JPS59114739A - Rotary anode for x-ray tube - Google Patents

Abstract

PURPOSE:To check completely carbon diffusion from a graphite base substance to the target base substance by interposing a three layer carbon diffusion checking layer consisting of an Re layer, carbide and an Re foil en bloc between the graphite base substance and the target base substance in a state of closely contacting of the Re foil with the target base substance. CONSTITUTION:An Re thin layer in thickness of 5-20mum is formed on one side of a graphite disk by making the graphite disk to perform a reaction of gaseous growth in a reactor while making a mixed gas of an ReF6 gas and an H2 gas to flow in. Thereafter, an Mo2C layer in thickness of 10-30mum on the Re thin layer by a gas type solvent method or the like. Next, the Re foil is placed on said Mo2C layer and after laminating the side of an Mo plate of the target base substance further thereon, the whole is united en bloc by impressing pressure from up and down under an atmosphere of inert nitrogen or the like through a compressive medium of boronnitride powder or the like, whereby carbon diffusion can be completely checked.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a rotating anode for an Xffl1j tube, and more particularly to a rotating anode for an X-ray tube in which a novel carbon diffusion inhibitor N is interposed between a graphite substrate and a target substrate. .

[Technical background of the invention and its problems]

Rotating anodes, which have a large heat capacity and generate high-output X-rays, have traditionally had a high melting point, excellent heat resistance strength, and thermal shock resistance.

It is constructed as a target base in the form of a composite plate made of tungsten (5) or W alloy that efficiently generates stable xi, or a relatively thick molybdenum (Mo) plate integrally bonded to the back side of these as a heat absorber. .

In recent years, with the advancement of X-ray technology, there has been a strong demand for rotary anodes with larger heat capacities that can withstand continuous loads or instantaneous high load inputs.

In order to increase the heat capacity and achieve high output, it is only necessary to increase the size of one piece of the target substrate.

However, when the weight of the target substrate is increased,
If the load on other structural members of the X-ray tube, especially the rotation mechanism, becomes excessive, the weight of the target substrate will be restricted.

For this reason, recently, rotating anodes have been developed that are based on graphite, which has a low density and excellent thermal radiation, and by integrally bonding a relatively thin tar or gent substrate on top of this graphite substrate, the overall weight of the anode is completely reduced. is being developed.

However, at this rotating anode, the target substrate is irradiated with the Toyo beam.

The surface generates heat of approximately 2500 to 2600°C, and therefore the joint between the target substrate and the graphite substrate also becomes high temperature5.
When the temperature of the joint reaches 1300C or higher, carbon in the graphite base diffuses to the upper target base, and a carbide layer such as tungsten carbide (WC) or molybdenum carbide (MO2C) is formed at the joint. be done.

□ Also, such a carbide layer is generated when the graphite substrate and the target substrate are integrally joined by hot press bonding.

The carbide layer produced by the above-mentioned carbonization reaction is mechanically fragile and may be damaged by external forces such as vibrations during high-speed rotation of the one-turn anode. the result.

This often leads to inconvenient situations such as partial separation of the joint between the target substrate and the graphite substrate, uneven heat conduction due to this, and local abnormal heat generation.

For this reason, conventionally, between the graphite base and the target base,
Measures have been taken to interpose a layer that does not form carbides with carbon and prevents carbon from diffusing into the target substrate.

Up to now, such a carbon diffusion inhibiting layer is a layer in which rhenium (Re) metal powder is bound with a suitable binder and coated on the coated surface of a graphite substrate.

Known are layers deposited on the surface of a graphite substrate by CVD or PVD, or Re foils processed by conventional powder metallurgy. These Reti do not exhibit their effects if they are too thin, and the thickness is usually about 50 to 200 μm.

However, Re is a very expensive metal and also has a characteristically low thermal conductivity. Therefore, if only the Re layer with a thickness of about 200 μm is used as the above-mentioned carbon diffusion inhibiting layer, the cost will be extremely high.
The lower thermal conductivity coefficient of moths reduces the rapid heat transfer from the target substrate to the graphite substrate, thereby counteracting the good thermal radiation properties of the graphite substrate.

Therefore, there is a strong desire to develop an inhibition layer that is as thin as possible and completely blocks VC from diffusion of carbon from the graphite substrate to the target substrate.

[Object of the invention] The object of the present invention is to provide a rotating anode for an X# tube that is equipped with a novel carbon diffusion inhibiting layer that almost completely shields the carbon chamber that diffuses from the graphite substrate to the target substrate and has a thin thickness. shall be.

(Summary of the Invention) In the rotating anode for an X-ray tube of the present invention, the carbon diffusion inhibiting layer is not composed of a single layer of Re.

The parts connected to the graphite base and target base are R.
e, but it has a three-layer structure with a carbide layer in the middle. That is, the rotary depolarization for an X-ray tube of the present invention is
A three-story carbon diffusion inhibiting layer consisting of a Re thin layer, a carbide layer, and a Re foil is integrally interposed between the graphite substrate and the target substrate with the Re foil and the target substrate in contact with each other. It is characterized by being made of

First, the Re thin layer according to the present invention is a layer that is formed in close and intimate contact with the coating surface of the graphite substrate, that is, the bonding surface with the target substrate. Carbon diffused from the graphite substrate is first avoided by this Re thin layer.

In order to form the thin J-threat, 1. Since the graphite that is the substrate has a porous structure and a substantial surface area, 1. PVD methods such as vacuum evaporation method and sputtering method are used from the viewpoint of increasing the adhesion between the two. (Physical Vapor Depo
-sition) or CVD method (Chemical
- It is preferable to apply a true wall thin film forming method such as Vaper Deposition.

The thickness of the Re thin layer to be formed is usually preferably 5 to 20 μm; if it is less than 5 μm, the effect of suppressing carbon diffusion will not be exhibited, and if it exceeds 20 μm, the effect will not be noticeable and it will be uneconomical. It is.

The carbide layer according to the present invention is formed by laminating on the above-mentioned Re thin layer. The carbide layer functions to capture carbon that is not completely blocked by the Re thin layer and diffuses through the thin layer. The carbide layer is molybdenum carbide (
Examples include layers of MO2C), carbon IF = tungsten (WC), tantalum carbide (TaC), and titanium carbide (Tic). Among these, the M020 layer is particularly useful. The thickness of the carbide layer is usually 10 to 30 μm. When the thickness is less than 10 μm, the carbon trapping effect described above is small.

Moreover, if the thickness exceeds 30 μm, the amount of carbon trapped will be too large, causing the layer to collapse, resulting in a decrease in mechanical strength.

In order to form this entire carbide layer, thermal spraying, CVD,
Although methods such as PVD can be applied, it should have good adhesion to the Re thin layer and be easy to form.

For these reasons, it is preferable to apply the thermal spraying method.

Does the Re foil laminated on top of this carbide layer function as a final barrier to the carbon that is generated by the decomposition of the lower carbide layer and diffuses into the upper layer? fulfill For this purpose, the Re foil needs to have a dense structure. in particular,
It is a dense foil made by processing sintered 1*, which is made by sintering Re powder using a powder metallurgy method, using the required processing method, so that each grain boundary is intricately intertwined. During this processing, the processing rate is usually 50 to 90.
%, it is possible to obtain Re foil that meets the purpose of the present invention.

The thickness of this Re foil is preferably 50 to 100 μm; if it is less than 50 μm, carbon diffusion cannot be completely inhibited, and if it exceeds 100 μm, the carbon diffusion inhibiting effect will not be significantly improved, but on the contrary, it will cause rapid heat generation. This is inconvenient because it leads to a situation where conduction deteriorates.

The rotating anode of the present invention can be manufactured as follows.

That is, first, a pre-processed graphite substrate is set in a vacuum thin film forming apparatus, a Re foil of a predetermined thickness is overlaid on the surface of the graphite substrate, and a pre-processed target substrate is placed on top of it. In this method, the entire tube is placed in a hot-pressing device, and the entire tube is integrally joined by hot pressure pressing under vacuum.

[Embodiments of the invention]

υ Diameter 130m + s Thickness 2.5111 manufactured by the usual method of manufacturing Ghent substrates
A tungsten plate with a diameter of 13011B and a molybdenum plate with a thickness of 15 degrees were prepared. The tungsten plate was placed on the molybdenum plate and heated at 1600C, 25°C in a hydrogen atmosphere.
Hot pressure pressing was carried out at 0 Kf/-. After the tungsten plate and molybdenum plate were integrally joined, the bottom surface of the molybdenum plate was smoothed to form a composite target base.

2) Preparation of Re foil Fill a mold with Re powder having a particle size of 1 to 3 μm at room temperature,
After pre-compression molding at 1.5 torVc+4, the obtained green compact was subjected to isostatic compression molding at k 2 ton/J. This molded body was heated in a vacuum furnace at lXl0 Torr at 22,000 Torr.
Baked at a temperature of Height: 10 Q wb, Width: 5 Q
A sintered body with wtv and a thickness of 2 m was obtained.

This is hot forged at a temperature of 1700 to 1900C.

Furthermore, after hot rolling at 1700C, cold rolling was performed to obtain a processing rate of 8.
0% (thickness: 0.4 m) Re foil.

3) Manufacture of rotating anode A graphite disk with a diameter of 130 mm and a thickness of 301 mm is placed in the reactor of a kcVD apparatus, and a mixed gas of Vc, ReFs gas, and ReFs gas is introduced into the reactor to perform a vapor phase growth reaction, and graphite is One side of the disk was coated with a thin layer of Re with a thickness of 10 μm.

Thereafter, the graphite disc was taken out from the acidic acid, and an M020 layer having a thickness of 1511B was formed on the Rei'1 layer by gas spraying.

Next, the Re foil prepared in 2) was placed on this MotC layer, and the Mo of the target substrate prepared in 1) was placed on top of it.
After overlapping all sides of the board, the whole was treated with 1500C1 nitrogen (inert).
Boron nitride powder as a whole compressed medium under atmosphere,
Approximately 250 Ky/- pressure is applied from the top and bottom, and approximately 1
It remained in that state for an hour. As a result, it was confirmed that the entire structure was integrally joined.

For comparison, particles with an average particle size of 1 to 3 μm were placed on a graphite substrate.
A slurry made by adding 0.29 k of organic binder to 20 F (10 st/) of rhenium powder to a thickness of about 500 μm
After the binder was heated and removed, a rotating anode was fabricated by similarly bonding a composite target plate thereon.

4) Deterrent effect on carbon diffusion Two rotating anodes obtained in this way.

It was left for 10 hours at a temperature of about 14,000° C. in a vacuum oven at I.times.10-'Torr. After cooling, the one-rotation anodes were taken out and each was cut vertically to expose the bonding surface.

The cut surface was observed under a microscope to determine the M of the target substrate.

Is there a carbide layer formed on the board? I looked into it.

As a result, in the case of the rotating anode of the present invention, no carbide layer was formed on the Mo plate. On the other hand, in the rotating anode of the comparative example, it was confirmed that a carbide layer of about 100 μm was formed non-uniformly.

〔Effect of the invention〕

In the rotating anode of the present invention, carbon diffusion can be almost completely inhibited even though the carbon diffusion inhibiting layer between the graphite base and the target base is thin. Since the Re layer is thin, it is inexpensive and heat conduction from the target substrate to the graphite substrate proceeds quickly. As a result, the heat capacity increases and high output becomes possible. It has the following effects and has great industrial value.

Claims (1)

[Claims] 1. A state in which a three-layer carbon diffusion inhibiting layer consisting of a thin rhenium layer, a carbide layer, and a rhenium foil is placed between a graphite base and a target base, and the #rhenium foil and the target base are in contact with each other. A rotating anode for an X-ray tube, characterized in that it has a structure in which the anode is integrally interposed with the anode. 2. The rotating anode for an X-ray tube according to claim 1, wherein the thin rhenium layer has a thickness of 5 to 20 μm. 3. The rotating anode for an X-ray tube according to claim 1 or 2, wherein the rhenium thin layer is a thin layer formed by a vacuum thin film forming method. 4. The rotating anode for an X-ray tube according to claim 1, wherein the carbide layer has a thickness of 10 to 30 μm. 5. The rotating anode for an X-ray tube according to claim 1 or claim 4, wherein the carbide layer is a layer formed by a thermal spraying method. 6. The rotating anode for an X-ray tube according to any one of claims 1, 4, and 5, wherein the carbide layer is a layer of molybdenum carbide. 7. The rotating anode for an X-ray tube according to claim 1, wherein the rhenium foil has a thickness of 50 to 100 μm. 8. The rotating anode for an X-ray tube according to claim 1 or 7, wherein the rhenium foil is a foil obtained by processing a powder sintered body.