JP2585548B2 - Hermetic ceramic coating and method for producing the same - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an air-tight ceramic coating film formed on a metal surface having a relatively large area such as various types of machinery, plant equipment, towers and tanks, and a method for producing the same. is there. The present invention, especially stainless steel, chemical resistance on the surface of carbon steel, etc.,
It relates to ceramic coating technology for the purpose of protecting the surface of a base material used in a high-temperature region where the oxidation resistance is insufficient and the plastic coating or glass lining surface cannot be used because of heat resistance. Things.

(Prior art)

Although carbon steel and stainless steel have different degrees of oxidation resistance and chemical resistance between the two, deterioration of the material is inevitable under the use conditions. A common method for increasing the chemical resistance of these metals by coating is plastic coating or glass lining. However, a disadvantage of these coating methods is that they cannot be used for equipment exposed to high temperatures. Even a Teflon coating or polyamide coating, which is said to withstand the highest temperatures as a plastic coating, cannot practically withstand use at 300 ° C. or higher. Further, the glass lining does not withstand use at 300 ° C. or higher, and its use is generally limited to 250 ° C. or lower. The former temperature limit is due to the onset of decomposition of organic substances, and the latter is due to the inability of the glass to withstand an increase in stress due to the difference in the coefficient of thermal expansion between the metal and the glass.

In recent years, in order to improve the defect in heat resistance of plastic coating, a coating material in which a carbosilane resin such as a silicon resin having a higher decomposition temperature than plastic is mixed with ceramic fine particles has been developed.
However, even if this resin exceeds 400 ° C., decomposition of the Si—C bond starts, so that it cannot withstand use at 450 ° C. or higher. As described above, at present, there is no coating method for forming an airtight film at 450 ° C. or higher, so that not only high-temperature corrosion resistance but also a coating method for preventing oxidation of a metal which is a problem in a high-temperature region does not exist at present.

However, if the coverage is small, 45
There are several ways to make an airtight membrane that can withstand use above 0 ° C. The first is a method of forming a coating film on the surface of a base metal from a gas phase, such as a PVD method or a CVD method. However, in this method, decompression is required to form a coating film, and it is difficult to construct a coating film exceeding 1 m ² . Next, as a recently proposed method, the surface of a ceramic sprayed coating as disclosed in JP-A-59-96273, JP-A-60-11287 and JP-A-61-30658 is irradiated with laser. Then, there is a method of sealing the ceramic surface and increasing airtightness. However, a disadvantage of this method is that the cost and time required for thermal spraying are so great that it is virtually unsuitable for coating large areas, such as over 1 m ² .

〔Purpose〕

The present invention provides a ceramic coating film that withstands a high temperature of 450 ° C. or more and has excellent airtightness, and a coating technique capable of rapidly forming the coating film on a large substrate surface of 1 m ² or more. Aim.

〔Constitution〕

According to the present invention, as a first invention, there is provided a ceramic coating film composed of high melting point ceramic particles and glassy silica formed on the surface of a substrate, wherein the glassy silica is formed by laser treatment of a carbosilane resin film. An airtight ceramic coating is provided which is non-porous formed via fused silica. As a second invention, a high melting point ceramic particle and a carbosilane resin formed on a substrate surface are provided. A method for producing a hermetic ceramic coating film, comprising decomposing the carbosilane resin by laser treatment of a coating film comprising: and forming a glassy substance containing silica as a main component via fused silica. You.

The production of the coating film of the present invention is characterized by subjecting the coating film composed of the high melting point ceramic particles and the carbosilane resin formed on the surface of the base material to laser treatment. When a coating film composed of ceramic particles and a carbosilane resin is gradually heated by a normal method, the coating film is decomposed at a high temperature of 450 ° C. or higher, and silica is finally filled between the ceramic particles. It becomes a ceramic coating. However, since the silica in this coating film has not passed through a molten state, it has a porous structure peculiar to an aggregate of fine particles, lacks airtightness, and has poor performance as a chemical-resistant and oxidation-resistant coating film. Is enough.

On the other hand, when a coating consisting of ceramic particles and a carbosilane resin is irradiated with a CO ₂ laser or YAG laser, the resin instantaneously decomposes due to the high heat generated by the laser irradiation, producing silica (SiO ₂ ) in a molten state. . This fused silica is conveniently leached onto the coating surface where it is quenched to glassy silica. Accordingly, the space between the ceramic particles near the surface of the coating film is filled with silica glass, and the uppermost layer is covered with a glass film containing no ceramic particles. As is well known, such glassy silica is non-porous, has good airtightness, and enables complete insulation between the base metal and the outside world. Demonstrate. In particular, the generated silica glass depends on other components contained therein, but usually,
The difficulty point is 800 ° C or higher, and the chemical resistance is extremely excellent except for strong alkali.
Long-term stable coating film.

Another major feature of the present invention is that a high-melting point ceramic particle to be contained in a resin as a filler has a coefficient of thermal expansion close to that of the base metal, so that a bonding surface between the base metal and the coating film at a high temperature can be obtained. In addition to minimizing the occurrence of stress in the coating, coatings that withstand thermal stress can be used even when using a ceramic having a coefficient of thermal expansion that is significantly different from the base metal in terms of chemical resistance, strength, and other factors. It is possible to manufacture a film. The reason is that, during the laser irradiation, the carbosilane resin between the ceramic particles decomposes and moves to the surface layer, so that the ceramic particle portion bonded to the base metal is extremely porous, which is effective in reducing thermal stress. This is to give structure. This structure is smaller in compressive strength than a coating film formed by firing the original organic coating film as it is,
It is suitable for giving a coating film with excellent thermal shock resistance against rapid heat and rapid cooling.

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

The carbosilane resin used as one component of the coating agent in the present invention is a conventionally known carbosilane resin, and a silicic acid polymer having a hydrocarbon side chain or many different elements, for example, boron,
It is a silicic acid polymer containing titanium. In this case, a methyl group, a phenyl group, or the like is used as the hydrocarbon side chain. The hydrocarbon side chain is 1 to 1 per silicon element.
Two ordinary carbosilane resins are copolymers of one having one hydrocarbon group per silicon element and one having two hydrocarbon groups. If it contains foreign elements,
The foreign element usually bonds to the silicon element via oxygen.

Among the carbosilane resins used in the present invention, those containing a different element (heterocarbosilane resin) are compared with ceramic coatings formed from those containing no different element (straight silicon resin) due to the action of the different element. Thus, a coating film having different properties in chemical resistance typified by alkali resistance and the like is produced. A carbosilane resin containing a foreign element is also conventionally known, and examples of commercially available products include a borosiloxane resin containing boron as a foreign element and a polytitanocarbosilane resin containing titanium.

In the present invention, a coating agent is prepared by adding and mixing a filler composed of ceramic particles to a carbosilane resin. In this case, as the ceramic particles, those having a high melting point, usually those having a melting point of 1000 ° C. or higher are used, and as such particles, conventionally known various particles can be used, for example, titania, silica, In addition to metal oxides such as alumina, zirconia, silica alumina, and magnesia, metal carbides such as silicon carbide (SiC) and titanium carbide (TiC); metal nitrides such as silicon nitride (Si ₃ N ₄ ); forsterite and zircon Phenasite, chrysoberyl and the like; mineral particles such as mica and the like. In particular, in terms of heat resistance, chemical resistance and affinity with silica glass formed by laser treatment of carbosilane resin, titania, silica,
It is preferable to use alumina, silica alumina, zirconia, silicon carbide, silicon nitride, titanium carbide, and the like. In addition, when a material having a large thermal expansion coefficient is required in consideration of the thermal stress with the base metal, chemical resistance is used. However, magnesia, forsterite, zirconia mica and the like are preferably used. The particle size of the ceramic particles is preferably 10 μm or less, and the smaller the particle size, the better the uniform dispersion in the carbosilane resin. The ceramic particles are used in a proportion of 30 to 70% by volume, preferably 40 to 60% by volume, based on the total amount of the carbosilane resin and the ceramic particles. In the present invention, if necessary,
In order to improve the adhesion between the coating agent and the base metal, an adhesion agent or the like can be added and mixed.

In order to produce the ceramic coating film of the present invention, the carbosilane resin and the ceramic particles are mixed with a solvent, and this mixture is applied to the surface of a substrate. In this case, as the solvent,
What shows solubility or dispersibility with respect to a carbosilane resin is used, such as, for example, ethylcellosolve acetate, N-methyl-2-pyrrolidone,
Xylene and the like can be mentioned. As a method of applying to the surface of the base metal, a conventional method such as an immersion method, a spray method, and a brush application method is employed.

Next, the coating agent coated surface formed as described above is subjected to a laser treatment after drying or baking the coating agent. Drying is performed at room temperature to 250 ° C, preferably 150 to
It is performed at a temperature of 250 ° C, and the baking process is 400-800
C., preferably at a temperature of 600-800C. The laser treatment only needs to generate a high temperature by the treatment. For example, a conventionally known laser treatment such as a CO ₂ laser treatment or a VAG laser treatment can be employed. It is considered that this laser treatment instantaneously heats the coating film to a high temperature of 800 ° C. or higher, and a coating film composed of a mixture of fused silica and ceramic particles formed from a carbosilane resin is formed on the substrate surface. Then, this coating film is cooled, and finally becomes a coating film composed of a mixture of glassy silica and ceramic particles. As described above, this coating film is not porous but airtight because the glassy silica is formed through fused silica.

Next, the cross-sectional structure of the coating film obtained by the present invention is shown in the drawings. In the drawings, A is a substrate, B is a ceramic coating film, 1 is ceramic particles, 2 is glassy silica, 3
Denotes an adhesive or a diffusion bonding layer, and 4 denotes a void. The thickness of the ceramic coating is usually 10 to 300 μm, preferably 50 to 150 μ
m.

In the present invention, the coating film obtained as described above is advantageously subjected to a high-temperature treatment at 600 ° C. or higher prior to its use. By this high-temperature treatment, diffusion of the metal component from the base metal surface to the ceramic coating film occurs, and a diffusion bonding layer composed of metal oxide diffused between the base metal surface and the ceramic coating film is formed. As a result, the ceramic coating formed on the surface of the base metal has significantly increased adhesion to the base metal. Of course, 60
When heated to a high temperature of 0 ° C. or higher, the same effect as the high-temperature heat treatment as described above can be obtained.

Further, the improvement of the adhesion of the ceramic coating film to the surface of the base metal can also be achieved by using an adhesion agent instead of the high-temperature treatment. Although the coating temperature rises with laser treatment, the base metal temperature does not rise so much,
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 hot-melt adhesive is mixed into the coating, the adhesive will melt due to the heat generated by the coating during the laser treatment, and the action of the molten adhesive will cause the ceramic coating to adhere to the substrate surface. Is improved. In this case, as the adhesive, a metal or an inorganic compound that does not evaporate and melt at the temperature at the time of the laser treatment and is used, such as, for example, an active metal such as titanium, a low-melting glass, Various types such as various enamel frit and the like can be mentioned, and an appropriate one is used according to the type of ceramic particles and base metal used.

The substrate metal to be coated in the present invention is not particularly limited, and may be any commonly used metal. In particular, from the viewpoint of chemical resistance and oxidation resistance, carbon steel, stainless steel, heat-resistant steel, and the like. Iron or aluminum.
Further, the base material targeted in 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 having poor chemical resistance, oxidation resistance and heat resistance. It may be a material.

〔effect〕

Ceramic coating formed on the substrate surface from the present invention,
It is a ceramic coating film having excellent heat resistance composed of glassy silica and ceramic particles, wherein the glassy silica is non-porous formed through fused silica. Therefore, the ceramic coating film according to the present invention has airtightness, protects the surface of the substrate from the action of oxygen and chemicals at high temperatures, and significantly improves the durability of the substrate.

〔Example〕

 Next, the present invention will be described in more detail with reference to examples.

Example 1 A coating agent containing about 40% by weight of a methyl-based straight silicone resin (trade name: SH806A, manufactured by Toray Silicone Co., Ltd.), about 58% by weight of synthetic mica, and 2% by weight of an adhesive (potassium phosphate) was dispersed in ethyl cellosolve acetate. , Test stainless steel substrate P (made of SUS304, area: 60mm x 50mm, thickness:
A 4.5 mm plate) was spray-coated and dried at 250 ° C. for 3 hours to obtain three coated test pieces having a film thickness of about 60 μm.

Next, two of the test pieces were placed in an electric furnace, and
Baking at 0 ° C for 1 hour, the surface of one of the samples
Irradiation was performed with a CO ₂ laser under the conditions shown in 1 to vitrify the coated surface. Thus, the sample A (I) subjected to the calcination and the CO ₂ laser treatment, and the sample A (II) subjected to the calcination only
I got

Further, the remaining one of the test pieces was subjected to the conditions shown in Table-1.
Sample A (III) fired at 500 ° C after CO ₂ laser treatment
I got

Next, the samples A (I), A (II) and A (II
I) was divided into two equal parts, one was kept as a spare, and the other was subjected to an acid resistance test. In this case, the acid resistance test
All surfaces except the surface irradiated with the laser were covered with silicon celite, immersed in a glass bottle containing 200 cc of a 50% sulfuric acid solution, and immersed in a 55 ° C. constant temperature bath. Table 2 shows the results of the acid resistance test. As can be seen from the results, the laser-irradiated coating film samples A (I) and A (III) show remarkable durability as compared with the non-treated coating film sample A (II).

Example 2 Borosiloxane resin (manufactured by Showa Electric Cable Co., Ltd., trade name: SMR)
109) A coating agent containing 42 wt%, silica sand 56 wt%, and an adhesive (B ₂ O ₃ -Pbo glass powder) 2 wt% was dispersed in an N-methyl-2-pyrrolidone solvent, and a base material Q (carbon steel, area: 60 mm) was used. × 5
(A plate having a thickness of 0 mm and a thickness of 4.5 mm) was spray-coated three times by spraying to prepare three full-surface coated test pieces having a film thickness of about 40 μm. The test piece was dried at 250 ° C. for 1 hour after each application. Next, the surface of the first test piece was exposed to CO _{2 under the} conditions shown in Table 1.
Sample B after laser treatment and baking at 600 ° C for 3 hours
(I) was obtained. Next, a second test piece was prepared under the conditions shown in Table 1.
Sample B fired at 600 ° C for 3 hours after treatment with YAG laser
(II) was obtained. Finally, the remaining test piece was calcined at 600 ° C. for 3 hours to obtain a sample B (III).

Next, the samples B (I), B (II) and B (II
Each of I) was cut and divided into two equal parts, one of which was left as a spare, and the other was subjected to an acid resistance test in the same manner as in Example 1. Table 2 shows the results of the acid resistance test. This test examined the effect of laser treatment on the corrosion-resistant ceramic coating of equipment exposed to a high temperature of about 600 ° C. From the results shown in Table 2, the CO ₂ laser and YAG
The effectiveness of laser irradiation can be clearly confirmed.

Example 3 Preliminary samples B (I), B (II) and B (II) obtained in Example 2
A bare carbon steel obtained by dividing the base material Q into two equal parts as I) and Comparative Sample B (IV) was placed in an electric furnace and kept at 800 ° C. for 50 hours.
Thereafter, the sample was taken out, the center of each sample was cut, and the oxidation state of the cross section was examined with a scanning electron microscope. Samples B (I) and B
For (II), the thickness of the oxide layer from the surface of the substrate in contact with the laser-irradiated coating film, and for Samples B (III) and B (IV), the thickness of the metallic iron portion in the cross section of the sample Q
And the thickness of the oxide layer was determined by dividing it by two. Table 3 shows the results.

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

Example 4 Samples A (I) and A (I)
A bare plate of stainless steel (SUS304) (substrate P is divided into two) as I), A (III) and comparative sample A (IV)
Was used to test the durability of the ceramic coating film of the present invention to vanadium attack by the following test method.

Testing method Applying Gakushin method, put vanadium synthetic ash on the sample,
It was decided to compare how much each sample was oxidized by exposure to high temperature. Vanadium synthetic ash is V ₂ O ₅
85 wt% and 15 wt% of Na ₂ SO ₄ are crushed and mixed, and 0.5 g of the mixture is
It was prepared by molding with a doublet machine into a disk of mm. This tableted vanadium synthetic ash,
Samples A (I), A (II), and A (IV) were placed on the center, 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 passed through the center of the sample, and the cross section was photographed with a scanning electron microscope to determine the thickness of the stainless steel oxide layer of each sample. It was measured. The smaller the thickness of the oxide layer, the stronger the resistance of the coating film to vanadium attack.

Next, the thickness of the oxide layer of each sample obtained by the above test is shown.

[Brief description of the drawings]

The drawing shows an explanatory sectional view of the ceramic coating. 1 ... ceramic particles, 2 ... glassy silica, 3 ...
Adhesive or diffusion bonding layer, 4 voids, A substrate, B
…… Ceramic coating.

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Shigeru Aoki 3050-32 Inokoyama, Kawashima-machi, Asahi-ku, Yokohama-shi, Kanagawa Prefecture (56) References JP-A-63-24077 (JP, A) JP-A-60-2697 ( JP, A) JP-A-51-143016 (JP, A)

Claims (4)

(57) [Claims] 1. A ceramic coating film comprising high melting point ceramic particles and glassy silica formed on a substrate surface,
The hermetic ceramic coating film, wherein the glassy silica is a non-porous material formed via fused silica generated by laser treatment of a carbosilane resin. 2. The coating according to claim 1, wherein the substrate is a metal. 3. A glassy substance containing silica as a main component via a fused silica via a laser treatment of a coating film comprising high melting point ceramic particles and a carbosilane resin formed on the surface of a base material to decompose the carbosilane resin. A method for producing a hermetic ceramic coating film, characterized in that: 4. The method of claim 3 wherein said substrate is a metal.