JPH08133877A - Method for coating graphite with ceramic - Google Patents

Abstract

PURPOSE: To provide a process for applying a ceramic coating to graphite in improved adhesivity of the ceramic coating film to the graphite, i.e., improved peeling resistance of the coating film. CONSTITUTION: The intermediate coating layer to be used in this coating method is made of a material having heat-resistance required for the working environment, easily bondable by reacting with graphite and having affinity to a ceramic coating film to be coated, e.g. a ceramic such as SiC layer 3. The intermediate layer is formed on the surface of graphite 1 e.g. by a CVD method (chemical vapor deposition method) and a ceramic coating film 2 is formed on the surface of the intermediate coating layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of coating graphite with ceramics, and more particularly, to a method for improving peeling resistance.

[0002]

2. Description of the Related Art In the case where graphite has reactivity with a molten metal, or when the graphite is used in a high temperature oxidizing atmosphere, the reactivity is lowered. Therefore, as shown in FIG. A ceramic film 6 having corrosion resistance is coated on the.

Here, the example shown in FIG. 2 is constructed by a thermal spraying method, and in this method, the ceramic coating 6 does not penetrate into the pores 5 of the graphite 1. This is because the graphite 1 has releasability, and the ceramic film 6 is unlikely to penetrate into the graphite pores 5. Therefore, in this construction method, the pores 5 of the graphite 1 are
Therefore, the anchor effect of adhering the ceramic film 6 to the graphite 1 could not be expected.

On the other hand, as another method of coating the ceramic film on the graphite, there is a method of applying a slurry prepared by mixing ceramic powder and an inorganic or organic binder such as carboxymethyl cellulose with water or alcohol onto the surface of the graphite. In this construction, the anchor effect of adhering graphite can be expected with the inorganic or organic binder.

[0005]

As described above, in the conventional construction method, the graphite 1 has releasability,
The ceramic coating 6 has a property of hardly penetrating into the graphite pores 5, and the anchoring effect of the inorganic or organic binder has limited the ability to adhere to graphite.

Therefore, in the conventional construction method, the adhesion force at the interface between the graphite and the ceramic film is very weak,
Peeling was likely to occur due to the difference in thermal expansion between graphite and ceramics due to the temperature rise during use, and also to peeling due to cooling during the suspension of operation. The present invention has been made in view of the above-mentioned conventional technique, and an object of the present invention is to provide a method for coating a graphite with improved adhesion of a ceramic film to graphite, in other words, exfoliation resistance.

[0007]

[Means for Solving the Problems] The structure of the present invention which achieves such an object has the heat resistance required from the use environment, further facilitates reactive bonding with graphite, and is compatible with the ceramic film to be coated. CVD using a material, for example, a ceramic layer such as SiC as an intermediate layer
The method is characterized in that the surface of graphite is coated with (chemical vapor deposition) or the like, and a ceramic film is formed on the surface layer.

[0008]

The intermediate layer, for example, the SiC layer, has a chemical bonding effect with the ceramic film to be coated, and the ceramic that has penetrated into the pores or irregularities of the SiC has an anchoring effect. , The adhesion is greatly improved. The intermediate layer, for example, the ceramics layer, has the same anchor effect with graphite as before, and is dominated by more effective chemical (reactive) joining, so it is compared to conventional construction methods. However, the adhesiveness is greatly improved.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the embodiments shown in the drawings. FIG. 1 shows a structure constructed by an embodiment of the ceramic coating method for graphite of the present invention.

As shown in the figure, a SiC layer 3 as an intermediate layer is laminated on the surface of graphite 1 and a ceramic film 2 is formed on the surface layer thereof. The SiC layer 3 is, for example, coated by a CVD (chemical vapor deposition) method. The adhesive force between the graphite 1 and the SiC layer 3 is governed by not only the anchor effect in the conventional construction method but also chemical (reactive) bonding which is more advantageous than the anchor effect. Although the SiC layer 3 was used as the intermediate layer in the present embodiment, the present invention is not limited to this, and it has the heat resistance required from the operating environment, is more easily reactively bonded to the graphite 1, and is the ceramic to be coated. A material having compatibility with the coating 2 can be widely used.

The ceramic film 2 can be formed by a conventional method. For example, it may be formed by a thermal spraying method, or a slurry in which an inorganic or organic binder and ceramics powder are mixed with water or alcohol is applied by a brush or a spray and dried, and then subjected to high temperature treatment or use environment. You may raise temperature below. By forming in this way, the ceramic layer 4 is formed in the SiC layer 3 in an anchor shape.

As described above, in this embodiment, the adhesive force between the graphite 1 and the SiC layer 3 has a more advantageous chemical (reactive) effect than the anchor effect in the conventional method.
Dominated by joining. Further, since the ceramics 4 penetrates into the pores or irregularities of the SiC layer 3, the anchor effect of the ceramics formed in the SiC layer 3 in an anchor shape causes
Compared with the conventional case, the SiC layer 3 and the ceramic film 2 can be more firmly adhered.

Therefore, even when the graphite has reactivity with the molten metal, or when the graphite is used in a high temperature oxidizing atmosphere, the ceramic coating 2 is adhered to the surface of the graphite and is resistant to the molten metal or environment. Since it has excellent reactivity, it does not peel off. In particular, by applying the ceramic coating of the present invention to the portion of the graphite crucible containing the molten metal that is in contact with the molten metal and the graphite material, the reaction between the molten metal and the graphite is prevented, and oxidation at high temperature is also prevented. It becomes possible to do.

[0014]

As described above in detail with reference to Examples, according to the present invention, an intermediate layer between the graphite surface and the ceramic coating has heat resistance required from the use environment, and Since a material that is easy to bond to the ceramics and is compatible with the ceramics film to be coated is formed, the anchor effect of the ceramics that has penetrated into the pores or irregularities of the intermediate layer is matched to the chemical bonding effect of the ceramics to be coated. The peel resistance of the ceramic film can be enhanced. Therefore,
INDUSTRIAL APPLICABILITY The present invention is useful for various melting processes, casting processes, vacuum deposition, and other film forming processes premised on metal melting processes, and is widely applicable to heat-resistant members used in the atmosphere. Is.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a structure constructed by a ceramic coating method on graphite according to an embodiment of the present invention.

FIG. 2 is a sectional view showing a structure constructed by a conventional thermal spraying method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Graphite 2 Ceramics film 3 SiC layer 4 Ceramic layer formed in an anchor shape in SiC 5 Graphite pores 6 Thermal sprayed ceramic film

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takashige Shigeji 1-1-1, Niihama, Arai-cho, Takasago, Hyogo Prefecture Mitsubishi Heavy Industries, Ltd. Takasago Research Institute (72) Tomikane Saida 2-chome, Niihama, Arai-cho, Takasago, Hyogo Prefecture No. 1 Mitsubishi Heavy Industries, Ltd. Takasago Laboratory (72) Inventor Ichigo Mori 2-1-1, Niihama, Arai-cho, Takasago, Hyogo Prefecture Mitsubishi Heavy Industries Ltd., Takasago Laboratory

Claims (2)

[Claims] 1. In the method of coating ceramics on graphite, a material having heat resistance required from a use environment, being easy to bond with ceramics, and having compatibility with a ceramic film to be coated is used as an intermediate layer on the surface of graphite. A method for coating ceramics on graphite, characterized in that the graphite is coated on the surface and a ceramic film is formed on the surface thereof. 2. The method for coating ceramics on graphite according to claim 1, wherein a ceramic layer such as a SiC layer is used as the intermediate layer.