KR100859672B1 - Splay coating method - Google Patents

Abstract

A thermal spray coating method is provided to form a coating film with a low porosity on a matrix by melting a ceramic powder using a plasmarized heat source gas, and to suppress the generation of voids that may remain in the coating film by performing the thermal spray coating process. A thermal spray coating method comprises: a step(S110) of preparing a matrix; a step(S120) of plasmarizing a heat source gas comprising argon as a principal gas and helium and hydrogen gases as supporting gases in the atmospheric state to apply a thermal spray coating onto the matrix; a step(S130) of melting ceramic material using the plasmarized heat source gas; and a step(S140) of spraying the melted ceramic material toward the matrix to form a coating film on the matrix, wherein the heat source gas comprises 20 to 40% by volume of argon, 5 to 20% by volume of hydrogen gas, and the balance of helium gas, the ceramic material comprises carbon as an additive, and the step of preparing the matrix comprises pre-treating the face to be coated so as to improve adhesion force of the coating film with a face to be coated of the matrix.

Description

Spray coating method {SPLAY COATING METHOD}

The present invention relates to a thermal spray coating method. More particularly, the present invention relates to a spray coating method of forming a coating film on an object by melting a ceramic material using a heat source gas.

Generally, thermal spray coating is performed by heating and melting fine powders and spraying the molten powders toward the coated surface of the base material. The sprayed molten powder is quenched to solidify the molten powder and is laminated on the surface to be coated mainly by mechanical bonding force.

Plasma spray coating for melting the powders using a hot plasma flame of the thermal spray coating is essentially used for the coating of metals and ceramics such as tungsten or molybdenum at high melting point. The thermal spray coating is advantageous in producing high functional materials exhibiting characteristics of wear resistance, corrosion resistance, heat and heat barrier, cemented carbide, oxidation resistance, insulation, friction properties, heat dissipation, and bio functional radiation resistance by utilizing the material properties of the base material. In addition, compared to other coating methods such as chemical vapor deposition or physical vapor deposition, a large area of the object can be coated in a short time.

Meanwhile, argon is used as a primary gas and helium or hydrogen gas is used as a secondary gas as a plasma source for melting the powders. Since the argon gas has a relatively low temperature of about 5,000 ° C. in the plasma state, the argon gas does not correspond to a temperature for melting the ceramic powder when the powder is a ceramic powder. Thus helium or hydrogen gas is used as secondary gas and as a catalyst of heat source for melting the powder. However, when argon-coated with ceramic powders such as yttria, if only argon and hydrogen gas are used as the heat source gas, the plasma temperature is high but the life of the plasma gun is shortened and the coating becomes red or quenched. The problem arises that voids arise. On the other hand, when only argon and helium gas is used as the heat source gas, a low plasma temperature may cause the ceramic powder not to be sufficiently melted.

1 is an electron micrograph of a coating film formed using a spray coating method according to the prior art.

Referring to FIG. 1, the ceramic powder was melted using only argon and helium gas as the heat source gas, and then a coating film was formed on the base material of the molten ceramic material. Powder P that was not melted was present in the coating film. Therefore, the bonding force between the coating film and the base material is relatively low. As a result, a phenomenon that the coating film peels from the base material may occur.

In addition, voids (V) remained in the coating film, and the porosity of the coating film was relatively high. Leakage current may occur through the pores of the coating film or the coating film may be peeled from the base material.

Accordingly, the present invention has been made in view of such a problem, and an object of the present invention is to provide a spray coating method capable of lowering porosity and reducing voids.

In order to achieve the object of the present invention described above, in the spray coating method according to the present invention, after arranging the base material, in order to coat the sprayed material on the base material, argon as the main gas, helium and hydrogen gas as the auxiliary gas Plasma heat source gas. Thereafter, the ceramic material is melted using the plasmaized heat source gas, and then the molten ceramic material is sprayed toward the base material to form a coating film on the base material. Here, the heat source gas includes argon having a volume mixing ratio of 20 to 40, hydrogen having a volume mixing ratio of 5 to 20, and excess helium gas. In addition, the plasma step may be formed using a current of 400 to 700 A. On the other hand, the plasma step may be performed in a reduced pressure atmosphere of 50 to 600hPa.

In one embodiment of the present invention, the ceramic material includes white yttria and carbon, and the step of plasmaming may be performed at atmospheric pressure. Here, the mass ratio of the carbon to the white yttria may be in the range of 3 to 5%. In addition, the ceramic material may include Al 2 O 3, Y 2 O 3, Al 2 O 3 / Y 2 O 3, ZrO 2, AlC, TiN, AlN, TiC, MgO, CaO, CeO 2, TiO 2, BxCy, BN, SiO 2, SiC, YAG, Mullite, AlF 3, and the like. have. In addition, these may be used alone or in combination of two or more.

In one embodiment of the present invention, the base material may be formed of a fixed to pre-treat the coated surface in order to improve the adhesion of the coated surface and the thermal sprayed coating of the base material. Here, the pretreatment of the surface to be coated of the base material may be plasma treated so that the base material is at a temperature of 80 to 150 ℃. In addition, pretreatment of the surface to be coated of the base material may be laser processed. On the other hand, pre-treatment of the coated surface of the base material can be improved by the water blast (water blast) treatment to improve the average roughness of the surface to be coated.

According to the thermal spray coating method of the present invention, a heat source gas containing argon, helium, and hydrogen may be plasma formed to melt the ceramic powder using the plasmaized heat source gas to form a coating film having a low porosity on the base material. In addition, the generation of voids that may remain in the coating film by the thermal spray coating method of the present invention can be suppressed.

On the other hand, by melting the ceramic powder containing carbon to form a black coating film on the base material can implement a coating film with improved thermal properties.

With reference to the accompanying drawings will be described in detail a spray coating method according to an embodiment of the present invention. As the inventive concept allows for various changes and numerous embodiments, particular embodiments will be illustrated in the drawings and described in detail in the text. However, this is not intended to limit the present invention to the specific form disclosed, it should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention. In describing the drawings, similar reference numerals are used for similar elements. In the accompanying drawings, the dimensions of the structure is shown to be larger than the actual size for clarity of the invention, or to reduce the actual size to understand the schematic configuration.

In addition, terms such as first and second may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be referred to as the second component, and similarly, the second component may also be referred to as the first component.

On the other hand, unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art. Terms such as those defined in the commonly used dictionaries should be construed as having meanings consistent with the meanings in the context of the related art and shall not be construed in ideal or excessively formal meanings unless expressly defined in this application. Do not.

2 is a cross-sectional view illustrating a plasma gun for implementing a spray coating method according to an embodiment of the present invention.

In order to implement the spray coating method according to an embodiment of the present invention, a plasma gun will be described first with reference to FIG. 2.

Referring to FIG. 2, the plasma gun 10 includes a cathode 12, an anode 14, an outer circumferential portion 15, a support base 16, and a powder injection hole 17. Then, the heat source gas is injected through the gas injection port 11 formed in the plasma gun 10.

Specifically, the gas injection hole is formed between the outer circumferential portion 15 and the cathode 12 and finally extends to a narrow space between the anodes 14. The heat source gas injected into the gas inlet is changed into a plasma flame by the high voltage DC high power applied between the cathode 12 and the anode 14 and is injected from the plasma gun 10.

At this time, the high voltage DC high power should have a sufficient value to change the heat source gas into a plasma flame and is generally applied under a voltage condition of about 30 kV to about 100 kv and a current condition of about 400 A to about 1000 A.

As shown in FIG. 2, the end portion of the cathode 12 has a sharp shape in order to easily generate a plasma flame. In addition, the ends of the cathode 12 typically include materials having physically high strength and hardness to prevent damage such as erosion due to the generation of plasma flame. For example, the end portion of the cathode 12 includes tungsten or a tungsten reinforced metal or the like.

The anode 14 generally comprises a conductive material such as copper or a copper alloy. In addition, a cooling passage 13 is formed inside the anode 14. Heat applied to the anode 14 may be discharged to the outside through the cooling passage 13. Thus, the anode 14 having the cooling passage 13 formed therein can minimize the thermal damage applied and consequently extend the life of the anode 14.

The outer circumferential portion 15 is a portion located at the outer shell of the plasma gun 10, and a cathode 12 is positioned inside the plasma gun 10 to support the anode 14. The outer circumferential portion 15 is also preferably made of a material that can minimize thermal damage due to the generation of plasma flame.

Support 16 is fastened to one side of the outer peripheral portion (15). The powder inlet 17 is fastened to the support 16. Ceramic powder may be provided to the plasma flame through the powder inlet 17. The ceramic powder provided to the plasma flame through the powder inlet 17 is melted and sprayed toward the substrate 1 facing the plasma gun 10.

The sprayed ceramic powder 18 is bonded to the base material 1 to form a coating film 19. In general, the ceramic powder may be used as powder, all non-metal inorganic solids that can form a coating film. However, the present invention is not limited thereto and may be used for coating not only ceramic powder but also metal powder.

3 is a process flow chart for explaining the spray coating method according to an embodiment of the present invention.

Referring to Figure 3, first to prepare a base material (S110). The base material may be made of alumina, quartz, silicon carbide, or silicon. The base material may be applied as part of a chamber or an electrostatic chuck of a chemical vapor deposition apparatus.

In one embodiment of the present invention, in order to improve the adhesion between the base material and the subsequent coating film, the base material may be pre-treat. Examples of the pretreatment process for pretreatment of the base material include a plasma treatment process of plasma treatment of the base material, a laser treatment process of laser treatment of the base material, or a water blast process of roughening the surface of the base material using water pressure. Can be.

According to the plasma treatment process, the temperature of the base material is controlled using the source gas in the plasma state. At this time, the plasma source gas is injected in a state in which the thermal spraying powder is not supplied onto the base material in the plasma processing step to adjust the temperature of the base material. The temperature of the base material can be adjusted by changing the separation distance between the plasma gun and the base material injecting the source gas in the plasma state. For example, the base material is adjusted to have a temperature in the range of about 80 to 150 ℃. If the temperature of the base material is less than 80 ° C., the thermal spraying material is cooled when the thermal spraying material is attached to the base material in a subsequent coating process, thereby weakening the cohesion between the coating film and the base material. As a result, the adhesion between the coating film and the base material may be lowered. Alternatively, if the temperature of the base material exceeds 150 ℃ thermal damage to the base material may occur.

According to the laser treatment process, the laser beam is irradiated to the base material to increase the temperature of the base material. For example, a laser beam injects light energy such as flashing light into a solid medium, Nd: YAG, to make a neodymium (Nd) atom in a high energy state (excitation state). And a Nd: YAG laser beam that generates a laser while changing to a stable state). In particular, the laser treatment process may be particularly applied when the thickness of the base material is relatively thin or when it is a hard material. In addition, the laser used in the laser treatment process may have a wavelength of 0.9 to 1.1 millimeters.

According to the water blasting process, water having a high water pressure is used to increase the average roughness of the coated surface of the base material. In this case, the surface to be coated has an effect of being cleaned. It is preferable that surface roughness Ra of the to-be-coated surface of the said base material is 1-15 micrometers. When the surface roughness is less than 1 μm, the coating film may be easily peeled off from the base material. On the other hand, when surface roughness exceeds 15 micrometers, it is difficult to flatten the surface of a coating film, and it may be difficult to suppress the etching by a plasma or a corrosive gas.

In one embodiment of the present invention, the water applied to the base material in the water blasting process may have a water pressure of 600 to 1500 bar. The sprayed water can also be supplied to the substrate at 100 liters per minute. On the other hand, the water applied to the base material may be sprayed from the nozzle toward the base material in a front spray method that is vertically sprayed with respect to the coated surface of the base material.

Hereinafter, Table 1 shows the values of the adhesion of the coating film according to the thickness of the coating film when the coating film is formed on the base material after pretreatment of the base material when the yttria coating film is formed on the alumina base material.

1) Preparation of the base metal

A base material was prepared by performing a step of pretreating the base material using a plasma processing step, a laser processing step, or a water blasting step. As a comparative example, blasting using alumina powder was illustrated.

2) Preparation of thermal spray raw material

After the binder was mixed with the yttria powder, a granulated powder was obtained by a spray dryer. The granulated powder was degreased and then sintered to obtain a sintered powder.

3) Formation of coating film

By using the raw material powder prepared in 2) and the plasma gun shown in Fig. 3, argon and hydrogen gas were flowed into the heat source gas to move the thermal spray to generate a plasma at a power of 400 kW to melt the raw material powder using the generated plasma. The coating film was formed in the base material. The coating film was formed to have a thickness of 100㎛, 200㎛, 300㎛ and 400㎛, respectively.

4) Performance Evaluation

Tensile force was applied to the coating film formed on the base material to measure the tensile force at the time when the coating film was separated from the base material. As described in Table 1, it can be confirmed that adhesion is improved by having a value of 37 MPa or more through plasma treatment, laser treatment, or water blast treatment than blasting treatment.

<Table 1>

Subsequently, a plasma source gas including argon as a main gas and helium and hydrogen as an auxiliary gas is converted into plasma (S120). The volume ratio of argon constituting the plasma source gas is 10 to 40, the volume ratio of hydrogen is 5 to 20, and helium has an extra volume ratio.

If the volume ratio of argon is greater than 40, the temperature of the plasma state may not have sufficient temperature to melt the ceramic powder. Therefore, unmelted powder in the ceramic powder may remain in the coating film. On the contrary, if the volume ratio of argon is less than 10%, the source gas may not be sufficiently plasmaded.

In addition, when helium is too low in volume ratio, the plasma temperature of the source gas does not reach the plasma temperature for melting the ceramic powder. On the contrary, if the volume ratio of helium is too high, the life of the plasma gun may be shortened and the powder and the heat source gas may cause a mutual chemical reaction.

On the other hand, a high voltage DC high power applied between the anode and the cathode is applied to plasma the source gas. In this case, a current of 400 to 700 A is allowed to flow.

In an embodiment of the present invention, the process of plasmalizing the source gas may include an atmospheric pressure plasma method performed at atmospheric pressure. In the case of the atmospheric pressure plasma method, the subsequent formed coating film has a white color.

In another embodiment of the present invention, the process of plasmalizing the source gas may be performed under a reduced pressure. For example, the plasmaation process may be performed in a reduced pressure atmosphere of 50 to 600 hPa.

Subsequently, the ceramic material is melted using the plasmalized source gas (S130). The molten ceramic material is directed to the substrate along the path of travel of the plasmalized source gas.

The ceramic material may include white yttria and carbon, and the plasma may be performed by an atmospheric pressure plasma method. In this case, the coating film coated on the base material may have a black color. The coating film having black color may have a color difference meter L in a range of -75 to -65. Here, the carbon to the white yttria may have a mass ratio of 3 to 5%. If the carbon has a mass ratio of less than 3%, the color difference meter (L) of the coating film corresponds to about -20 and thus does not have a relatively good black color. On the other hand, when the carbon has a mass ratio of more than 5%, it can act as a source of contamination of the ceramic powder.

The ceramic material may include Al 2 O 3, Y 2 O 3, Al 2 O 3 / Y 2 O 3, ZrO 2, AlC, TiN, AlN, TiC, MgO, CaO, CeO 2, TiO 2, BxCy, BN, SiO 2, SiC, YAG, Mullite, AlF 3, and the like. These may be used alone or in combination.

By spraying the molten ceramic material to form a coating film on the base material (S140). As a result, the spray coating process is completed.

Hereinafter, the porosity, adhesion, and color difference meter of the yttria coating layer according to the volume ratio of the source gas and the applied current were measured.

(1) volume ratio of source gas

Types of source gas and volume ratios of argon, helium and hydrogen gas are shown in Tables 2 to 4 below. In Comparative Examples 1 to 4 and Comparative Examples 10 to 13, only argon and hydrogen gas were used as the plasma source gas. In Comparative Examples 5 to 8 and Comparative Examples 14 to 17, only argon and helium gas were used as the plasma source gas. In addition, in Comparative Example 9 and Comparative Example 18, the volume ratio of argon to helium to hydrogen gas was set to 15:60:25. On the other hand, in Examples 1 to 7, a plasma source gas containing argon, helium and hydrogen gas was used. In particular, the plasma source gas was adjusted to include argon having a volume mixing ratio of 20 to 40, hydrogen having a volume mixing ratio of 5 to 20, and excess helium gas.

(2) Psalms of the Base Material

As the base material, yttria was used, and Examples 1 to 14 and Comparative Examples 1 to 18 used yttria containing no carbon. Examples 15 to 21 and Comparative Examples 19 to 27 were used at 3 to 5% yttria. Yttria containing carbon having a mass ratio to was used.

(3) current flowing to the anode and cathode

It was to have a range of 400 to 685A.

(4) plasma pressure

At atmospheric pressure and in a reduced pressure atmosphere of 300 hPa.

(5) Porosity, adhesion and colorimeter evaluation

For each of the comparative examples and examples, porosity, adhesion strength, and color difference meters (a, L) of the coating film were measured. The adhesion strength was based on the adhesion strength test method according to JIS H8666 ceramic spray coating test method regulation.

Looking at the adhesion strength to the base material of the coating film, the adhesion strength of 50 MPa or more higher than in Comparative Examples 1 to 9 in Examples 1 to 7. In addition, in Examples 8 to 14, adhesive strength of 60 MPa or more, which is relatively higher than Comparative Examples 10 to 18, is shown. In addition, in Examples 15 to 21, the adhesive strength of 55 MPa or more is higher than that of Comparative Examples 23 to 26 and somewhat lower than Comparative Examples 19 to 22.

Regarding the porosity of the coating film, the porosity of 5 to 7% is shown in Examples 1 to 7, and the porosity of 2 to 4% is shown in Examples 8 to 14 and Examples 15 to 21.

Regarding the color difference meter, the coating film having a good white color is realized by showing the 1.8 to 2.5 color difference meter (a) in Examples 1 to 7.

By showing the color difference meter L of -70 or less in Examples 8 to 14 and Examples 15 to 21, a coating film having a good black color is realized. Coating film having a good black color is excellent in thermal properties. For example, the black coating film has a high heat absorption so that heat can be efficiently released to other heat dissipation units.

<Table 2>

<Table 3>

<Table 4>

Figure 4 is an electron micrograph of the coating film formed according to the spray coating method according to an embodiment of the present invention.

Referring to FIG. 4, a heat source gas having a volume mixing ratio of argon to helium to hydrogen gas of 30:60:10 was plasma-formed to form a coating film on a substrate made of yttria. As shown, no pores were found inside the coating film. Therefore, it can be seen that a coating film having a significantly reduced porosity is formed on the base material.

Although the detailed description of the present invention has been described with reference to the preferred embodiments of the present invention, those skilled in the art or those skilled in the art will have the idea of the present invention described in the claims to be described later. It will be understood that various modifications and variations can be made in the present invention without departing from the scope of the present invention.

According to the thermal spray coating method according to the present invention, by coating a plasma source heat source gas containing argon, helium and hydrogen to melt the ceramic powder using a plasma source heat source can be formed on the base material coating film having a low porosity . In addition, the generation of voids that may remain in the coating film by the thermal spray coating method of the present invention can be suppressed.

On the other hand, by melting the ceramic powder containing carbon to form a black coating film on the base material can implement a coating film with improved thermal properties.

1 is an electron micrograph of a coating film formed according to a conventional spray coating method.

2 is a cross-sectional view illustrating a plasma gun for implementing a spray coating method according to an embodiment of the present invention.

3 is a process flow chart for explaining the spray coating method according to an embodiment of the present invention.

Figure 4 is an electron micrograph of the coating film formed according to the spray coating method according to an embodiment of the present invention.

<Explanation of symbols for the main parts of the drawings>

10 plasma gun 12 cathode

14: anode 15: outer peripheral portion

16: support 17: powder inlet

Claims (11)

Preparing a base material; Plasma coating a heat source gas including argon as a main gas and helium and hydrogen gas as an auxiliary gas in an atmospheric pressure state to coat the thermal spray on the base material; Melting a ceramic material using the plasmaized heat source gas; And Injecting the molten ceramic material toward the base material to form a coating film on the base material, The heat source gas includes argon having a volume mixing ratio of 20 to 40, hydrogen having a volume mixing ratio of 5 to 20, and excess helium gas, The ceramic material comprises carbon as additive; The preparing of the base material may include spraying the surface to be coated in order to improve adhesion between the surface of the base material and the coating layer. delete The spray coating method of claim 1, wherein the plasma forming is performed using a current of 400 to 700 A. delete The method of claim 1, wherein the ceramic material comprises white yttria. The method of claim 5, wherein the mass ratio of carbon to white yttria is in the range of 3 to 5%. The method of claim 1, wherein the ceramic material is Al2O3, Y2O3, Al2O3 / Y2O3, ZrO2, AlC, TiN, AlN, TiC, MgO, CaO, CeO2, TiO2, BxCy, BN, SiO2, SiC, YAG, Mullite and AlF3 Spray coating method comprising at least one selected from the group consisting of. delete The method of claim 1, wherein the pre-treating the coated surface of the base material is a plasma coating method characterized in that the base material is a plasma treatment so that the temperature is 80 to 150 ℃. The method of claim 1, wherein the pre-treating the coated surface of the base material is a laser treatment. The method of claim 1, wherein the pretreating the coated surface of the base material comprises water blasting to improve the average roughness of the coated surface.

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