming a coating layer of the metal carbide by a carbonization reaction.

[0006]

In the conventional method using the above-mentioned electric discharge treatment, a property peculiar to the coating layer is imparted to the surface by the coating layer formed on the base material. However, the method disclosed in JP-A-5-148615 described above is
Two types of processes are required: a process of preliminarily depositing a coating material on the base material and a process of re-melting by a discharge for densifying the deposited layer, and a discharge in accordance with the thickness of the deposited layer is required. Conditions must be set, which is disadvantageous in terms of work, and in terms of quality, it is particularly difficult to control surface roughness.

The processing method disclosed in Japanese Patent Application Laid-Open No. Hei 8-300227 also requires two discharge processing steps, primary and secondary, and has the advantage that the same electrode can be used in the secondary discharge processing. Therefore, during the secondary discharge treatment, it is necessary to change the polarity of the electrode and set the heat input to the coating layer,
Such setting work was complicated, and the surface roughness of the obtained coating layer was large and insufficient. In order to make the surface roughness sufficiently small, it is necessary to perform the discharge treatment with a sufficiently low discharge input in the secondary discharge treatment process.However, when the discharge input is reduced, many pinholes are generated on the surface. , This is a mold for applications requiring a relatively smooth surface (for example, a mold for cold forging, a mold for plastic), and machine parts,
It could not be used as is.

In the method disclosed in Japanese Patent Application Laid-Open No. 9-198929, the discharge treatment is completed in one step, but it is necessary to cause a carbonization reaction at the same time as the fusion, so that the amount of carbide in the coating layer is controlled to a desired amount. It was difficult to do. Further, the point that only metal such as W or Ti can be used as an electrode only by preliminary sintering is convenient for electrically transferring to the base material side by electric discharge, but this is necessary to secure the strength of the electrode. It was difficult. In particular, it is necessary to cut or grind the electrode into a predetermined shape in order to make the electrode correspond to the shape of the treated surface of the material to be treated. If the sintering process is not performed for a long time, the bonding force is weak, so that there is a problem that the chipping is likely to occur due to peeling.

[0009] In view of the above problems, the present invention provides
By using an electric discharge machining technology, a consumable electrode is used, and a single electric discharge treatment process is only required to change and adjust the input to provide a surface treatment method for forming a coating layer having excellent surface properties of a material to be treated. Is what you do.

[0010]

SUMMARY OF THE INVENTION The present invention relates to a processing method for applying a pulse discharge between a consumable electrode and a material to be processed in a liquid using a DC pulse power supply to coat the surface of the material to be processed. However, the consumable electrode uses a powder compact of a refractory metal compound and an iron-based metal, and forms a coating layer having a smooth surface on the surface of the material to be treated by electric discharge.

Further, in the method for treating discharge according to the present invention, the composition is transferred from the consumable electrode to the surface of the material to be treated by a large current at the beginning of the discharge, and the discharge current is reduced to a small current at the end of the discharge. In this case, the surface of the coating layer is densified to obtain a smooth surface.

In the present invention, the pulse current is supplied with the consumable electrode side as the negative electrode and the material to be processed side as the positive electrode in both the large current stage and the small current stage. The negative electrode on the consumable electrode side promotes dissolution of the high-melting-point compound of the consumable electrode and the metal. The layer is dissolved, and the surface melt of the powder compact is transferred to the melt side of the surface layer of the material to be processed and diffused and mixed in the surface layer of the material to be processed to form a coating layer.

A pulse arc in a large current region is locally generated and melted on the electrode and a specific surface of the material to be processed for each pulse, and is moved to another part of the pulse arc to form a molten metal on the material to be processed. Is rapidly cooled. With the lapse of time of the pulse arc treatment, a coating layer is formed by discharging on the entire processing surface of the material facing the electrode, and the coating layer is grown to a desired thickness.

In the method of the present invention, preferably, at the end of discharge, a pulse arc of a small current is applied to melt at least the metal component in the powder compact of the consumable electrode.
The surface of the coating layer is partially melted, in particular, the surface projections are dissolved to smooth the coating layer. The present invention greatly improves the surface roughness of the coating layer by providing a pulse arc stage of a small current at the end of discharge.

The use of the negative electrode as the electrode is more advantageous in that the surface of the consumable electrode is heated to a high temperature by electric discharge, as compared with the case of using the positive electrode, and the molten component of the electrode is transferred. The negative polarity of the consumable electrode is maintained even at the low current stage. The discharge during the treatment is performed by immersing both the consumable electrode and the material to be treated in the liquid, or by supplying the liquid to the gap between the consumable electrode and the material to be treated. Can be rapidly cooled by stopping the discharge of the pulse, and the oxidation of the melt can be prevented. Water or oil is used for such a liquid.

The electrode used here is a periodic table IVa
With high melting point compounds of Group IVa, Va, and VIa elements
A powder compact of a mixed powder consisting of an iron-based metal as the metal
is there. The high melting point compounds include Group IVa of the periodic table (Ti, Z
r), Va group (V, Nb, Ta), and VIa group (C
(r, Mo, W) element carbides, nitrides, carbonitrides and
One or more selected from borides
Can be used. Carbides, nitrides, carbonitrides of the above elements
Has excellent abrasion resistance and high-temperature strength.
And WC, MoC.
/ Mo _TwoC and TiC are used.

On the other hand, the above-mentioned iron-based metal in this specification includes Mn, Cr, Fe, Ni and Co,
The consumable electrode includes one or more selected from these metal elements.

[0018] The other iron-based metal is used as a bonding metal in forming the electrode to provide toughness to the electrode and to strengthen the electrode.
Improve molding. Iron-based metals, in addition to the action of the binding metal, Cr, Fe, Ni or Co is used alone or in combination of two or more as a component of the matrix of the coating layer,
Cr, Ni or Co can be used from the viewpoint of oxidation resistance of the coating layer, and Cr or Ni-Cr alloy system is used from the viewpoint of corrosion resistance.

As the consumable electrode, a powder compact is used. The compact is compression-molded from a powder of the above-mentioned high melting point compound and iron-based metal, and is processed into a desired shape by cutting or grinding. It is preferable that the molded body contains an iron-based metal in a range of 2 to 50% (% by weight, the same applies hereinafter). The lower limit of 2% is necessary for forming electrodes by securing conductivity by using an iron-based metal as a bonding metal, and in particular, missing or collapse of a part of an electrode in a process of cutting or grinding when forming into a desired electrode shape. Can be prevented. In particular, the content of the iron-based metal is preferably 4% or more.

On the other hand, the content of the high melting point compound is preferably at least 50% in order to utilize the wear resistance of the high melting point compound in the coating layer, and particularly preferably from the viewpoint of imparting high wear resistance to the coating layer. , 75% or more, particularly preferably 80% or more, so that the content of the iron-based metal is 4 to 20% and the other high melting point compound is preferably 80 to 96%.

The above-mentioned consumable electrode is used after being compression-molded. In particular, in the present invention, since the electrode contains an iron-based metal, the compact is fired in advance and heated to a temperature not lower than the sintering temperature of the bonding metal. Sintered ones are preferred. By using a sintered body, the processability of cutting and grinding the consumable electrode can be further improved, and the electrode can be easily formed into an electrode shape corresponding to the complicated shape of the processed surface of the workpiece.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a conceptual diagram of a surface treatment apparatus. Generally, a material 2 having a surface 20 to be subjected to surface treatment is placed in a liquid 4, for example, in water. The consumable electrode 1 is immersed and has a discharge processing surface 10 having a dimension and a shape adapted to the processing target surface 20, and the driving device 3 (so that the discharge processing surface 10 faces the processing target surface 20 at regular intervals. (Not shown). The power supply 5 generates a DC pulse current, the current control device 6 controls the pulse current, and the negative conductor 61 of the output of the current control device is connected to the consumable electrode 1.
Conductive wires 62 on the positive electrode side are connected to the workpiece 2 respectively.

As the material to be treated, a conductive metal can be used for the coating treatment, and is particularly applied to steel such as carbon steel, special steel and stainless steel, copper alloy, aluminum alloy and nickel alloy. . The material to be treated is formed from these materials, and a desired surface to be treated for coating the surface is formed in advance by machining or chemical processing.

As described above, the consumable electrode is selected from the above-mentioned high melting point compounds and iron-based alloys in consideration of the properties to be imparted, and is determined in consideration of the properties to be imparted to the coating surface. For imparting abrasion, WC, MoC / Mo ₂ C, T
iC is available and the other ferrous metals are Fe, Ni and C
o is used. Particularly, from the viewpoint of oxidation resistance, Ni or C
o can be used, and Cr alone or Cr-Fe
System or Ni-Cr system is used. For example, the consumable electrode can be a combination of WC-Ni and WC-Co,
Further, a combination of WC-Cr-Ni is also possible.

The high melting point compound and the iron-based metal are compression-molded, preferably sintered and densified, and the electric discharge treated surface is formed by machining to form the surface to be treated. . Since the electrode of the present invention contains the above-mentioned iron-based metal as a binder, compression molding such as pressing from powder is easy, and if it is sintered at a temperature higher than the diffusion temperature range of the iron-based metal, a complicated shape can be obtained. There is an advantage that processing is easy. When Fe, Co or Ni is selected as the iron-based metal, the firing temperature is selected in the range of 500 to 1100 ° C.

In the discharge treatment, a pulse current is supplied between the electrode and the material to be treated with the consumable electrode as the negative electrode and the material to be treated as the positive electrode. The pulse is, for example, about 1 kHz to 30 kHz.
A frequency of kHz is chosen. If the pulse frequency is too low, the discharge is likely to stop, depending on the pulse duty.On the other hand, if the pulse frequency is high, the discharge will occur or stop for each pulse, making it unstable and causing surface roughness. Become. From this point, it is particularly preferable that the pulse frequency is about 3 to 12 kHz since the discharge phenomenon is stabilized and the surface roughness after the treatment can be reduced. Regarding the pulse waveform of the discharge current, it is preferable to set the pulse duty (the ratio of the current conduction time in one cycle of the pulse) to 50% or less in order to stabilize the discharge and improve the surface properties. In particular, by setting the pulse duty to 25% or less, good surface roughness can be obtained both at the first stage and at the end of discharge.
The duty of the pulse is preferably 0.1% or more, particularly 1.0%.

In the present invention, the reason why the negative electrode is used on the electrode side is that the dissolution rate of the electrode material is higher than when the positive electrode is used. In the present invention, it is necessary to switch the polarity during the discharge treatment. By maintaining the electrode side at the negative electrode even in the small current region at the end of the period, only the metal component having a relatively low melting point in the composition of the consumable electrode can be melted and transferred, and formed by a large current. The formed coating layer surface can be more smoothly formed in this small current region. In the treatment method of the present invention, the surface of the consumable electrode is melted by the pulse arc in this manner, and a coating layer having a desired thickness is formed on the material to be treated by the pulse input and the treatment time. The thickness of the coating layer is determined depending on the use of the material to be processed, but may be, for example, in the range of 3 to 50 μm.

In the present invention, the treatment process can be carried out with a substantially constant large current. However, a large current is supplied at the initial stage of the discharge so that a coating layer having a desired thickness is formed. In order to smooth the surface of the deposited layer, it is preferable to perform a discharge treatment with a small current without changing the polarity. The current supply pattern can be variously modified. FIG. 2 shows an example of a current pattern. FIG. 2A shows a simple pattern in which a discharge process is performed in two stages of a large current at the beginning and a small current at the end. In FIG. 2B, control is performed in three stages: a large current at the initial stage, a middle current at the middle stage, and a small current at the last stage. FIG.
(D) and (E) show changes in current in multiple stages. In addition, the discharge current can be continuously reduced. In the high current region alone, for example, the WC-Co-based coating layer had a surface maximum roughness of about 10 to 20 μm, but by providing such a small current region, a similar WC-Co-based coating layer was formed. The maximum surface roughness can be reduced to the range of 10 to 5 μm. Thus, according to the treatment method of the present invention, a smooth surface can be obtained only by the discharge treatment.

The current is adjusted so that, for example, in the initial large current region, the electrode can be sufficiently dissolved and transferred to the surface to be processed by discharging, and the terminal small current region is set in the initial maximum current region. The current is controlled to be set, for example, in a range of 5 to 30%. Further, it is preferable that the current in the terminal small current region is set to 5% or less as described above, and in the terminal small current region, the discharge is minimized to thereby reduce the surface roughness.

In order to control such a discharge current, a discharge current control device is used as a pulse power supply. Although it may be integrated with the DC pulse generation power supply, as shown in FIG. 1, a current control device 6 connected between the DC pulse generation power supply 5 and the workpiece 2 and the electrode 1 may be used. it can. For example, a DC pulse power supply for electric discharge machining may be used for such a DC pulse generation power supply device 5.

The current control device shown in FIG. 3 has a configuration in which a variable resistor VR1 for current control is arranged in series with a DC pulse generating power supply, and a variable capacitor VC is connected in parallel to the output side thereof. The negative side of the output of the control device is connected to the electrode, and the positive side is connected to the material to be processed. The pulse current can be adjusted continuously or semi-continuously by the variable resistor VR1, and the variable capacitor VC is also changed with the change of VR1, so that the falling of the pulse waveform is adjusted to be smooth.

In the current control device of this example, the variable resistor VR1 for current control is connected to a rotary switch for switching taps from a number of series resistors, and the switching terminal of the rotary switch is connected to the end of the series resistor. Have been. The variable capacitor VC is also switched by a rotary switch, and the rotary switch for the variable resistor VR and the rotary switch for the variable capacitor VC are rotationally driven by a motor in conjunction with each other.
Multi-stage current control as shown in FIG. However, it is also possible to preset the holding time of each stage of the rotary switch with a timer and control the rotary switching with the timer. In the circuit in FIG. 3, a semi-fixed variable resistor VR2 for setting the minimum current is connected in parallel with the variable resistor VR1 for current control so that the terminal minimum current can be set in advance. Has been. Such a control device can control the current for one time of surface treatment by one change of the variable resistance, and is convenient for repetition of mass-produced surface treatment of a material to be treated.

[0033]

[Example 1] As a consumable electrode, 90% by weight of tungsten carbide powder and 10% by weight of nickel powder were mixed and compression-molded, and the compact was heated to 900 ° C in a vacuum atmosphere.
, And sintered to obtain an electrode having a diameter of 20 mm. As a material to be treated, structural carbon steel S45C was used.

In the coating treatment, the consumable electrode is used as a negative electrode, the material to be treated is used as a positive electrode, the frequency is 4 kHz, the discharge condition is set in three stages, and the material is immersed in water, and the consumable electrode is operated close to the material to be treated. I did it. Control of the discharge current was performed in the upper stage. The initial current of the first stage is about 12 A and about 2 minutes of processing, the second phase of about 60% of the initial current is about 60% of the initial current, and the third phase of the last is about 2 minutes. The processing was performed for about 1 minute at about 10%, and the processing was performed for 5 minutes in total in all processes.

According to microscopic observation, the thickness of the coating layer of the material to be treated is 30 μm on average, and the maximum surface roughness Ry is 10.
At 5 μm, the Vickers hardness HV was 2000 to 2500 according to the hardness measurement of the coating layer surface.

Example 2 As a consumable electrode, 90% by weight of tungsten carbide powder, 9% by weight of nickel powder and 1% by weight of chromium powder were mixed and compression-molded, and the compact was heated to 900 ° C. in a vacuum atmosphere. Heating, sintering, and cutting were performed to form an electrode having a diameter of 20 mm. As a material to be treated, structural carbon steel S45C was used. Regarding the processing material after performing the first stage, the second stage and the third stage, respectively,
The surface roughness of the coating layer was measured, and the results are shown in FIG. A chart for measuring the surface roughness of the coating layer after the first step is as shown in FIG. 5A, and the maximum roughness Ry is 11.1 μm.
m, and the surface roughness after the second and third steps is the maximum roughness R, as shown in FIG. 5B and FIG.
y is 9.8 μm and 8.9 μm, respectively, and the second
It can be seen that the surface roughness is improved by performing the step and, in particular, the third step at a low current.

[Third Embodiment] As another embodiment, a surface treatment was performed by a multi-step current control as schematically shown in FIG. 2D using the current control device shown in FIG. As the consumable electrode and the material to be processed, a combination of the WC-Ni-based consumable electrode and the S45C steel as the material to be processed was used, as in Example 1. As a result, the coating layer of the material to be treated has an average thickness of 3
At 0 μm, the surface roughness was Ry 7.8 μm, and the surface hardness was about 2000 to 2500.

[0038]

The surface coating method according to the present invention is a method for coating the surface of a material to be treated by a pulse discharge in a liquid between a consumable electrode and a conductive material. Is a powder compact of a mixed powder composed of a high melting point compound of an element of group IVa, Va or group VIa of the periodic table and an iron-based metal as a binding metal. The surface coating layer can be formed on the treatment material without any change or replacement of the electrodes and the like, and a smooth surface coating layer can be formed.

Further, by adjusting the discharge input to be large at the beginning of discharge and small at the end of discharge, the coating surface can be further smoothed.

Since the high melting point compound is selected from carbides, nitrides, carbonitrides and borides of the above elements, and the iron-based metal is selected from Cr, Fe, Ni and Co, The layer can be provided with properties such as abrasion resistance by a hard material of a high melting point compound and corrosion resistance and oxidation resistance by an iron-based metal.

The consumable electrode is such that the consumable electrode corresponds to the periodic table IV.
a high melting point compound of a group a, group Va or and group VIa element;
Since it is a powder compact of a mixed powder consisting of an iron-based metal as the binding metal, the iron-based metal functions as a binding material during molding, and the electrode surface shape corresponds to the surface shape of the material to be treated. Is easy to machine, and there is no fear of peeling or missing during the machining, and it is possible to provide an electrode having a complicated shape.

The high melting point compound is selected from carbides, nitrides, carbonitrides and borides of the above elements, and the iron-based metal is selected from Cr, Fe, Ni and Co. The layer can be imparted to the coating layer with properties specific to a high melting point compound and an iron-based metal, and in particular, wear resistance of a high melting point compound of a hard material, corrosion resistance of an iron-based metal, oxidation resistance, etc. A surface coating layer having excellent properties can be formed.

In particular, by forming the consumable electrode into a sintered body obtained by heating the formed body to the range of the diffusion temperature of the bonding metal, a complicated electrode shape can be easily realized.

According to the method of the present invention, there is provided a discharge current control device used in a treatment method for coating the surface of a material to be treated by pulse discharge in a liquid between a consumable electrode and a conductive material to be treated. In addition, current control becomes easy, and particularly, by connecting the discharge current control device to a conventional electric discharge machine, it is possible to easily configure the surface coating treatment machine.

The discharge current control device is connected in parallel with a variable resistor connected in series between the input and output, with the input side connected to the pulse generating power supply, the output side connected between the consumable electrode and the conductive material to be processed. With the configuration including the arranged variable capacitors, a surface coating treatment machine can be realized with a simple configuration.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram showing an arrangement of a consumable electrode and a material to be processed used in a surface coating method of the present invention, and connection of a DC pulse power supply.

FIG. 2 is a diagram (A to D) showing a pattern of a current supplied between a consumable electrode and a material to be processed in the surface coating method of the present invention.

FIG. 3 shows an example of a circuit diagram of a current control device used for the surface coating method in the embodiment of the present invention.

FIG. 4 is a roughness test chart showing a surface roughness distribution of a coating layer according to an example of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Consumable electrode 2 Material to be processed 4 Liquid 5 Pulse power supply 6 Current control device

Continuing from the front page (72) Inventor Masaaki Ikebe 487-1, Koro-cho, Kodera-cho, Kanzaki-gun, Hyogo Prefecture F-term in Sanalloy Industry Co., Ltd. 3C059 AA01 AB01 BA21 BB07 CG04 DC01 HA03

Claims (10)

[Claims] 1. A method for coating a surface of a material to be treated by a pulse discharge in a liquid between a consumable electrode and a conductive material to be treated, wherein the consumable electrode comprises a group IVa of the periodic table, Va A surface coating treatment method comprising a powder compact of a mixed powder comprising a high melting point compound of any one of Group IVa and Group VIa and an iron-based metal as a binding metal. 2. The method according to claim 1, wherein a pulse current is supplied between the consumable electrode and the material to be treated by using the consumable electrode as a negative electrode, and a discharge input is increased in the initial stage of discharge to reduce the composition of the consumable electrode. 3. The surface coating treatment method according to claim 2, wherein the coating is transferred to the surface of the substrate, and at the end of discharge, the discharge input is reduced to smooth the coated surface without changing the discharge polarity. 3. The surface coating treatment according to claim 2, wherein the treatment method further comprises a step of sequentially reducing the current to one step or two or more steps between the initial stage and the final stage of the discharge. Method. 4. The high melting point compound is one or more selected from carbides, nitrides, carbonitrides, and borides of the element, and the iron-based metal is The surface coating method according to any one of claims 1 to 3, wherein the method is at least one selected from Mn, Cr, Fe, Ni, and Co. 5. A consumable electrode for forming a coating layer containing a consumable electrode component on a surface of a material to be processed by discharging between the consumable electrode and the material to be processed, wherein the consumable electrode is formed of a periodic table IVa. Group, Va group or and VI
A consumable electrode for a surface coating layer, which is a powder compact of a mixed powder comprising a high melting point compound of a group a element and an iron-based metal as a binding metal. 6. The high melting point compound is at least one selected from carbides, nitrides, carbonitrides, and borides of the element, and the iron-based metal is The consumable electrode according to claim 5, wherein the consumable electrode is at least one selected from Mn, Cr, Fe, Ni, and Co. 7. The consumable electrode according to claim 1, wherein the consumable electrode includes the ferrous metal.
The consumable electrode according to claim 5, comprising 5 to 50% by weight. 8. The sintered body obtained by heating the molded body to a bonding metal diffusion temperature range.
8. The consumable electrode according to any one of items 7 to 7. 9. A discharge current control device used in a treatment method for coating a surface of a material to be treated by pulse discharge in a liquid between a consumable electrode and a conductive material to be treated, wherein the consumable electrode has a periodic pattern. Table IVa, a powder compact of a mixed powder comprising a high-melting compound of a Group Va, Group Va or Group VIa element, and an iron-based metal as a binding metal, wherein a discharge current control device controls a pulse current to form a consumable electrode. A discharge current control device, wherein a discharge input is adjusted to at least a large discharge input at the beginning of discharge and a small discharge current at the end of discharge. 10. A discharge current control device, comprising: a variable resistor having an input side connected to a pulse generating power supply, an output side connected between a consumable electrode and a conductive workpiece, and arranged in series between input and output. 10. The discharge current control device according to claim 9, comprising a variable capacitor arranged in parallel.