JPH0674193B2 - Method for metallizing graphite and member using this method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for metallizing a refractory metal molybdenum or tungsten and a zirconium eutectic alloy into graphite, and a member using the same.

[Conventional technology]

Due to the excellent properties of graphite such as heat resistance, conductivity, and thermal shock resistance, there are great expectations for industrial applications as heat resistant, electrode, structure, and sliding ceramics. However, there are still many points to be improved in order to expand the applications. For example, when it is used as a structural material, the joining technology between graphite and metal is one of the important issues for expanding the application, because it is a suitable material in the right place where each characteristic is produced and in terms of production cost.

For joining graphite and metal, it is necessary to form a metallized layer of metal on the surface of graphite. As a conventional metallization method for graphite, the Telefunken method widely used for metallizing ceramics such as silicon carbide, silicon nitride, and alumina is considered effective as described in Kobe Kogyo Giho (No. 36). However, there are the following difficulties. That is, in the case of graphite metallization by the Telefunken method, first, the surface of graphite is coated with a metal powder of molybdenum-manganese, which is baked at a high temperature in a non-oxidizing atmosphere, and then subjected to metal plating treatment. Further, in order to stabilize the coating, it is a method of heating again in a non-oxidizing atmosphere to perform metallization. If necessary, a method of brazing metal after the metallization treatment may be adopted. As described above, the conventional metallization method has a drawback that the working process is very complicated. In addition, it is necessary to completely remove oxygen contained in the metal powder in the steps of baking the metal powder and the metal plating. I can't. For this reason, the metallized layer is apt to cause voids and peeling. In addition, the formed metallized layer is thick, and when obtaining a bonded body with a later metal,
The bonding layer inevitably becomes thick, and as a result, there is a drawback that the bonding strength is likely to decrease.

[Problems to be Solved by the Invention] The above-mentioned conventional technique has a big drawback that the working process is long and complicated. Further, in the conventional method, no measures have been taken to sufficiently reduce oxygen although the metal powder of molybdenum or manganese used as the coating material is active. Therefore, the oxidation of the metallized layer is promoted by the water, impurities and dissociated oxides discharged from the metal powder during heating. Therefore, there has been a problem that the wettability of the metallized material is obstructed and a metallized layer with many peelings and holes is formed.

In order to solve the above-mentioned drawbacks of the prior art, JP-A-59-212188
Issue has been proposed. Here, to explain its outline,
First, molybdenum-zirconium or tungsten-zirconium eutectic alloy is melted in a clean state by, for example, arc melting. Next, these eutectic alloys are used as a brazing material, embedded in a portion where a molybdenum or tungsten plate and a graphite plate are superposed, and then heated to a temperature higher than the eutectic point of the brazing material. In this case, the wettability is improved by the reducing action due to the generation of CO gas, and the small gap between the molybdenum or tungsten plate and the graphite plate becomes a capillary phenomenon so that the brazing material permeates. As a result, a composite of molybdenum or tungsten and graphite is obtained. That is what provided.

The present invention has been made as a result of a continuous study based on the findings of the above-mentioned JP-A-59-212188, and its purpose is to arrange a high melting point alloy on the surface of graphite and heat it in a vacuum and an inert gas atmosphere. It is to provide a graphite metallizing method, a member using the same, and a method for manufacturing the member.

[Means for Solving the Problems]

As a result of various investigations by the present inventor, the eutectic alloy was well-wetted over the entire graphite surface by a simple operation of arranging it on the graphite surface without depending on the capillary phenomenon and then heating it in vacuum or in an inert gas, and metallized it. The present inventors have completed the present invention by finding that a metallized layer having a small layer thickness and a high relative density and a uniform density can be formed. Further, it was also recognized that the graphite metallized material obtained in the present invention was excellent in strength, bonding strength, conductive corrosion resistance and the like.

The molybdenum-zirconium alloy was also well wetted with graphite particles and fibers, and it was possible to produce graphite-containing alloys and graphite fiber reinforced alloys by using the graphite particles or graphite fibers metallized by this method. .

To illustrate the invention, molybdenum or an alloy of tungsten and zirconium is deposited on the graphite surface. Then, the melting point of the alloy of molybdenum or tungsten and zirconium is heated to a higher temperature in a vacuum or an inert gas atmosphere to perform metallization.

The alloy to be the metallized layer in the present invention is a eutectic alloy of molybdenum or tungsten and zirconium, and the composition of these alloys is specifically 26 to 36% by weight of molybdenum.
The balance zirconium or tungsten may be 15 to 25 wt% balance zirconium, and more preferably 31 wt% molybdenum 31 wt% balance zirconium or 19 wt% balance zirconium eutectic alloy.

These alloys are obtained as a clean molten alloy ingot by arc melting or the like.

Next, the metallizing method of the present invention will be described. The molten alloy is placed on the surface of graphite. Next, for example, when heated to a temperature higher than the melting point of the ingot alloy in a vacuum atmosphere or an inert atmosphere, carbon of graphite reacts with oxygen to release CO gas. The reducing action by this CO gas improves the wettability, and the surface tension action coats the graphite surface. As a result, there are no defects such as voids or peeling, and the thickness is as thin as 5 to 70 μm, and the relative density is 98% or more. It is possible to form a dense and uniform metallization layer.

If the thickness of the metallized layer is less than 5 μm, the strength will be insufficient, and if it exceeds 70 μm, the strength will be insufficient and the surface of the metallized layer will not be a good smooth surface. The range of 5 to 70 μm is preferable.

Thus, various metals can be easily bonded to the graphite having the metallized layer formed thereon, if necessary, for example, by brazing or nickel plating. Further, in the present invention, the graphite to be metallized can form a uniform metallized layer without being limited in size and shape such as plate, cylinder, powder and fiber.

The application range is expanded by metallizing the graphite powder and the graphite fiber. For example, by forming a metallized layer on the surface of graphite particles or fibers, it becomes possible to manufacture an alloy with a metal such as copper, magnesium or aluminum which is said to be incompatible with graphite particles or graphite fibers.

That is, in the method for producing the graphite-containing alloy,
It is more effective to apply the casting technique than the powder metallurgy technique in terms of mechanical strength and cost, but the latter, that is, a metal that hardly dissolves with graphite in the casting technique, that is, metallurgically compatible with graphite. It has heretofore been difficult to disperse graphite particles in copper, magnesium, aluminum or their alloys or other metals which are said to have no property without floating. However, it has been revealed that the use of the present invention makes it possible to form a material in which graphite particles, fibers, or the like are compounded in a metal. In this case, molybdenum, zirconium or tungsten
Graphite particles obtained by metallizing a zirconium alloy on the surface of graphite are introduced into a melt of copper, magnesium, aluminum or its alloy or other metal, and dispersed and solidified.

For example, the graphite-containing copper alloy obtained by the present invention has graphite particles dispersed almost uniformly over the entire area. Further, the graphite particles once contained and dispersed in the copper alloy do not re-float even after re-melting, and remain in the melting state. In this case, as a method of metallizing molybdenum-zirconium or tungsten-zirconium alloy of graphite particles, graphite particles are filled in a container such as alumina, and the graphite alloy particles are coarsely crushed into the molten alloy ingot. It can be obtained by a method of deploying and then heating above the eutectic temperature of the alloy in a vacuum or an inert gas atmosphere.

Further, in the production of a graphite fiber reinforced alloy, a graphite fiber having a metallized layer formed on the surface of the graphite fiber can be obtained by first placing the molten alloy on a graphite fiber carrier and heating as described above. Next, a so-called graphite fiber reinforced aluminum alloy or magnesium alloy (CFRAl or CFR) in which the gaps between the graphite fibers with the metallized layer formed are impregnated with molten metal of aluminum, magnesium or copper
Mg alloy) or copper alloy can be produced.

The graphite fiber reinforced alloy according to the present invention can prevent the graphite from reacting with aluminum and being significantly deteriorated.

In addition, the molybdenum, zirconium or tungsten
Since the zirconium alloy penetrates into the small gaps where graphite and graphite are superposed, it is possible to join graphite materials together. By this method, graphite particles or graphite fibers joined by a metallized layer, or both graphite particles and fibers are present. The material that does

The present invention can be used to form a composite target for an X-ray tube rotating anode, which is composed of tungsten or its alloy / graphite. That is, recently X-rays for medical devices
Demand for X-ray tubes for CT (Computed, tomography) is high,
In order to make the image clear and to shorten the shooting time, a large capacity is required. The target for this purpose needs to have a large diameter and a light weight, but according to the method of the present invention, a tungsten layer is formed only on the electron impact surface, and the back surface has a small specific gravity and a large specific heat. It is possible to manufacture a target that incorporates a metallized body of graphite.

[Work]

When a eutectic alloy of molybdenum or tungsten and zirconium is arranged on the graphite surface as described above, and the material is heated and melted in a vacuum atmosphere or an inert gas atmosphere, the eutectic alloy is well-wetted over the entire graphite surface and has a thickness of It is possible to form a thin, dense and uniform metallized layer.

Then, the metallization layer is formed by the present method on the surface of graphite particles, graphite fibers, etc. that are originally incompatible with the metal to impart compatibility with the metal, and a graphite-containing alloy in which these are dispersed in the metal, etc. Can be manufactured.

〔Example〕

 Examples of the present invention will be described below.

Example 1 A 31 wt% molybdenum-zirconium and 19 wt% tungsten-zirconium eutectic alloy was melted by arc melting to obtain an alloy ingot.

This alloy ingot 2 was placed on the inner surface of a tubular graphite 1 having a space of 60 mm in height, 110 mm in width, and 700 mm in length, and then vacuum-heated. The heating temperature and time in this case are: Mo-Zr alloy; 1600 ° C x 0.5h W-Zr alloy; 1750 ° C x 0.5h
And

As a result of observing the cross-sectional structure near the metallized layer thus obtained, the molybdenum
The metallized layer composed of zirconium and a tungsten-zirconium alloy was a sound one without voids, and its thickness was 10 to 30 μm and was thin and uniform.

Further, the graphite metallized body obtained in this example was subjected to a peeling test by pulling. The peeling test was performed using a test piece in which a graphite material was bonded to the surface portions of the graphite and the metallized layer with a commercially available adhesive. As a result, all fractured with graphite. This means that the bonding strength of the metallized layer is high.

Example 2 Using the molybdenum-zirconium alloy obtained in Example 1, it was heated in vacuum at 1600 ° C. for 0.5 h while applying a static pressure to obtain a bonded body of graphite.

As a result of observing the cross-sectional structure of the joint portion thus obtained, the joint layer had a thickness of 5 to 50 μm and was uniform without defects such as voids. Further, with respect to the tungsten-zirconium alloy obtained in Example 1, a graphite-graphite bonded body was manufactured in the same manner, and the cross-sectional structure was observed. As a result, the thickness and morphology of the bonding layer is molybdenum
There was almost no change compared to the graphite-to-graphite joint using a zirconium alloy.

The graphite-graphite bonded body obtained in Example 2 was subjected to a peeling test by tensile, and as a result, it was found that each of them was broken by graphite and the strength of the bonding layer was high.

Example 3 Graphite particles of 30 to 150 μm were metallized with the molybdenum-zirconium and tungsten-zirconium alloys of Example 1 to a thickness of 5 to 10 μm. In the metallizing treatment, the molybdenum-zirconium- or tungsten-alloy lump was placed in one portion of the graphite container filled with the graphite particles in a dropped state, and heated in vacuum.
The heating temperature is molybdenum / zirconium: 1600 ° C ×
0.5h, tungsten / zirconium: 1750 ° C × 0.5h, and the degree of vacuum was kept at 10 ^-5 torr or less. These metallized graphite particles were put into a copper melt and stirred. The melting temperature was 1200 ° C. In addition, the amount of graphite particles added was 20% by volume. As a result, the charged graphite particles stayed during melting and no floating was observed. These melts are cast into a mold and have a diameter of 60 mm and a length of 100 m.
When an ingot of m was produced and the structure of the longitudinal section was observed, it was found that graphite particles were uniformly dispersed throughout the ingot. Further, after the molybdenum-zirconium and tungsten-zirconium alloys were metallized on the graphite-containing alloy according to the present invention, it was possible to bond it to various materials such as the graphite-containing alloy, graphite or tungsten, molybdenum materials.

Example 4 Graphite fibers having a diameter of 10 μm were metallized with the molybdenum-zirconium or tungsten-zirconium alloy of Example 1. The metallizing process was performed in the same manner as in Example 1. The aluminum melt was impregnated into the spring-loaded gaps of these metallized graphite fibers. The impregnation was heated to 700 ° C x 0.5h in hydrogen. A longitudinal section of these graphite impregnated bodies was observed, and no deteriorated layer in which graphite reacted with aluminum was observed, and a graphite fiber alloy well impregnated with aluminum was obtained. Further, when the graphite fiber alloys were superposed on each other and heated in hydrogen at 700 ° C. for 0.5 h for bonding, a well bonded and integrated graphite fiber alloy could be obtained.

〔The invention's effect〕

INDUSTRIAL APPLICABILITY According to the present invention, a metallized layer can be formed on the surface of graphite by a very simple operation of placing molybdenum or a eutectic alloy of tungsten and zirconium on the surface of graphite and heating in a vacuum and an inert gas atmosphere. Since the metallized layer is thin and has no voids, it has the effects of excellent thermal conductivity and conductivity, and high adhesive strength.

Further, according to the present invention, since the metallized layer can be formed without being limited to the shape of graphite, it is possible to manufacture a graphite-containing alloy and a graphite fiber reinforced alloy. Graphite-containing alloys are used as solid lubricants for graphite in sliding contact components in internal combustion engines, for example:
Used in alloys containing solid lubricants such as bearings, gears, pistons, cylinders, so-called wear resistant parts, and
Graphite fiber reinforced alloys are used in aircraft materials and the like. In addition, a joined body formed by joining a metal material and graphite has many industrial uses.

Furthermore, since the present invention has confirmed that graphites can be joined together, the present invention is particularly effective for producing a joined body of graphites having complicated shapes and graphite.

Further, according to the present invention, a metallized layer can be formed on the surface of graphite constituting the composite target for an X-ray tube rotating anode, whereby the target can be reduced in weight and a target having a large diameter can be manufactured. We can meet the demand for larger capacity X-ray CT for medical equipment.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Shigeo Maeno 4026 Kuji Town, Hitachi City, Hitachi, Ibaraki Prefecture Hiritsu Manufacturing Co., Ltd.Hitachi Laboratory Ltd. Inside Hitachi Research Laboratory (56) Reference JP-A-49-102519 (JP, A) JP-A-49-110504 (JP, A)

Claims (10)

[Claims] 1. A eutectic alloy of molybdenum and zirconium having 26 to 36 weight percent molybdenum and the balance zirconium or a eutectic alloy of tungsten and zirconium having 15 to 25 weight percent tungsten and the balance zirconium. A method of metallizing graphite, which is characterized in that it is placed in a vacuum atmosphere or an inert gas atmosphere together with graphite to be heated and melted by heating to form the alloy layer on the surface of the graphite. 2. The method for metallizing graphite according to claim 1, wherein the metallized layer has a thickness of 5 to 70 μm. 3. A graphite particle, wherein a layer of molybdenum or a eutectic alloy of tungsten and zirconium is formed on the surface of the graphite particle by the method according to claim 1. 4. A graphite-containing alloy, characterized in that the graphite particles according to claim 3 are dispersed in copper or its alloy, aluminum or its alloy, magnesium or its alloy. 5. A joined body obtained by joining a metal material to the graphite-containing alloy according to claim 4. 6. A graphite fiber, wherein a layer of molybdenum or a eutectic alloy of tungsten and zirconium is formed on the surface of the graphite fiber by the method according to claim 1 or 2. 7. A graphite fiber reinforced alloy characterized in that the graphite fiber according to claim 6 is dispersed in copper or its alloy, aluminum or its alloy, magnesium or its alloy. 8. A bonded body obtained by bonding a metal material to the graphite fiber reinforced alloy according to claim 7. 9. A composite target for an X-ray tube rotary anode comprising tungsten or an alloy thereof and graphite, wherein molybdenum or tungsten and zirconium are formed on the back surface of the electron impact surface comprising tungsten or an alloy by the method according to claim 1. A composite target for an X-ray tube rotating anode, characterized in that the graphite having a metallized layer formed of the eutectic alloy is incorporated. 10. The composite target for an X-ray tube rotating anode according to claim 9, wherein tungsten or an alloy layer thereof is formed on the surface of the metallized layer of graphite.