KR20120024336A - Low temperature silicon carbide coating - Google Patents

Abstract

A low temperature silicon carbide coating layer formation method is proposed. The surface of the coating object is coated with a silicon carbide precursor coating solution at a temperature higher than room temperature, and dried to heat treatment in the range of 250 ~ 650 ℃ to form an amorphous silicon carbide coating layer on the surface of the coating. Silicon carbide layers coated at low temperatures without a buffer layer enhance the durability, chemical resistance, and heat resistance of various coating objects.

Description

Low temperature silicon carbide coating layer formation method {LOW TEMPERATURE SILICON CARBIDE COATING}

The present invention relates to a method of forming a silicon carbide coating layer, and in particular, a method of forming a silicon carbide coating layer on a coating target without a buffer layer through a low temperature process.

Silicon carbide (SiC) is a ceramic material excellent in chemical resistance, oxidation resistance, heat resistance, and wear resistance. By coating the material such as metal or ceramic using the excellent physical properties of silicon carbide can improve the chemical resistance, oxidation resistance, heat resistance and wear resistance.

Silicon carbide is also present as a natural stone, but can also be produced by synthesizing silica and carbon by chemical reaction, it is possible to form a silicon carbide reinforcement layer on the surface of the material by coating or chemical vapor deposition (CVD) method.

In general, the silicon carbide reinforcement layer is formed by a chemical reaction such as vapor deposition. The gaseous state compound containing Si and the gaseous state compound containing C are reacted to coat a solid silicon carbide layer on the base material. The advantages of vapor deposition are that the composition can be easily controlled and the detailed structure of the deposited material is also easy.

However, the silicon carbide reinforcement layer produced by vapor deposition shows a rapid change in chemical composition at the interface with the base material, so residual stress tends not to be sufficiently relaxed, and peeling or cracking occurs due to the difference in thermal expansion coefficient between materials. easy. In order to solve this drawback, there is a problem in that the residual stress must be relieved through the formation of a buffer layer in advance between the reinforcing layer and the base material or through the interfacial coating of the gradient composition.

In addition, since the vapor deposition layer forms a silicon carbide reinforcement layer at a high temperature through chemical reaction with the base material, the base material capable of forming the reinforcement layer is limited. That is, a metal having a low melting point in the process of depositing silicon carbide on the surface of the metal by chemical vapor deposition using a process temperature of 1000 ° C. or more may cause problems such as melting of the metal.

On the other hand, silicon carbide coating using a polymer precursor has been proposed. For example, the Si-C-containing polymer is coated on the surface of the base material in a solution state to form a silicon carbide coating layer. However, in this case, the thickness of the coating layer is very small, so that the repeated coating process must be performed, and the type of the base material to be coated must be limited because it must maintain a high temperature of about 1000 ° C. in the heat treatment process after coating. Depending on the conditions such as the heat treatment process, the concentration of the coating solution, impurity is contained, it is not possible to obtain a stoichiometric silicon carbide layer or poor physical properties of the formed coating layer to perform a function as a reinforcing layer.

In particular, the heat treatment of the metal to be coated at a high temperature of 1000 ~ 1500 ℃ may not be able to use the product itself due to the deformation of the metal, cracks or peeling due to the difference in thermal expansion coefficient between the coating object and the coating layer during the high temperature heat treatment process There is a problem that occurs. In order to solve this problem, there is a case in which a coating layer is formed after adding a buffer layer to a coating object, but it is difficult to apply industrially due to complicated process and increased manufacturing cost.

The present invention has been made under the foregoing technical background, and an object of the present invention is to provide a method for forming a silicon carbide coating layer at a low temperature on various coating objects.

Another object of the present invention is to provide a silicon carbide coating layer to which no buffer layer or gradient composition layer is added.

Other objects and technical features of the present invention will be presented in more detail in the following detailed description.

In order to achieve the above object, the present invention is to prepare a coating object, to prepare a powder or liquid silicon carbide precursor material and a solvent as a coating solution and to mix while maintaining a first temperature higher than the room temperature, the coating solution to the coating object Coating while maintaining the first temperature, drying the coating object at a second temperature higher than the first temperature, and heat treating the coating object at a third temperature in the range of 250 to 650 ° C. higher than the second temperature. It provides a low temperature silicon carbide coating layer forming method comprising the step of forming an amorphous silicon carbide coating layer on the surface of the coating object.

The coating solution may be repeatedly coated on the surface of the coating object to form a coating layer having a thickness of 5 to 200 μm, and the thickness of the coating layer may be increased by mixing silicon carbide powder or silica powder with the coating solution.

In the preparing of the coating solution and in the coating step, the first temperature is preferably maintained at 50 to 100 ° C., and the second temperature is preferably in the range of 150 to 250 ° C. in the drying step of the coating object.

According to the present invention, a silicon carbide coating layer may be formed on the surface of various coating target materials such as metals having low melting points or ceramics. In addition, the thickness of the silicon carbide layer can be easily adjusted by repeat coating. In addition, there is no need for a buffer layer or a gradient composition layer between the coating object and the coating layer to simplify the process and reduce manufacturing costs.

1 is a process chart showing a method for forming a silicon carbide coating layer of the present invention.
Figure 2 is a photograph showing a silicon carbide coating layer formed on the aluminum surface according to Example 1 of the present invention.
Figure 3 is a graph showing the pressure resistance test results for the silicon carbide coating layer according to Example 1.
Figure 4 is a photograph showing a silicon carbide coating layer formed on the aluminum surface according to Example 2 of the present invention.
Figure 5 is a graph showing the chemical test results for the silicon carbide coating layer according to Example 2.
Figure 6 is a photograph showing a silicon carbide coating layer formed on the surface of SUS according to Example 3 of the present invention.
Figure 7 is a graph showing the chemical test results for the silicon carbide coating layer according to Example 3.
Figure 8 is a photograph showing a silicon carbide coating layer formed on the surface of SUS according to Example 4 of the present invention.
9 is a graph showing the results of the high temperature oxidation test on the silicon carbide coating layer according to Example 4.
Figure 10 is a photograph showing a silicon carbide coating layer formed at a low temperature in accordance with the present invention.
FIG. 11 is an enlarged photo of the silicon carbide coating layer surface of FIG. 10; FIG.
12 is a photograph showing a silicon carbide coating layer formed at a high temperature for comparison.
FIG. 13 is an enlarged photo of the silicon carbide coating layer surface of FIG. 12; FIG.

The present invention can form a functional carbide layer on a variety of coating objects by forming a silicon carbide coating layer at a low temperature, unlike the existing high temperature coating process, and prevents the coating layer from peeling or damage during the coating layer formation process of excellent quality silicon carbide coating layer To provide the formed products.

Silicon carbide coated on the metal surface is subjected to a heat treatment at a high temperature of 1000 ~ 1500 ℃ because the low melting point metal could not form a coating layer. In addition, in the process of heat treatment at high temperature, the metal, which is the coating object, may be deformed due to thermal expansion. That is, due to the thermal deformation of the coating object was changed in shape or changed in dimensions it could not be used as the product. For this reason, the precise part was impossible to form the coating layer itself, and even if the coating material was a crack or peeling occurred at the coating interface due to the difference in thermal expansion coefficient between the coating layer and the coating object. This problem was even worse in the case of rotary components in semiconductor equipment.

On the other hand, the present invention by developing a process for forming a silicon carbide coating layer at a low temperature on the surface of the coating object such as metal to prevent deformation of the metal during the coating process, improve the quality of the coating layer, as well as widen the range of the coating object Diversify its use.

A low temperature silicon carbide coating layer forming process according to the present invention will be described in detail with reference to FIG. 1.

First, to prepare a coating object is made of silicon carbide coating (step S 10). The coating object may have various shapes depending on the application product, and may have a disk shape, a hexahedron, various other geometric shapes, and a porous structure such as a metal foam may also be included in the coating object. The coating object may be composed of a single material, but a separate coating layer may be formed on the surface thereof, and a structure of a composite material may be used.

The coating object may be subjected to a pretreatment process for surface treatment, if necessary. For example, a cleaning step may be performed to remove contaminants on the surface, or the surface may be treated with a solution to facilitate adhesion of the coating layer on the surface.

Next, prepare a coating solution (step S 20). As the silicon carbide precursor material for coating, a polymer material containing Si and C may be used. For example, the silicon carbide precursor may be polycarbosilane (POLYCARBOSILANE), polyphenylcarbosilane (POLYPHENYLCARBOSILANE), polyallylphenyl carbosilane (POLYALLYLPHENYCARBOSILANE). Any one material selected from) may be used. The amount of the precursor may be adjusted in the range of 5 to 50 wt%. As a solvent, an organic solvent which is easy to disperse the silicon carbide precursor and volatilizes at low temperature is suitable. In addition to the silicon carbide precursor material, the coating solution may be further mixed with silicon carbide powder or silica powder to increase the thickness of the final coating layer and to improve the physical properties of the coating layer. Further, the particle size of the silicon carbide powder or silica powder to be mixed is preferably in the range of 50 nm to 100 μm, and the amount of addition is preferably in the range of 5 to 50 wt%.

In the step of preparing the coating solution, it is preferable to maintain a temperature of 50 ~ 100 ℃ not room temperature. Thus, by preparing the coating solution at a temperature higher than room temperature, the silicon carbide precursor is easily dissolved in the solvent and the dispersibility is improved, so that the coating is well formed on the coating material or the base material which is difficult to penetrate the surface of the complex shape. It is possible to form a coating layer through, to enhance the quality and properties of the final coating layer.

The coating solution can control the viscosity by adjusting the amount of precursor in powder or liquid phase. By adjusting the viscosity of the coating solution it is possible to improve the adhesion to the coating object when forming the coating layer and to maximize the drying and heat treatment effect.

Coating is performed on the surface of the coating object with the prepared coating solution (step S 30). The coating method may vary depending on the physical properties or the shape of the coating target, and various methods such as general dipping or spraying may be used. In the coating process, it is possible to obtain a coating thickness suitable for a purpose by performing repeated coating rather than one coating. When the coating thickness is small, a low molecular weight in the coating layer may be evaporated during the heat treatment of the coating layer to cause defects on the surface of the coating layer. In the present invention, repeated coating is performed several times to suppress the occurrence of defects on the surface of the coating layer and to realize a coating thickness for a desired use. If the coating layer is too thin, the effect as a reinforcing layer of the coating object cannot be obtained, and the excessive coating layer controls the coating thickness in the range of 5 to 200 μm because cracks or peeling may occur during the heat treatment process or use.

After the coating is completed, the coating object is dried (step S 40). The drying temperature is a suitable temperature range in which the solvent in the solution can be removed. For example, when toluene is used as the solvent and polycarbosilane is used as the precursor, the boiling point of the solvent is 110.8 ° C, and the curing temperature of the precursor is 200 ° C. Since it is above, even a low temperature 250 degreeC or less can remove a solvent. It is carried out for about 2 hours at a drying temperature of 150 ~ 250 ℃. As a dry atmosphere, an inert gas atmosphere or a vacuum atmosphere can be maintained.

After drying, the coating object is heat-treated at a temperature higher than the drying temperature. The heat treatment temperature is preferably in the range of 250 to 650 ° C. When the temperature is excessively increased, it is difficult to prevent thermal expansion of the coating object, and peeling of the coating layer and cracking of the coating layer may occur. Heat treatment is applied to heat at a rate of temperature increase of 2 ~ 10 ℃ per minute to maintain about 1 hour to 2 hours at the final temperature, and then slowly lowered to room temperature after the heat treatment is completed.

When the polycarbosilane is used as the silicon carbide precursor material, since the thermal curing is performed at 200 ° C. or more, a silicon carbide coating layer that is amorphous in the range of 250 to 650 ° C., which is a heat treatment temperature according to the present invention, may be obtained. Such a low temperature heat treatment may not only cause deformation of the coating object but also secure interfacial adhesion with the coating layer, thereby improving quality of the coating layer. In particular, the silicon carbide coating process is very simple and can be completed at a low cost since a buffer layer is not required to eliminate the adhesion failure due to the difference in thermal expansion coefficient between the coating object and the coating layer.

Hereinafter, the features of the present invention will be described in more detail with reference to preferred embodiments of the present invention.

Silicon Carbide Low Temperature Coating

Example  One

A silicon carbide coating layer was formed on the aluminum workpiece. The coating solution was mixed with 25 wt% of polyphenylcarbosilane using toluene as a solvent. The surface of the coating object was washed and dried at 80 ° C. in an oven.

The coating solution was maintained at a temperature of 50 ℃, the coating object was formed by dipping the coating layer. In the dipping method, the coating object was immersed in the coating liquid at a speed of 1 mm / sec, held in the coating liquid for 10 seconds, and then taken out again at a speed of 1 mm / sec. The coating was repeated twice in the same process sequence.

After the coating was completed, the object to be coated was heated at a rate of 2 ° C./min, and then cured by drying at an air temperature of 200 ° C. for 2 hours. Then, the coating object was heated up at a rate of 2 ℃ / min N ₂ Heat treatment was carried out for 2 hours at a temperature of 400 ℃ in the atmosphere.

2 shows a silicon carbide coating layer formed on the surface of the coating object after the heat treatment is completed. The coating layer formed was 18.6 μm thick. In order to confirm the durability of the silicon carbide coating layer, the test sample was put in a high pressure container, and the N ₂ gas was introduced into a pressure of 50 atm and maintained for 3 hours, and the results are shown in FIG. 3. The initial weight was 104.2350g, and after the pressure resistance test, the weight was 104.2349g, and the weight change before and after the test was only 0.0001g. Through this result, it was confirmed that the silicon carbide layer formed according to the present invention maintains excellent properties without changing the coating layer even at high pressure.

Example  2

Two coating compositions were prepared. The first coating solution was mixed with toluene as solvent and 25 wt% of polyphenylcarbosilane and 10 wt% of silicon carbide powder having a particle size of 200 nm were stirred for 30 minutes. As the second solution, 25 wt% of polyphenylcarbosilane was mixed using toluene as a solvent. The aluminum workpiece as a coating object was washed and dried at 80 ° C. in an oven.

The temperature of the coating liquid was maintained at 50 ° C. In the case of the first solution, stirring was performed while raising the temperature to prevent precipitation of silicon carbide powder. The coating object was sprayed to form a coating layer. The coating was repeated three times in the same manner, the first and second coatings using the first solution and the third coating using the second solution.

After the coating was completed, the object to be coated was heated at a rate of 2 ° C./min, and then cured by drying at an air temperature of 200 ° C. for 2 hours. Then, the coating object was heated up at a rate of 2 ℃ / min N ₂ Heat treatment was carried out for 2 hours at a temperature of 400 ℃ in the atmosphere.

4 shows a silicon carbide coating layer formed on the surface of the coating object after the heat treatment is completed. The thickness of the formed coating layer was 26 μm. After performing a chemical test to confirm the durability of the silicon carbide coating layer is shown in Figure 5 the results. A sample with a coating layer formed in the Hume ejection part of highly corrosive dichlorodimethylsilane was investigated to investigate the surface condition and weight change according to the change of time (72Hr, 144Hr). In the case of the sample without the coating layer, the weight change rate was 0.62% after 72 hours due to surface corrosion and the weight change rate was 1.12% after 144 hours, but the silicon carbide layer was formed according to the present invention. There was almost no surface corrosion, so the weight change rate was 0.11% after 72 hours and 0.18% after 144 hours. From this result, it was confirmed that the silicon carbide layer formed according to the present invention is excellent in chemical resistance and oxidation resistance.

Example  3

SUS 304 was prepared as a coating object. The coating solution was prepared in two compositions as in Example 2. The first coating solution was mixed with 30 wt% of polycarbosilane and 10 wt% of silicon carbide powder having a particle size of 100 nm using toluene as a solvent and stirred for 30 minutes. The second solution was mixed with 30 wt% of polycarbosilane using toluene as a solvent. The coating object was washed and dried at 100 ° C. in an oven.

The temperature of the coating liquid was maintained at 60 ° C. The coating object was sprayed to form a coating layer. The coating was repeated twice in the same way, the first coating using the first solution and the second coating using the second solution.

After the coating was completed, the object to be coated was heated at a rate of 3 ° C./min, and then cured by drying at 250 ° C. for 2 hours in an air atmosphere. Then, the temperature of the coating object was raised at a rate of 3 ℃ / min N ₂ Heat treatment was performed at an atmosphere of 650 ° C. for 2 hours.

6 shows a silicon carbide coating layer formed on the surface of the coating object after heat treatment is completed. The thickness of the formed coating layer was 21 μm. After performing a chemical test to confirm the durability of the silicon carbide coating layer is shown in Figure 7 the results. A sample with a coating layer formed in the Hume ejection part of highly corrosive dichlorodimethylsilane was investigated to investigate the surface condition and weight change according to the change of time (72Hr, 144Hr). In the case of the sample without the coating layer, the weight change rate increased to 0.15% after 72 hours due to surface corrosion and the weight change rate increased to 0.26% after 144 hours, but the silicon carbide layer was formed according to the present invention. The sample had almost no surface corrosion and the weight change rate was 0.05% after 72 hours, and the weight change rate was 0.08% after 144 hours.

Example  4

SUS 316 was prepared as a coating object, and the coating solution was mixed with 30 wt% of polycarbosilane and 10 wt% of silicon carbide powder having a particle size of 1 μm using toluene as a solvent, followed by stirring for 30 minutes. The coating object was washed and dried at 100 ° C. in an oven.

The temperature of the coating liquid was maintained at 60 ° C. A coating layer was formed by mixing the coating object with a spray by dipping and spraying. A total of five coatings were carried out, the first and second coatings by dipping, the third and fourth spraying, and the last by dipping.

After the coating was completed, the object to be coated was heated at a rate of 3 ° C./min, and then cured by drying at 250 ° C. for 2 hours in an air atmosphere. Then, the temperature of the coating object was raised at a rate of 3 ℃ / min N ₂ Heat treatment was performed at an atmosphere of 650 ° C. for 2 hours.

8 shows a silicon carbide coating layer formed on the surface of the coating object after heat treatment is completed. The thickness of the formed coating layer was 85.8 μm. In order to confirm the durability of the silicon carbide coating layer, the test sample was placed in a high-pressure container, and N ₂ was introduced to 50 atm, and the pressure test was performed for 3 hours. Moreover, the result of having performed the high temperature oxidation test in order to confirm heat resistance is shown in FIG. After maintaining the sample with the silicon carbide coating layer formed according to the present invention and the sample without a coating layer for 48 hours at a temperature of 800 ℃ as a result of analyzing the weight change, the sample according to the present invention was the weight change rate was -0.0071%, The sample without the coating layer oxidized the surface and showed a weight change rate of 0.1204%. Since the oxide layer was not formed on the surface of the sample having the silicon carbide layer according to the present invention, there was almost no change in weight, and it was confirmed that the heat resistance and the high temperature oxidation resistance were very excellent.

Comparison of Coating Layer Quality According to Annealing Temperature

10 shows a sample surface heat-treated at a temperature of 650 ° C. after forming a coating layer with a silicon carbide coating solution on the surface using SUS as a coating object. It can be seen that the coating layer was not peeled or damaged and coated with excellent adhesion with the coating object. FIG. 11 is an enlarged view of the surface structure of the silicon carbide coating layer formed on the surface of the coating object of FIG. 10, and it is confirmed that a uniform surface structure is formed and a coating layer having excellent quality is formed.

On the other hand, referring to Figure 12 to form a coating layer with a silicon carbide coating solution without a buffer layer or gradient composition layer on the surface of the same coating object to show a sample surface heat-treated at a temperature of 800 ℃, between the coating object and the coating layer during the heat treatment process It can be seen that due to the difference in thermal expansion coefficient of the coating layer is partially peeled off and the quality of the entire coating layer is very poor. In addition, as can be seen in Figure 13 to enlarge the surface of the coating layer, the coating layer was confirmed that the overall cracking can not perform a function as a surface reinforcing layer.

The present invention has been exemplarily described through the preferred embodiments, but the present invention is not limited to such specific embodiments, and various forms within the scope of the technical idea presented in the present invention, specifically, the claims. May be modified, changed, or improved.

Claims (10)

Prepare the coating object,
As a coating solution, a powder or liquid silicon carbide precursor material and a solvent are prepared and mixed while maintaining the first temperature higher than room temperature,
The coating solution is coated on the coating object while maintaining the first temperature,
Drying the coating object at a second temperature higher than the first temperature,
Heat treating the coating object at a third temperature in the range of 250 to 650 ° C. higher than the second temperature to form an amorphous silicon carbide coating layer on the surface of the coating object.
Low temperature silicon carbide coating layer formation method. The method of claim 1, wherein the coating solution is repeatedly coated on the surface of the coating object to form a coating layer having a thickness of 5 ~ 200㎛. 2. The method of claim 1, wherein the first temperature is maintained at 50 to 100 ° C. in the preparing of the coating solution and in the coating step. The method of claim 1, wherein the silicon carbide precursor amount in the preparing of the coating solution is adjusted to 5 to 50wt%. The method of claim 1, wherein the drying is carried out in an inert gas atmosphere or a vacuum atmosphere in the drying step of the coating object. The method of claim 1, wherein the second temperature in the drying step of the coating object is a method of forming a low temperature silicon carbide coating layer, characterized in that the range of 150 ~ 250 ℃. The method of claim 1, wherein the silicon carbide precursor is any one selected from polycarbosilane (POLYCARBOSILANE), polyphenylcarbosilane (POLYPHENYLCARBOSILANE), and polyallylphenylcarbosilane (POLYALLYLPHENYCARBOSILANE). 2. The method of claim 1, comprising pretreating the surface of the coating object prior to coating of the material to be coated. The method of claim 1, wherein the material to be coated comprises a geometric structure such as a disk, a hexahedron, and a porous structure such as a foamed metal. The method of claim 1, wherein the silicon carbide powder or silica powder having a particle size in a range of 50 nm to 100 μm is added to the coating solution in a range of 5 to 50 wt%.

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