JPH05238856A - Method for forming coating film of metal carbide - Google Patents

Abstract

PURPOSE:To simply obtain a coating film of a metal carbide having a large surface, unlikely to cause cracks during formation of a coating film by coating the surface of a carbonaceous material with a composition comprising metallic powder, carbon black and a specific thermosetting resin and heating. CONSTITUTION:The surface of a carbonaceous material is coated with a raw material composition obtained by blending metal powder with carbon black and a thermosetting resin composed of at least one of phenol resin and furan resin and heated. The formed coating film of carbide becomes dense with reduction in particle diameter of the metal powder. When the particle diameter of the metallic powder exceeds 100 meshes, unfavorably voids in the coating film are widened and defects occur. The particle diameter is preferably <=300 meshes. Carbon black has suppressing action on generation of cracks during formation of the coating film of carbide besides being a carbon supply source for reaction with the metal powder to form a metal carbide. A carbon material, graphite material, carbon fiber-reinforced carbon material, etc., may be cited as the carbonaceous material as a substrate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for coating the surface of a carbonaceous material such as carbon, graphite, carbon fiber reinforced carbon material (C / C composite) with metal carbide.

[0002]

2. Description of the Related Art Carbonaceous materials are used in many fields as high temperature members because of their excellent heat resistance. However, in order to improve oxidation resistance and corrosion resistance, the surface of carbonaceous materials is made of Si.
Coating with a carbide such as C is performed.

A method for forming a metal carbide coating on the surface of a carbonaceous material is to apply a solution of a precursor such as polycarbosilane in an organic solvent to form a coating, and then heat the carbonaceous material to form a surface. A method of reacting to generate a carbide (Japanese Patent Laid-Open No. 1-103976, etc.), or C by a gas phase reaction.
A VD (chemical vapor deposition) method (Japanese Patent Laid-Open Nos. 2-164873 and 3-75372, etc.) is known.

[0004]

Since the temperature for forming the metal carbide coating is as high as 1000 ° C. or higher, the thermal stress due to the difference in the coefficient of thermal expansion between the carbonaceous material and the coating is compared with the coating strength. Therefore, there is a problem that the coating film is cracked because of its large size.

Further, the CVD method is difficult to cover a large area when it is applied to a structural material or the like, and the equipment is not simple.

An object of the present invention is to provide a manufacturing method in which cracks are less likely to occur during film formation than in the conventional methods and a large area coating can be carried out easily.

[0007]

According to the present invention, a raw material composition obtained by mixing a metal powder, a carbon black, and a thermosetting resin containing at least one of a phenol resin and a furan resin is provided on the surface of a carbonaceous material. It is a method for forming a metal carbide coating, which comprises heating after coating.

The contents of the present invention will be described in more detail.

The raw material composition contains the above-mentioned metal powder, carbon black and thermosetting resin, is mixed with a diluent and the like if necessary, and is kneaded to be used in a paste or liquid form.

Metal powders include Si, Ti, W, Nb and Z.
Fine particles of r and Ta are used, and these may be used alone or as a mixed powder of two or more kinds. The particle size of this metal powder is preferably 100 mesh or less.

The resulting carbide coating is denser as the particle size of the metal powder is smaller, and if it exceeds 100 mesh, voids will spread in the coating and defects will occur, which is not preferable. It is preferably 300 mesh or less.

The carbon black serves as a carbon source for reacting with the metal powder to generate a carbide, and also has an effect of suppressing cracks when a carbide film is formed.

That is, since carbon black has an average particle diameter of 10 to 100 nm and a large surface area, it easily reacts with the metal powder during heat treatment to form a carbide.

For this reason, when carbon black is present at the grain boundaries of the metal powder, carbides are easily generated between the metal particles and the grain boundaries are strongly bonded, so that cracks are less likely to occur between the metal particles during the formation of the carbides. Become.

The mixing ratio of carbon black and metal powder is 0.05 in terms of molar ratio (carbon black / metal powder).
It is preferably in the range of to 0.9.

If this molar ratio is less than 0.05, the effect of suppressing cracks is small, and if it exceeds 0.9, the film formability deteriorates.

As the thermosetting resin, a carbonizable resin such as a phenol resin or a furan resin can be used.

These may be used alone or in combination. This resin acts as a binder for fixing the metal powder and the carbon black as a film by curing.

The resin charcoal produced by heating the resin serves as a carbon supply source for reacting with the metal powder.

The thermosetting resin is blended in such a manner that the total carbon content and carbonization content in the raw material composition (carbon black + resin charcoal)
Molar ratio of (A) and metal powder (B) ((B) / (A))
Is preferably in the range of 1.0 to 2.0.

If the molar ratio is less than 1.0, carbonized components remain in the formed coating and the coating tends to peel off, while if it exceeds 2.0, unreacted metal powder remains and a complete carbide coating is formed. Can not.

At this time, the metal powder reacts not only with the carbonized components in the coating film but also with the surface and inside of the base material to form a carbide, so that the coating film forms a strong bond with the interface.

Examples of the carbonaceous material as the base material include a carbon material, a graphite material, a carbon fiber reinforced carbon material (C / C composite), and the shape thereof is not particularly limited.

The application of the present invention to this base material is partially performed where oxidation resistance, corrosion resistance and the like are directly required, and may be applied to the entire surface if necessary.

The diluent is blended in any proportion as needed so that the above-mentioned raw material composition has a viscosity that makes it easy to apply it to the surface of the carbonaceous material.

The diluent is preferably one that dissolves a thermosetting resin such as phenol resin or furan resin, and examples thereof include alcohols such as methanol and ethanol, and ketones such as acetone and ethyl methyl ketone. Be done.

The raw material composition prepared as described above is applied to the carbonaceous material by brush coating, spraying, etc., and then dried and cured with a thermosetting resin to form a coating of the raw material composition on the surface of the carbonaceous material. Is formed.

The thickness of the coating film at this time can be controlled by adjusting the viscosity of the raw material composition or by adjusting the number of times of coating.

The coating film formed is not always composed of a single metal composition, but may have a structure in which a single layer contains different metal compositions, or coating films having different metal compositions are laminated in multiple layers. Good.

After forming the raw material composition coating film, the carbonaceous material is transferred to a heating furnace and heated in a non-oxidizing atmosphere to carbonize the thermosetting resin in the raw material composition, and further the metal powder is added to carbon black and resin charcoal. React with to form a metal carbide coating.

The heating temperature is preferably in the range of 1500 to 2500 ° C., and the heating may be performed for about 30 to 300 minutes. Moreover, it is preferable to heat at a heating rate of 10 ° C./min or less.

If it is faster than 10 ° C./min, cracks are likely to occur in the coating, and a carbide coating with many defects tends to be formed. In this way, it is possible to form a metal carbide on the surface of the carbonaceous material and form a metal carbide coating without cracks.

[0033]

In the present invention, by incorporating carbon black as the raw material composition, a strong bond can be formed at the grain boundaries of the metal powder when the metal carbide is formed, and cracks are less likely to occur in the coating film.

Further, since the metal powder also reacts with the surface of the carbonaceous material, the coating film is firmly attached even at the interface, and peeling hardly occurs. Furthermore, since the coating film is formed by coating, a large area can be coated by a simple method.

[0035]

EXAMPLES Next, the present invention will be specifically described by way of Examples in comparison with Comparative Examples.

[0036]

Example 1 Si powder (<350 mesh) and carbon black (Niteron # 10 manufactured by Nippon Steel Chemical Co., Ltd., average particle diameter 39 nm) were mixed (blended with a liquid resol type phenol resin (carbonization yield 45%)). The weight was specified in Table 1), and then an appropriate amount of ethanol was added to adjust the viscosity to obtain a raw material composition.

This is brush-painted on a plate-shaped graphite material, and the temperature is 80 ° C.
And dried and cured. After that, in the Tammann furnace,
1700 ° C in an argon gas atmosphere (heating rate 2 ° C / mi
n) A heat treatment was carried out for 2 hours to form a silicon carbide coating.

The surface of the obtained silicon carbide coating was a good one with no cracks observed by scanning electron microscope observation.

Observation of the interface between the coating and the substrate revealed that Si diffused into the graphite substrate, and the coating was firmly bonded at the interface.

[0040]

Example 2 A titanium carbide coating film was formed in the same manner as in Example 1 except that Ti was used instead of Si as the metal powder and the heat treatment temperature was set to 1900 ° C.

The surface of the obtained titanium carbide coating film was found to have cracks with a maximum width of 5 μm by observation with a scanning electron microscope, but the cross-section observation showed that the cracks had propagated to the graphite substrate. No exposure of the graphite material surface was observed.

[0042]

Example 3 A tungsten carbide coating film was formed in the same manner as in Example 1 except that W was used as the metal powder instead of Si, and the heat treatment temperature was 2100 ° C.

The surface of the obtained tungsten carbide coating is
Observation with a scanning electron microscope revealed that no cracks were generated.

[0044]

Example 4 A niobium carbide coating was formed in the same manner as in Example 1 except that Nb was used as the metal powder instead of Si, and the heat treatment temperature was maintained at 2000 ° C. for 3 hours.

On the surface of the obtained niobium carbide coating, cracks with a maximum width of 5 μm were found by observation with a scanning electron microscope, but by observation of the cross section, the cracks did not extend to the graphite substrate. No exposure of the graphite material surface was observed.

[0046]

Example 5 A zirconium carbide coating was formed in the same manner as in Example 1 except that Zr was used as the metal powder instead of Si, and the heat treatment temperature was maintained at 2000 ° C. for 3 hours.

The surface of the obtained zirconium carbide coating is
According to the scanning electron microscope observation, the generation of cracks having a maximum width of 5 μm was recognized, but the observation of the cross section revealed that the cracks did not extend to the graphite base material and the surface of the graphite material was not exposed.

[0048]

Example 6 A tantalum carbide coating was formed in the same manner as in Example 1 except that Ta was used as the metal powder instead of Si, and the heat treatment temperature was kept at 2000 ° C. for 3 hours.

On the surface of the obtained tantalum carbide coating, cracks with a maximum width of 5 μm were found by observation with a scanning electron microscope, but by observation of the cross section, the cracks did not extend to the graphite substrate. No exposure of the graphite material surface was observed.

[0050]

[Example 7] S obtained in Example 1 on the surface of a plate-shaped graphite material
The i-containing raw material composition was applied with a brush and dried at 80 ° C., and then the Ti-containing raw material composition obtained in Example 2 was overcoated and dried again at 80 ° C.

The film thicknesses of the two different eyebrows obtained here were about the same and were about 110 μm. After that, in a Tammann furnace, the temperature was 1800 ° C. (heating rate 2 ° C./mi
n) Hold for 2 hours to perform heat treatment to form a carbide coating.

On the surface of the obtained carbide coating, a crack having a maximum width of 5 μm was found by observation with a scanning electron microscope, but the cross section observation showed that the crack did not extend to the graphite substrate. No exposure of the surface of the graphite material was observed.

[0053]

Example 8 The Si-containing raw material composition obtained in Example 1 and the Ti-containing raw material composition obtained in Example 2 were mixed in a weight ratio of 1: 1 to obtain a plate-shaped graphite material. The surface was brushed and dried at 80 ° C.

Then, in a Tammann furnace, 1700 ° C.
(Temperature increase rate: 2 ° C./min) Hold for 2 hours to perform heat treatment to form a carbide coating.

On the surface of the obtained carbide coating, a crack having a maximum width of 5 μm was found by observation with a scanning electron microscope, but the cross section observation showed that the crack did not extend to the graphite substrate. No exposure of the surface of the graphite material was observed.

[0056]

Example 9 A silicon carbide coating was formed in the same manner as in Example 1 except that a furan resin (carbonization yield 20%) was used as the thermosetting resin instead of the phenol resin (compounding weight is shown in Table 1). Specified).

The surface of the obtained silicon carbide coating was a good one with no cracks observed by scanning electron microscope observation.

[0058]

Example 10 A titanium carbide coating film was formed in the same manner as in Example 2 except that a furan resin (carbonization yield 20%) was used as the thermosetting resin instead of the phenol resin (compounding weight is shown in Table 1). Specified).

The surface of the obtained titanium carbide coating film was good under the observation of a scanning electron microscope without the occurrence of cracks.

[0060]

[Comparative Example 1] A silicon carbide coating was formed in the same manner as in Example 1 except that carbon black was not blended (the blending weight is specified in Table 1).

The surface of the obtained silicon carbide coating film was found to have cracks with a maximum width of 150 μm by scanning electron microscope observation, and the cross-section observation showed that the cracks reached the surface of the graphite base material. The surface was exposed.

[0062]

[Comparative Example 2] A titanium carbide coating was formed in the same manner as in Example 2 except that carbon black was not blended (the blending weight is specified in Table 1).

The surface of the obtained titanium carbide coating film was found to have cracks with a maximum width of 200 μm by observation with a scanning electron microscope, and the cross-section observation showed that the cracks reached the surface of the graphite base material. The surface was exposed.

[0064]

Comparative Example 3 A tungsten carbide coating was formed by the same operation as in Example 3 except that carbon black was not blended (the blending weight is specified in Table 1).

The surface of the obtained tungsten carbide coating is
According to scanning electron microscope observation, the generation of cracks with a maximum width of 150 μm was recognized, and according to the cross-section observation, the cracks reached the surface of the graphite base material and the surface of the graphite material was exposed.

[0066]

[Table 1]

[0067]

[Table 2]

[0068]

Industrial Applicability According to the present invention, a method for forming a metal carbide coating obtained by applying a raw material composition obtained by mixing a metal powder and carbon black with a thermosetting resin onto the surface of a carbonaceous material and then heating the composition is A good metal carbide coating film can be obtained because it diffuses to the surface and inside of the carbonaceous material to form a strong bond at the interface, and cracks hardly occur on the coating surface.

Therefore, it is extremely effective for improving the oxidation resistance and corrosion resistance of the carbonaceous material, and can be applied to, for example, electrodes, crucibles, heaters, jigs for manufacturing various electronic materials, and the like.

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[Procedure amendment]

[Submission date] May 20, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0051

[Correction method] Change

[Correction content]

[0051] Here, the obtained two different layers thickness Si layer
Was about 180 μm and the Ti layer was about 30 μm . Then, in a Tammann furnace, the temperature was 1800 ° C (temperature rising rate 2 ° C /
min) and heat treatment was performed for 2 hours to form a carbide coating.

Front page continued (72) Inventor Takeshi Sasaki 1618 Ida, Nakahara-ku, Kawasaki Shin Nippon Steel Co., Ltd., Advanced Technology Research Laboratories (72) Inventor Koichiro Mukai 1618 Ida, Nakahara-ku, Kawasaki City New Nippon Steel Co., Ltd. Company Advanced Technology Research Center

Claims (2)

[Claims] 1. A raw material composition obtained by mixing a metal powder, a carbon black, and a thermosetting resin containing at least one of a phenol resin and a furan resin is applied to the surface of a carbonaceous material, and then heated. A method for forming a characteristic metal carbide coating film. 2. The metal powder is Si, Ti, W, Nb, Z.
The method for forming a metal carbide coating film according to claim 1, wherein the powder is a powder containing at least one of r and Ta.