JPH07135092A - Plasma thermal spraying device - Google Patents

Abstract

PURPOSE:To facilitate thermal spraying film layer-multiplying work, and reduce work time by providing plural powder charging parts. CONSTITUTION:Different sorts of material powder 5, 50 are contained in powder containers 7, 70. In layer-multiplying work to flame coating film 170, a powder charging part 14 is actuated first, and the material powder 5 is charged into plasma jet 4 to form a first layer of the film 170. Next, action of the charging part 14 is stopped, a powder charging part 140 is actuated, and the material powder 50 is charged into the jet 4. A second layer of the film 170 is thus formed. The charging parts 14, 140 are then actuated repeatedly to form multiple layers of the film 170. By charging the same material powder from the charging parts 7, 70 simultaneously into the jet 4, thickness of the film 170 can be controlled, or by charging the different sorts of the material powder from the charging parts 7, 70 simultaneously, the film 170 comprising mixture of the different sorts of the material can be formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for spraying a molten powder on the surface of a solid substrate to form a film.

[0002]

2. Description of the Related Art A plasma spraying apparatus heats and melts powdery ceramics, or a spraying material such as metal or plastic with plasma to form liquid fine particles, and these liquid fine particles are rapidly jetted onto the surface of a solid base material by a plasma jet. It is for colliding (spraying) and forming a film on the solid substrate. By coating the solid base material, ring resistance, wear resistance, electrical insulation, etc. are improved.

FIG. 6 is a system diagram showing the structure of a conventional plasma spraying apparatus. A plasma torch 1 ejects a plasma jet 4 containing liquid fine particles toward the surface of a solid substrate 2 on which a film is to be formed. A pulse power supply 18 is connected to the anode terminal 20A and the cathode terminal 22A of the plasma cheat 1 via the wiring 13. Further, the gas spraying part 15 is connected to the gas spray port 15A provided in the plasma torch 1 from the gas cylinder 9 through the pipe 12A. Further, the powder charging section 14 is connected from the powder container 7 containing the raw material powder 5 to the powder charging port 14A provided in the plasma torch 1 via the piping 12B. A gas cylinder 8 is connected to the pipe 12B.

FIG. 7 is a sectional view showing the internal structure of the plasma torch 1 of FIG. The plasma torch 1 is provided with a cathode 22 having a cathode terminal 22A at the axial center.
The positive electrode 20 is arranged on the outer periphery of the negative electrode 22 via an insulator 21. The positive electrode 20 includes a positive electrode 20A and forms a nozzle portion 24. As described above, the plasma torch 1 is provided with the gas blowing port 15A,
The working gas 10 is sprayed onto the tip 22B of the negative electrode 22. Further, the plasma torch 1 is provided with a powder charging port 14A, and the raw material powder 5 is charged into the plasma jet 4.

In FIG. 7, a voltage is applied between the positive electrode 20 and the negative electrode 22 to generate a plasma arc at the tip 22B of the negative electrode 22. A working gas 10, for example, argon gas is blown to this plasma arc, and a plasma jet 4 is ejected in the direction of arrow 25. At that time, the raw material powder 5 is charged into the plasma jet 4, and the raw material powder 5 is melted by plasma heat to become liquid fine particles. The plasma jet 4 is ejected from the nozzle 24 together with the liquid particles.

Returning to FIG. 6, the pulsed power supply 18 causes dielectric breakdown between the electrodes and causes a large current to flow between the electrodes to generate high temperature plasma. The gas cylinder 9 has a working gas 10
Is filled. The gas cylinder 8 is filled with a carrier gas 6, for example, argon gas. The carrier gas 6 is used to send the raw material powder 5 to the powder charging port 14 </ b> A by its wind pressure and to charge it into the plasma jet 4.

In FIG. 6, a solid body 2 is arranged facing a plasma torch 1 with a gap length G therebetween. The plasma jet 4 spreads in the radial direction as it progresses through the gap length G, and forms a circular spray coating 17 having a diameter D in the range on the surface of the solid body 2. For example, when alumina powder having a melting temperature of 2300 ° K is used as the raw material powder 5, tens of thousands of K plasma jet 4 is generated,
Alumina powder is sprayed onto the solid body 2.

Further, in the apparatus of FIG. 6, the pulse power source 18 is used as a current source, and the gap length G is several cm.
It has become a degree. As an example of a different conventional device, there is a device in which the current source is a DC power source and the gap length G is about 10 cm. However, if the gap length G is made too large, the thin sprayed coating 17 having a thickness of several μm cannot be uniformly formed, and it becomes uneven depending on the location. Thermal spray coating 1
The central part of 7 rises to a thickness of several hundred μm, which is quite thick. If the gap length G is reduced to several cm or less, the thin sprayed coating 17 can be formed uniformly. When the gap length G is reduced, the solid base material 2 itself may be damaged by the heat of the plasma jet 4. Therefore, the current source is the pulse power source 18
The same applicant has already applied for a patent for a method of suppressing the temperature rise of the solid substrate 2 itself by injecting the plasma jet 4 only for a very short time. By plasma spraying using the pulse power supply 18, a sprayed coating 17 having a uniform thickness and a thin thickness (several μm thick) is formed, and the adhesion to the solid substrate 2 is far superior to that obtained by the DC power supply. A sprayed coating 17 is obtained.

[0009]

However, the conventional apparatus as described above has a problem that the work of forming the composite layer of the thermal spray coating is complicated. That is, when it is desired to form a plurality of spray coatings by spraying different raw material powders, conventionally, it is necessary to clean the inside of the pipe 12B in the powder feeding section and replace the raw material powder in the powder container with a different one. there were. Therefore, the larger the number of layers, the more labor is required, and the longer the preparation time for plasma spraying is.

An object of the present invention is to facilitate the work of forming a composite layer of a thermal spray coating.

[0011]

In order to achieve the above object, according to the present invention, an electrode pair for generating plasma,
A power supply connected to this electrode pair to output a pulse voltage, a gas spraying unit for spraying a working gas to plasma to form a plasma jet, a powder charging unit for charging a raw material powder into the plasma jet, and a raw material powder melted by plasma heat. It is preferable that a plurality of powder feeding parts are provided in the nozzle configured to inject with the plasma jet.

Further, in such a construction, it is preferable that the plurality of powder feeding portions can feed different raw material powders into the plasma jet. Further, in such a configuration, it is preferable that a plurality of power supplies be provided and a switcher capable of switching the connection between each of the power supplies and the electrode pair to be provided.

[0013]

According to the structure of the present invention, a plurality of powder feeding parts are provided. By sequentially feeding different powder raw materials from the respective powder feeding portions to the plasma jet in the nozzle portion, it becomes unnecessary to exchange the powder raw materials even when the thermal spray coating is formed into a composite layer, and the thermal spraying work is facilitated. In addition, the thickness of the sprayed coating can be easily controlled by simultaneously charging the same powder raw material from the respective powder charging sections to the plasma jet in the nozzle section. Also, by spraying different raw material powders from the respective powder charging parts at the same time to the plasma jet in the nozzle part, it is possible to form a thermal spray coating in which different materials are mixed.

Further, in this structure, a plurality of power supplies are provided, and a switcher capable of switching the connection between each of the power supplies and the electrode pair is provided. This makes it possible to control the injection energy for melting the raw material powder charged from each powder charging unit only by operating the switching device. Therefore, the work of changing the connection of the power source and the adjustment work become unnecessary, and the spraying work becomes easy.

[0015]

EXAMPLES The present invention will be described below based on examples. FIG. 1 is a system diagram showing the configuration of a plasma spraying apparatus according to an embodiment of the present invention. Another powder feeding part 14
0 is the pipe 12 from the powder container 70 containing the raw powder 50
0B, it is connected to the powder inlet 140A provided in the plasma torch 100 by piping. In addition, the pipe 120
A gas cylinder 80 is pipe-connected to B.

FIG. 2 is a sectional view showing the internal structure of the plasma torch 100 of FIG. The plasma torch 100 is provided with another powder charging port 140A, and the raw material powder 50 is charged into the plasma jet 4. Others of FIG. 1 and FIG. 2 are the same as the configurations of the conventional apparatus of FIG. 6 and FIG. 7. The same parts are designated by the same reference numerals, and detailed description thereof will be omitted. In FIG. 1, if the powder containers 7 and 70 contain the raw material powders 5 and 50 different from each other, for example, when it is desired to form the thermal spray coating 170 into a composite layer, the thermal spraying operation can be performed very easily, and It can be carried out in a short time. That is, first, the powder charging unit 1
4 is operated to feed the raw material powder 5 into the plasma jet 4 to form the first layer of the thermal spray coating 170. Next, after stopping the operation of the powder charging unit 14, the powder charging unit 140 is operated to charge the raw material powder 50 into the plasma jet 4. As a result, the thermal spray coating 170 is formed into a two-layer coating. After that, by repeatedly operating the powder charging units 14 and 140, it is possible to form the sprayed coating 170 in which multiple layers are stacked.

FIG. 3 is a system diagram showing the structure of a plasma spraying apparatus according to another embodiment of the present invention. The powder charging parts 14 and 140 have a common powder charging port 14C, and are connected to the plasma torch 101 via a switching valve 16 by piping. FIG. 4 is a sectional view showing the internal structure of the plasma torch 101 of FIG. The plasma torch 101 is provided with a powder charging port 14C which is divided into two parts.

Others of FIGS. 3 and 4 are the same as the configurations of FIGS. 1 and 2, respectively. Whichever of the raw material powders 5 and 50 is sent, it can be injected into the plasma jet 4, and the thermal spray coating 170 can be easily formed into a composite layer. The configuration of FIG. 1 or FIG. 3 is the case where there are two powder feeding parts, but three or more, generally three or more layers, a plurality of layers are provided by providing a plurality of powder feeding parts with different stored raw material powders. It is possible to easily form the thermal sprayed coating. Further, by using the same kind of raw material powder in the plurality of powder feeding parts, the amount of raw material powder to be fed into the plasma jet can be adjusted, and the film thickness of the thermal spray coating can be easily controlled. .

Further, in the structure of FIG. 1 or FIG. 3, it is also possible to form the thermal spray coating 170 in which the raw material powders 5 and 50 are mixed at an arbitrary ratio by operating the powder charging parts 14 and 140 at the same time. FIG. 5 is a system diagram showing the configuration of a plasma spraying apparatus according to a further different embodiment of the present invention. Another pulse power supply 180 is provided and is connected to the plasma torch 100 via the switch 19. Others are the same as the configuration of FIG.

In FIG. 5, the switching device 19 is adapted to the pulse power source 1 according to the powder feeding parts 14 and 140 on the operating side.
8,180 can be switched. by this,
Even if the melting temperatures of the raw material powders 5 and 50 are different, the thermal spraying work can be easily performed. The melting temperatures of the raw material powders 5 and 50 generally vary, and for example, nickel oxide is 1,998 ° C. and zirconium oxide is 2,7.
It is 00 ° C. When it is desired to form a composite sprayed coating 170 using these, each pulse power source 18,
If the energy injection corresponding to that can be performed from 180, the thermal spraying work will be very easy. Especially,
If the output energy is to be changed by one pulse power source, the internal circuit must be changed in order to change the charging voltage, the output current, the pulse width, etc., which requires a great deal of labor and time.

The pulse power supplies 18 and 18 shown in FIG.
0 may be provided in the device of FIG. 3 and the same effect as described above can be obtained. Further, as described above, when three or more powder charging units are provided, a plurality of pulse power supplies may be provided corresponding to the respective powder charging units.

[0022]

As described above, according to the present invention, by providing a plurality of powder feeding parts, the work of forming the composite layer of the sprayed coating becomes very easy, and the working time is greatly shortened. Further, according to the apparatus of the present invention, the thickness of the sprayed coating can be easily controlled, and the sprayed coating in which different materials are mixed can be easily formed.

Furthermore, by providing a plurality of power sources that can be switched and connected by the switch, the work of changing the wiring of the power sources and the adjustment work become unnecessary, the thermal spraying work becomes easier, and the working time is further shortened.

[Brief description of drawings]

FIG. 1 is a system diagram showing a configuration of a plasma spraying apparatus according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing the internal configuration of the plasma torch of FIG.

FIG. 3 is a system diagram showing a configuration of a plasma spraying apparatus according to another embodiment of the present invention.

4 is a cross-sectional view showing the internal configuration of the plasma torch of FIG.

FIG. 5 is a system diagram showing a configuration of a plasma spraying apparatus according to still another embodiment of the present invention.

FIG. 6 is a system diagram showing a configuration of a conventional plasma spraying apparatus.

7 is a sectional view showing the internal structure of the plasma torch of FIG.

[Explanation of symbols]

100, 101: plasma torch, 2: solid substrate, 4:
Plasma jet, 5,50: Raw material powder, 6: Carrier gas, 7,70: Powder container, 8,80, 9: Gas cylinder, 10: Working gas, 12A, 12B, 120B: Piping, 13: Wiring, 14,140 : Powder feeding section, 14A,
140A, 14C: Powder charging port, 15: Gas spraying part, 1
5: Gas spray port, 16: Open / close valve, 170: Thermal spray coating, 1
8, 180: pulse power supply, 19: switching device, 20: positive electrode, 20A: anode terminal, 21: insulator, 22: negative electrode,
22A: Cathode terminal, 22B: Tip part, 24: Ejection port

Claims (3)

[Claims] 1. A pair of electrodes for generating plasma, a power source connected to the pair of electrodes for outputting a pulse voltage, a gas spraying unit for spraying a working gas onto the plasma to form a plasma jet, and a raw material powder charged into the plasma jet. A plasma spraying apparatus comprising a plurality of powder charging parts and a nozzle part for injecting a raw material powder melted by plasma heat together with a plasma jet. 2. The plasma spraying apparatus according to claim 1, wherein the plurality of powder charging parts can charge different raw material powders into the plasma jet. 3. The plasma spray according to claim 1 or 2, further comprising a plurality of power sources, and a switching device capable of switching the connection between each of the power sources and the electrode pair. apparatus.