KR101266302B1 - Method for forming ceramic coating layer on aluminum substrate - Google Patents

Abstract

The present invention provides an electrolytic cell containing an electrolytic solution, disposing an electrode equipped with an aluminum substrate in the electrolytic cell, arranging an AC power supply means for supplying AC power to the electrode, and providing a voltage to the electrolytic solution. Arranging a power supply means for supplying an overcurrent, applying an AC power to the electrode through the AC power supply means, and supplying a voltage and a current to the electrolyte through the power supply means to the aluminum substrate. And forming a ceramic coating film, wherein the electrolyte includes deionized water, Na ₂ SiO _3, and Na ₂ WO ₄ · 2H ₂ O, and further includes at least one material selected from KOH, KF, and NaOH. A method of forming a heat resistant ceramic coating film on a substrate. According to the present invention, a ceramic coating film having high heat resistance and scratch resistance can be easily formed on an aluminum substrate having a lower melting point than other metals by wet surface treatment.

Description

Method for forming a heat resistant ceramic coating layer on an aluminum substrate {Method for forming ceramic coating layer on aluminum substrate}

The present invention relates to a method for forming a heat resistant ceramic coating film, and more particularly, to a method of forming a ceramic coating film having high heat resistance and scratch resistance on a wetted aluminum surface having a lower melting point than other metals.

Metals are known to have a lower melting point than ceramics and are poor in corrosion resistance, plasma resistance, scratch resistance, and the like. Thus, there have been studies to coat ceramics on metal or metal alloy surfaces. However, it is known that aluminum substrates, such as aluminum or aluminum alloys, have a smooth surface and are very difficult to coat the ceramic.

Attempts to coat ceramics on metal surfaces have been attempted by researchers around the world in a number of ways, the most widely known of which is plasma spray coating. Plasma spray coating is to spray a ceramic powder together with a gas to form a plasma to the surface of the coating to form a coating layer. At this time, the temperature of the plasma gas is a high temperature of 20,000 ° C to melt the ceramic powder instantaneously. When the molten particles adhere to the coated object, a coating layer is formed through a solidification process.

However, in this high temperature process, the coated material is also exposed to high temperature, and after cooling, a large residual stress exists at the interface between the coating layer and the coated material, and there is a disadvantage in that expensive equipment and expensive raw material powder for coating are used. In particular, when the workpiece is a metal material, there is a problem of oxidizing when the metal is exposed to high temperature, so that plasma spray coating must be performed in a vacuum, thereby requiring more expensive equipment. Therefore, many researchers have made various attempts to coat ceramics on the surface of metal materials in various ways, but it is not easy to perform ceramic coatings that are dense and free from cracks and defects.

In Japanese Patent Laid-Open No. 10-0801913, Yoshio Harada of Japan describes a thermal spray coating member having excellent plasma corrosion resistance and a method of manufacturing the same. With this structure, in order to reduce damage in corrosive environment, including the halogen _{compound, Al 2 O 3, Y 2} O 3 and so on which is located an outermost surface layer portion of the surface of the thermal sprayed coating formed by the upper than the center of the roughness profile of the film surface in the height direction Only the needle-shaped convex portion becomes an electron beam irradiation layer changed into a trapezoidal convex portion by melt-solidification accompanying electron beam irradiation, and is excellent in adhesion and deposition characteristics of particles and the like, and effectively prevents re-spreading. In addition, it is said that a member having excellent plasma resistance can be made. However, by forming the coating layer by the electron beam again to overcome the disadvantages on the plasma spray layer of about 50 ~ 2000㎛, the cost of the equipment is further increased, there is a disadvantage that the process is more complicated.

Yoshio Kobayashi of Japan et al. In Korea Patent Publication No. 10-0618630 discloses a invention for a plasma member having a ceramic surface composed of Y ₂ O ₃ or YAG suitable for use in a semiconductor manufacturing apparatus and a process for manufacturing the same. It is describing. According to this invention, Y ₂ O ₃ or YAG is coated on the alumina substrate with a surface roughness of 5 µm or more and 15 µm or less. The surface layer of the alumina substrate at this time has a porosity of 20% or more and 60% or less, and it is said that a plasma member having improved adhesion can be provided by making the porous material having a depth of 10 μm or more and 100 μm or less. However, this method includes a process of performing chemical etching on the substrate and a thermal spraying process. In the case of chemical etching, the acid etching solution at 180 ° C. to 240 ° C. must be treated at 1.0 MPa to 3.3 MPa for 3 hours to 10 hours. There is a difficulty in that, and after the etching treatment, there is a need to perform annealing treatment for 4 hours to 8 hours at a temperature of 1500 ° C to 1800 ° C. In addition, by performing thermal spraying such as plasma spraying, there may be a risk of cracking due to thermal stress generated according to the thickness of the coating layer.

Japanese Laid-Open Patent Publication No. 2007-0095716 discloses a technique for a ceramic composite, a susceptor for a semiconductor manufacturing apparatus, and a power module substrate having excellent adhesion and reliability of a film formed on an aerosol substrate. According to this invention, the film | membrane formed by the aerosol method is formed in the surface of the composite which consists of a some metal, or the film | membrane formed by the aerosol method is provided on the surface of the composite which consists of metal and ceramics. According to Japanese Laid-Open Patent Publication No. 2007-0095716, the thermal conductivity of the composite is preferably 100 W / mK or more, and the thermal conductivity of the film formed by the aerosol method is preferably 1 W / mK or less. However, when the ceramic directly coated on the aluminum metal in this way, there is a risk of cracking due to the difference in the coefficient of thermal expansion. In particular, when the crack occurs when used at a temperature during the semiconductor process, foreign matter particles are generated due to the erosion of the corrosive gas, thus there is a risk of failure in semiconductor production, there is a concern that the durability of the semiconductor equipment.

An object of the present invention is to provide a method of forming a ceramic coating film having a high heat resistance and scratch resistance through a wet surface treatment on an aluminum substrate having a lower melting point than other metals.

The present invention provides an electrolytic cell containing an electrolytic solution, disposing an electrode equipped with an aluminum substrate in the electrolytic cell, arranging an AC power supply means for supplying AC power to the electrode, and providing a voltage to the electrolytic solution. Arranging a power supply means for supplying an overcurrent, applying an AC power to the electrode through the AC power supply means, and supplying a voltage and a current to the electrolyte through the power supply means to the aluminum substrate. And forming a ceramic coating film, wherein the electrolyte includes deionized water, Na ₂ SiO _3, and Na ₂ WO ₄ · 2H ₂ O, and further includes at least one material selected from KOH, KF, and NaOH. A method of forming a heat resistant ceramic coating film on a substrate is provided.

In the method of forming a heat-resistant ceramic coating film on the aluminum substrate, AC power of 10 to 200 Hz is applied to the electrode through the AC power supply means, and a voltage of 150 to 550 V and 10 to 150 V to the electrolyte through the power supply means. It is preferable to apply a current of 1000 A.

It is preferable that a magnetic bar is disposed in the electrolytic cell, and the electrolytic solution is constantly stirred using the magnetic bar.

It is preferable that a heating plate is arranged in the electrolytic cell, and the heating plate keeps the temperature of the electrolyte solution constant at a temperature in the range of 10 to 50 ° C.

The Na ₂ SiO ₃ is contained from 0.001 to 0.05 mole with respect to the electrolyte, the Na ₂ WO ₄ · 2H ₂ O is contained from 0.001 to 0.05 mole with respect to the electrolyte, at least one or more selected from the KOH, KF and NaOH It is preferable that a substance contains 0.001-0.05 mol with respect to the said electrolyte solution.

The electrolytic solution may further include K ₃ PO _4, the K ₃ PO ₄ is preferably contained in 0.001 to 0.05 mole of a liquid electrolyte.

Aluminum substrates such as aluminum or aluminum alloys are very difficult to coat ceramics due to the smooth surface, but according to the present invention, it is possible to easily form a ceramic coating film having high heat resistance and scratch resistance on the aluminum substrate surface.

In addition, according to the present invention, while the conventional anodizing method requires a pretreatment such as sulfuric acid, it is possible to form a ceramic coating film excellent in heat resistance and scratch resistance directly on the surface of the aluminum substrate without any pretreatment, thereby making it environmentally friendly. In addition, compared to the conventional anodizing method, the ceramic coating film formed with a high operating voltage of 10 times or more is much stronger, and has excellent advantages such as corrosion resistance and adhesion.

In addition, according to the present invention, it is possible to form a ceramic coating film in the vicinity of room temperature, there is no stress due to mismatch of the coefficient of thermal expansion occurring in the same manner as plasma spraying, excellent adhesion, much higher voltage than the conventional anodizing method Since the ceramic coating film is formed at, it is excellent in hardness and chemical resistance.

1 schematically illustrates an arc plasma anodizing apparatus for wet surface treatment.
Figure 2a is a photograph showing the appearance of the aluminum substrate before the wet surface treatment and the aluminum substrate after the wet surface treatment.
FIG. 2B shows a photograph of the aluminum substrate not subjected to the wet surface treatment and the aluminum substrate formed by the wet surface treatment to form a ceramic coating film after heating at 800 ° C.
3 is a scanning electron microscope (SEM) photograph showing a cross section of an aluminum substrate on which a wet surface treatment is performed to form a ceramic coating layer.
4 is a scanning electron microscope (SEM) photograph showing a cross section of an aluminum substrate on which a wet surface treatment is performed to form a ceramic coating layer.
FIG. 5 is a scanning electron micrograph showing a cross section after heating at 800 ° C. for an aluminum substrate having a wet surface treatment to form a ceramic coating film.
FIG. 6 is a scanning electron micrograph showing the surface after heating at 800 ° C. on an aluminum substrate having a wet surface treatment to form a ceramic coating film.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the following embodiments are provided to those skilled in the art to fully understand the present invention, and may be modified in various forms, and the scope of the present invention is limited to the embodiments described below. It doesn't happen. Wherein like reference numerals refer to like elements throughout.

It is known that aluminum substrates, such as aluminum or aluminum alloys, have a smooth surface and are very difficult to coat the ceramic. The present invention proposes a method of forming a ceramic coating film on a surface by wet surface treatment on an aluminum substrate having a lower melting point than other metals to provide high heat resistance and scratch resistance. Hereinafter, the aluminum base is used to mean aluminum or aluminum alloy which is a metal.

In the present invention, an arc plasma anodizing (APA) method is used for the wet surface treatment. The arc plasma anodizing (APA) method of the present invention is environmentally friendly because the conventional anodizing method requires a pretreatment such as sulfuric acid, so that a strong ceramic coating film can be formed directly on the surface without any pretreatment. In addition, the ceramic coating film generated by the operation voltage is more than 10 times is much stronger, and has excellent advantages such as corrosion resistance and adhesion. In addition, the aluminum alloy system for die casting, which is known to be impossible to surface-treat by conventional anodizing, has the advantage of being surface-treated.

Hereinafter, a method of forming a ceramic coating film on the surface of an aluminum substrate by using a wet surface treatment will be described. 1 schematically illustrates an arc plasma anodizing apparatus for wet surface treatment.

The wet surface treatment for forming the ceramic coating film uses an arc plasma anodizing method. An arc plasma anodizing apparatus for wet surface treatment includes an electrochemical bath 100, an electrode 110 on which a positive voltage is applied and on which an aluminum substrate 115 is mounted, and an electrolyte solution 120 contained in the electrolytic bath 100. ), An AC power supply unit 130 for applying AC power to the electrode 110, a power supply unit 140 for supplying a voltage to the electrolyte 120, and a lower portion of the electrolytic cell 100. It is installed in the magnetic bar (magnetic bar) (150) for constantly stirring the electrolyte (120). In addition, a temperature control device such as a hot plate 160 for maintaining a constant temperature in the electrolytic cell 100 may be provided.

The electrode 110 is equipped with an aluminum substrate 115 made of aluminum or an aluminum alloy, and installed to be immersed in the electrolyte 120. The electrolyte may be a mixture of deionized water (DI water), Na ₂ SiO ₃ , KOH and Na ₂ WO ₄ · 2H ₂ O. Na ₂ SiO ₃ increases the hardness and scratch resistance at the time of surface treatment, it is preferable to contain about 0.001 to 0.05 mol with respect to the electrolyte. KOH improves the corrosion resistance during the surface treatment, it is preferable to contain about 0.001 to 0.05 mol with respect to the electrolyte. KF or NaOH may be used instead of KOH. That is, the electrolyte may include at least one material selected from KOH, KF, and NaOH. In this case, at least one material selected from KOH, KF, and NaOH may be contained in an amount of 0.001 to 0.05 mole based on the electrolyte. Do. Na ₂ WO ₄ · 2H ₂ O is able to withstand high heat during surface treatment, forms a hard coating (ceramic coating film), imparts plasma resistance, and is preferably contained in an amount of about 0.001 to 0.05 mol with respect to the electrolyte. And the electrolytic solution is K ₃ PO ₄ may further include the K ₃ PO ₄ is preferable to be included in an amount about 0.001 to 0.05 mole of a liquid electrolyte.

The electrolyte is preferably maintained at a temperature of 10 ~ 70 ℃ constant through the heating plate. The ceramic coating film treatment of the aluminum substrate 115 by the arc plasma anodizing (APA) method applied in the present invention may be performed at room temperature because the ceramic coating film is formed in an electrolyte based on water. As a result, there is no stress due to mismatch of thermal expansion coefficient which occurs in the same way as plasma spraying, and it has excellent adhesion. It has advantages.

The aluminum substrate 115 is degreased with a material such as isopropyl alcohol, and then dried. When grease or impurities remain on the surface of the aluminum substrate 115, a ceramic coating film having a uniform thickness may not be formed, which may cause a decrease in adhesion between the aluminum substrate 115 and the ceramic coating film. To perform a degreasing process.

After immersing the aluminum substrate 115 in the electrolyte solution 120 configured as described above, while applying an alternating current of about 10 to 200 Hz to the electrode 110 on which the aluminum substrate 115 is mounted, 150 to 550 V may be applied to the electrolyte solution 120. Apply a voltage and a current of 10 to 1000 A. At this time, by operating the magnetic bar 150, the electrolyte 120 is constantly stirred. Bubbles generated in the electrolyte 120 by plasma arc generation by an AC power supply are oxidized with the aluminum substrate 115 to form a ceramic coating film on the surface of the aluminum substrate 115. Conventional surface treatment has the disadvantage of being vulnerable to heat and scratch resistance. While the conventional anodizing method applies a voltage within 15-30V, in the present invention, a high voltage of 150-550V is applied to form a ceramic coating film. The electrolyte solution 120 is Na ₂ SiO ₃ which improves hardness and scratch resistance in DI water, KOH which improves corrosion resistance, and Na ₂ WO ₄ which can withstand high heat and forms a hard film and imparts plasma resistance. Contains 2H ₂ O.

The thickness of the ceramic coating film is 100 μm or more through the surface treatment for about 2 hours, and a rough layer is formed on the surface, but a hard dense ceramic coating film is formed inside, and thus has a high hardness. When the surface and state were observed by heating the aluminum specimen without surface treatment and the specimen having the ceramic coating film of 100 μm or more according to the present invention at about 800 ° C., which is 660 ° C. or higher, In the case of aluminum specimens, the shape was unrecognizable, but the surface-treated specimens with ceramic coatings maintained their original shape, and only the rough coating layer was peeled off and the dense inside. The layer remained unaffected and kept in its original form.

Hereinafter, an embodiment of a method of forming a heat resistant ceramic coating film on an aluminum substrate will be described in more detail, and the present invention is not limited to the following examples.

<Examples>

The aluminum alloy was made of aluminum, greased with isopropyl alcohol, and then placed in a vacuum dryer and sufficiently dried at a temperature of about 60 ° C. for 3 hours.

The specimen thus prepared was subjected to a wet surface treatment for 240 minutes using an arc plasma anodizing (APA) device to form a ceramic coating film on the aluminum substrate.

Specifically, as an electrolyte for performing arc plasma anodizing, 1600 ml of DI water, 0.015 mol of Na ₂ SiO ₃ to improve hardness and scratch resistance, 0.01 mol of KOH to increase corrosion resistance, and high heat resistance and rigidity A mixed solution of 0.015 mol of Na ₂ WO ₄ .2H ₂ O, which forms a film and imparts plasma resistance, was used. AC power supply 60Hz was applied to the electrode equipped with aluminum base material, 400V voltage and 600A current were applied to the electrolyte solution, and wet surface treatment was carried out by stirring using a magnetic bar at a temperature of 30 ° C. for 100 to 350 hours. A ceramic coating film having a thickness of about μm was formed.

Figure 2a is a photograph showing the appearance of the aluminum substrate before the wet surface treatment and the aluminum substrate after the wet surface treatment. The aluminum substrate before the wet surface treatment is shown on the left side in FIG. 2A, and the aluminum substrate having the wet surface treatment and the ceramic coating film is shown on the right side in FIG. 2A. FIG. 3 is a scanning electron microscope (SEM) photograph showing a cross section of an aluminum substrate having a wet surface treated with a ceramic coating film, and FIG. 4 is a scanning electron microscope showing a cross section of an aluminum substrate having a wet coated surface with a ceramic coated film. (SEM) picture.

The thickness of the ceramic coating film was 100 μm or more through the surface treatment for about 2 hours, and the surface was formed with a rough layer, but a hard dense ceramic coating film was formed inside to have a high hardness.

When the surface and state were observed by heating the aluminum specimen without surface treatment and the specimen having the ceramic coating film of 100 μm or more according to the present invention at about 800 ° C., which is 660 ° C. or higher, In the case of aluminum specimens, the shape was unrecognizable, but the surface-treated specimens with ceramic coatings maintained their original shape, and only the rough coating layer was peeled off and the dense inside. The layer remained unaffected and kept in its original form.

In FIG. 2B, the left side is a photograph observed after heating an aluminum substrate having no wet surface treatment at 800 ° C., and the right side in FIG. 2B is a wet surface treatment at 800 ° C. with respect to an aluminum substrate having a ceramic coating film formed thereon. It is a photograph observed after heating. FIG. 5 is a scanning electron micrograph showing a cross section after heating at 800 ° C. for an aluminum substrate having a wet surface treatment to form a ceramic coating film. FIG. 6 is a scanning electron micrograph showing the surface after heating at 800 ° C. on an aluminum substrate having a wet surface treatment to form a ceramic coating film.

The untreated aluminum specimen was melted at 800 ° C., and many deformations occurred. However, the surface-treated specimen with the ceramic coating film showed that the aluminum substrate was protected by the ceramic coating film to maintain the original shape without melting and deformation. It can be seen that only a rough coating layer is partially peeled off and the dense layer inside retains its original shape.

By forming a ceramic coating film on the aluminum substrate, which is susceptible to heat through wet surface treatment, heat and scratch resistance as well as corrosion resistance and plasma resistance can be compensated for.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, This is possible.

100: electrolytic cell 110: electrode
115: aluminum substrate 120: electrolyte solution
130: AC power supply means 140: power supply means
150: magnetic bar 160: heating plate

Claims (6)

Preparing an electrolytic cell containing an electrolytic solution, and disposing an electrode on which an aluminum substrate is mounted in the electrolytic cell;
Arranging AC power supply means for supplying AC power to the electrode;
Disposing a power supply means for supplying voltage and current to the electrolyte;
Applying an AC power to the electrode through the AC power supply means, and supplying a voltage and a current to the electrolyte through the power supply means to form a ceramic coating film on the aluminum substrate,
The electrolyte solution includes deionized water, Na ₂ SiO ₃ and Na ₂ WO ₄ · 2H ₂ O, further comprises KF,
Applying AC power of 10 ~ 200Hz to the electrode through the AC power supply means,
And applying a voltage of 150 to 550 V and a current of 10 to 1000 A to the electrolyte through the power supply means.
delete The method of claim 1, wherein a magnetic bar is disposed in the electrolytic cell, and the electrolytic solution is agitated using the magnetic bar.
The method of claim 1, wherein a heating plate is disposed in the electrolytic cell, and the temperature of the electrolyte is maintained constant by the heating plate at a temperature in the range of 10 to 50 ° C.
The method according to claim 1, wherein the Na ₂ SiO ₃ is contained in 0.001 to 0.05 mole with respect to the electrolyte, the Na ₂ WO ₄ · 2H ₂ O is contained in 0.001 to 0.05 mole with respect to the electrolyte, the KF is contained in the electrolyte A method for forming a heat-resistant ceramic coating film on an aluminum substrate, characterized by containing 0.001 to 0.05 molar relative to.
The method of claim 1, wherein the electrolyte is a method of forming the K ₃ PO _4, further comprising a said K ₃ PO ₄ are heat-resistant ceramic coating on an aluminum substrate, characterized in that contained 0.001 to 0.05 mole of a liquid electrolyte.

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