JP5670026B2 - Method for suppressing adhesion of powder for coating, powder conveying system for coating, and coating apparatus - Google Patents

Description

  The present invention relates to a coating powder adhesion suppression method, a coating powder conveyance method, and a coating powder conveyance system that suppresses the coating powder that is air-flow conveyed by gas from adhering to the wall surface portion of the conveyance path. Further, the present invention relates to a coating apparatus and a coating method for forming a coating on the surface of the coating powder that has been conveyed by bringing the coating powder into a molten state and colliding it with the surface of a substrate.

  Conventionally, as a method of transporting powder by a required amount and supplying it into the apparatus, there is a method in which powder is fed into a tube-shaped transport tube and gas is flowed in the transport direction along with the powder to the transport port. It has been taken. As an apparatus utilizing such a conveying method, a thermal spraying apparatus for forming a film on the surface of a substrate by thermal spraying can be mentioned. Thermal spraying is a process in which a thermal spray powder (coating powder) such as ceramic is melted by a heat source to form thermal spray particles, which are then collided with a substrate to form a thermal spray coating. Heat resistance and the like can be improved.

  As the thermal spraying device, a thermal spraying torch, a tube-shaped transport pipe that introduces thermal spray powder into the thermal spray torch, and a powder feeder that supplies thermal spray powder to the transport pipe are known (for example, Patent Document 1). The spraying torch is provided with an anode part and a cathode part. When an arc is generated between the anode part and the cathode part, the working gas introduced into the spraying torch becomes plasma and is ejected as a plasma jet. The thermal spray powder is introduced and melted to form thermal spray particles, and the thermal spray coating is formed by colliding the thermal spray particles with the substrate. In this thermal spraying apparatus, a transport gas is passed through a transport pipe, and the sprayed powder is transported in an air stream on the gas flow. In order to allow the spraying torch to move freely with respect to the fixed powder feeder, a relatively long resin made of flexible resin is used for the transfer tube.

JP 2004-81915 A

  As shown in FIG. 5, when the sprayed powder 103 passes through the transport path 101 of the transport pipe 100 by the gas flow of the gas 102, the sprayed powder 103 rubs against the wall surface 101 a of the transport path 101, thereby Charges having different signs (for example, the wall surface 101 a of the conveyance path 101 is positive and the thermal spray powder 103 is negative), and the Coulomb force thereby acts on the thermal spray powder 103. As a result, as shown in the figure, the sprayed powder 103 adheres to and accumulates on the wall surface 101a.

  As the deposition amount of the thermal spray powder 103 on the wall surface 101a of the transport path 101 increases while the film forming process continues, the transport amount per unit time of the thermal spray powder 103 transported by the transport pipe 100 decreases. It becomes difficult to maintain uniform conditions in the film forming process for a long time. If conditions change during the film forming process, it becomes difficult to obtain a sprayed coating having a uniform film thickness and film quality over a large area. Further, when the adhesion amount of the sprayed powder 103 further increases and the conveyance path 101 is blocked by the sprayed powder 103, the film forming process must be interrupted. If the film forming process is interrupted, the film quality may be changed, which is not preferable.

  Therefore, it is conceivable to increase the gas flow rate so that the sprayed powder does not adhere due to the viscous resistance caused by the gas flow. However, since the gas flow rate has a limit value determined by the diameter of the transport pipe, the gas pressure, and the like, the adhesion of the sprayed powder cannot be sufficiently suppressed. Further, when the gas flow rate becomes excessive, the film quality may be deteriorated.

  On the other hand, it is also conceivable to prevent electrification by enclosing the outer periphery of the transport tube with a mesh-like lead wire and grounding the lead wire. However, only the portion of the outer periphery of the transport pipe that is in contact with the conducting wire is neutralized, and the wall surface of the transport path that is constantly rubbing against the sprayed powder remains charged. Therefore, wrapping the outer periphery of the transport pipe with a mesh-like conductor cannot solve the problem that the sprayed powder adheres to the wall surface of the transport path.

In view of the above-described problems of the prior art, the present invention can keep the amount of coating powder transported uniform over a long period of time by suppressing the adhesion of the coating powder to the wall surface of the transport path. (e.g., a long time can be maintained uniform conditions in the film forming process) method for suppressing adhesion coating powder, and an object thereof is to provide a powder transport system及 beauty coating equipment for the covering.

In order to achieve the above object, the following technical measures were taken.
That is, the method for suppressing the adhesion of coating powder according to the present invention is performed when the coating powder is air-flowed toward the transport port of the transport path using a transport pipe having a transport path through which gas flows. Is a method for suppressing the adhesion of the coating powder to the wall surface portion of the transport path, and is wound in a spiral in the same direction with a gap alternately on the outer peripheral surface of the transport pipe by applying a voltage to the plurality of electrodes consisting of elongated conductor causes an electric field of strength in the conveyance path of fluororesin of the conveying tube, the said coating powder by the electric field of the intensity Within the transport path, the phase of the voltage applied to the plurality of electrodes is mutually (360) when the number of the plurality of electrodes is n. ° / n) with shifting, and satisfies the following expression Is shall.
Fp> Fa
However, Fp: Coulomb force generated in the coating powder by the electric field, Fa: Adhesive force of the coating powder generated by charging of the coating powder and the conveyance path due to both charging to the conveyance path.
When the coating powder is air-flow conveyed by the conveying tube, if the coating powder adhesion suppression method of the present invention is used, the voltage can be applied to a plurality of electrodes arranged outside the conveying tube. The generated electric field causes the coating powder to fly and move in a direction different from the gas flow direction, so that the coating powder is separated from the wall surface portion of the transport path, and the adhesion of the coating powder to the wall surface portion is suppressed. can do. The powder for coating in the present invention is limited to the thermal spraying powder used for thermal spraying, and the powder used for the aerosol deposition method and the powder build-up welding method.

The coating powder conveyance system according to the present invention includes a fluororesin conveyance tube having a conveyance path for conveying the coating powder by gas in an air stream, and the coating powder toward the conveyance port of the conveyance path. A gas supply means for supplying the gas to the transport path and an electric field generated in the transport path so as to be transported by air current, and the coating powder is caused to fly in a direction different from the gas flow direction by the electric field. Electric field generating means for suppressing adhesion of the coating powder to the wall surface portion of the transport path, and the electric field generating means are spirally staggered in the same direction on the outer peripheral surface of the transport pipe. Jo to have a plurality of electrodes consisting of wound elongated conductors are, the plurality of electrodes are flying within the transport path of the coating powder by an electric field intensity that caused by the conveying path The direction of movement is directly above one of the electrodes Beauty with a gap from each other so that a longitudinal oblique direction are wound, shifted from each other (360 ° / n) the phase of the voltage applied to the plurality of electrodes when the number of said plurality of electrodes is n In addition, the following formula is satisfied .
Fp> Fa
However, Fp: Coulomb force generated in the coating powder by the electric field, Fa: Adhesive force of the coating powder generated by charging of the coating powder and the conveyance path due to both charging to the conveyance path.
According to the coating powder conveying system of the present invention, an electric field is generated in the conveying path, and the coating powder is caused to fly and move in a direction different from the gas flow direction by this electric field, thereby covering the wall surface portion of the conveying path. It is equipped with electric field generation means that suppresses the adhesion of powder for coating, so that adhesion of powder for coating on the wall surface of the conveyance path is suppressed, and the amount of coating powder transported is kept uniform over a long period of time. Can do. Thereby, uniform conditions can be maintained for a long time in various film forming processes using the coating powder conveyance system. The powder for coating in the present invention is limited to the thermal spraying powder used for thermal spraying, and the powder used for the aerosol deposition method and the powder build-up welding method.

The coating apparatus of the present invention stores a film forming unit that forms a film on the surface of the base material by melting the powder for coating and colliding with the base material, and the powder for coating introduced into the film forming unit. A coating apparatus comprising: a powder supply unit that discharges the powder; and a coating powder transport system that transports the coating powder from the powder supply unit to the film forming unit. The body conveyance system is the above-described powder conveyance system for coating.

  According to the coating apparatus of the present invention, an electric field is generated in the transport path for transporting the coating powder, and the coating powder is caused to fly and move in a direction different from the gas flow direction by this electric field. Since it is equipped with electric field generating means that suppresses the adhesion of the coating powder to the wall surface part, the adhesion of the coating powder to the wall surface part of the conveying path is suppressed, and the conveyance amount of the coating powder is increased for a long time. Can be kept uniform. The powder for coating in the present invention is limited to the thermal spraying powder used for thermal spraying, and the powder used for the aerosol deposition method and the powder build-up welding method.

  As described above, according to the present invention, the coating powder (for example, the sprayed powder) is separated from the wall surface portion of the conveyance path by the electric field generated in the conveyance path, and the coating powder on the wall surface portion of the conveyance path. Since the adhesion of the body is suppressed, the amount of coating powder transported can be kept uniform over a long period of time. In the film forming process, uniform conditions can be maintained for a long time.

It is a systematic diagram showing the whole structure of the plasma spraying apparatus which concerns on the 1st Embodiment of this invention. It is a side view which shows the state by which the 1st, 2nd electrode is wound around the conveyance pipe. It is explanatory drawing showing the state which the thermal spray powder is flying and moving in the direction different with respect to the flow direction of gas with the electric field generated in the conveyance path. It is a systematic diagram showing the principal part structure of the plasma spraying apparatus which concerns on the 2nd Embodiment of this invention. It is explanatory drawing which shows the state by which the thermal spray powder is conveyed with the conventional powder conveyance system.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a system diagram showing the overall configuration of a thermal spraying apparatus (coating apparatus) 1 according to one embodiment (first embodiment) of the present invention. The thermal spraying device 1 is configured as a plasma thermal spraying device 1, and includes a thermal spraying torch (film forming unit) 2 that is a plasma generating unit, a DC power source 3 that supplies current to the thermal spraying torch 2, and a thermal spraying torch 2. A chiller 4 for cooling the powder, a powder feeder (powder supply unit) 6 for storing and discharging sprayed powder (coating powder) 5 to be introduced into the spraying torch 2, and the sprayed powder 5 from the powder feeder 6. A control unit 8 for controlling a coating powder transfer system 7 (hereinafter referred to as a powder transfer system) for transferring to the thermal spraying torch 2, a DC power source 3, a chiller 4, a powder feeder 6, and a powder transfer system 7. And is mainly composed.

  The plasma spraying apparatus 1 heats and melts a thermal spray powder 5 such as powdered ceramics with plasma to form a thermal spray particle of liquid fine particles. The thermal spray particle collides with a surface of a base material (not shown) at high speed. This is for forming a sprayed coating (film) on the surface. By forming a thermal spray coating on the surface of the substrate, the wear resistance, electrical insulation, etc. of the substrate are improved.

  As the thermal spraying torch 2, a known one can be used. For example, the negative electrode 11 having a tapered tip portion 11a and the negative electrode 11 are provided so as to surround the negative electrode 11 while being insulated from the negative electrode 11. And a positive electrode 12 on which a nozzle portion 12a for ejecting spray particles is formed. The thermal spraying torch 2 is provided with a power supply connecting portion 13 for supplying a current from the DC power supply 3 to the positive electrode 12 and the negative electrode 11, and the power supply connecting portion 13 and the DC power supply 3 are connected via a wiring 14. Are electrically connected. Further, the spraying torch 2 has a positive electrode 12 and a negative electrode 11 for cooling the positive electrode 12, a cooling port 15 for allowing cooling water from the chiller 4 to flow into and out of the negative electrode 11, and a plasma operation for the thermal spraying torch 2. A working gas supply port 17 for feeding the gas 16 is provided.

  The chiller 4 is configured as a water-cooled cooling device, and the cooling port 15 and the chiller 4 are connected by a cooling pipe 18 for flowing cooling water, and the positive electrode is connected via the cooling port 15. A cooling water having a predetermined temperature is circulated through the anode 12 and the negative electrode 11. Thereby, the temperature of the positive electrode 12 and the negative electrode 11 can be controlled. A mass flow controller 20 is connected to the working gas supply port 17 via a gas pipe 19, and a gas cylinder 22 is connected to the mass flow controller 20 via a gas common pipe 21. The gas cylinder 22 is filled with a gas such as argon, nitrogen, hydrogen, and helium as the plasma working gas 16. Thus, the plasma working gas 16 can be supplied from the gas cylinder 22 toward the thermal spraying torch 2, and the flow rate of the plasma working gas 16 can be adjusted. The plasma working gas 16 is not limited.

  The positive electrode 12 of the thermal spraying torch 2 is provided with a powder supply port 23 for introducing the thermal spray powder 5, and the thermal spray powder 5 is supplied to the generated plasma jet through the powder supply port 23. Is to be supplied. The powder feeder 6 in which the sprayed powder 5 is stored includes a storage tank 6A and a measuring unit 6B for discharging the sprayed powder 5 stored in the storage tank 6A by a predetermined amount. The weighing unit 6B includes a rotating disk (not shown) that is rotated by a motor, and the sprayed powder 5 stored in the storage tank 6A is put out on the surface of the rotating disk. The supply amount of the thermal spray powder 5 is adjusted by controlling the rotational speed of the rotary disk.

  The powder transfer system 7 includes a transfer pipe 27 having a transfer path 26 for transferring the sprayed powder 5 by air flow with a carrier gas (gas) 25, and a spray powder toward a transfer port 26 a that is an outlet of the transfer path 26. 5 is provided with gas supply means 28 for supplying the carrier gas 25 to the conveyance path 26 so that the gas 5 is conveyed by airflow. The gas supply means 28 includes a mass flow controller 20 connected to the powder feeder 6 via a carrier gas pipe 29, and a gas cylinder 22 connected to the mass flow controller 20 via a gas common pipe 21. The gas cylinder 22 to the mass flow controller 20 are the same as those used to supply the plasma working gas 16, thereby reducing the manufacturing cost of the plasma spraying apparatus 1 and reducing the installation space of the apparatus 1. The carrier gas 25 is not limited, but argon or nitrogen is used in this embodiment.

  The conveyance tube 27 is made of a fluororesin tube having an outer diameter of 4 mm, and has a low surface friction coefficient, high insulation, and the like. As shown in FIG. 1, the conveying port 26 a (conveying tube outlet) is connected to the powder supply port 23 of the thermal spraying torch 2, whereby the powder feeder 6 and the thermal spraying torch 2 are connected to each other through the conveying path 26. The thermal spray powder 5 is introduced from the powder feeder 6 to the thermal spray torch 2. Further, the thermal spraying torch 2 is attached to a scanning mechanism (not shown), and the thermal spraying torch 2 can relatively move on the surface of a base material (not shown) by this scanning mechanism. Therefore, about 2 m of the transfer pipe 27 is used so that the thermal spraying torch 2 can move freely with respect to the fixed powder feeder 6. The material, diameter, and length of the transport tube 27 are not limited and can be changed as appropriate.

The sprayed powder 5 stored in the powder feeder 6 is placed on the carrier gas 25 whose supply amount is adjusted by the measuring unit 6B and the flow rate of which is adjusted by the mass flow controller 20 by the powder transfer system 7, and the transfer pipe 27 is sent to the thermal spraying torch 2 through the conveyance path 26 (air flow conveyance).
The control unit 8 of the plasma spraying apparatus 1 is connected to the chiller 4, the DC power supply 3, the mass flow controller 20, the powder feeder 6, and the powder conveyance system 7. The control unit 8 is provided with an operation panel 31 for an operator to scan. By operating the operation panel 31, the control unit 8 of the plasma spraying apparatus 1 includes the chiller 4 and the DC power supply 3. The operation parameters of the mass flow controller 19, the powder feeder 6, and the powder conveying system 7 are controlled.

  With the plasma spraying apparatus 1 having the above-described configuration, a sprayed coating is formed on the surface of the substrate as follows. A voltage is applied from the DC power source 3 between the positive electrode 12 and the negative electrode 11 of the thermal spraying torch 2 to generate arc plasma at the tip 11 a of the negative electrode 11. A plasma working gas 16 is sprayed on the arc plasma to form a high-temperature plasma jet, and the sprayed powder 5 fed by the powder conveying system 7 is supplied thereto. The sprayed powder 5 is heated and melted to form liquid fine particles (sprayed particles) and is ejected together with the plasma jet. The sprayed sprayed particles collide with the surface of the substrate at a high speed and are stacked on the surface, so that a sprayed coating is formed on the surface.

  In the powder conveyance system 7 of the present embodiment, an electric field generating means 32 that generates an electric field in the conveyance path 26 is provided. The electric field generating means 32 is for suppressing the sprayed powder 5 passing through the transport path 26 from adhering to the wall surface portion 26 h of the transport path 26, and the electrode portion D disposed outside the transport pipe 27. And a power supply unit 34 and a ground unit 33 connected to the electrode unit D.

  The electrode part D is composed of a first electrode 35 and a second electrode 36, and both the first and second electrodes 35 and 36 are formed of elongated conductive wires. The material of the conducting wire is not limited, and copper, aluminum or the like is used. The first and second electrodes 35 and 36 are spirally wound around the outer periphery in the vicinity of one end of the transport tube 27 (in the vicinity of the powder feeder 6) (see FIG. 2).

  As the form of the first and second electrodes 35 and 36, the outer periphery of the transport tube 27 is encased in the first and second electrodes 35 and 36 by using the elongated conductive shape as in this embodiment. Thus, an electric field can be generated in the entire transport path 26. In the present embodiment, the first and second electrodes 35 and 36 are wound around the outer periphery of the transport tube 27 with a slight gap as shown in FIG. The method of winding the electrodes 35 and 36 is not limited. For example, the electrodes 35 and 36 may be wound with a gap larger than that shown in FIG.

  The power supply unit 34 is configured as a power transformer, and outputs a voltage of 5 kV at a frequency of 60 Hz, for example. An AC voltage is applied to the electrode D by the power source 34. Of the first and second electrodes 35, 36, the first electrode 35 is electrically connected to the power supply unit 34, and the second electrode 36 is electrically connected to the ground unit 33. When an AC voltage is applied to the first electrode 35 by the power supply unit 34, an electric field E1 is generated in the transport path 26 (see FIG. 3). That is, the electric field E1 can be generated in the transport path 26 of the transport tube 27 whose outer periphery is surrounded by the first and second electrodes 35 and 36.

  The electric field E1 is directed in the substantially radial direction (substantially transverse direction) of the transport path 26. When the thermal spray powder 5 is conveyed to the conveyance path 26 where the electric field E1 is generated, the thermal spray powder 5 made of ceramic, for example, is charged by the electric field E1. At that time, the Coulomb force in the electric field direction (substantially radial direction of the conveyance path 26) acts on the thermal spray powder 5, and the thermal spray powder 5 flies and moves in the approximate radial direction of the conveyance path 26, and the wall surface portion 26h. Get away from.

  In addition, the substantially radial direction (substantially transverse direction) of the conveyance path 26 here means not only the radial direction of the conveyance path 26, that is, the vertical direction in FIG. 3, but a wide range including the radial direction. It shall be said. Specifically, the gas flow direction (when the direction directly above the first electrode 35 (upward direction in FIG. 3) shown as a cross section below the transport pipe 27 in FIG. This includes a range from the 60 ° direction (to the right in FIG. 3) to the −60 ° direction from the gas flow direction to the backflow direction (left direction in FIG. 3). This range varies depending on the strength of the electric field E1 and the like, and is not limited to this.

  Actually, the conveyance path 26 includes a range where a strong electric field E1 is generated, a range where a weaker electric field E1 is generated, and a range where a minute electric field E1 is generated. Therefore, the sprayed powder 5 that comes near the first electrode 35 in the wall surface portion 26h of the transport path 26 is moved and moved in a substantially transverse direction by a strong electric field E, and a weak electric field E1 is generated or is in a very small range. Flying toward the range where the electric field E1 is generated. The wall surface portion 26h does not mean only the surface of the wall surface of the conveyance path 26, but a surface layer portion including a portion close to the surface.

Therefore, the thermal spray powder 5 conveyed by the conveyance path 26 flies and moves in multiple directions (a direction different from the flow direction of the carrier gas 25) by the electric field E1 generated by the electric field generating means 32 as shown in FIG. Since the sprayed powder 5 flies and moves in multiple directions, the adhesion of the sprayed powder 5 to the wall surface portion 26h of the transport path 26 can be suppressed in combination with the viscous resistance force caused by the flow of the carrier gas 25.
Each condition such as the strength of the electric field E1, the particle size and density of the sprayed powder 5, the flow rate of the carrier gas, the diameter of the transfer tube, and the like is determined so as to satisfy the following equation.
Fp> Fa
Fp: Coulomb force generated in the sprayed powder 5 by the electric field E1.
Fa: Adhesive force of the sprayed powder 5 to the transport path 26 caused by the friction between the sprayed powder 5 and the transport path 26 due to charging of both.

  According to the plasma spraying apparatus 1 including the powder transfer system 7 of the present embodiment, the electric field generating means 32 for generating the electric field E1 in the transfer path 26 of the spray powder 5 sprays the wall surface portion 26h of the transfer path 26. Since the adhesion of the powder 5 is suppressed, the conveyance amount of the thermal spray powder 5 can be kept uniform for a long time. Further, it is possible to prevent the conveyance path 26 from being blocked by the sprayed powder 5. As the electric field generating means 32, an electric field is generated with a simple configuration in which the power supply unit 34 is connected to one of the first and second electrodes 35, 36 provided outside the transport tube 27 and the ground unit 33 is connected to the other. The powder transfer system 7 can be easily manufactured, and the manufacturing cost of the plasma spraying apparatus 1 can be suppressed.

  Furthermore, the present invention forms a thermal spray coating on the surface of the base material by melting the powder for coating introduced into the film forming section by air flow by the gas flowing through the transport path of the transport pipe and colliding with the base material As a method for forming the coating, the plasma spraying apparatus 1 is used to suppress the spraying powder (coating powder) 5 from adhering to the wall surface portion 26h of the conveyance path 26, and the spraying powder 5 Can be introduced into the thermal spraying torch (film forming unit) 2 to form a film. According to this film forming method, the transport amount of the thermal spray powder 5 introduced into the thermal spray torch 2 can be kept uniform over a long period of time.

  Thereby, in the film forming process using the above-described film forming method, the amount of the sprayed powder 5 introduced into the thermal spraying torch 2 is kept constant for a long time, and uniform conditions can be maintained for a long time. In addition, since the conveyance path 26 can be prevented from being blocked by the thermal spray powder 5, there is no need to interrupt the film formation process and there is no possibility of causing a change in film quality. Therefore, even when spraying over a large area of the substrate, a high-quality sprayed coating having a uniform film thickness and film quality can be obtained.

  In particular, when the particle size of the thermal spray powder 5 introduced into the thermal spray torch 2 is small (for example, 10 μm or less), the thermal spray powder 5 generally tends to adhere to the conveyance path 26 and easily deposit. If the sprayed coating is formed by the plasma spraying apparatus 1 provided with the powder transfer system 7 of the above embodiment, the adhesion of the sprayed powder 5 is suppressed. It is maintained for a long time, and a high quality sprayed coating can be obtained.

  The powder transfer system 7 provided in the plasma spraying apparatus 1 of the present embodiment is a configuration example for using the coating powder powder adhesion suppressing method and the coating powder transfer method according to the present invention. is there. That is, when the coating powder is conveyed by air flow toward the conveyance port of the conveyance path by the conveyance pipe having the conveyance path through which the gas flows, the coating powder is prevented from adhering to the wall surface portion of the conveyance path. As a method for suppressing the adhesion of the coating powder according to the present invention, a voltage is applied to the two first and second electrodes 35 and 36 arranged outside the transport tube 27 as in the above embodiment. An example is a method in which an electric field E1 is generated in the transport path 26, and the sprayed powder 5 is caused to fly and move in a direction different from the flow direction of the carrier gas 25 by the electric field E1. According to this method, the thermal spray powder 5 is separated from the wall surface portion 26 h of the transport path 26, and adhesion of the thermal spray powder 5 to the wall surface portion 26 h of the transport path 26 can be suppressed.

  Further, as a method for conveying a coating powder according to the present invention in which a coating powder having a conveyance path through which a gas flows is air-flow conveyed toward a conveyance port of the conveyance path, as in the above-described embodiment, A state in which the sprayed powder 5 is caused to fly and move in a direction different from the flow direction of the carrier gas 25 by the electric field E1 generated in the path 26, and the sprayed powder 5 is prevented from adhering to the wall surface portion 26h of the transport path 26. Thus, a method of conveying the sprayed powder 5 by airflow can be mentioned. According to this method, the sprayed powder 5 can be transported in a state where adhesion of the sprayed powder 5 to the inner wall portion 26 h of the transport path 26 is suppressed.

  FIG. 4 shows a second embodiment according to the plasma spraying apparatus of the present invention. The plasma spraying device 40 of the present embodiment is different from the first embodiment in that the first and second electrodes 41 and 42 are different from the positions where they are arranged on the outer periphery of the transfer tube 27. is there. FIG. 4 shows the vicinity of the outlet of the powder feeder 6 and the thermal spraying torch 2. Note that, in the plasma spraying apparatus 40 of the present embodiment, configurations other than the first and second electrodes 41 and 42 and the power supply unit 34 are the same as those of the first embodiment. As can be seen from the figure, the conveyance pipe inlet 27a of the conveyance pipe 27 is connected to the powder feeder 6, and the cross-sectional area of the passage of the sprayed powder 5 is abruptly reduced. When the cross-sectional area of the passage is suddenly reduced, there is a problem that the sprayed powder 5 is likely to adhere to the connecting portion between the powder feeder 6 and the transport pipe inlet 27a. The plasma spraying apparatus 40 of the present embodiment aims to solve this problem.

  The first and second electrodes 41 and 42 are both constituted by a conductive plate (ring-shaped plate) having a required thickness formed in a ring shape. The inner diameters of the first and second electrodes 41 and 42 are approximately the same as the outer diameter of the transport tube 27, and the transport tube 27 can be inserted through the first and second electrodes 41 and 42. The outer diameters of the first and second electrodes 41 and 42 are 10 mm. These inner and outer diameter dimensions are not limited, and may be appropriately changed depending on the outer diameter dimension of the transport pipe 27 and the like. The second electrode 42 is mounted at a position adjacent to the powder feeder 6 on the outer periphery of the transport tube 27, and the first electrode 41 is mounted with a required distance from the second electrode 42. Thus, the 1st, 2nd electrodes 41 and 42 are mounted | worn with the entrance 26t of the conveyance path 26 (refer FIG. 4). Note that the distance between the first electrode 41 and the second electrode 42 is not limited.

  The first electrode 41 is electrically connected to the power supply unit 34, and the second electrode 42 is electrically connected to the ground unit 33. When an AC voltage is applied to the first electrode 41, an electric field E2 can be generated at the inlet 26t of the transport path 26 sandwiched between the first and second electrodes 41 and 42.

  When the thermal spray powder 5 comes to the inlet 26t of the conveyance path 26 where the electric field E2 is generated, the thermal spray powder 5 made of ceramic, for example, is charged by the electric field E2. At that time, a Coulomb force in the electric field direction (the direction opposite to the gas flow direction; the lower direction in FIG. 4) acts on the thermal spray powder 5, and the thermal spray powder 5 trying to collect at the inlet 26 t flies in the electric field direction. Try to move. Therefore, the thermal spray powder 5 coming to the inlet 26t does not collect at the inlet 26t but is smoothly introduced into the transport path 26. As described above, by arranging the first and second electrodes 41 and 42 in the local portion of the transport tube 27, it is possible to suppress the sprayed powder 5 from adhering and depositing on the local portion. it can.

  In the second embodiment shown in FIG. 4, the first electrode 41 and the second electrode 42 are not only applied to the entrance 26 t of the transport path 26 but also to the transport port 26 a that is the exit of the transport path 26. Alternatively, it may be provided only at the transport port 26 a of the transport path 26. At the transfer port 26a connected to the powder supply port 23 of the thermal spraying torch 2, the diameter of the transfer port 26a is smaller than the diameter of the other part of the transfer path 26, so that the sprayed powder 5 is transferred to the transfer port 26a. However, the sprayed powder 5 can be prevented from accumulating by providing the first electrode 41 and the second electrode 42 also at the transfer port 26a.

  Hereinafter, the present invention will be described in more detail with reference to examples. In addition, this invention is not limited to this Example.

(Example)
The same powder conveyance system and powder feeder as in the first embodiment were used. The carrier gas was allowed to flow at a flow rate of 10 L / min while introducing the sprayed powder in an amount of 10 g per minute into a transport tube having an outer diameter of 4 mm, and the sprayed powder was passed through the transport tube. The state of the thermal spray powder adhering to the transport path and the transport amount of the thermal spray powder were confirmed. As the thermal spray powder, alumina powder having an average particle diameter of 3 μm was used, and an AC voltage of 5 kV was continuously applied to the first electrode by the power supply unit. In addition, about the state of the thermal spraying powder adhering to a conveyance path, it confirmed from the outside of the translucent conveyance pipe | tube during the test, and cut | disconnected the conveyance pipe | tube after the test and confirmed. About the conveyance amount of the thermal spray powder, the exit of the conveyance pipe was confirmed visually.
The state of the sprayed powder adhering to the conveyance path: Some sprayed powder adhered spirally, but the amount of adhesion did not increase over time, and the conveyance path was not blocked.
Amount of sprayed powder transport: not decreased.

(Comparative example)
The electric field generating means was removed from the powder transfer system of the above example, and the process was performed without generating an electric field in the transfer path. The sprayed powder was passed through the transfer tube under the same conditions as in the above example. As in the example, alumina powder having an average particle diameter of 3 μm was used as the spray powder, and the state of the spray powder adhering to the transport path and the transport amount of the spray powder were confirmed.
The state of the sprayed powder adhering to the transport path: The phenomenon that the sprayed powder that started to adhere immediately after the start of the test and a large amount of agglomerated powder flows at once, and the sprayed powder that has aggregated in a small amount to the transport path The phenomenon of remaining attached was repeated.
Amount of sprayed powder transported: The transported amount became non-constant by starting to decrease immediately after the start of the test and repeating the above phenomenon. Furthermore, the amount of conveyance decreased with the passage of time, and after 10 minutes, the conveyance path was blocked with the sprayed powder, making conveyance impossible.

  From the above Examples and Comparative Examples, it can be seen that if an electric field is generated in the transport path using the electric field generating means, the adhesion of the sprayed powder to the transport path is drastically suppressed.

  In addition, each embodiment and Example disclosed above are examples, and are not restrictive. The conveyance pipe, gas supply means, and electric field generation means used in the powder conveyance system can be used in various forms depending on the application. In particular, with regard to the electric field generating means, in the first embodiment, one electrode is connected to the power supply unit and the other electrode is connected to the ground unit. However, as another form, it is not connected to the ground unit. In addition, the phase of the voltage applied to both electrodes may be shifted by 180 °. In this case, for example, a phase adjusting means for shifting the phases of the voltages applied to the plurality of electrodes may be further provided. By shifting the phase of the voltage applied to the two electrodes, the sprayed powder can be moved in multiple directions by two electric fields generated in the transport path.

  Moreover, the electrode which comprises an electrode part is not restricted to two, You may comprise the said electrode part by three or four or more electrodes. Hereinafter, the plurality of electrodes including the first and second electrodes refer to electrodes in which voltages applied to the electrodes are different or phases of voltages applied to the electrodes are shifted. For example, when the electrode portion is composed of three electrodes, one of the three electrodes may be connected to the ground portion, and the phases of the voltages applied to the remaining two electrodes may be shifted from each other by 180 °. In addition, none of the three electrodes may be connected to the ground portion, and the phases of the voltages applied to the three electrodes may be shifted from each other by 120 °. Furthermore, when the number of electrodes is four or more, when the number of electrodes is n, none of the n electrodes are connected to the ground portion, and the phases of the voltages applied to the n electrodes are mutually different. It may be shifted by 360 ° / n. In this way, an effective electric field is generated in the transport path by changing the number of electrodes constituting the electrode part, the presence / absence of connection of the ground part to these electrodes, and the degree to which the voltages applied to these electrodes are shifted from each other. Just do it.

  In the above embodiment, the conductive wire and the ring-shaped plate are used as the first and second electrodes, but other shapes can be used as long as an effective electric field can be generated in the transport path. For example, the first and second electrodes may be metal foils extending along the length of the transport path (transport pipe). Examples of the metal foil include aluminum foil and copper foil. In other words, the first and second electrodes made of metal foil are provided opposite to each other so that the conveyance path is sandwiched between the first and second electrodes. Moreover, you may provide three or more electrodes which consist of metal foil extended along the length of such a conveyance path. Even in this case, an effective electric field is generated in the transport path by changing the number of electrodes constituting the electrode part, the presence / absence of connection of the ground part to these electrodes, and the degree to which the voltages applied to these electrodes are shifted from each other. You can do it.

  Furthermore, the first and second electrodes are conductive plates (ring-shaped plates) having a required thickness formed in a ring shape in the second embodiment, and these are transported not only at the transport pipe inlet and the transport pipe outlet. A plurality of them may be provided at a necessary interval alternately from the pipe inlet to the transport pipe outlet. Even in this case, an effective electric field is generated in the transport path by changing the number of electrodes constituting the electrode part, the presence / absence of connection of the ground part to these electrodes, and the degree to which the voltages applied to these electrodes are shifted from each other. You can do it.

  In the first embodiment, the elongated first electrode and the second electrode constituting the electrode part D may be spirally wound around the outer periphery of the transport pipe from the transport pipe inlet to the transport pipe outlet. . As a result, the entire outer periphery from the conveyance pipe inlet to the conveyance pipe outlet of the conveyance pipe is wrapped by the first and second electrodes 35 and 36, and from the conveyance path inlet wrapped by the first and second electrodes. In addition, an electric field can be generated in a wider range up to the transport opening that is the exit of the transport path.

  A plasma spraying apparatus has been described as an example of a method for suppressing the adhesion of powder for coating, a method for transporting powder for coating, and a powder transport system for coating. However, these methods and systems flow carrier gas through a transport pipe. Therefore, the present invention can be applied to various other apparatuses that pump the coating powder. Accordingly, the coating powder to be conveyed is not limited to the thermal spraying powder, and the present invention can be applied to any powder as long as it is used for coating a substrate. For example, in the above embodiments, the plasma spraying apparatus has been described as an example using a sprayed powder. However, the present invention can be applied to a spraying apparatus of a type that introduces a sprayed powder into a sprayed part, such as a flame spraying apparatus. is there. Further, the first embodiment and the second embodiment can be combined. In this case, the powder from the powder feeder is smoothly introduced into the conveyance path and is prevented from adhering to the entire wall surface of the conveyance path, so that uniform conditions are used in the film forming process or various manufacturing processes. Can be maintained for a long time, and a higher quality product can be obtained.

Further, the coating method in the aerosol deposition method and the powder build-up welding method is applied to the coating powder adhesion suppressing method, the coating powder transport method, and the coating powder transport system according to the present invention. Conveyance of the powder for use.
(Aerosol deposition method)
In the aerosol deposition method (hereinafter referred to as AD method), powder (coating powder) made of ceramics or metal fine particles with a particle size of several tens of nanometers to several μm is mixed with gas to form an aerosol and decompressed. This is a technique for forming a film by spraying onto a substrate through a nozzle in the atmosphere described above. In recent years, the AD method has attracted attention as a method capable of forming a dense film having a crystal structure similar to that of fine particles as a raw material at a low substrate temperature and at a high film formation rate.

  A film forming apparatus using the AD method includes, for example, an aerosol chamber, a film forming chamber, a gas cylinder, a flow controller, and the like connected by a transfer pipe. The inside of the film forming chamber is depressurized by a vacuum pump, and the dry powder is agitated and mixed with gas in the aerosol chamber to be aerosolized. Due to the gas flow generated by the pressure difference between the two chambers, the powder is transferred to the film forming chamber, accelerated through the nozzle, and sprayed onto the substrate.

The coating powder adhesion suppressing method, the coating powder transport method, and the coating powder transport system according to the present invention can be applied to the powder transport in the film forming apparatus using the AD method. .
In this case, in the manufacturing process in which the film forming apparatus using the AD method is used, the transport amount of the powder is kept uniform for a long time, and the uniform condition can be maintained for a long time.

(Powder overlay welding method)
In the powder build-up welding method, high-temperature plasma gas is squeezed with a water-cooled nozzle to reach the base material as a plasma arc with high energy density, and an arc current is passed through the base material to form a molten pool on the surface of the base material. The powder (coating powder) conveyed by the carrier gas is fed into the plasma arc and melted, and then charged into the molten pool on the base material to form a built-up layer.

  In the above-mentioned powder build-up welding method, powder is used as the build-up material, so build-up welding is possible with high-hardness materials and ceramics, which are difficult to process materials that could not be processed into wires and rods. By changing costs, it is possible to form coatings for various purposes, with excellent peel resistance, and thick coatings. Oil, ships, aircraft, transportation equipment, and nuclear power generation that require first-class quality control Etc., and has a wide range of applications.

As a powder conveyance system in the film forming apparatus using the powder build-up welding method, a system substantially the same as the powder conveyance system shown in FIG. 1 to which the present invention is applied can be used. In this case, in the manufacturing process in which the film deposition apparatus using the powder build-up welding method is used, the amount of powder transport can be kept uniform over a long period of time, and uniform manufacturing conditions can be maintained for a long time. .
The scope of the present invention is not limited to the above-described embodiments and examples, but is indicated by the scope of the claims, and includes meanings equivalent to the scope of the claims and all modifications within the scope.

  INDUSTRIAL APPLICABILITY The present invention is effectively applied to a method and an apparatus in which a gas is allowed to flow through a transport pipe and the coating powder is pumped there.

DESCRIPTION OF SYMBOLS 1 Plasma spraying apparatus 2 Spraying torch 5 Spraying powder 6 Powder feeder 7 Powder conveyance system 25 Carrier gas 26 Conveyance path 27 Conveyance pipe 32 Electric field generation means 33 Grounding part 34 Power supply part 35 1st electrode 36 2nd electrode

Claims (3)

A coating that suppresses the coating powder from adhering to the wall surface portion of the transport path when the coating powder is transported by air flow toward the transport port of the transport path with a transport pipe having a transport path through which gas flows. A method for suppressing adhesion of powder for use,
By applying a voltage to the plurality of electrodes to alternately consisting elongated conductor wound in the same direction of the spiral with a gap on the outer peripheral surface of the transport tube, the fluororesin of the transport tube A strong electric field is generated in the transport path, and the coating powder is caused to fly and move in the transport path in a direction directly above one of the electrodes and in an oblique direction before and after the electrode .
A method for suppressing the adhesion of powder for coating, wherein the number of the plurality of electrodes is n, the phases of voltages applied to the plurality of electrodes are shifted from each other (360 ° / n), and the following equation is satisfied : .
Fp> Fa
However, Fp: Coulomb force generated in the coating powder by the electric field, Fa: Adhesive force of the coating powder generated by charging of the coating powder and the conveyance path due to both charging to the conveyance path. A fluororesin transport pipe having a transport path for air-flowing the coating powder by gas;
Gas supply means for supplying the gas to the transport path so that the coating powder is air-flow transported toward the transport port of the transport path;
An electric field is generated in the transport path, and the coating powder is caused to fly and move in a direction different from the gas flow direction, thereby preventing the coating powder from adhering to the wall surface portion of the transport path. And an electric field generating means for
Said electric field generating means, have a plurality of electrodes consisting of elongated conductor which alternately wound in the same direction of the spiral on the outer peripheral surface of the transport pipe, the plurality of electrodes, in the conveying path The coating powder is wound with a gap between each other so that the flying movement direction of the coating powder in the conveyance path is directly above the one of the electrodes and obliquely in front and back thereof by the generated strong and weak electric field. And
A coating powder transport system , wherein when the number of the plurality of electrodes is n, the phases of voltages applied to the plurality of electrodes are shifted from each other (360 ° / n) and the following equation is satisfied .
Fp> Fa
However, Fp: Coulomb force generated in the coating powder by the electric field, Fa: Adhesive force of the coating powder generated by charging of the coating powder and the conveyance path due to both charging to the conveyance path. A film forming unit that forms a film on the surface of the substrate by melting the powder for coating and colliding with the substrate;
A powder supply unit for storing and discharging the coating powder to be introduced into the film forming unit;
A coating apparatus comprising: a coating powder conveyance system configured to convey the coating powder from the powder supply unit to the film forming unit;
3. The coating apparatus according to claim 2, wherein the coating powder transport system is the coating powder transport system according to claim 2.

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