JPS6376886A - Airtight ceramic coated film and its production - Google Patents

Abstract

PURPOSE:To rapidly produce the title ceramic coated film having excellent heat resistance by forming a coated film consisting of high-m.p. ceramic particles and carbosilane resin on the surface of a substrate, and treating the material with laser to form vitreous silica. CONSTITUTION:The coated film consisting of high-m.p. ceramic particles and carbosilane resin is formed on the surface of the substrate made of a metal. TiO2, SiC, etc., are used for the ceramic particles, and the particle diameter is preferably controlled to <=about 10mum. The coated film is dried or baked, and then treated with CO2 laser, etc. As a result, the resin is instantaneously decomposed, and molten silica is formed. The molten silica oozes out to the coated film surface, and is then quenched to form vitreous silica 2. The ceramic particles 1 in the coated film form a porous layer contg. voids 4 and having excellent thermal shock resistance. The material is then preferably heat-treated at >=about 600 deg.C to form a diffusion joint 3. Consequently, an airtight ceramic coated film capable of withstanding a high temp. of >=about 450 deg.C is obtained.

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to an airtight ceramic coating formed on a metal surface having a relatively large area such as various mechanical devices, plant equipment, towers and tanks, and a method for manufacturing the same. be. The present invention is particularly suitable for substrates used in high-temperature areas where surfaces such as stainless steel and carbon steel have insufficient chemical resistance and oxidation resistance, and plastic coatings and glass lining surfaces cannot be used due to heat resistance. The present invention relates to ceramic coating technology for the purpose of protecting the surface of a base material.

[Prior art]

Carbon steel and stainless steel have oxidation resistance between them.

Although there are varying degrees of chemical resistance, all materials are subject to material deterioration under usage conditions. Common methods for increasing the chemical resistance of these metals by coating are plastic coatings or glass linings. However, a drawback of these coating methods is that they cannot be used for equipment exposed to high temperatures.

Even Teflon coatings and polyamide coatings, which are the most durable plastic coatings to withstand high temperatures, cannot substantially withstand use at temperatures above 300°C. Furthermore, glass lining cannot withstand use at temperatures above 300°C, and its use is generally limited to temperatures below 250°C. The former temperature limit is due to the onset of decomposition of organic matter, and the latter humidity limit is due to the inability of glass to withstand increased stress due to the difference in thermal expansion coefficients between metal and glass.

In recent years, in order to improve the heat resistance defects of plastic coatings, coating materials have been developed in which ceramic fine particles are mixed with carbosilane resins such as silicone resins, which have a higher decomposition temperature than plastics.

However, this resin cannot withstand use at temperatures above 450°C because the 5i-C bonds begin to decompose when the temperature exceeds 400°C. As there is currently no coating method that forms an airtight film above 450°C, there is currently no coating method that not only provides high-temperature corrosion resistance but also prevents metal oxidation, which is a problem in high-temperature regions.

However, if the coverage area is small, 45
There are several methods for making airtight membranes that can withstand use at temperatures above 0°C. The first method is to generate a coating film on the surface of the base metal from the gas phase. There are PVD methods, CVD methods, etc.

However, this method requires reduced pressure to form a coating film, and
Construction is difficult for objects exceeding r.Recently proposed methods of 0th order include JP-A-59-96273, JP-A-60-11287, and JP-A-61-30.
The surface of the ceramic sprayed coating as seen in Publication No. 658 etc. is irradiated with a laser to seal the ceramic surface,
There are ways to increase airtightness. However, the disadvantage of this method is that the cost and time required for thermal spraying are very large, making it virtually unsuitable for coating large areas exceeding 1M.

〔the purpose〕

The present invention provides a ceramic coating film that can withstand high temperatures of 450° C. or higher and has excellent airtightness, and a ceramic coating film that can be used to fry this coating film. The object of the present invention is to provide a coating technique that can quickly form a coating on the surface of a large base material.

〔composition〕

According to the present invention, a first aspect of the present invention is a ceramic coating film formed on the surface of a base material and comprising high melting point ceramic particles and glassy silica, the glassy silica being formed via fused silica. An airtight ceramic coating film characterized by being non-porous is provided, and as a second invention, a coating film made of high boiling point ceramic particles and carbosilane resin formed on the surface of a base material is treated with a laser. A method for producing an airtight ceramic coating film is provided, which comprises decomposing the carbosilane resin to produce a glassy substance containing silica as a main component.

The production of the coating film of the present invention is characterized in that the coating film made of high melting point ceramic particles and carbosilane resin formed on the surface of a base material is subjected to laser treatment. When a coating film made of ceramic particles and carbosilane resin is gradually heat-treated using a conventional method, the coating film decomposes at high temperatures of 450°C or higher, and eventually silica fills the spaces between the ceramic particles. It becomes a ceramic coating. However, since the silica in this coating film has not undergone a molten state, it has a porous structure unique to an aggregate of fine particles, and lacks airtightness, and its performance as a chemical-resistant and oxidation-resistant coating film is poor. That's enough.

On the other hand, when a coating film made of ceramic particles and carbosilane resin is irradiated with a CO2 laser or YAG laser,
The resin is instantaneously decomposed by the high heat generated by the laser irradiation, producing molten silica (SiO□). This fused silica conveniently leaches to the coating surface where it is rapidly cooled to glassy silica. Therefore, the spaces between the ceramic particles near the surface of the coating film are filled with silica glass, and the uppermost layer is completely covered with a glass film containing no ceramic particles. As is well known, glassy silica is non-porous, has good airtightness, and can completely isolate the base metal from the outside world, making it suitable for use as a chemical-resistant and oxidation-resistant film. demonstrate. In particular, the silica glass produced differs depending on the other components contained in it, but it usually has a strengthening point of 800°C or higher, has excellent chemical resistance except for strong alkalis, and has high hardness, so it can be used for a long time. The coating film is stable over a period of time.

Another major feature of the present invention is that the high melting point ceramic particles contained in the resin as a filler have a coefficient of thermal expansion close to that of the base metal, so that the bonding surface between the base metal and the coating film at high temperatures can be improved. Not only can stress generation be minimized, but also chemical resistance,
Even when using a ceramic having a thermal expansion coefficient significantly different from that of the base metal in terms of strength and other M points, it is possible to produce a coating film that can withstand thermal stress. The reason for this is that during laser irradiation, the carbosilane resin between the ceramic particles decomposes and moves to the surface layer, making the part of the ceramic particles bonded to the base metal extremely porous, which is effective in alleviating thermal stress. This is to give structure. This structure has a lower compressive strength than a coating made by firing the original organic coating as is, but
It is suitable for providing coating films that are resistant to rapid cooling and have excellent thermal shock resistance.

Next, the coating agent used in the present invention will be explained in detail.

The carbosilane resin used as one component of the coating agent in the present invention is a conventionally known one.

Silicic acid polymers with hydrocarbon side chains or containing other foreign elements such as boron, titanium. In this case, a methyl group, a phenyl group, or the like is used as the hydrocarbon side chain. In addition, the number of hydrocarbon side chains is 1 to 2 per silicon element, and ordinary carbosilane resins have one hydrocarbon group and two hydrocarbon groups per silicon element. It is a copolymer with When a foreign element is included, the foreign element usually binds to the silicium through oxygen.

Among the carbosilane resins used in the present invention, those containing a different element (heterocarbosilane hatsumode) are more effective than ceramic coatings formed from those that do not contain a different element (straight silicone resin) due to the action of the different element. This produces coating films with different properties in terms of chemical resistance, such as alkali resistance. Carbosilane resins containing different elements are also conventionally known, and commercially available products include, for example, borosiloxane resins containing boron as a different element, polytitanocarbosilane resins containing titanium, and the like.

In the present invention, a coating agent is prepared by adding and mixing a filler made of ceramic particles to a carbosilane resin. In this case, the ceramic particles have a high melting point,
Usually, those having a melting point of 100° C. or higher are used, but various conventionally known ones can be used as such, for example.

In addition to metal oxides such as titania, silica, alumina, zirconia, silica alumina, and magnesia, silicon carbide (Si
C), metal carbides such as titanium carbide (TiC); metal nitrides of silicon nitride (Si, N4); mineral particles such as Holsterei 1, zircon, zenasite, chrysoberyl, etc. = mica, and the like. In particular, from the viewpoint of heat resistance, chemical resistance, and compatibility with silica glass formed by laser treatment of carbosilane resin, titania, silica, alumina, silica alumina, zirconia, silicon carbide, silicon nitride, titanium carbide, etc. In addition, when a material with a large coefficient of thermal expansion is required in consideration of thermal stress with the base metal, magnesia, holsterite, zirconia mica, etc. are preferably used, although they have slightly inferior chemical resistance. It will be done.

The particle size of the ceramic particles is preferably 10 μm or less, and as long as uniform dispersion in the carbosilane resin is possible, the smaller the particle size is, the more preferable. The ceramic particles are used in an amount of 30 to 70% by volume, preferably 40 to 60% by volume, based on the total amount of carbosilane resin and ceramic particles. Further, in the present invention, an adhesive agent or the like may be added and mixed, if necessary, in order to improve the adhesion between the coating agent and the base metal.

To produce the ceramic coating of the present invention, the carbosilane resin and ceramic particles are mixed with a solvent, and this mixture is applied to the surface of a substrate. In this case, the solvent used is one that exhibits solubility or dispersibility in the carbosilane resin, such as ethyl cellosolve acetate, N-methyl-2-pyrrolidone, xylene, etc. It will be done. Conventional methods such as dipping, spraying, and brushing can be used to coat the surface of the base metal.

Next, the surface coated with the coating agent formed as described above is subjected to a drying treatment or a baking treatment, and then a laser treatment. The drying process is carried out at room temperature -250°C, preferably at 15°C.
The firing process is carried out at a temperature of 0 to 250°C, and the firing process is carried out at a temperature of 40°C.
It is carried out at a temperature of 0 to 800°C, preferably 600 to 800°C. The laser treatment may be anything that generates high temperatures, such as CO□ laser treatment,
Conventionally known laser processing such as WAG laser processing can be employed. It is thought that the coating film is instantaneously heated to a high temperature of 800° C. or higher by this laser treatment, and a coating film made of a mixture of fused silica formed from a carbosilane resin and ceramic particles is formed on the surface of the substrate.

This coating film is then cooled and finally becomes a coating film consisting of a mixture of glassy silica and ceramic particles. As mentioned above, this coating film is not porous but airtight because the glassy silica is formed through fused silica.

Next, in 6 drawings showing the cross-sectional structure of the coating film obtained by the present invention, A indicates the base material, B indicates the ceramic coating film, 1 indicates ceramic particles, 2 indicates glassy silica, and 3 indicates adhesive or diffusion. In the bonding layer, 4 indicates voids. The thickness of the ceramic coating is usually 10-300 μm, preferably 50-300 μm.
tSOμm.

In the present invention, it is advantageous that the coating film obtained as described above is subjected to a high temperature treatment at 600° C. or higher prior to its use. This high-temperature treatment causes diffusion of metal components from the base metal surface into the ceramic coating film, and a diffusion bonding layer consisting of the diffused metal oxide is formed between the base metal surface and the ceramic coating film. As a result, the ceramic coating film formed on the surface of the base metal has significantly increased adhesion to the base metal. Of course, the paint film will be damaged during use.
When heated to a high temperature of 00° C. or higher, the same effects as the above-mentioned high temperature heat treatment can be obtained.

Further, the adhesion of the ceramic coating film to the base metal surface can be improved not by the above-mentioned high-temperature treatment but also by using an adhesive. Although the temperature of the coating film increases in laser treatment, the temperature of the base metal does not increase by that much, so the formation of a diffusion bonding layer based on the diffusion of the metal component into the ceramic layer cannot be expected. However, if a heat-melting adhesive is mixed into the coating film, the adhesive will melt due to the heat generated by the coating film during laser treatment, and the action of this melting adhesive will cause the ceramic coating film to adhere to the substrate surface. sex is improved. In this case, the adhesive used is a metal or an inorganic compound that does not vaporize and melts at the temperature during laser treatment, such as active metals such as titanium.

Various materials such as low melting point glass and various types of frits for waxing are mentioned, and appropriate materials are used depending on the type of ceramic particles and base metal used.

The base metal to be coated in the present invention is not particularly limited and may be any commonly used metal, but in particular,
Carbon steel, stainless steel,
Iron materials such as heat-resistant steel, aluminum, etc. are used. In addition, the substrate targeted by the present invention is generally a metal material, but as is clear from the principle of the present invention, non-metallic materials such as ceramic materials with poor chemical resistance, oxidation resistance, heat resistance, etc. It may be a material.

〔effect〕

The ceramic coating film formed on the surface of the substrate according to the present invention is a ceramic coating film with excellent heat resistance consisting of glassy silica and ceramic particles, and the glassy silica is formed via fused silica. It is characterized by being non-porous. Therefore, the ceramic coating film according to the present invention is airtight, protects the surface of the substrate from the effects of oxygen and chemicals at high temperatures, and significantly improves the durability of the substrate.

〔Example〕

Next, the present invention will be explained in more detail with reference to Examples.

Example 1 Methyl-based straight silicone resin (manufactured by Toray Silicon Co., Ltd., trade name: SK+ 806 A) approximately 40wt%1 synthetic mica approximately 58νt1, adhesive (potassium phosphate) 2wt%
A coating agent containing
Made of 304, area: 60mm x 50mm, thickness: 4.
The coating was applied to the entire surface of a 5 mm plate by spraying and dried at 250° C. for 3 hours to obtain 3 coated test pieces having a film thickness of about 60 μm.

Next, two of these test pieces were placed in an electric furnace and exposed to air for 50 minutes.
After baking at 0°C for 1 hour, one of the sample surfaces was coated with the following coating.
The coated surface was vitrified by irradiation with a CO□ laser under the conditions shown in 1. In this way, sample A (1) which was subjected to firing treatment and CO and laser treatment, and sample A (1) which was only subjected to firing treatment (
n) was obtained.

In addition, the remaining one of the test pieces was tested under the conditions shown in Table 1.
Sample A (I
II) was obtained.

Next, the samples A(1), A(n), A(I
II) into two equal parts, leaving one side as a reserve,
The other was subjected to an acid resistance test. In this case, the acid resistance test is performed by covering all surfaces except the laser irradiated surface with silicone sealant, immersing this in a glass bottle containing 200 cc of 50% sulfur M solution, and immersing this in a constant temperature bath at 55 ° C. I went by that. The results of the acid resistance test are shown in Table 2. As can be seen from the results, the laser irradiated coating samples A(1) and A(III) were the same as the untreated coating sample A(f[
) shows remarkable durability.

Example 2 Borosiloxane resin (manufactured by Showa Denshin Co., Ltd., trade name: SM
R10109) 42%, silica sand 56wt%, adhesive (Bz
A coating agent containing 2vt% of O3-PbO glass powder) was dispersed in N-methyl-2-pyrrolidone solvent to coat the base material Q (
Carbon steel 1 area: 60+m+a x 50mm, thickness: 4
．． 5mm plate) by spraying 3 times, approx.
Three fully coated test specimens with a film thickness of 0μ were prepared. The specimens were dried at 250° C. for 1 hour after each application. Next, the surface of the first test piece was treated with a CO2 laser under the conditions shown in Table 1, and then baked at 600°C for 3 hours.
) was obtained. Next, the second test piece was YA under the conditions shown in Table 1.
After treatment with G laser, the sample was baked at 600° C. for 3 hours to obtain sample B (■). Finally, add the remaining test piece to 600
Sample B (nl) was obtained by baking at ℃ for 3 hours.

Next, samples 13(1), B(II), B(1) obtained above were prepared.
1) was cut into two equal parts, one of which was kept as a reserve, and each of the other parts was subjected to an acid resistance test in the same manner as in Example 1. The acid resistance test results are shown in Table 2. This test investigated the effect of laser treatment on the corrosion resistant ceramic coating of equipment exposed to high temperatures of around 600°C. The effectiveness of laser and YAG laser irradiation can be clearly confirmed.

(Sea 1 - Conditions) Example 3 Preliminary samples B (1), n (n), 8 (■) obtained in Example 2
And as comparative sample B (IV), bare carbon steel obtained by dividing base material Q into two equal parts was placed in an electric furnace and held at aOO°C for 50 hours.

Thereafter, each sample was taken out and cut at the center, and the oxidation state of the cross section was examined using a scanning electron microscope. Sample 11 (1),
Regarding B(It), the thickness of the oxidized layer from the base material surface in contact with the laser irradiated coating film, and sample B(III) mouth (r
Regarding V), the thickness of the oxidized layer was determined by subtracting the thickness of the metal iron portion of the sample cross section from the thickness of the original base material Q and dividing it by 2.

The results are shown in Table-3.

Table 3 This experiment confirms that the laser treated film is extremely effective in preventing oxidation of the base metal.

Example 4 Samples A(1) and A(II) left as preliminary in Example 1
), A (m) and comparative sample A (IV) using stainless steel (SO3304) wire plates (substrate P divided into two equal parts) to evaluate the durability of the ceramic coating film according to the present invention against vanadium attack. It was tested using the following test method.

By applying the Jakusho Jakushin method, we placed a vanadium composite on a sample and exposed it to high temperature to compare the degree to which each sample was oxidized. The synthetic state of vanadium is V, 0
．． It was prepared by pulverizing and mixing 85 wt% of NaaSo and 15 wt% of NaaSo, and molding 0.5 g of the mixture into a disk shape with a diameter of 10 mm using a tablet machine. This tabletted synthetic form of vanadium was prepared as sample A (ri, ^(n),
It was placed on the center of A(III) and A(IV), placed in an electric furnace, and heated at 800° C. for 20 hours. After cooling, each sample was taken out, cut in a straight line so that the cut end passed through the center of the sample, and the cross section was photographed using a scanning electron microscope to determine the thickness of the oxidized layer in the stainless steel layer of each sample. The smaller the measured oxide layer thickness, the more resistant the coating is to vanadium attack.

Next, the thickness of the oxide layer of each sample obtained in the above test will be shown.

Table-4

[Brief explanation of the drawing]

The drawing shows an explanatory cross-sectional view of a ceramic coating. 1... Ceramic particles, 2... Glassy silica, 3
...Adhesive agent or diffusion bonding layer, 4...Void, A...
·Base material. B... Ceramic coating film.

Claims (4)

[Claims] (1) It is a ceramic coating film formed on the surface of a base material consisting of high melting point ceramic particles and glassy silica, and the glassy silica is non-porous and is formed via fused silica. Features an airtight ceramic coating. (2) The coating film according to claim 1, wherein the base material is metal. (3) A coating film made of high-boiling ceramic particles and carbosilane resin formed on the surface of the base material is treated with laser to decompose the carbosilane resin and generate a glassy substance mainly composed of silica. Method for producing airtight ceramic coatings. (4) The method according to claim 3, wherein the base material is metal.