JP4806291B2 - Film formation method - Google Patents

Description

  The present invention relates to a film forming method in which powder is applied to the surface of a metal member and a film is formed from the powder.

  As one type of technique for modifying the surface of a metal member, coating has been widely adopted. That is, if a different kind of film is provided on the surface of the metal member, the surface exhibits characteristics based on the material of the film regardless of the material of the metal member. For example, Patent Document 1 proposes providing an oxide film on the surface of a member made of an iron-based alloy, thereby improving insulation, heat resistance, and wear resistance.

  Known methods for forming a film include plating, thermal spraying, ion plating, sputtering, physical vapor deposition (PVD), chemical vapor deposition (CVD) and the like. However, in plating and thermal spraying, since the bonding force between the formed film and the base is not so strong, there is a problem that the film is relatively easy to peel off. In addition, PVD and CVD have the disadvantages that a long time is required for forming a film and that the shape of the workpiece is limited in order to accommodate the workpiece in the processing chamber.

  Therefore, Patent Document 2 proposes that an Al-Cu alloyed layer is provided by adding an alloy component from a Cu-Si alloy wire under a predetermined condition while melting the surface of Al or an Al alloy. ing.

JP-A-7-233460 JP-A-5-148666

  However, an oxide film (passive) spontaneously formed by combining with oxygen in the air exists on the surface of a work made of Al or an Al-based alloy. In a work in which this kind of oxide film exists, it is difficult to form a film.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a film forming method in which it is extremely easy to form a film on a workpiece made of various metals.

In order to achieve the above object, the present invention is a film forming method for forming a film on the surface of a metal member,
Applying raw material powder to be a film on the surface of the metal member;
Electrically connecting only a negative electrode of a DC power source to the metal member;
Forming a film from the raw material powder by generating a magnetic field and applying vibration by electromagnetic force to a portion of the metal member to which the negative electrode is electrically connected to which the raw material powder is applied;
It is characterized by having.

  When a magnetic field is generated in a state where only the negative electrode of the DC power source is electrically connected, and vibration due to electromagnetic force is applied thereby, the raw material powder is less than in the case where vibration due to electromagnetic force is applied without connecting the negative electrode. Diffusion of constituent atoms into the metal member is facilitated. A film is formed by this diffusion.

  The reason why diffusion is facilitated in this way is that when only the negative electrode of the DC power supply is electrically connected, negative charges are supplied to the oxide film, so that the reduction action on the oxide film functions, and as a result, This is presumably because the surface of the metal member is activated.

  Thus, according to the present invention, it is possible to easily and simply provide a film on a metal member having an oxide film. In addition, this film is difficult to peel off from the metal member and is not easily damaged.

  The workpiece may be of any shape and size as long as it is a member made of metal, and the material is not particularly limited. Preferable examples of the material include Fe alloys such as Fe and steel, Al, Al alloys, Cu, Cu alloys, Mg, Mg alloys and the like.

  In addition, the case where the process of apply | coating raw material powder is included in this invention after the process of electrically connecting only the negative electrode of DC power supply with respect to metal members is included. That is, in the present invention, these two steps are performed in any order.

  The application of vibration by electromagnetic force may be performed by glow discharge or the like, but is more preferably performed by corona discharge. This is because corona discharge has advantages such as easy application of local electromagnetic vibration and easy control of the oscillation frequency. Moreover, since local heating is possible as a result, large-scale equipment such as a heat treatment furnace is not required, and the time required for film formation is shortened. That is, in this case, the film formation cost can be reduced and the film formation efficiency is also improved.

  When a metal member made of an iron-based alloy is selected, the corona discharge is preferably performed with an induction frequency of 30 MHz to 3.5 GHz. On the other hand, a preferable induction frequency when a film is formed on a metal member made of an aluminum-based alloy is 60 MHz to 3.5 GHz. Thereby, it can avoid that pitting corrosion generate | occur | produces in metal members, or that excessive energy concentration arises.

  In any case, it is preferable to preheat the metal member to 100 to 180 ° C. after electrically connecting the negative electrode to the metal member. Thereby, film formation is promoted at the time of applying vibration by electromagnetic force such as corona discharge. That is, the film can be formed more efficiently.

  In the present invention, only the negative electrode of the direct current power source is electrically connected to the metal member, and in this state, vibrations due to electromagnetic force are applied, so that the constituent atoms of the raw material powder applied to the surface of the metal member are changed. The metal member is diffused. In this case, the diffusion of the constituent atoms is facilitated as compared with the case where vibration due to electromagnetic force is applied without connecting the negative electrode. Moreover, the film formed by this diffusion is difficult to peel from the metal member.

  That is, according to the present invention, an effect that a film that is difficult to peel can be efficiently formed at low energy and at low cost on a metal member having an oxide film.

  Hereinafter, the film forming method according to the present invention will be described in detail with reference to the accompanying drawings by exemplifying a case in which a film is provided on a workpiece made of an Fe-based alloy and by illustrating a preferred embodiment.

  The film forming method according to the present embodiment includes a first step of applying raw material powder to the surface of a workpiece, a second step of electrically connecting only the negative electrode of a DC power source to the workpiece, and the negative electrode being electrically And a third step of imparting vibration by electromagnetic force to the portion of the workpiece connected to the substrate where the raw material powder is applied.

  As shown in FIG. 1, the workpiece 10 includes a base 12 made of an Fe-based alloy and an oxide film 14 that is spontaneously generated by combining the Fe-based alloy with oxygen in the atmosphere. Prior to the first step, it is preferable to apply a detergent to the surface of the oxide film 14. In this case, it is because a film | membrane comes to be formed comparatively easily in the 3rd process mentioned later.

  In the first step, as shown in FIG. 2, raw material powder is applied onto the oxide film 14 of the workpiece 10. In addition, in order to connect the lead wire 16 mentioned later to the workpiece | work 10, the exposed location which does not apply | coat raw material powder is provided in this workpiece | work 10. FIG.

  Here, application | coating of raw material powder can be performed by apply | coating the coating agent 18 prepared by disperse | distributing this raw material powder to a solvent, for example. As the solvent, it is preferable to select an organic solvent that easily evaporates, such as acetone or alcohol. Or you may make it apply | coat the paste which mixed the solution which uses an epoxy resin etc. as a binder, and raw material powder.

  As the raw material powder, a substance that exhibits characteristics to be imparted to the workpiece 10 is selected. For example, when a cemented carbide film is formed, a mixture of WC powder and Co powder may be selected.

  As described above, the workpiece 10 made of an Fe-based alloy has the oxide film 14 on the surface thereof. Therefore, it is preferable that the coating agent 18 or the paste is mixed with a reducing agent capable of reducing the oxide film 14, for example, carbon.

  The coating agent 18 or paste including the raw material powder is applied by a known method such as a spray coating method or a brush coating method, and then the lead wire 16 is connected to the exposed portion of the workpiece 10.

  The lead wire 16 is electrically connected to the negative electrode of the DC power supply 22. On the other hand, the positive electrode of the DC power supply 22 is not connected to the workpiece 10. That is, the DC power supply 22 and the workpiece 10 are in an electrically open circuit state.

The generated voltage of the DC power supply 22 is set according to the dimensions of the workpiece 10, particularly the surface area. In other words, the generated voltage of the DC power supply 22 is set so that the voltage applied per unit area of the workpiece 10 is within a predetermined range, for example, 0.3 to 3.0 V / 10 cm ² . The generated voltage here is a voltage to which the DC power supply 22 can be applied, but the work 10 is not actually energized. This is because the DC power source 22 and the work 10 do not electrically form a closed circuit as described above.

  Next, the workpiece 10 is preheated in a state where the negative electrode of the DC power supply 22 is electrically connected. If the negative electrode and the workpiece 10 are insulated, the workpiece 10 may be oxidized at this time. When metal powder is contained in the raw material powder, oxidation of the metal powder also occurs.

  In addition, it is preferable to perform preheating until the temperature of the workpiece | work 10 becomes in the range of 100-180 degreeC, and it is more preferable to set it in the range of 110-160 degreeC.

  Next, in the third step, vibration due to electromagnetic force is applied to the portion where the raw material powder (coating agent 18 or paste) is applied. In the present embodiment, this vibration application is performed by corona discharge. Corona discharge can be applied with local vibrations, which can efficiently heat a predetermined part, eliminating the need for large-scale equipment such as a heat treatment furnace and controlling the frequency by controlling the frequency. 10 has an advantage that pitting corrosion can be avoided.

  That is, as shown in FIG. 3, the dielectric coil 24, which is an oscillator, is brought close to a portion of the workpiece 10 to which the raw material powder is applied, in other words, a vibration applying portion (heating portion). Then, oscillation is performed with an oscillation frequency of 30 MHz to 3.5 GHz. When the frequency is less than 30 MHz, it is difficult for electric discharge to occur, and even if electric discharge occurs, pitting corrosion may occur on the workpiece 10. Moreover, when it exceeds 3.5 GHz, melting damage may occur due to excessive energy concentration on the surface of the workpiece 10.

  Along with this corona discharge, the solvent volatilizes from the coating agent 18 or the paste. Further, when a reducing agent such as carbon is added to the coating agent 18 or the paste, the oxide film 14 is reduced and the base 12 is exposed. Furthermore, the constituent atoms of the raw material powder diffuse into the exposed base 12.

  As described above, as a result of the diffusion from the raw material powder to the base 12 (work 10), the work 10 having the film 26 formed on the surface is obtained as shown in FIG.

  In general high-frequency heating, the temperature of the workpiece 10 reaches about 1000 ° C., but when corona discharge is performed at a frequency within the above-described range, the surface temperature of the workpiece 10 becomes about 500 ° C. For this reason, even if the thermal expansion coefficients of the workpiece 10 and the coating 26 are greatly different, the tensile stress acting between the workpiece 10 and the coating 26 is reduced. For this reason, the film | membrane 26 cannot peel from the workpiece | work 10, and damage to a film | membrane does not occur easily.

  By connecting the negative electrode of the DC power source 22 and the work 10, diffusion of constituent atoms of the raw material powder into the work 10 occurs in a relatively low temperature region as described above. This is presumably because the surface of the base 12 is activated as a result of negative charges being supplied from the DC power source 22 to the oxide film 14 and the oxide film 14 being easily reduced.

  Even when the reducing agent is not added to the coating agent 18 or the paste, by setting the frequency of the dielectric coil 24 high within the range up to 3.5 GHz, it is compatible with the negative charge supply described above. Thus, the oxide film 14 can be reduced. That is, even in this case, the constituent atoms of the raw material powder can reach the workpiece 10.

  In the above-described embodiment, the Fe-based alloy is exemplified as the material of the workpiece 10. However, the embodiment is not particularly limited thereto, and may be an Al-based alloy. In this case, since the oxide film 14 is chemically stable as compared with the Fe-based alloy, the oscillation frequency of the dielectric coil 24 is set to 60 MHz to 3.5 GHz, more preferably several hundred MHz to 3.5 GHz.

  Moreover, when forming a film | membrane with respect to the workpiece | work 10 which consists of Al or Al type alloy, it is preferable that at least any one of Si or B is included in raw material powder. This is because the oxide film 14 on the workpiece surface and a low melting point compound are formed, so that constituent atoms of other components contained in the raw material powder can easily diffuse into the workpiece 10.

  In either case, the order of the first step and the second step may be interchanged. That is, after electrically connecting the negative electrode of the DC power source 22 to the workpiece 10, the coating agent 18 or the paste may be applied to another part.

  Each powder of WC, Co, Cr, Fe, Al, Ti, Mn and C is 86: 10.8: 0.3: 2: 0.2: 0.3: 0.2: 0.2 Ratio, the same applies hereinafter) to obtain a raw material powder. This raw material powder was mixed with a solution containing an epoxy resin as a binder to prepare paste 30 (see FIG. 5).

  On the other hand, the pressing portion 34 of the forging punch 32 made of SKH 54 and having the shape and dimensions shown in FIG. 5 was degreased, and then the paste 30 was applied to the pressing portion 34 with a thickness of 1 mm.

After the paste 30 was air-dried, the negative electrode of the DC power supply 22 was electrically connected to the exposed portion of the forging punch 32 via the lead wire 16. The generated voltage of the DC power source 22 was 10 V per 10 cm ² of surface area of the forging punch 32.

  After 20 seconds, the dielectric coil 24 was brought close to the paste application site in the forging punch 32, and the oscillation frequency was 240 MHz and heating was performed by applying vibration by electromagnetic force for 15 seconds. After leaving still for 6 seconds, the heated part was cooled with cooling water.

  The above operation is performed on another forging punch 32, one of which is subjected to a finishing process of grinding 0.2 mm to the paste application site (vibration application site), and then the fracture is performed. Observations were made. As a result, a melted portion of 70 to 100 μm was found on the surface layer of the forging punch 32, and an altered portion of about 100 μm was found below the melted portion. That is, the film 26 was formed by the diffusion of constituent atoms of the raw material powder. Moreover, the surface was smooth with respect to the film | membrane provided by plating or thermal spraying, and the numerical value of the surface roughness specified by JIS was about 1/3 to 1/4.

  On the other hand, when forging was performed using the remaining one, galling occurred in the pressed portion 34 when about 40,000 shots were completed.

  For comparison, forging was performed using a SKH54 forging punch 32 having the same shape and dimensions in which a 5 μm TiN coating was applied to the pressing portion 34. In this case, galling occurred when about 7000 shots were completed. That is, the number of shots until galling occurs, in other words, the lifetime is significantly shortened.

  Each powder of Cu, Al, Si, Mn, Ni, Fe, B, C, Ti, Cr, Mo and Zn was added to 20: 8: 6: 28: 15: 3: 3: 0.2: 6: 4: 3 : Mixed at a ratio of 3.8 to obtain raw material powder. This raw material powder was added to a mixed solution of epoxy resin, acetone and alcohol to obtain a paste.

  This paste was made of SKH54 and applied to the top 42 of the AC4A test piece 40 having the shape and dimensions shown in FIG. 6 so that the thickness was 0.5 mm and the diameter was 10 mm.

  After the paste was air-dried, the negative electrode of the DC power source 22 was electrically connected to the exposed portion of the test piece 40 via the lead wire 16. The generated voltage of the DC power source 22 was 90V.

  In this state, the test piece 40 was preheated to 120 ° C. and held for 2 minutes, and heated by applying vibration by electromagnetic force for 15 seconds with an oscillation frequency of 300 MHz. After standing for 8 seconds, the heated part was cooled with cooling water.

  The vicinity of the paste application site (vibration application site) was broken along the depth direction, and the cross-section was observed. As a result, the thickness of the applied product is reduced to 0.2 mm, a penetration portion of about 0.3 mm is formed, and further, the alteration is about 0.6 to 0.7 mm below the penetration portion. It was recognized that a part (diffusion part) was formed. That is, also in this case, the film 26 was formed by diffusion of constituent atoms of the raw material powder.

  When the Brinell hardness of the diffusion portion was measured, it was 356, and the Brinell hardness before film formation was 150, whereas an increase of about 200 hardness was recognized.

It is a schematic sectional explanatory drawing in alignment with the depth direction of the workpiece | work (metallic member) in which the film formation method concerning this Embodiment is implemented. FIG. 2 is a schematic cross-sectional explanatory diagram illustrating a state in which raw material powder is applied to the workpiece of FIG. 1 and a negative electrode of a DC power source is electrically connected. It is a schematic sectional explanatory drawing which shows the state which has given the vibration by electromagnetic force by performing corona discharge with respect to the workpiece | work which apply | coated raw material powder and the negative electrode of DC power supply was electrically connected. It is a schematic sectional explanatory drawing along the depth direction of the workpiece | work in which the membrane | film | coat was formed. It is a general | schematic whole side view in alignment with the axial direction of the punch for forging process (product made from Fe type alloy) which forms a film | membrane. It is a schematic whole perspective view of the test piece (product made from Al type alloy) which forms a membrane | film | coat.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Work 12 ... Base 14 ... Oxide film 18 ... Coating agent 22 ... DC power supply 24 ... Dielectric coil 26 ... Film 30 ... Paste 32 ... Forging punch

Claims (5)

A film forming method for forming a film on the surface of a metal member,
Applying raw material powder to be a film on the surface of the metal member;
Electrically connecting only a negative electrode of a DC power source to the metal member;
Forming a film from the raw material powder by generating a magnetic field and applying vibration by electromagnetic force to a portion of the metal member to which the negative electrode is electrically connected to which the raw material powder is applied;
A film forming method characterized by comprising:   2. The film forming method according to claim 1, wherein the application of vibration by the electromagnetic force is performed by corona discharge.   3. The film forming method according to claim 2, wherein the metal member is made of an iron-based alloy, and the corona discharge is performed at an induction frequency of 30 MHz to 3.5 GHz.   3. The film forming method according to claim 2, wherein the metal member is made of an aluminum alloy and the corona discharge is performed at an induction frequency of 60 MHz to 3.5 GHz.   5. The film forming method according to claim 1, wherein the negative electrode is electrically connected to the metal member, the metal member is preheated to 100 to 180 ° C., and then the raw material. A method for forming a film, comprising applying vibration by electromagnetic force to a portion where powder is applied.

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