JP2004060013A - Electrode for discharge surface treatment and discharge surface treatment method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To form a film with a uniformized content by reducing the dispersion and further to form a thick film, which has been conventionally difficult. <P>SOLUTION: An electrode is a green compact made by compression-molding an alloy powder 101 consisting of blended predetermined electrode materials, or a heat-treated compact formed of the green compact, and includes 50 wt.% or more metallic materials which do not form or hardly form carbides in the alloy. The surface treatment method is characterized by discharging the electrode made of the above green compact or the above heat-treated compact to form a film on a workpiece. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention generates a pulsed discharge between an electrode having at least one of a metal, a metal compound, and ceramics as an electrode material and a work, and forms a film of the electrode material on the work surface by the discharge energy. Also, the present invention relates to a discharge surface treatment electrode and a discharge surface treatment method for forming a film of a substance in which an electrode material has reacted by discharge energy on a work surface.
[0002]
[Prior art]
A technique of coating the surface of a metal material by a submerged electric discharge machining method to improve corrosion resistance and abrasion resistance is already known. The following is an example of the technology.
[0003]
For example, in Japanese Patent Application Laid-Open No. 5-148615, the electrode material is deposited on a work by performing in-liquid pulse discharge with an electrode formed by mixing WC (tungsten carbide) and Co powder and compression-molding the electrode. A method is disclosed in which remelting discharge machining is performed by using the electrode (for example, a copper electrode or a graphite electrode) to obtain higher hardness and higher adhesion. That is, using a WC-Co mixed green compact electrode, the workpiece (base material S50C) is subjected to electrical discharge machining in a liquid to deposit WC-Co on the workpiece (primary machining), and then to a copper electrode. Re-melt processing (secondary processing) is performed using electrodes that are not so consumed. As a result, in the primary processing, the deposited structure had a hardness (Vickers hardness Hv) of about Hv = 1410, and had many cavities. However, the cavities of the coating layer disappeared by the remelting processing of the secondary processing. The hardness is also improved to Hv = 1750. By this method, a coating layer that is hard and has good adhesion to a steel material as a work can be obtained.
[0004]
However, with the above-described method, it is difficult to form a coating layer having strong adhesion on the surface of a sintered material such as a cemented carbide as a work. In this regard, according to a study by the present inventors, when a material such as Ti that forms a hard carbide is used as an electrode and a discharge is generated between the work and the work, a strong hard film can be formed on the work without a remelting process. It was found that it can be formed on the metal surface. This is due to the fact that the electrode material consumed by the discharge reacts with carbon C, which is a component in the working fluid, to generate TiC.
[0005]
In Japanese Patent Application Laid-Open No. 9-192937, when a discharge is generated between a workpiece and a metal hydride compact such as TiH2 (titanium hydride) as an electrode, a material such as Ti is used. A technique capable of forming a hard film faster and with better adhesiveness is disclosed. Furthermore, when a discharge is generated between a workpiece and a compact formed by mixing another metal or ceramic with a hydride such as TiH2 (titanium hydride), various properties such as hardness and abrasion resistance are obtained. There is also disclosed a technique capable of quickly forming a hard coating having a thickness.
[0006]
Further, as another technique, Japanese Patent No. 3227454 discloses that a high-strength surface-treated electrode can be manufactured by preliminary sintering. That is, when manufacturing an electrode for discharge surface treatment comprising a powder obtained by mixing a WC powder and a Co powder, a green compact formed by mixing the WC powder and the Co powder and compression molding is obtained by mixing the WC powder and the Co powder. Although only compression molding may be performed, the compactability of the green compact is improved if compression molding is performed after mixing the wax.
[0007]
In this case, the wax is an insulating substance, and if it remains in a large amount in the electrode, the electrical resistance of the electrode increases and the discharge performance deteriorates. Therefore, the wax is removed by placing the green compact electrode in a vacuum furnace and heating. are doing. At this time, if the heating temperature is too low, the wax cannot be removed, and if the temperature is too high, the wax becomes soot and deteriorates the purity of the electrode. It must be kept below.
[0008]
Then, the green compact in the vacuum furnace is heated by a high-frequency coil or the like, and is baked to, for example, a hardness of about black ink so as to give strength enough to withstand machining and not to harden (this is a pre-sintering state). Called). In this case, mutual bonding proceeds at the contact portion between the carbides, but the bonding is weak because the sintering temperature is relatively low and the sintering is not reached. It has been found that when a discharge surface treatment is performed with such an electrode, a dense and uniform coating can be formed.
[0009]
[Problems to be solved by the invention]
However, in the above-described conventional discharge surface treatment, as an electrode, a powder of a material to be formed into a film, for example, as shown in FIG. 5, a Co powder 107, a Cr powder 108, and a Ni powder 109 are mixed, and the mixed powder is compression-molded. A green compact or a green compact that has been subjected to a heat treatment thereafter is used. As another example, when forming a film of a cemented carbide (WC-Co-Cr) component, a WC (tungsten carbide) powder, a Co (cobalt) powder, and a Cr (chromium) powder are mixed. The electrode is a green compact obtained by mixing and compression-molding the mixed powder, or a powder compact that has been subjected to a heat treatment thereafter.
[0010]
A dense film can be formed by discharging the electrode of the green compact. However, since the electrode is manufactured by mixing powder, when the film is observed microscopically (microscopic), the powder of the electrode, Variations in mixing and variations during melting due to the size of the powder particle size do not result in a uniform component coating. This degree of micro-variation is unavoidable because the mixed powder is discharged as an electrode. The dispersion of the components does not cause a problem in a normal coating film, but may cause a problem in a special environment, for example, when used in a high-temperature environment such as an aircraft engine.
[0011]
Further, in the conventional electric discharge surface treatment as described above, the main focus was on forming a hard coating, so that the electrode material was a hard ceramic material or an oil component in the working fluid due to the energy of electric discharge. The main component is a material that forms a hard carbide by chemically reacting with certain C (carbon). However, a hard material generally has characteristics such as a high melting point and poor heat conduction. Although a thin film of about 10 μm can be formed densely, it is extremely difficult to form a dense thick film of several hundred μm or more. there were.
[0012]
WC-Co (9: 1) is based on the research of the present inventors ("Thick film formation by discharge surface treatment (EDC)", Akihiro Goto et al., Mold Technology, (1999), Nikkan Kogyo Shimbun). It was shown that a thick film of about 3 mm could be formed using the electrode, but it was difficult to reproduce the film because the film formation was not stable. There are problems such as the fact that the material of the coating varies depending on the particle size of the original powder as described above, which is a level that is difficult for practical use.
[0013]
The present invention has been made in view of the above, and an object of the present invention is to provide a discharge surface treatment electrode and a discharge surface treatment method, which make uniform and eliminate variations in coating components, which has been difficult in the past.
[0014]
In addition, the present invention has been made in view of the above, and an object of the present invention is to provide an electrode for electric discharge surface treatment and an electric discharge surface treatment method for forming a thick film which has been conventionally difficult by conventional pulsed electric discharge machining in liquid. And
[0015]
[Means for Solving the Problems]
In order to achieve the above object, an electrode for discharge surface treatment according to the present invention comprises a pulsed discharge between a workpiece and an electrode having at least one of a metal, a metal compound, and ceramics as an electrode material in a working fluid. In the discharge surface treatment of forming a film of the electrode material on the work surface by the discharge energy or forming a film of the substance reacted with the electrode material on the work surface by the discharge energy, the electrode is mixed with a predetermined electrode material. It is characterized in that it is formed of a green compact obtained by compression-molding an alloy powder or a green compact obtained by heat-treating the green compact.
[0016]
According to the present invention, since the alloy powder is used as the electrode material, the components of the coating film formed on the workpiece by the discharge surface treatment can be eliminated and uniformized.
[0017]
The discharge surface treatment electrode according to the next invention is characterized in that, in the above invention, the alloy contains 50% by weight or more of a metal material which does not or hardly forms carbide in the alloy.
[0018]
According to the present invention, it is possible to form a thick film by depositing the same material, which has been difficult in the related art, as well as uniformizing the film by eliminating the variation of the film components.
[0019]
The discharge surface treatment method according to the next invention is characterized in that a pulse-like discharge is generated between an electrode having at least one of a metal, a compound of a metal, and ceramics in an electrode material and a workpiece in a working fluid, and the discharge energy is generated. In the discharge surface treatment of forming a coating of the electrode material on the work surface or forming a coating of a substance in which the electrode material has reacted by the discharge energy on the work surface, a compact formed by compression molding an alloy powder containing a predetermined electrode material A film is formed on a workpiece by discharging an electrode made of a body or a body obtained by heat-treating the compact.
[0020]
According to the present invention, the coating composition of the workpiece can be made uniform by the surface treatment using the alloy as an electrode.
[0021]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.
[0022]
Embodiment 1 FIG.
FIG. 1 is a simplified configuration diagram of a discharge surface treatment electrode manufacturing apparatus according to Embodiment 1 of the present invention. In FIG. 1, a space surrounded by a mold upper punch 103, a mold lower punch 104, and a mold die 105 contains, for example, an alloy such as stellite (Cr (chromium), Co (cobalt), Ni (nickel), etc. ) The powder 101 is filled. Then, a green compact is formed by compression-molding the alloy powder 101, or a compact obtained by heating the green compact is formed. In the discharge surface treatment, the green compact or a heated green compact is used as a discharge electrode.
[0023]
Here, the alloy powder 101 is a powder made by melting and pulverizing an alloy (for example, stellite) made by mixing Co (cobalt), Cr (chromium), Ni (nickel), and the like. Is a powder having a uniform particle size. That is, each grain of the powder is an alloy.
[0024]
In FIG. 1, the alloy powder 101 is compression-molded by a die 105 and punches 103 and 104. Then, in some cases, a heat treatment is performed thereafter to increase the strength of the electrode. Using such an electrode, a pulse-like discharge is generated in the oil in the working fluid.
[0025]
FIG. 2 is a simplified diagram of a discharge surface treatment apparatus showing a state during discharge. In FIG. 2, an electrode 202 is a green compact of alloy powder particles 201, and the electrode 202 and a work 203 are arranged opposite to each other in a working fluid 204 which is oil, and the electrode 202 is connected to the electrode 202 by a discharge surface treatment power supply 205. A pulse-like voltage is applied between the work 203 and the pulse 203 to generate a pulse-like discharge to form a discharge arc column 206, and a film is formed on the work 203.
[0026]
FIG. 3 shows a voltage waveform applied between the electrode 202 and the work 203 and a pulse-like discharge current waveform. The discharge is performed with the negative polarity on the electrode 202 side and the positive polarity on the work 203 side.
[0027]
The electrode material is supplied to the work for each discharge. Since the electrode material is made of one kind of alloy and has a uniform component, a film having no component variation can be formed.
[0028]
Embodiment 2 FIG.
Next, a second embodiment of the present invention will be described. In Embodiment 1 described above, the powder of the electrode 202 is an alloy powder. In Embodiment 2, the component composition of the alloy is specified.
[0029]
According to experiments performed by the present inventors, it has been found that the film can be made thicker as a material that does not form carbides or hardly forms carbides is added to the components of the electrode material. Conventionally, a large proportion of a material that easily forms a carbide is contained. For example, when a material such as Ti is included in an electrode, a chemical reaction is caused by electric discharge in oil, and the film is called TiC (titanium carbide). Becomes a hard carbide. As the surface treatment progresses, the material of the work surface changes from steel material (when steel material is processed) to TiC which is ceramics, and accordingly, characteristics such as heat conduction and melting point change. However, when a material that is not carbonized or hardly carbonized is added to the electrode, the coating does not become a carbide, and a phenomenon that the amount of material remaining in the coating as a metal increases. It has been found that the selection of the electrode material has a significant meaning in thickening the coating. In this case, it is natural that hardness, denseness, and uniformity are satisfied, and it is a premise that a thick film is formed.
[0030]
FIG. 4 shows the coating thickness with respect to the components of an alloy made by mixing Co (cobalt), Cr (chromium), Ni (nickel), etc. Here, Co (cobalt) and Ni (nickel), which are hard to carbonize, are shown. 2) shows the relationship between the total weight% and the thickness of the coating.
[0031]
In expressing this relationship, the discharge pulse conditions used were such that the peak current value ie = 10 A, the discharge duration (discharge pulse width) te = 64 μs, the pause time to = 128 μs, and the electrode having an area of 15 mm × 15 mm in FIG. A coating was formed. The processing time is 15 minutes.
[0032]
Due to the discharge in the oil, some of the Cr in the electrode becomes carbide such as Cr3C2 (chromium carbide), but Co (cobalt) and Ni (nickel), which are difficult to carbonize, remain intact in the film. Component. As the amount of Co (cobalt) and Ni (nickel) in the electrode increases, the film can be formed thicker. That is, when the electrode contains 50% by weight or more of a metal material in which carbide is not formed or hardly formed in the coating due to electric discharge, the coating becomes extremely thick, and according to FIG. Has a film thickness of about 10 μm, but gradually increases from a Co and Ni content of about 30%, and increases to a thickness of about 10,000 μm when the Co and Ni content exceeds 50%.
[0033]
In this case, when forming the pressure film, by forming the powder of the electrode into an alloy, it is possible to form a uniform film without causing non-uniform components in the film. In addition, although stellite has been described as an alloy, it is also applicable to Inconel, which is an alloy of Ni, Cr, and Fe having a Ni content of 50% by weight or more.
[0034]
【The invention's effect】
As described above, according to the invention of this electrode, the electrode is formed by compressing or molding a powder of an alloy containing a predetermined electrode material or by heating this compact. Since the alloy powder was used as the electrode material, the components of the film formed on the workpiece by the discharge surface treatment were eliminated and uniformized.
[0035]
According to the invention of the next electrode, not only is it possible to eliminate variations in coating components but also to make the alloy uniform by including at least 50% by weight of a metal material that does not or hardly forms carbide in the alloy, which has conventionally been difficult. The same material can be deposited, and a thick film can be formed.
[0036]
According to the invention of the following surface treatment method, a coating is formed on a work by discharging an electrode made of a green compact obtained by compression-molding an alloy powder containing a predetermined electrode material or a heat-treated green compact. The coating composition of the workpiece could be made uniform by the surface treatment using the alloy as an electrode.
[Brief description of the drawings]
FIG. 1 is a simplified configuration diagram of an apparatus for manufacturing an electrode for discharge surface treatment according to the present invention.
FIG. 2 is a simplified diagram of a discharge surface treatment apparatus showing a state during discharge.
FIG. 3 is a diagram showing voltage and current waveforms at electrodes.
FIG. 4 is a characteristic diagram showing a relationship between Ni and Co weight% with respect to film thickness.
FIG. 5 is a simplified configuration diagram of a conventional electrode surface manufacturing apparatus for treating a discharge surface for showing a green compact.
[Explanation of symbols]
101 Stellite powder.

Claims (3)

A pulse-like discharge is generated between an electrode and a work having at least one of a metal, a compound of a metal, and ceramics as an electrode material in a working fluid, and a film of the electrode material is formed on the work surface by the discharge energy. Alternatively, in a discharge surface treatment for forming a film of a substance in which an electrode material has reacted by discharge energy on a work surface,
An electrode for discharge surface treatment, wherein the electrode is formed of a green compact obtained by compression-molding an alloy powder containing a predetermined electrode material or a heat-treated green compact. The discharge surface treatment electrode according to claim 1, wherein the alloy contains 50% by weight or more of a metal material that does not or hardly forms carbide in the alloy. A pulse-like discharge is generated between an electrode and a work having at least one of a metal, a compound of a metal, and ceramics as an electrode material in a working fluid, and a film of the electrode material is formed on the work surface by the discharge energy. Alternatively, in a discharge surface treatment for forming a film of a substance in which an electrode material has reacted by discharge energy on a work surface,
A discharge surface treatment method characterized by forming a coating on a work by discharging an electrode made of a green compact obtained by compression-molding an alloy powder containing a predetermined electrode material or a heat-treated green compact. .

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