JPH0931621A - Film formation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily form a thin film having a dense and smooth surface by supplying an aqueous solution of metallic compound into the plasma jet produced by means of a tungsten electrode and a nozzle electrode, allowing it to collide and to be laminated with and on the surface of a work, and forming a film on the surface. SOLUTION: A working gas is formed into plasmic state by means of the arc formed between a tungsten electrode 27 and a nozzle electrode 28 made of copper and sprayed as a plasma jet through a nozzle 40 at the end of the nozzle electrode 28. An aqueous solution, in which a metallic compound such as CuCl2 .2H2 O is dissolved, is supplied as film formation material into the plasma jet via an inlet 43 in a sprayed state, allowed to fly while being melted, allowed to collide with a work, and laminated on it, by which a film is formed on the surface of the work. By this method, the thin film of <=1μm thick, having smooth surface, can be formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improvement of a plasma spraying method, which is one of so-called thermal spraying methods for modifying the properties of a work surface.

[0002]

[Prior Art] Welding and Joining Handbook (Edited by Welding Society, published: 1
Publisher, Maruzen, September 990. Pp. 712 to 718 (hereinafter referred to as Document 1), spraying droplets of a material having excellent wear resistance, corrosion resistance, oxidation resistance or heat / electrical insulation properties onto a work at a high speed to improve the surface performance of the work. , Or various thermal spraying methods suitable for adding functions have been described. Among them, the plasma spraying method can use a high temperature exceeding 10 ⁴ K, can control the flow velocity of the plasma jet from a subsonic speed to a supersonic speed range, and can use various gases such as Ar gas, He gas, N ₂ gas and H ₂ gas. Because it can be used,
It is the mainstream of the current thermal spraying method (Nos. 715 to 515 of Reference 1).
716). Furthermore, in order to form a denser and better bondable film, a plasma jet is operated in a reduced pressure atmosphere to expand the high temperature region and increase the flow velocity, and a low pressure plasma spraying method (page 717 of Document 1), A water-stabilized plasma spraying method has been developed in which an arc is generated in a tunnel-shaped space created when water is swirled at high speed, and O ₂ and H ₂ generated from steam generated from a water surface corresponding to a wall surface are used as working gases. (Pages 716 to 717 of Document 1).

[0003]

In the above-mentioned conventional plasma spraying method, a coating material having a particle size of several μm to several 100 μm is used. Therefore, the thickness is several tens to several hundreds μ.
Although a m-thick film can be easily formed, it is difficult to form a film having a thickness of 10 μm or less, and a thin film having a thickness of 1 μm or less can hardly be formed. In addition, the surface roughness of the formed film is considerably rough. Further, depending on the shape and particle size of the powder, the powder supply may be discontinuous.

The object of the present invention is to solve the above problems,
The surface is dense and smooth, and the thickness is 1 μm or less to 10 μm.
Another object of the present invention is to provide a method for forming a film capable of forming a thin film, and easily supplying a film forming material.

[0005]

Means for Solving the Problems The above-mentioned problem is that the working gas is turned into plasma by the arc generated between the tungsten electrode and the nozzle electrode, and the film-forming material is supplied into the plasma jet ejected from the tip of the nozzle electrode. Then, in the film forming method of forming a film on the surface of the work by causing the film forming material to fly while being melted in a plasma jet and colliding and stacking with the work, an aqueous solution in which a metal compound is dissolved is used as the film forming material. Will be solved. Furthermore, the solution can be more effectively solved by atomizing an aqueous solution in which a metal compound is dissolved and supplying it into a plasma jet.

That is, the solute metal compound in the aqueous solution is ionized into positive metal ions and negative non-metal ions. When this aqueous solution is supplied into the plasma jet, the positive metal ions combine with negative gas ions or the like existing in the atmosphere to generate a metal compound. The particle size of the newly formed metal compound is extremely smaller than that of the conventional powder. As a result, a thin film having a smooth surface can be formed.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an overall configuration diagram showing an embodiment of the present invention. In the figure, 1 is a direct current power source for supplying electric power to the plasma gun 2. A control device 3 controls the power supply 1. Reference numeral 4 is a cooling water device for cooling the plasma gun 2. 5 is a gas container filled with Ar gas used as a working gas for generating a plasma jet. 6a,
Reference numeral 6b is a pressure regulator that lowers the high-pressure Ar gas to a predetermined pressure, 6a is a working gas, and 6b is a shield gas. 7a and 7b are flow rate regulators that control the flow rate of Ar gas. 8a and 8b are solenoid valves. 9 is a container of an aqueous solution 10 in which a metal compound is dissolved. 11 is a flow rate regulator that controls the flow rate of the aqueous solution. 12 is a pump for delivering the aqueous solution. 1
3 is a work.

FIG. 2 is a sectional view of the main part of the plasma gun 2. In the figure, reference numerals 21 and 22 denote energizing terminals, the terminal 21 is connected to the negative output terminal of the power supply 1, and the terminal 22 is connected to the positive output terminal of the power supply 1. 23, 2
A cooling water terminal 4 is connected to the cooling water device 4. Two
Reference numeral 5 is an insulator, which is formed integrally with the terminals 21 and 22. Two
6 is an inlet terminal of Ar gas as a working gas, which is connected to the flow rate regulator 7a. A tungsten electrode 27 is detachably held by the terminal 21. A nozzle electrode 28 made of copper is detachably held in the hole 29 of the terminal 22 by means not shown. 30 is a hole provided in the center of the nozzle electrode 28. Reference numeral 31 is a space formed between the nozzle electrode 28 and the terminal 22. A shield nozzle 32 made of ceramic is detachably held on the outer periphery of the terminal 22 by means not shown. 33 is an inlet of Ar gas as a shield gas, which is connected to the flow rate regulator 7b. 34 is terminal 2
3 is a hole connecting the hole 29. A ceramic nozzle 40 is detachably fixed to the end face 41 of the nozzle electrode 28 by means not shown. 42 is the nozzle 40
Hole in the center of the. The nozzle 40 is connected to the nozzle electrode 2
When fixed to position 8, hole 30 and hole 42 are substantially coaxial.
43 is an inlet for the aqueous solution. With the above configuration, when a start switch (not shown) is turned on, first, the cooling water device 4 is activated, and the cooling water returns to the cooling water device 4 via the terminal 23, the hole 34, the space 31, and the terminal 24. Further, the solenoid valves 8a and 8b are opened, and Ar gas is supplied to the inlet terminals 26 and 33.
Is supplied to. Next, the power supply 1 is turned on, an arc is generated between the tungsten electrode 27 and the nozzle electrode 28, and a plasma jet J is generated.

The detailed operation will be described below with reference to FIG. 3 showing the operating principle. When the spraying start switch (not shown) is turned on in the above state, the pump 12 supplies the aqueous solution 10 in which the metal compound is dissolved to the inlet 43. As is well known, the metal compound in the aqueous solution 10 is ionized into positive metal ions and negative non-metal ions. When this aqueous solution is supplied into the plasma jet, most of the water vaporizes, but part of it dissociates into hydrogen ions and oxygen ions due to heat. Then, the positive metal ions are negative gas ions existing in the atmosphere (for example, the above-mentioned oxygen ions generated by thermal dissociation of water, oxygen ions generated by thermal dissociation of oxygen in the air, etc.). They are combined to form a new metal compound (hereinafter referred to as a produced metal), blown off by the plasma jet J, and collide with the surface of the work 13. The solute non-metal ions are further decomposed or combined with the hydrogen ions generated by the thermal dissociation of water to be gasified and released to the peripheral portion. The particle size of the produced metal is extremely small compared with the conventional powder. As a result, a thin film having a smooth surface can be formed.

In the above embodiment, the aqueous solution 10 is supplied in a liquid state, but the aqueous solution 10 may be supplied in a mist state. Hereinafter, a detailed description will be given with reference to FIG.
FIG. 4 shows an embodiment of an apparatus for supplying the aqueous solution 10 in the form of mist. In the figure, 50a and 50b are pressure regulators, and 51 and 52 are flow rate regulators. 53 is a sprayer. The container 9 in this embodiment is a closed container.

The operation will be described below. The aqueous solution 10 in the container 9 is pressurized at the pressure set by the pressure regulator 50a, and the flow rate set by the flow rate regulator 52 is delivered to the sprayer 53. Then, in the atomizer 53, it is atomized by the Ar gas controlled by the pressure regulator 50b and the flow rate regulator 51, and the plasma jet J is passed through the inlet 43.
Is supplied to.

[0012]

EXAMPLES Examples of experimental results will be described below. Example 1 (1) Spraying conditions Arc current: 150 A Distance between nozzle end face and work surface: 100 mm Type and flow rate of working gas: Ar gas, 40 l / min Amount of aqueous solution supplied: 2.7 ml / min Solute in aqueous solution _{type: Fe (NO 3) 3 ·} 9H 2 O , saturated aqueous traveling speed: 25 mm / min (1 pass) (2) results the surface roughness of the measurement results are shown in Table 1. For comparison,
The general surface roughness obtained by the plasma spraying method using a conventional powder and the gas spraying method is also described. A photograph of the appearance is shown in FIG.

[0013]

[Table 1] As is clear from Table 1, the surface roughness of the obtained film is
Rmax is about 1/5 and Ra is about 1/1 compared to the conventional one
It was 0. The film thickness was about 5 μm. Further, the film was subjected to X-ray diffraction analysis, and it was found that the analysis spectrum had no peak showing a crystal structure and was in an amorphous state. The aqueous solution 10 was supplied to the plasma jet J in a liquid state.

Example 2 (1) Spraying conditions Arc current: 200 A Distance between nozzle end face and work surface: 100 mm Type of working gas: Ar gas Amount of aqueous solution supply: 3.0 ml / min Type of solute in aqueous solution: FeCl ₃ · 6H ₂ O, saturated aqueous spray time: 30sec 20~60l the working gas flow rate under the above conditions / min
Varied between. (2) Results As shown in FIG. 6 which is an external photograph, the flow rate of the working gas is 2
A good film could be formed in the range of 0 to 60 l / min. It was also confirmed that the surface roughness tends to become slightly rough as the flow rate of the working gas increases. The aqueous solution 10 was atomized and supplied to the plasma jet J.

Example 3 (1) Spraying conditions Arc current: 80 A Distance between nozzle end face and work surface: 100 mm Type and flow rate of working gas: Ar gas, 30 l / min Amount of aqueous solution supplied: 2.0 ml / min Spraying time ： 30sec Under the above conditions, change the solute type to CuCl ₂ · 2H ₂ O
And Cu (NO ₃ ) ₃ .3H ₂ O and (CH ₃ COO) ₂
The experiment was conducted using Cu.H ₂ O. In addition, all were made into a saturated aqueous solution, atomized, and supplied to the plasma jet J. (2) Results As shown in FIG. 7, which is a photograph of the appearance, it was confirmed that any of the above aqueous solutions could form a film.

In the above three examples, the saturated aqueous solution in which the solute is saturated was used, but an unsaturated aqueous solution may be used. Alternatively, the aqueous solution may be dropped from the container 9 by using gravity without providing a special supply device. Further, the compound of iron and copper has been described as the solute, but it goes without saying that other metal compounds can be used depending on the application. In this embodiment, both the shield gas and the working gas are Ar.
Although the gas is used as the gas, the shield gas and the working gas may be different types. Moreover, when there is no practical problem, the shield gas may not be used.

[0017]

As described above, according to the present invention,
An aqueous solution in which a metal compound is dissolved is supplied as a film forming material into a plasma jet to newly generate a metal compound in the plasma jet. As a result, the particle size of the produced metal compound is extremely smaller than that of the conventionally used powder, so that there is an effect that a smooth surface can be formed and a thin film of 1 μm or less to 10 μm can be formed. Further, there is an effect that the supply of the film forming material becomes easy. Further, when the aqueous solution is prepared, the shape of the metal compound may be a lump, and it is not necessary to make it into a powder or to make the particle sizes uniform, so that the material cost can be reduced. In addition, the heat of vaporization accompanying the evaporation of water in the aqueous solution causes the plasma to be tightened, and the temperature of the plasma jet can be increased, which also has the effect of making the film more compact and improving the adhesion.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram showing an embodiment of the present invention.

FIG. 2 is a sectional view of a main part of a plasma gun 2.

FIG. 3 is an explanatory diagram showing an operation principle.

FIG. 4 is a configuration diagram when an aqueous solution is atomized and supplied.

FIG. 5 is a photograph showing the appearance of the film.

FIG. 6 is a photograph showing the appearance of the film.

FIG. 7 is a photograph showing the appearance of the film.

[Explanation of symbols]

 9 Container 10 Aqueous Solution 27 Tungsten Electrode 28 Nozzle Electrode 40 Nozzle 43 Inlet 53 Nebulizer J Plasma Jet

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[Procedure amendment]

[Submission date] December 7, 1995

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Brief description of drawings

[Correction method] Change

[Correction contents]

[Brief description of drawings]

FIG. 1 is an overall configuration diagram showing an embodiment of the present invention.

FIG. 2 is a sectional view of a main part of a plasma gun 2.

FIG. 3 is an explanatory diagram showing an operation principle.

FIG. 4 is a configuration diagram when an aqueous solution is atomized and supplied.

FIG. 5 is a micrograph showing the appearance of the film.

FIG. 6 is a micrograph showing the appearance of a film.

FIG. 7 is a micrograph showing the appearance of a film.

Claims (2)

[Claims] 1. A working gas is turned into plasma by an arc generated between a tungsten electrode and a nozzle electrode, and the film-forming material is supplied into a plasma jet ejected from the tip of the nozzle electrode. In a film forming method for forming a film on the surface of a work by causing the film to melt and fly while colliding and stacking on the work, an aqueous solution in which a metal compound is dissolved is used as a film forming material. 2. The film forming method according to claim 1, wherein an aqueous solution in which the metal compound is dissolved is atomized and supplied into the plasma jet.