JP2716844B2 - Thermal spray composite film forming method - Google Patents

Description

The present invention relates to a method for forming a thermal spray composite film.

[Conventional technology]

A schematic view of a conventional plasma spraying method is shown in FIG. 3. A plasma spray gun for performing spraying on a surface 21a of an object 21 to be sprayed includes an anode nozzle 22 cooled by a cooling water passage 22a and the same nozzle. 22 and a cathode 23 fixed to the base of the anode 22 via an insulator 24.
A spraying material powder supply port 25 is drilled in the front part, and a powder supply port 26 is connected, while a working gas supply port 27 is opened in the rear part, and further between the anode nozzle 22 and the cathode 23, A DC power supply 28 and a high-frequency generator 29 are connected in parallel.

To perform plasma spraying, first, Ar gas is supplied as a working gas into the anode nozzle 22 from the working gas supply port 27, and the DC power supply 28 is turned on to apply a no-load voltage between the anode nozzle 22 and the cathode 23. When the high-frequency generator 29 is turned on to generate an arc discharge between the anode nozzle 22 and the cathode nozzle 23, a continuous arc is generated by the power from the DC power supply 28, the working gas becomes a plasma gas, and the nozzle
From 22, a high-temperature plasma jet 30 is ejected. Then, the sprayed material powder supplied from the powder supply device (not shown) into the anode nozzle 22 through the sprayed material powder supply port 25 from the powder supply port 26 by the Ar gas is heated and accelerated by the plasma jet 30, and the high-temperature and high-speed As the thermal spray particles 31, they fly toward the surface 21a of the object to be sprayed, and collide with and adhere to the surface 21a of the object to be sprayed to form a thermal spray coating.

However, the state of formation of the sprayed coating by such a method is as shown in the sectional view of FIG.
31 collides with the surface 21a of the object to be sprayed and becomes flattened, which is deposited to form a sprayed coating 32, and the flattened sprayed particles are formed.
The voids 33 are formed at the grain boundaries due to the overlap of the 31s, and as a whole, a porous film is formed. Therefore, even if such a thermal spray coating 32 is excellent in abrasion resistance and heat insulating properties, when applied as a corrosion resistant film, corrosive substances penetrate into the porous film and cause corrosion of the base material 21 in the thermal spray coating. . In addition, since the voids 33 are present at the grain boundaries, the contact portions between the particles are small and the adhesion is small, so that the peeling may start from the voids 33 and propagate to the surrounding healthy part.

[Problems to be solved by the invention]

The present invention has been proposed in view of such circumstances, and the object to be sprayed is prevented from being corroded by a dense vapor-deposited film layer and is not corroded. It is an object of the present invention to provide a method for forming a sprayed composite film, which has sufficient wear resistance and heat insulation by the sprayed coating layer on the layer.

[Means for solving the problem]

Therefore, the present invention, when supplying the thermal spray material powder into the high frequency induction plasma and spraying on the object to be sprayed, at the beginning of thermal spraying, increase the amount of heat input to the thermal spray material powder or reduce the particle diameter of the thermal spray material powder. Forming a vapor-deposited film layer on the surface of the object to be sprayed, and forming a thermal-sprayed film layer on the vapor-deposited film layer by reducing the heat input amount or increasing the particle size as the thermal spraying proceeds. It is characterized by.

[Action]

In the method of forming a sprayed composite film of the present invention, a deposited film is formed when the heat input to the sprayed material powder at the initial stage of spraying is large or the particle size of the sprayed material powder is small, which is more dense than a conventional sprayed coating. Since the film is a thin film, the corrosive substance is cut off from the object to be sprayed by the deposited film, so that the object to be sprayed is not damaged by the corrosion, and the sprayed film does not peel off. Further, by reducing the amount of heat input to the thermal spray material powder or increasing the particle diameter of the thermal spray material powder during thermal spraying, a thermal spray coating layer is formed on the deposited film, which is similar to a conventional thermal spray coating. In addition, it has abrasion resistance and heat insulation.

〔Example〕

An embodiment of the method for forming a sprayed composite film according to the present invention will be described with reference to the drawings. FIG. 1 is a longitudinal sectional view showing an embodiment of the method of the present invention, and FIG.

In FIG. 1, an object 1 to be sprayed is accommodated in an atmosphere control chamber 2, and an exhaust port 3 is provided on a side of the chamber 2 and connected to an exhaust device (not shown). An insulating cylinder 4 made of, for example, a quartz gas tube and having an appropriate diameter and closed at the upper end is mounted on the central opening of the upper end of the atmosphere control chamber 2. 5 is wound and, for example, a maximum output of 80
It is connected to a high-frequency oscillator 6 having a frequency of 4 kW and a frequency of 4 MHz. Further, a high frequency induction plasma 9 is applied to the peripheral portion of the closed end of the insulating cylinder 4.
Spray gas supply nozzle through which a working gas introduction hole 7 into which a working gas is introduced is provided, and a spray material powder which is melted by a high frequency induction plasma 9 and becomes a spray particle 10 is supplied to a central portion of the closed end. 8 are provided.

A first embodiment for performing thermal spraying by adjusting the amount of heat input to the thermal spray material powder in such an apparatus configuration will be described below.

First, the inside of the atmosphere control chamber 2 is evacuated from the exhaust port 3 by an exhaust device (not shown), and exhausted to a degree of vacuum of several Torr. This is to prevent the gas in the atmosphere from being mixed as impurities into the formed thermal spray composite film. Subsequently, a high-frequency current flows from the high-frequency oscillator 6 to the application coil 5 while introducing a working gas having a mixture of Ar: 40 / min and H ₂ : 5 / min into the insulating cylinder 4 through the working gas introduction hole 7. Then, an alternating magnetic field is generated in the insulating cylinder 4, and the working gas flowing therein is excited to become the high-frequency induction plasma 9.

Thereafter, the exhaust amount of the exhaust device was adjusted, and the pressure in the atmosphere control chamber 2 was reduced to atmospheric pressure or slightly reduced (approximately
(500 Torr to atmospheric pressure), and at the same time, adjust the output of the high-frequency oscillator 6 to the set output of 60 kW.

Therefore, a high frequency induction plasma 9 is supplied from a spray material powder supply nozzle 8 together with a carrier gas of 5 / min Ar at a supply amount of 5 to 10 g / min of a spray material powder of Al ₂ O ₃ having a particle size of 10 to 40 μm.
Supply inside. Thermal spray particles 10 generated by rapidly heating and melting the thermal spray material powder by high frequency induction plasma 9
Evaporates from the surface and eventually all evaporates. Then, the evaporant flows along the flow of the high-frequency induction plasma 9 and reaches the object 1 to be sprayed, and as shown in FIG.

Thereafter, by gradually decreasing the output of the high-frequency oscillator 6, the amount of heat input to the spray particles 10 is reduced, the amount of evaporation from the surface is also reduced, and finally the spray particles 10 are melted. In this state only, the thermal spray coating layer 12 is formed on the vapor deposition film layer 11, as shown in FIG.

Thus, in the first embodiment, as shown in FIG. 2, the output of the high-frequency oscillator 6 is gradually reduced from 60 kW to 20 kW to form a dense film structure on the surface 1a of the object to be sprayed. A composite film is formed by continuously spraying the deposited film layer 11 and the sprayed coating layer 12 having a gap 13 between the sprayed particles 10 thereon.

Next, a second embodiment in which the thermal spraying is performed by adjusting the particle size of the thermal spray material powder will be described below.

In the same manner as in the first embodiment, a working gas of Ar: 40 / min and H ₂ : 5 / min was flowed, and a sprayed material powder having a particle size of 10 to 40 μm was introduced into a high-frequency induction plasma 9 generated at a power of 60 kW. 10g / mi
n with the supply amount of n and 5 / min Ar carrier gas.
As shown in the drawing, a deposited film layer 11 is formed on the surface 1a of the object to be sprayed.

Next, the sprayed material powder is supplied into the high-frequency induction plasma 9 while changing the particle size from 80 to 100 μm. At this time, the high frequency output, the working gas flow rate and the carrier gas flow rate are not changed.

Then, since the particle diameter becomes large, the sprayed particles 10 generated by heating and melting the thermal spray material powder are only melted, and the amount of evaporation from the particle surface becomes very small. Deposited as a thermal spray coating layer 12 on layer 11. Therefore, by changing the particle size of the sprayed material powder from a small one of 10 to 40 μm to a large one of 80 to 100 μm,
A composite film composed of the deposited film layer 11 and the thermal spray coating layer 12 is formed.

Thus, in the composite film shown in FIG. 2 formed by the first embodiment and the second embodiment, the corroded material is shielded from the spray target 1 by the dense vapor deposition film layer 11, so that the surface of the spray target is prevented. 1a is no longer corroded, and the dense deposited film layer 11 is in close contact with the surface 1a of the object to be sprayed.
11 and the thermal spray coating layer 12 do not peel off. Further, since the thermal spray coating layer 12 is provided on the vapor deposition film layer 11, it can also have the same abrasion resistance and heat insulating properties as in the related art.

[Effects of the Invention] In short, according to the present invention, in supplying the thermal spray material powder into the high frequency induction plasma and spraying the material to be sprayed, the initial thermal spraying is to increase the amount of heat input to the thermal spray material powder or the thermal spray material. A vapor deposition film layer is formed on the surface of the object to be sprayed by reducing the particle diameter of the powder, and the amount of heat input is reduced or the particle diameter is increased as the thermal spraying proceeds to spray on the vapor deposition film layer. By forming the coating layer, the object to be sprayed is prevented from being corroded by the dense vapor-deposited film layer and is not corroded. The present invention is extremely useful industrially because a method for forming a sprayed composite film having sufficient abrasion and heat insulating properties is obtained.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing an embodiment of a method for forming a sprayed composite film of the present invention, and FIG. 2 is a sectional view of the sprayed composite film in the same method. FIG. 3 is a schematic view showing a conventional plasma spraying method, and FIG. 4 is a sectional view of the sprayed coating. 1 ... spray target, 1a ... spray target surface, 2 ... atmosphere control chamber, 3 ... exhaust port, 4 ... insulating cylinder, 5 ...
Application coil, 6 high frequency oscillator, 7 working gas introduction hole, 8 spraying material powder supply nozzle, 9 high frequency induction plasma, 10 spray particles, 11 deposited film layer, 12 Sprayed coating layer, 13 ... void

Claims (1)

(57) [Claims] When supplying thermal spray material powder into a high frequency induction plasma and spraying the material to be sprayed, the amount of heat input to the thermal spray material powder is increased or the particle diameter of the thermal spray material powder is reduced in the initial stage of thermal spraying. Forming a vapor-deposited film layer on the surface of the object to be sprayed, and forming a thermal-sprayed film layer on the vapor-deposited film layer by reducing the heat input or increasing the particle size as the thermal spraying proceeds. A method for forming a sprayed composite film, which is characterized in that: