JP2008240067A - Discharge surface treatment method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To form a thin film having excellent adhesive strength and uniformity on the surface of a base materials made of aluminum or an aluminum alloy. <P>SOLUTION: Regarding the discharge surface treatment method where a formed body obtained by subjecting metal powder or the like to compression molding is used as an electrode 11, pulsatile discharge is generated between the surface of a base material S made of aluminum or an aluminum alloy and the electrode 11, and, while locally melting the surface of the base material S by the discharge energy, the material of the electrode 11 or the reactant of the material is stuck to the melted part Sa of the base material, so as to form a film on the surface of the base material S, in the waveform of the discharge pulse current fed between the electrode 11 and the base material S, the peak current value in the initial stage part is higher than the peak current value in the part on and after the middle stage, and the peak current value in the part on and after the middle stage in the waveform part of the discharge pulse current is <10 A. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention is one of surface treatment methods, and relates to a discharge surface treatment method for forming a film having, for example, wear resistance on the surface of a substrate by discharge energy.

  Various techniques have been developed for surface treatment methods for forming a coating on the surface of a substrate. In recent years, development of discharge surface treatment methods using discharge energy (see Patent Document 1 and Patent Document 2) has become active. The

In this discharge surface treatment method, a compact obtained by compression-molding a metal powder or the like is used as an electrode, and in an electrically insulating liquid, between the surface of the base material made of steel, cobalt alloy, or nickel alloy and the electrode. To generate a pulsed discharge. By this, while the surface of the substrate is locally melted by the discharge energy, the electrode material or the reactant of the material is adhered to the melted portion of the substrate to form a film on the surface of the substrate. Can do.
JP-A-8-300287 JP 2005-213554 A

  By the way, aluminum or aluminum alloy that is lightweight and excellent in durability is used in various fields. In recent years, not only base materials made of steel, cobalt alloy, or nickel alloy but also base materials made of aluminum or aluminum alloy. The demand for forming a coating film on a material by discharge surface treatment is rapidly increasing.

  However, since aluminum or aluminum alloy has a much higher thermal conductivity than steel, etc., even if a base material made of aluminum or aluminum alloy is locally melted by discharge energy, The temperature rapidly decreases, and the electrode material or the reactant of the material hardly adheres to the molten portion of the base material, and a film having excellent adhesion (adhesion strength) cannot be formed on the base material. In addition, since aluminum or aluminum alloy has a very low melting point compared to steel, etc., if the discharge energy is increased in consideration of the temperature drop in the molten part of the base material, the surface of the base material itself is subjected to electrical discharge machining. End up. Therefore, there is a problem that the discharge surface treatment technique cannot be effectively used for a base material made of aluminum or an aluminum alloy, and the range of use of the discharge surface treatment technique cannot be expanded to various fields.

  Therefore, in order to solve the above-mentioned problems, the present invention provides a discharge surface treatment method having a novel configuration capable of forming a coating having excellent adhesion strength and uniformity on the surface of a substrate made of aluminum or an aluminum alloy. The purpose is to provide.

  In order to solve the above-mentioned problems, the invention of the present invention has conducted an experiment on discharge surface treatment while changing discharge conditions for a substrate made of aluminum or an aluminum alloy. The peak current value of the initial part in the waveform of the discharge pulse current supplied between them is higher than the peak current value of the part after the middle period, and the peak current value of the part after the middle part in the waveform of the discharge pulse current is less than 10A. By satisfying these conditions, a novel finding that a film excellent in adhesion (adhesion strength) and uniformity of the film can be formed on the surface of the base material made of aluminum or aluminum alloy can be obtained. It came to complete.

  The first feature of the present invention (features of the invention described in claims 1 to 3 and claim 8) is that a molded body obtained by compression molding a metal powder, a metal compound powder, or a ceramic powder is used as an electrode. In a liquid or air having electrical insulation properties, a pulsed discharge is generated between the surface of the substrate made of aluminum or aluminum alloy and the electrode, and the discharge energy of the substrate A discharge surface treatment method for forming a film on the surface of the base material by locally melting the surface and adhering the material of the electrode or a reactant of the material to the melted portion of the base material, The waveform of the discharge pulse current supplied between the electrode and the substrate is such that the peak current value of the initial part is higher than the peak current value of the part after the middle period, and the part after the middle period in the waveform of the discharge pulse current Peak current value , And summarized in that less than 10A.

  According to the first feature, the peak current value of the initial part in the waveform of the discharge pulse current is higher than the peak current value of the part after the middle period, and the peak of the part after the middle part in the waveform of the discharge pulse current. Since the current value is less than 10 A, in consideration of the above-described novel findings, the coating film excellent in adhesion and uniformity can be formed on the surface of the base material made of aluminum or aluminum alloy.

  The second feature of the present invention (the feature of the invention described in claims 4 to 8) is that a molded body obtained by compression molding a metal powder, a metal compound powder, or a ceramic powder is used as an electrode. In an insulating liquid or in the air, a pulsed discharge is generated between the surface of the substrate made of aluminum or aluminum alloy and the electrode, and the surface of the substrate is locally localized by the discharge energy. A first treatment step of forming a thin film on the surface of the base material by adhering the electrode material or a reactant of the material to the melted portion of the base material, After completion, in the first treatment step, a pulsed discharge is generated between the surface of the base material and the electrode in the electrically insulating liquid or air, and the discharge energy is used in the first treatment step. Of the thin film formed A second processing step of causing the thin film to grow into the thick film by locally melting the surface and adhering the material of the electrode or a reactant of the material to the melted portion of the thin film. In the discharge surface treatment method, in the first treatment step, the waveform of the discharge pulse current supplied between the electrode and the substrate is such that the peak current value in the initial part is higher than the peak current value in the middle and subsequent parts. In the waveform of the discharge pulse current, the peak current value after the middle period is less than 10 A, and the deposition rate per unit area in the second processing step is the unit in the first processing step. The gist is that it is faster than the deposition rate per area.

  According to the second feature, in the first processing step, the peak current value of the initial part in the waveform of the discharge pulse current is higher than the peak current value of the part after the middle period, and the waveform of the discharge pulse current In the first treatment step, in the first treatment step, the peak current value of the portion after the middle stage in the middle stage is less than 10 A. In the first treatment step, the surface of the base material made of aluminum or aluminum alloy is improved in adhesion and uniformity. An excellent thin film can be formed.

  In the second treatment step, the thin film is grown into a thick film. In other words, the thin film is formed on the surface of the thin film formed in the first treatment step. Since the film formation rate per unit area in the second treatment step is higher than the film formation rate per unit area in the first treatment step, the surface of the substrate made of aluminum or aluminum alloy The thick film can be formed on the surface of the base material in a short time while ensuring sufficient adhesion.

  According to the invention of any one of claims 1 to 8, the coating film (or the thin coating film) excellent in adhesion strength and uniformity on the surface of the base material made of aluminum or an aluminum alloy. ) Can be used effectively for the base material made of aluminum or an aluminum alloy, and the range of use of the discharge surface treatment technique can be expanded to various fields.

  In addition, according to the invention of any one of claims 4 to 8, the base material is sufficiently secured while sufficiently adhering to the surface of the base material made of aluminum or an aluminum alloy. Therefore, the workability (working efficiency) of the discharge surface treatment for the substrate made of aluminum or aluminum alloy can be improved.

(I) Before explaining the discharge surface treatment method according to the embodiment of the present invention, regarding the electrical discharge machining apparatus used for the discharge surface treatment and the new knowledge that is the premise of the discharge surface treatment method according to the embodiment of the present invention This will be described with reference to FIGS. Here, FIG. 2 is a diagram showing the waveform of the discharge pulse current and the waveform of the discharge pulse voltage when generating a pulsed discharge between the surface of the substrate and the electrode, and FIG. 3 is used for the discharge surface treatment. It is a schematic diagram of an electric discharge machining apparatus.

  As shown in FIG. 3, the electric discharge machining apparatus 1 used for the electric discharge surface treatment includes a bed 3, and the bed 3 is provided with a table 5. Further, the table 5 is provided with a liquid tank 7 for storing an electrically insulating liquid L such as oil, and a base material S made of aluminum or an aluminum alloy can be set in the liquid tank 7. A substrate jig 9 is provided.

  Above the table 5, an electrode holder 13 that holds the electrode 11 is provided so as to be movable in the X-axis direction, the Y-axis direction, and the Z-axis direction. The electrode holder 13 rotates about the Z axis as a rotation axis. It is possible. The electrode 11 is a molded body obtained by compression molding a powder of stellite metal or a metal powder mainly composed of stellite metal. Instead of a molded product obtained by compression molding a metal powder, a molded product obtained by compression molding a metal compound powder or ceramic powder may be used.

  A discharge power supply device is electrically connected to the base material jig and the electrode holder, and this discharge power supply device is disclosed in, for example, Japanese Patent Application Laid-Open No. 2005-213554 (FIGS. 4, 5, and 7, etc.). Such a known discharge power supply device includes a second power supply, a capacitor, a switching element, a resistor, and the like.

  As shown in FIGS. 2 and 3, the inventor of the present invention uses an electric discharge machining apparatus 1 to obtain aluminum or aluminum before obtaining new knowledge that is a premise of the electric discharge surface treatment method according to the embodiment of the present invention. Experiments on the discharge surface treatment were performed on the base material S made of an aluminum alloy while changing the discharge conditions. Here, the changed discharge conditions are the peak current value lp (0A, 30A, 40A) in the initial part of the waveform of the discharge pulse current supplied between the electrode 11 and the substrate S, and the peak current value ie in the middle and subsequent parts. (1A, 2A, 4.5A, 5.5A, 10A). The pulse width te of the discharge pulse current is 8 μs, and the pause time to is 64 μs.

The experimental results relating to the discharge surface treatment are summarized as shown in Table 1 below.

  Here, “◯” described in the column of “Presence / absence of film formation” in Table 1 indicates that a film has been formed, and is described in the column of “Presence / absence of film formation”. “X” indicates that the film could not be formed. In addition, “◯” described in the column “Uniformity of coating” in Table 1 indicates that the uniformity of the coating is good, and “Uniformity of coating” in Table 1 The “x” described in the column indicates that the uniformity of the coating is poor. Furthermore, “◎” described in the column of “Coating adhesion” in Table 1 indicates that the adhesion strength of the coating with the substrate S is extremely high. "○" described in the column of "" indicates that the adhesion strength with the substrate S is high, and "x" described in the column of "Coating adhesion" in Table 1 It shows that the adhesion strength with the substrate S is low. The uniformity of the coating is determined by visual inspection, and the adhesion of the coating is determined by the tensile strength detected by a tensile adhesion tester.

  As shown in Table 1, the peak current value lp in the initial part in the waveform of the discharge pulse current is higher than the peak current value ie in the part after the middle period, and the peak current value in the part after the middle part in the waveform of the discharge pulse current. By satisfying the two conditions that ie is less than 10 A, a film excellent in adhesion (adhesion strength) and uniformity can be formed on the surface of the substrate S made of aluminum or aluminum alloy. A new first finding was obtained. In particular, when the peak current value lp at the initial portion in the waveform of the discharge pulse current is 30 A, it was possible to obtain a new second finding that the adhesion of the film was further improved.

(II) A discharge surface treatment method according to an embodiment of the present invention will be described with reference to FIGS. 1 (a), 1 (b), 2, and 3. FIG.

  Here, FIG. 1A is a diagram showing a first treatment step in the discharge surface treatment method according to the embodiment of the present invention, and FIG. 1B is a diagram showing the first treatment step in the discharge surface treatment method according to the embodiment of the present invention. It is a figure which shows 2 process steps.

  As shown in FIGS. 1 (a) and 1 (b), a discharge surface treatment method according to an embodiment of the present invention uses a discharge energy to form a thick coating CH on the surface of a substrate S made of aluminum or an aluminum alloy. A processing method comprising a first processing step and a second processing step.

First treatment step As shown in FIG. 3, the base S made of aluminum or aluminum alloy is set on the base jig 9, and the electrode holder 13 is moved in the X-axis direction and / or the Y-axis direction. The material S is positioned with respect to the electrode 11. Then, the electrode 11 is moved back and forth in the Z-axis direction integrally with the electrode holder 13, and the surface of the base material S made of aluminum or aluminum alloy and the electrode 11 in the electrically insulating liquid L by the discharge power source device 15. A pulsed discharge is generated between the two. As a result, as shown in FIG. 1A, the material of the electrode 11 or the reactant of the material is transferred to the melting portion Sa of the substrate S while locally melting the surface of the substrate S by the discharge energy. A thin film C is formed on the surface of the substrate S by adhering.

  Here, in the first treatment step, in the waveform of the discharge pulse current supplied between the electrode 11 and the substrate S, the peak current value lp in the initial part is higher than the peak current value ie in the middle and subsequent parts. The peak current value ie after the middle period in the waveform of the discharge pulse current is less than 10 A (see FIG. 2). Further, the peak current value lp in the initial part of the waveform of the discharge pulse current is 30A. The peak current value lp at the initial portion in the waveform of the discharge pulse current is not limited to 30 A, and 20 according to the change in the type of the aluminum alloy constituting the substrate S, the material of the electrode 11, the required specifications, etc. It can be appropriately changed within the range of ˜35A.

  The thickness t of the thin coating C formed in the first treatment step is 10 μm or more, and more specifically 10 to 50 μm. Here, the thickness t of the thin coating C formed in the first processing step is set to 10 μm or more because the thickness t of the thin coating C is less than 10 μm and the surface of the thin coating C in the second processing step. This is because the surface of the substrate S may be exposed from the thin coating C by melting.

  The pulse width of the discharge pulse current in the first treatment step is 8 μs or less, more specifically 2 to 8 μs. Here, the pulse width of the discharge pulse current in the first treatment step is set to 8 μs or less. If the pulse width of the discharge pulse current exceeds 8 μs, it becomes difficult to sufficiently improve the adhesion of the thin film C. Because.

The film formation rate per unit area in the first treatment step is 10 to 30 μ · cm ² / min.

Second Treatment Step After the completion of the first treatment step, as shown in FIG. 3, the discharge power supply device 15 continues the electrode 11 in the electrically insulating liquid L while reciprocating the electrode 11 in the Z-axis direction. A pulsed discharge is generated between the surface of the substrate S and the electrode 11. As a result, as shown in FIG. 1B, the surface of the thin film C formed in the first processing step is locally melted by the discharge energy, and the material of the electrode 11 or the reactant of the material is changed. The thin film C is grown on the thick film CH by being attached to the melted portion Ca of the thin film C.

Here, the film forming rate per unit area in the second processing step is larger than the film forming rate per unit area in the first processing step, and more specifically, per unit area in the second processing step. The film formation speed of the film is 80 to 100 μ · cm ² / min.

  In the second processing step, the peak current value lp in the initial part of the waveform of the discharge pulse current is 35 to 50 A, and the peak current value ie in the middle part and later in the waveform of the discharge pulse current is 1 to 10 A ( (See FIG. 2). The pulse width of the discharge pulse current in the second processing step is 2 to 8 μs.

  Next, the operation and effect of the embodiment of the present invention will be described.

  In the first processing step, the peak current value lp of the initial part in the waveform of the discharge pulse current is higher than the peak current value ie of the part after the middle period, and the peak current value ie of the part after the middle part of the waveform of the discharge pulse current is In view of the above-mentioned new first knowledge, in the first treatment step, a thin coating C having excellent adhesion and uniformity is formed on the surface of the base material S made of aluminum or an aluminum alloy. Can be formed. In particular, since the peak current value lp of the initial portion in the waveform of the discharge pulse current is 30 A, the adhesiveness of the thin film C can be further improved in consideration of the above-described new second knowledge.

  In the second processing step, the thin film C is grown into a thick film CH, in other words, a film is formed on the surface of the thin film C formed in the first processing step. Since the film formation rate per unit area in the second treatment step is higher than the film formation rate per unit area in the first treatment step, the adhesion with the surface of the substrate S made of aluminum or aluminum alloy is improved. A thick coating CH can be formed on the surface of the substrate S in a short time while ensuring sufficient.

  As described above, according to the embodiment of the present invention, since the thin coating C having excellent adhesion strength and uniformity can be formed on the surface of the base material S made of aluminum or aluminum alloy, the base material S made of aluminum or aluminum alloy. In contrast, the discharge surface treatment technology can be effectively used, and the range of use of the discharge surface treatment technology can be expanded to various fields.

  In addition, since the thick coating CH can be formed on the surface of the base material S in a short time while sufficiently securing the adhesion with the surface of the base material S made of aluminum or aluminum alloy, it is made of aluminum or aluminum alloy. The workability (working efficiency) of the discharge surface treatment for the substrate S can be enhanced.

  In addition, this invention is not restricted to description of the above-mentioned embodiment, In addition, it can implement in a various aspect. Further, the scope of rights encompassed by the present invention is not limited to these embodiments.

FIG. 1A is a diagram showing a first treatment process in the discharge surface treatment method according to the embodiment of the present invention, and FIG. 1B is a second treatment process in the discharge surface treatment method according to the embodiment of the present invention. FIG. It is a figure which shows the waveform of the discharge pulse current at the time of generating a pulse-form discharge between the surface of a base material, and an electrode, and the waveform of a discharge pulse voltage. It is a typical figure of the electric discharge machining apparatus used for electric discharge surface treatment.

Explanation of symbols

S Substrate C Thin coating CH Thick coating 1 Electric discharge machining device 7 Liquid tank 11 Electrode 13 Electrode holder 15 Discharge power supply device

Claims (8)

The surface of the base material made of aluminum or aluminum alloy and the electrode in a liquid or air having an electrical insulation property, using a compact formed by compression molding a metal powder, a metal compound powder, or a ceramic powder as an electrode A pulsed discharge is generated between the electrode material and the surface of the base material is locally melted by the discharge energy, and the electrode material or the reactant of the material is attached to the melting portion of the base material. And a discharge surface treatment method for forming a film on the surface of the substrate,
The waveform of the discharge pulse current supplied between the electrode and the substrate is such that the peak current value of the initial part is higher than the peak current value of the part after the middle period, and after the middle period in the waveform of the discharge pulse current. The discharge surface treatment method, wherein the peak current value of the portion is less than 10 A.   The discharge surface treatment method according to claim 1, wherein a peak current value of the initial portion in the waveform of the discharge pulse current is 30 A.   The discharge surface treatment method according to claim 1, wherein a pulse width of the discharge pulse current is 8 μs or less. The surface of the base material made of aluminum or aluminum alloy and the electrode in a liquid or air having an electrical insulation property, using a compact formed by compression molding a metal powder, a metal compound powder, or a ceramic powder as an electrode A pulsed discharge is generated between the electrode material and the surface of the base material is locally melted by the discharge energy, and the electrode material or the reactant of the material is attached to the melting portion of the base material. A first treatment step of forming a thin film on the surface of the substrate;
After the end of the first treatment step, in a liquid or air having electrical insulation, a pulsed discharge is generated between the surface of the substrate and the electrode, and the discharge energy is used. While the surface of the thin film formed in the first treatment step is locally melted, the material of the electrode or the reactant of the material is adhered to the melted portion of the thin film, and the thin film is thickened. A discharge surface treatment method comprising:
In the first treatment step, the waveform of the discharge pulse current supplied between the electrode and the substrate is such that the peak current value in the initial portion is higher than the peak current value in the middle and subsequent portions, and the discharge pulse The peak current value of the middle and subsequent parts in the current waveform is less than 10A,
The discharge surface treatment method, wherein a film formation rate per unit area in the second treatment step is higher than a film formation rate per unit area in the first treatment step.   The discharge surface treatment method according to claim 4, wherein a thickness of the thin film formed in the first treatment step is 10 μm or more.   6. The discharge surface treatment method according to claim 4, wherein in the first treatment step, the peak current value of the initial portion in the waveform of the discharge pulse current is 30 A. 6.   7. The discharge surface treatment method according to claim 4, wherein a pulse width of the discharge pulse current in the first treatment step is 8 μs or less. 8.   The discharge surface treatment method according to any one of claims 1 to 7, wherein the metal powder is a powder of stellite metal or a metal powder mainly composed of stellite metal. .

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