JPS62213862A - Plasma flame-spraying method - Google Patents

Abstract

PURPOSE:To increase jet energy without increasing an arc current or voltage and to attain to enhance the quality of a film, by applying high frequency of a radio frequency region to the plasma jet injected from a nozzle from the outer circumference. CONSTITUTION:In operating a flame spraying gun, operation gas is supplied into an anode nozzle 2 and no-load voltage of 120V is applied between the anode nozzle 2 cooled by water and a cathode 3 and, when a high frequency generator 9 is turned ON, a plasma jet 11 is generated from the anode nozzle 2. Next, when the high frequency current from a radio frequency oscillator 12 is applied to the coil 10 arranged so as to surround the plasma jet 11, the atoms or molecules in the plasma jet are further excited to be heated to high temp. and the length of the plasma jet 11 is elongated. As a result, the densification and adhesion strength of a flame-sprayed film increase.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to improvements in plasma spraying methods.

(Prior Art) A second UfJ is an explanatory diagram showing an example of a conventional plasma spraying method. In the figure, 21 is an object to be irradiated, and 21a is its surface to be thermally sprayed. Reference numeral 22 denotes an anode nozzle of the plasma spray gun, and the anode nozzle is cooled by a cooling water passage 22a. 23 is a cathode, and the cathode and the anode nozzle 22 are electrically insulated by an insulator 24. 25 is a supply port for thermal spraying material powder, and 26 is a supply boat for thermal spraying material powder.

Further, 27 is a working gas supply port, 28 is a DC power supply, and 29 is a high frequency generator.

To perform plasma spraying in the above, first, Ar gas is supplied as a working gas into the anode nozzle 22 from the working gas supply port, and the DC power supply 28 is turned on to apply a no-load voltage between the opening nozzle 22 and the cathode 23. . Next, when the high frequency generator 29 is turned on and arc discharge is generated between the anode nozzle 22 and the cathode 23, the power from the DC power supply 28 causes i! Continuous arcing occurs. This arc turns the operating gas into a plasma gas, which is ejected from the nozzle as a high-temperature plasma jet 30. Next, thermal spray material powder is placed on Ar gas and supplied from a powder supply device (not shown). This thermal spray powder material is supplied into the anode nozzle 22 from the powder supply boat 26 through the thermal spray material supply port 25 . Furthermore, by being heated and accelerated by the plasma jet 30, the spray particles 31 become high temperature and high speed, and are sprayed onto the sprayed surface 21a.
It is injected toward the sprayed surface 21a and collides with and adheres to the sprayed surface 21a to form a sprayed coating.

Note that while plasma spraying is being performed, the cooling water passage 22
Water is forcibly flowed into the fil pole nozzle 22 to prevent the temperature from rising.

[Problem that the invention seeks to solve]

By the way, in order to form a high-quality thermal spray coating, it is generally necessary to increase the temperature and speed of the thermal spray particles, and for this purpose, the energy of the plasma jet must be increased.

In order to increase the energy of the plasma jet in the conventional plasma spraying method described above, it is sufficient to increase at least one of the current and voltage of the plasma arc.

However, this method is not practical because it causes significant wear and tear on the anode nozzle and the cathode and requires replacement of parts in a short period of time.

Increasing the flow rate of cooling water is also effective in reducing wear and tear on the anode nozzle, but considering the resistance of the cooling water passage, it is not realistic to increase the flow rate beyond the current level.

In view of the above circumstances, the technical object of the present invention is to increase the energy of a plasma jet without increasing the arc Ti flow and voltage in plasma spraying, and to obtain a high-quality thermal spray coating.

[Means for solving problems]

In order to solve the above problems, in the present invention, high frequency waves in the radio frequency range are externally applied to the plasma jet ejected from the nozzle, and the energy of the plasma jet is increased by exciting the atoms and molecules in the plasma jet. I decided to let him do it.

That is, in the plasma spraying method according to the present invention, high-temperature gas plasma generated by an arc generated between an anode and a cathode is ejected from a nozzle as a jet, and spraying material powder is supplied to the jet to spray the object to be thermally sprayed. In plasma spraying, a coil is installed at the tip of the nozzle so as to surround the jet, and a high frequency 1! in the radio frequency range is applied to the coil. This method is characterized by applying a current to perform plasma spraying.

[Effect]

In the plasma 2'FJfJJ method of the present invention, radio frequency V is emitted from the outside of the plasma jet formed by the plasma gun.
Since a high-frequency current in the 1-range is applied, atoms and molecules in the plasma jet are excited by this. As a result, the energy of the plasma jet increases and a high quality sprayed coating is obtained.

Moreover, in the present invention, the plasma arc current and voltage of the plasma gun itself may be the same as conventional ones, so the life of the plasma gun electrode will not be shortened.

〔Example〕

FIG. 1 is an explanatory diagram showing a plasma spraying method according to an embodiment of the present invention. In the figure, 1 is the object to be thermally sprayed, and 1a
is the surface to be thermally sprayed. 2 is an anode nozzle of a plasma spray gun, and the anode nozzle is cooled by a cold water passage 2a. 3 is a cathode, and the cathode and the positive I nozzle 2 are electrically insulated by an insulator 4. 5 is a supply port for thermal spraying material powder, and 6 is a supply boat for thermal spraying material powder. Further, 7 is an operating gas supply port, 8 is a DC power supply, and 9 is a high frequency generator. Up to this point, the plasma spray gun used in the conventional plasma spray method shown in FIG. 2 is the same, but in this example, a coil 10 arranged to surround the plasma jet 11 is used. Both ends of the coil are connected to a radio frequency oscillator 1
Connected to 2. In addition, 13 is a thermal spray powder.

An embodiment of the plasma spraying method using the apparatus shown in FIG. 1 will be described as follows.

The operation of the plasma spray gun is the same as before.
Ar50R/min as working gas in positive 1 to nozzle 2
, He 2i/min of mixed gas is supplied.

Then, when a no-load voltage of 120 V is applied between the water-cooled anode nozzle 2 and the cathode 3 and the high frequency generator is turned on, plasma arcs 1 to 11 are generated from the anode nozzle. At this time, the plasma arc current was 850A, and the plasma arc voltage was 36V.

Next, the radio frequency oscillator 12 is operated. The frequency was 13.56 MHz, and the -order input was 30 W. As a result, the atoms and molecules in the plasma jet are further excited and heated to a higher temperature, and the length of the plasma Gantz 1 to 11 is increased.

Next, Zr0z-8Y20 with a particle size distribution of 10 to 40 tan
2 as a thermal spraying material, the thermal spraying material was transferred from a powder supply device (not shown) to 3ag using Ar gas as a carrier gas,
'+in. This thermal spray material is introduced into the anode nozzle 2 from the powder supply boat 6 through the thermal spray material supply port 5 . Thermal spray material powder is plasma jet 1 here.
Thermal spray particles 13 are heated and accelerated by 1 and are at high temperature and high speed.
and is sprayed in the direction of the sprayed surface 1a. The sprayed particles 13 collide with the sprayed surface 1a and adhere to form a sprayed coating.

In the plasma spraying method of the above embodiment, as described above, the plasma jet 11 is heated to a high temperature by being excited by radio frequency, and its length is extended to increase its energy. For this reason, the thermal spray particles 13 are heated and collide with and adhere to the surface to be thermally sprayed with higher energy than in the conventional case. As a result, the thermal spray coating is made denser and the adhesion strength is increased, resulting in the formation of a high quality thermal spray coating.

Moreover, as a means of increasing the energy of the plasma jet, a method of applying radio frequency from outside the plasma gun is used, so even though the energy of the plasma shed is increased, the life of the plasma gun N pole is shortened. It will not be shorter than before.

(Effects of the Invention) As detailed above, according to the plasma spraying method of the present invention, it is possible to increase the energy of the plasma jet without increasing the arc current and voltage, thereby improving the quality of the sprayed coating. , and the rf of the plasma gun electrode
It has remarkable effects such as preventing shortening of life.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing a plasma spraying method according to an embodiment of the present invention, and FIG. 2 is an explanatory diagram of a conventional plasma spraying method. 1...-Object to be thermally sprayed, 1a... Surface to be thermally sprayed, 2... Anode nozzle of plasma spray gun, 2a... Cooling water passage 3...
- Cathode, 4... Insulator, 5... Thermal spraying material powder supply port, 6... Thermal spraying material powder supply boat, 7... Operating gas supply port, 8... DC power supply, 9. ...High frequency generator, 10... Coil, 11... Plasma jet, 1
2... Radio frequency oscillator, 13... Thermal spray powder applicant sub-agent Patent attorney Takehiko Suzue Figure 1

Claims (1)

[Claims] In plasma spraying, a high-temperature gas plasma generated by an arc generated between an anode and a cathode is ejected from a nozzle as a jet, and spray material powder is supplied to the jet to spray the object to be thermally sprayed. A plasma spraying method characterized in that a coil is installed so as to surround the jet, and plasma spraying is performed by applying a high frequency current in a radio frequency range to the coil.