JPS6315988B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a titanium carbide coating material having excellent high temperature thermal stability.

In the tokamak-type fusion reactor critical test equipment currently under construction in Japan and Europe and the United States, materials consisting of titanium carbide coated on graphite or molybdenum are being used as the first wall element material.

Graphite-based titanium carbide coatings have excellent thermal stability at high temperatures, but have problems in terms of heat removal. In this regard, titanium carbide coating materials that use a high-melting point metal base material such as molybdenum, which has high thermal conductivity at high temperatures, have a large heat-receiving ability and are highly expected to be used as fusion reactor materials. However, for example, in the titanium carbide coating material of molybdenum, the molybdenum base material and titanium carbide cause a high temperature reaction, and the titanium carbide vapor deposited film on the molybdenum base material is likely to have a defect structure, and the Ti-C bonding property is poor. As a high temperature coating material, it is extremely unreliable.

The purpose of the present invention is to eliminate these drawbacks by selecting the material for the base material and layering the coating to create titanium carbide, a high-melting point metal base material that has high-temperature thermal stability comparable to graphite base materials and excellent cooling performance. To provide coating materials.

The gist of the present invention is to provide high-temperature thermal stability made by providing an intermediate layer of tungsten or boron carbide on the surface of a high-melting metal material such as molybdenum or niobium with a melting point of 2000°C or higher, and coating titanium carbide on the surface. It is a titanium carbide coating material with excellent properties. Note that, if necessary, a carbon or graphite intermediate layer may be further provided on the intermediate layer.

To explain this in detail, a high melting point metal having a melting point of 2000° C. or higher, such as molybdenum or niobium, provided with a tungsten intermediate layer or a boron carbide intermediate layer is used as the base material. The method of providing a tungsten intermediate layer or a boron carbide intermediate layer on a high melting point metal material is as follows:
Although ordinary coating or bonding methods such as vapor deposition and cladding methods may be used, it is important to provide a layer with good adhesion. Tungsten is its carbide ( _W2C )
The free energy of formation of is larger than that of titanium carbide. Therefore, if it is used as a material on the base material side that is in contact with titanium carbide, it will react with titanium carbide, consume the carbon atoms in titanium carbide, and become tungsten carbide itself due to the interaction between the base material and the coating. Deterioration does not occur at high temperatures. There is no other high melting point metal other than tungsten that has such features.
In addition, boron carbide reacts with titanium carbide at high temperatures to produce titanium boride and carbon at the interface, but titanium boride and carbon are substances that have excellent high-temperature thermal stability as much as titanium carbide, so titanium is free and volatilized. Deterioration such as disappearance of the titanium carbide film does not occur.

Next, titanium carbide is coated on the base material either directly or after laminating an intermediate layer of carbon or graphite. The reason for providing an intermediate layer of carbon or graphite is that these layers can be expected as carbon source layers that supply carbon atoms to the titanium carbide coating layer at high temperatures. The diffused and supplied carbon atoms repair the defect structure of the titanium carbide layer, strengthen the Ti-C bonding force, and stabilize the titanium carbide film up to high temperatures.

The layered coating method for carbon, graphite, boron carbide, and titanium carbide is preferably a physical vapor deposition method such as chemical vapor deposition, ion plating, or sputtering. Especially in the coating process of titanium carbide,
It is important to strictly control the deposition conditions and form a film with as few structural defects as possible.

The titanium carbide coating material with excellent high temperature thermal stability according to the present invention was coated in a high vacuum of 5×10 ^-6 Torr and 2000°C.
As a result of exposure to high temperatures, conventional titanium carbide coating materials coated directly on molybdenum suffer from significant evaporation reduction, changes in surface condition, and deterioration due to the formation of a reaction layer at the interface, whereas recrystallization of the titanium carbide coating was observed. It was confirmed that both weight loss and diffusion deterioration were significantly suppressed, and that the material had excellent high-temperature thermal stability.

The refractory metal titanium carbide coating material of the present invention is
It is considered to be effective as a material for the first wall of a fusion reactor critical test device, as well as for the "next generation device" in which the core plasma temperature will be even higher, in terms of high-temperature strength and cooling performance. It can also be used as a heat-resistant and abrasion-resistant material used in vacuum equipment, especially materials surrounding electron beam guns exposed to high temperatures, and space engineering materials under high vacuum and high temperatures.

As mentioned above, it has excellent material performance.

Example 1 A coating material in which a titanium carbide layer is laminated on a molybdenum base material on which a tungsten layer has been previously provided.

A tungsten layer with a thickness of 5 to 20 μm was coated on a molybdenum material by magnetron sputtering. The substrate was installed in an ion plating device. The inside of the apparatus was sufficiently evacuated, ultra-high purity argon gas was filled to approximately 10 ^-2 Torr, and approximately 200 W of power was applied via a high-frequency coil placed below the substrate to induce glow discharge. On the other hand, about −
A bias voltage of 0.6 KV was applied, and ionized argon was bombarded onto the surface of the substrate, causing spatter to clean the surface. After that, the inside of the ion plating device was evacuated to a level of 10 ^-6 torr, and the electron beam was
Titanium in the water-cooled crucible was melted and evaporated at 1 KW, and at the same time acetylene gas was introduced to maintain the total reaction pressure at 5 x 10 ^-4 to 1 x 10 ^-3 Torr. DC +90V is applied to an auxiliary electrode placed near the crucible to induce discharge, and at the same time, a shutter placed directly below the substrate is opened to start vapor deposition. At this time, the substrate is heated to 700℃ and a negative voltage of 200V is applied. A bias voltage was applied. The deposition time was 1 hour, and a titanium carbide coating layer with a thickness of 10 to 15 μm was obtained. The results will be explained based on FIGS. 1 and 2.

2 in Figure 1 is a conventional material in which titanium carbide is directly coated on a molybdenum base material, but the thickness of the titanium carbide film decreases rapidly from a heating test temperature of 1600°C under a vacuum of 5 × 10 ^-6 Torr. . On the other hand, the titanium carbide film on the substrate provided with the tungsten intermediate layer of No. 1 shows almost no change in film thickness up to 2000°C.

As a result of X-ray microanalyzer analysis of the cross-section of the coating material, in 2, molybdenum carbide is generated at the interface between the coating and the base material, and at the same time titanium is volatilized and lost, whereas in 1, the tungsten layer acts as an effective barrier to interfacial reaction and carbonization occurs. It was confirmed that the titanium layer could exist stably.

FIG. 2a is a microscopic photograph of the surface of molybdenum immediately after it has been coated with titanium carbide. b shows the surface condition after heating the same coating material at 2000° C. for 30 minutes at 5×10 ⁻⁶ Torr.

On the other hand, c shows the surface condition after the same test as b of a material in which titanium carbide is laminated on a molybdenum base coated with a tungsten intermediate layer. Grain boundaries appear due to recrystallization of titanium carbide, but it can be seen that the stability of the titanium carbide coating is significantly improved compared to conventional material b.

Example 2 A material in which a carbon film is further applied on molybdenum on which a tungsten layer has been previously provided, and then titanium carbide is laminated and coated.

The molybdenum material previously provided with the tungsten intermediate layer described in Example 1 was attached to an ion plating apparatus. Acetylene gas was introduced and high frequency power of 200 W was applied at a total reaction pressure of 2 × 10 ^-2 Torr.
induced a glow discharge. The substrate was heated and maintained at approximately 900°C, and a highly adhesive carbon film was obtained on the substrate through a plasma chemical reaction. At this time, it is not preferable to apply a carbon film directly to the molybdenum material because significant peeling occurs from the molybdenum-carbon film interface during a high temperature test. Thereafter, titanium carbide is layered and coated using the same ion plating method and conditions as described above. The results will be explained based on FIG. Figure 3 1-a and 1-b show the surface condition before (a) and after (b) the 2000℃ high temperature test when titanium carbide is directly coated on the niobium base material, and 2-a, 2-
b is before (a) and after the 2000℃ high temperature test for the applicable coating material.
(b) shows the surface condition. In 2-b, crystal grains are clearly observed and the titanium carbide coating is found to be stable at high temperatures, whereas in 1-b, significant erosion is observed. In addition, measurements of weight changes before and after the test showed that niobium directly coated with titanium carbide showed -0.3 mg/cm ² in a heating test at 2000°C.
The coating material was -
The amount of evaporation was suppressed to a small amount of 0.05 mg/cm ² ·min.
Furthermore, when molybdenum was directly coated with titanium carbide, the amount of evaporation was -0.15 mg/cm ² ·min, which was still a large value.

Example 3 Material in which a titanium carbide layer was coated on a molybdenum substrate provided with a tungsten intermediate layer. In the same manner as described in Example 1, a tungsten intermediate layer was applied to a thickness of 5 μm, and then a titanium carbide layer was coated to a thickness of 20 μm.

The results will be explained based on FIG.

4. FIGS. 2-a and 2-b show the results of a thermal shock test using an electron beam on a molybdenum material coated with titanium carbide without an intermediate layer.

2-a is 1.5KW/cm ² , irradiation time is 0.8 seconds, 2-b
is a test result of 1.5KW/cm ² and irradiation time of 1.0 seconds.
In both cases, melting damage occurred on the surface. On the other hand, 1-a,
1-b is each of the said covering materials, 1.5KW/cm ² ,
These are test results for irradiation times of 0.8 seconds and 1.0 seconds.
Irradiation for up to 0.8 seconds does not cause any surface damage.
Melting begins after irradiation for 1.0 seconds, but the melting area is kept very small compared to 2-b, and the melting occurs locally.
It was confirmed that the coating material has excellent thermal stability even against thermal shocks exceeding 3000°C.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the relationship between the heating test temperature and titanium carbide film thickness of titanium carbide coating material, and Figure 2 is a micrograph of the coating surface before and after the heating test when a molybdenum base material is used. a: molybdenum base material The surface of the material directly coated with titanium carbide, b: The surface of the coating after the heating test of the coating material a, c: The surface of the coating after the heating test of the material where the molybdenum base material with the tungsten intermediate layer was coated with titanium carbide, Figure 3 is a photomicrograph of the coated surface before and after the heating test when using niobium and molybdenum base materials, 1 is a material in which titanium carbide is directly coated on niobium, 1-a
indicates before heating, and 1-b indicates after heating. 2 is a material in which a molybdenum base material provided with a tungsten intermediate layer is further laminated with a carbon film, and then coated with titanium carbide.
-a indicates before heating, and 2-b indicates after heating. Figure 4 is a photograph of the surface of the material after an electron beam thermal shock test. 1 shows a material in which titanium carbide is coated on a molybdenum base material provided with a tungsten intermediate layer, and 1-a shows a material in which titanium carbide is coated on a molybdenum base material provided with a tungsten intermediate layer.
1.5 KW/cm ² for 0.8 seconds; 1-b shows the time after 1 second of irradiation.
2 shows a material in which titanium carbide is directly coated on molybdenum, 2-a is 1.5KW/cm ² for 0.8 seconds, 2-b
indicates after 1 second irradiation.

Claims (1)

[Scope of Claims] 1. A high-temperature heat treatment device consisting of a high melting point metal material such as molybdenum or niobium with a melting point of 2000°C or higher, provided with an intermediate layer of tungsten or boron carbide, and coated with titanium carbide. Titanium carbide coated material with excellent stability. 2 A high-temperature stable material made of a high-melting point metal material such as molybdenum or niobium with a melting point of 2000°C or higher, provided with an intermediate layer of tungsten or boron carbide and an intermediate layer of carbon or graphite, and coated with titanium carbide. Titanium carbide coating material with excellent properties.