JP2001081561A - High temperature heat receiving body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a heat receiving body composed of different kinds of joined body wide in the difference in thermal expansion coefficients by directly joining a dense tungsten thick film at least to a part of a base material having a thermal expansion coefficient higher than that of tungsten without providing an intermediate layer. SOLUTION: The film thickness of a tungsten (W) thick film 2 is >=1 mm, and a base material 2 is a high temp. heat receiving body composed of copper or a copper alloy. Preferably, the joined face between the base material 2 and the W thick film 3 is subjected to groove working so as to make a trapezoidal shape in which the cross-section of the groove is opened toward the outside. The width of the opening part of the worked groove 1 whose cross-section has a trapezoidal shape is suitably controlled to the one equal to or above the depth of the groove. The worked groove 1 is formed on the joined face of the base material 2 composed of oxygen free copper, after cleaning and drying, W-CVD film deposition is executed by a hydrogen reducing method using tungsten hexafluoride as the raw material, and W is joined. After the joining, the side face and surface of the W part are finished by mechanical polishing. The high temperature heat receiving body composed of the joined body excellent in adhesive strength can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-temperature heat receiving body for an apparatus used under a high temperature and a high load, such as a power generator utilizing high energy density.

[0002]

2. Description of the Related Art In recent years, materials such as large current plasma electrodes, MHD power generation, nuclear fusion reactors, and devices utilizing high energy density beams have been required to withstand severe discharge loads and heat loads.

On the other hand, the use of tungsten (W) and a W alloy having a high melting point, high heat resistance, and low discharge consumption is desired.
Alternatively, due to the difficulty of bonding between members during assembly, a joint with a base material of another material, particularly copper (Cu) and a Cu alloy excellent in workability and thermal conductivity has been studied.

For example, in MHD power generation, an anode needs to withstand arc erosion and electrochemical corrosion, and therefore, a joint of W with little erosion and corrosion wear and Cu with high thermal conductivity and a large water cooling effect. It is considered that the use of the alloy makes it possible to lower the surface temperature and reduce the discharge consumption as compared with the anode of W alone. In addition, a fusion reactor or a high energy density beam-based device receives a large heat load,
The use of a bonded body of W having a small erosion loss due to a high energy charged particle beam and Cu having a large water cooling effect has been studied.

[0005] Incidentally, it is well known that W and Cu are a combination that does not form a solid solution with each other and are very difficult to join.

[0006] As a joining method generally used for joining dissimilar materials, there are a fusion joining (welding) using an arc, a TIG, a laser, an electron beam or the like, a brazing joining, a cast-in method and the like.

[0007] Among these, fusion welding is generally called "welding" and heats a portion of the base metal to be welded, and fuses the base metal alone or the base metal and the filler metal to form a molten metal. Make
This is a method of solidifying and joining it, and is widely used in the manufacture of structures, mainly iron-based metals.

However, in the fusion welding method, since the base material needs to be melted, it is essential to heat the base material to a temperature higher than the melting point of the base material. In addition, changes in the structure due to melting and solidification of the base material, that is, recrystallization and its coarsening are unavoidable. Occurs. Therefore, embrittlement due to coarsening of crystal grains accompanying melting and solidification is particularly remarkable.
It is difficult to apply to hard-to-melt metals. In particular,
In the case of joining W and Cu, almost no practical level of joining is possible due to the large difference in melting points and insolubility.

[0009] Brazing is also called brazing, in which a filler metal (brazing material) having a melting point lower than that of a base material is melted without melting the base material, and bonding is performed using a capillary phenomenon. This is a method of joining by spreading the gap between the surfaces. Therefore, crystal grains do not become coarse due to melting and solidification of the base material and embrittlement due to generation of metal intermetallic compounds does not occur, and thermal stress can be suppressed due to the low construction temperature, and there is no structural change in the base material etc. There are advantages. Furthermore, brazing is suitable for a material that requires high energy for melting a base material, such as a refractory metal, or a material that is liable to crack during solidification. It is also suitable for joining different materials.

[0010] However, brazing has a problem that not only the bonding strength is lower than that of the fusion welding method but also the reliability is low due to the large variation. In addition, there is a drawback that the working temperature is limited by the melting point of the brazing material used.

In addition, the cast-in method is often used for joining W and Cu. That is, high melting point W
This is a method in which a base material is set, and a molten material in which Cu having a low melting point is melted is poured and solidified to fix the W base material. In this case, Cu is held so as to hold at least a part around the W base material.
Need to wrap around. That is, joining of one surface is impossible, and the shape of an applicable joined body is limited.

Further, as a joining method other than the above, PVD is used.
There is a film forming method. However, in electrodes and the like, the demand for increasing the thickness of the W film to 1 mm or more is increasing in order to reduce the life and load of the cooling capacity. Even in the thermal spraying method capable of forming a relatively thick film, the limit is about 1 mm, and its adhesion strength and reliability are low, and the biggest problem is that densification is practically impossible, that is, Existence is inevitable.

Further, other PVs such as ion plating are used.
The D film forming method is a thin film forming method and has an adaptive film thickness of several tens of μm from the relation of the magnitude of the residual stress and the film forming speed, and cannot be applied to the above thick film of 1 mm or more.

As described above, since there is no bonding method that can provide practically sufficient strength for bonding W and Cu and is not limited by the applicable shape at present, its development is required.

[0015]

Therefore, in response to the above demands, the present inventors have studied the application of a high-efficiency, high-adhesion thick film forming method by the W-CVD method to a Cu base material. This C
Since the VD method uses a gas as a raw material, it is considered to be the most suitable for joining W and Cu since it can be joined without good wraparound and has no shape restriction and can be joined without reaction at the interface.

However, as described above, there is an increasing demand for thicker electrodes such as electrodes having a W film thickness of 1 mm or more in order to reduce the life and load of the cooling capacity. However, since the manufacturing cost is greatly increased with the increase in the film thickness, the maximum thickness requirement is 10 mm, generally about 5 mm. To meet such demands, a 5 mm-thick W
Was evaluated by forming a film by the CVD method. As a result, peeling occurred, which was presumed to be caused by a difference in thermal expansion coefficient between W and Cu.

Here, the coefficient of thermal expansion is unique to each element, and this factor cannot be changed, so that it is necessary to solve it with other factors. If the separation due to the difference in the thermal expansion coefficient can be eliminated, it can be applied to a dissimilar material joined body having a large difference in the thermal expansion coefficient other than the combination of W and Cu.

Here, the coefficient of thermal expansion is from 20 to 500 according to the metal data book (edited by the Japan Institute of Metals, revised 3rd edition).
At C, W: 4.6, Cu: 18.3, Ni: 1
5.2 (10 ⁻⁶ / K).

In view of the above circumstances, one technical problem of the present invention is to provide a high-temperature heat receiving body composed of a joined body of a high melting point metal W and a dissimilar material having a large difference in thermal expansion coefficient such as Cu. To provide.

Further, another technical problem of the present invention is that
It is an object of the present invention to provide a high-temperature heat receiving body made of a joined body having excellent adhesion strength between a high melting point metal W and a different material such as Cu or Ni having a large difference in thermal expansion coefficient.

Still another technical object of the present invention is to provide a high-temperature heat receiving body comprising a high-efficiency, high-adhesion thick-film joined body by forming a W thick film on a Cu base material by a CVD method. To provide.

[0022]

Means for Solving the Problems The present inventors have proposed a method for producing Cu
Even if W-CVD film formation is performed on the base material, the above-described technical problem can be solved by performing groove processing on the film formation surface of the Cu base material because the separation occurs as described above. It is what led to.

That is, according to the present invention, a dense tungsten thick film is directly joined to at least a part of a base material having a larger thermal expansion coefficient than tungsten without an intermediate layer by a CVD method. The body is obtained.

Further, according to the present invention, in the high-temperature heat receiving body, the high-temperature heat receiving body is characterized in that the tungsten thick film has a thickness of at least 1 mm.

Further, according to the present invention, in the high-temperature heat receiver, the base material is substantially made of copper or a copper alloy.

Further, according to the present invention, in the high-temperature heat receiving body, a groove is formed on a joint surface of the base material with the tungsten thick film, whereby a high-temperature heat receiving body is obtained. .

According to the present invention, in the high-temperature heat receiving body, the cross section of the groove formed by the groove processing of the base material has a trapezoidal shape that opens outward. Is obtained.

Further, according to the present invention, in the high-temperature heat receiving body, the width of the opening of the groove having a trapezoidal cross section formed by processing the groove of the base material is not less than the depth of the groove. A high-temperature heat receiving body is obtained.

[0029]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the present invention will be described more specifically.

The inventors of the present invention have invented a joined body having excellent adhesion strength between different materials such as W and Cu or Ni having a large difference in thermal expansion coefficient. In other words, the CVD
This is a method for obtaining a high-efficiency, high-adhesion thick-film joined body by forming W by a method. However, even if W-CVD film formation is performed on the Cu base material, the separation occurs as described above. Therefore, it has been found that the object can be achieved by performing the groove processing on the film formation surface of the Cu base material. .

Now, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view showing a high-temperature heat receiving body according to an embodiment of the present invention. FIGS. 2A, 2B, and 2C are cross-sectional views showing various examples of the groove shape of the base material of the high-temperature heat receiving body of FIG. 3A is a plan view showing an example of the arrangement of the base material in FIG. 1, and FIG. 3B is a cross-sectional view of the base material in FIG. 4A is a plan view showing another example of the groove arrangement of the base material in FIG. 1, and FIG. 4B is a cross-sectional view of the base material in FIG.

As shown in FIG. 1, the high-temperature heat receiving body 10 forms a processed groove 1 by performing groove processing on one surface of a base material 2 and forms a thick film 3 made of tungsten (W) on one surface thereof by CVD. It was done.

As shown in FIGS. 2 (a), 2 (b), and 2 (c), the processing grooves 1a to 1c formed in the base material 2 have a cross-sectional shape in which the opening side is larger than the bottom and the open trapezoid. It has a shape. In any of the processing grooves 1a to 1c, the width on the opening side has a dimension equal to or greater than the depth of the processing groove.

In the example shown in FIG. 3, the processing groove 1 is provided at right angles near the periphery of one surface on which a film is formed.

In the example shown in FIG. 4, the processed grooves are provided in a grid pattern on one surface on which a film is formed.

A method for manufacturing a high-temperature heat receiving body according to the above-described embodiment of the present invention will be described.

Here, an example will be described in which W having a thickness of 5 mm is bonded to an oxygen-free copper base material having a size of 20 mm and a thickness of 30 mm.

As shown in FIGS. 2 (a) to 2 (c), trapezoidal grooves 1a to 1c were formed on the bonding surface of the oxygen-free copper substrate by machining, washed, dried, and then W was bonded by CVD film formation. WC
The VD film formation was performed by a hydrogen reduction method using tungsten hexafluoride as a raw material.

After the joining, the side surface and the surface of the W portion were finished by mechanical polishing. For comparison, W-CVD film formation was performed on an oxygen-free copper base material without groove processing.

In the joined body using the oxygen-free copper base material without the groove processing, the peeling occurred at the time of the finish polishing processing, whereas in the joint body using the oxygen-free copper base material with the groove processing, all the finishes were finished. A joined body that can be processed and has good joining strength was obtained. This indicates that by performing the groove processing on the interface, the adhesion strength of the interface was improved as compared with the case where the interface was flat.

The following can be considered as the factors.

(I) The contact area has increased. (R) When thermal contraction occurs during cooling after film formation, since the contraction of the width of the groove of the oxygen-free copper base material is larger than the contraction amount of W formed inside the groove due to the difference in thermal expansion coefficient, The concave portion of Cu holds the convex portion of W in the groove portion, and exhibits a tightening effect. (A) From the thermal stress calculation, the residual stress generated when cooling the joined body generally joined at a high temperature is the largest at the outer periphery of the base material near the interface, and the magnitude increases when the plate pressure and the joining temperature are equal. However, propagation of the residual stress does not progress due to the groove, and the same effect as when the bonding area is subdivided is exerted.

Here, the W-CVD film was formed by a hydrogen reduction method using tungsten hexafluoride as a raw material. However, in the present invention, the heating temperature is not limited to this system, and the heating and melting are performed on the base material. If it is a system capable of low-temperature film formation that does not cause problems such as
Be adaptable.

In the above example, the base material is C
However, the present invention does not need to be pure Cu, and the present invention is applicable to metals and alloys having a coefficient of thermal expansion larger than W, such as Cu alloys, Ni and alloys thereof, and high alloy steels such as stainless steel. it can.

The shape of the substrate 2 can be joined without any problem as long as the groove can be formed not only on the above-mentioned flat surface but also on a curved surface.

The groove position, dimensions, shape and quantity are
The thickness may be determined according to the thickness of the formed film or the area or shape of the joint portion of the base material. However, as shown in FIGS. It is desirable to process the groove parallel to the outer periphery.

Further, as shown in FIG. 4, a groove may be formed in the inside of the base material depending on the area of the joint portion of the base material.

In the present invention, the end of the groove may reach the side surface of the base material as shown in FIGS. 3 and 4, or may be stopped at an intersection with another intersecting groove. That is, in the case of a square joint surface, it may be processed into a well-formed shape or a closed square shape, and may be determined from the ease of processing.

In the present invention, the manufacturing cost can be reduced if the groove depth is as shallow as possible.
Since the effects (1) to (3) cannot be expected, 5% or more of the film thickness is preferable.

If the groove depth is increased more than necessary, the effect is not proportional, and if the groove depth is too large, the groove width must be increased according to the depth. Only the number of parts increases and the manufacturing cost increases, and the maximum is preferably 30%, preferably 20%.

The groove shape may be a parallel groove such as a square or a U-shape. However, since the gas does not sufficiently flow to the bottom of the groove and voids are likely to be generated, the grooves are preferably formed as shown in FIGS. 2 (a) to 2 (c). As shown in the figure, it is desirable that the groove is open toward the joining surface of the base material, such as a trapezoidal groove or a V-shaped groove (not shown).

In the present invention, FIGS.
As shown in (c), the width of the opening is desirably equal to or greater than the depth of the groove so that the gas flows sufficiently to the bottom of the groove, but if it is too wide, the effect of tightening the groove of the base material is reduced. Therefore, the groove depth is desirably five times or less, preferably three times or less.

Hereinafter, a specific example of manufacturing the high-temperature heat receiving body according to the embodiment of the present invention will be described.

(Example 1) The trapezoidal processing grooves 1a, 1b and 1c shown in FIGS. 2A to 2C and having a groove depth of 0.5 mm and a groove depth / groove width ratio of 1: 1 to 1: 5 are used. An oxygen-free copper base material (□ 20 mm × thickness 30 mm) processed into the groove arrangement shown in FIGS. 3A and 3B was processed using a commercially available Cu etching solution (CPB-
After etching in step 50), the substrate was subjected to ultrasonic cleaning in the order of warm pure water and alcohol, and dried under vacuum. The back surface, side surface, and the like where film formation is unnecessary are masked, and one substrate having each trapezoidal groove shape is set in the same batch in a reaction tank. After the inside of the reaction tank was repeatedly vacuumed and Ar purged several times, 6 SLM of high-purity H ₂ was introduced from _two gas nozzles, the pressure was reduced to a predetermined degree, and the substrate temperature was heated to 600 ° C. After the temperature was stabilized, WF ₆ was introduced at 1.2 SLM, and W was coated 5.3 mm at the thinnest point by hydrogen reduction CVD film formation. After removing the mask, the protruding portion of the W film layer on the upper surface and the upper side surface and the W film layer that had reached the gap between the mask and the base material were finished to a thickness of 5 mm by mechanical polishing. As a result, there was no defect such as peeling or cracking of the three W film formation layers.
A joined body having an adhesion strength enough to withstand finish polishing was obtained.

As a result of observing the cross-section of the center and the center of the groove of the obtained joined body, no defects such as voids deteriorating the adhesion strength and the thermal conductivity were observed, and it was confirmed that the interface portion had good adhesion. confirmed. FIG. 1 shows a schematic sectional view of the obtained joined body.

Note that the film forming conditions in Example 1 are one example.
The film formation conditions are not limited to these. For example, the substrate temperature is 400 to 800 ° C., and the WF ₆ / H ₂ gas flow ratio is 1: 3 to
The range of 1: 7, the gas flow rate, the number of nozzles, and the nozzle diameter may be determined from the base material size, the set number, etc., that is, from the area required for film formation.

(Comparative Example 1) The above-described Example 1 was applied to an oxygen-free copper base material (□ 20 mm × thickness 30 mm) having no groove processing on the film forming surface.
In the same manner as described above, W was coated in sets of three per batch, and mechanical polishing was performed. As a result, although the upper surface could be polished after removing all three formed films, the protruding portion of the W film layer on the upper side surface was peeled off. In other words, it was confirmed that the W film layer on the upper side face had only an apparently close contact due to the holding effect of the protruding portion, and did not have sufficient adhesive strength to withstand the finish polishing.

Example 2 Trapezoidal grooves having a groove depth of 0.5 mm and a groove depth / groove width ratio of 1: 1 to 1: 5 shown in FIGS. 2A to 2C are arranged in the groove arrangement shown in FIG. Processed oxygen-free copper base material (□
50 mm x thickness 30 mm), as in Example 1 above,
After coating 5.4 mm at the thinnest point of W, finish polishing was performed. As a result, a bonded body was obtained which had no defects such as peeling and cracking of the three types of W film formation layers, and which had sufficient adhesion strength for finish polishing. Also,
No defects such as voids were observed by cross-sectional observation, and it was confirmed that the interface had good adhesion.

(Example 3) A trapezoidal groove having a groove depth of 0.5 mm and a groove depth / groove width ratio of 1: 1 to 1: 5 shown in FIGS. After etching a substrate made of pure Ni (□ 20 mm × thickness 30 mm) processed with dilute hydrochloric acid, ultrasonic cleaning was performed in the order of hot pure water and alcohol, and vacuum drying was performed. 5.3 at the thinnest point
After finish coating, finish polishing was performed. As a result, a bonded body was obtained which had no defects such as peeling or cracking of the three types of W film formation layers, and had sufficient adhesion strength to withstand finish polishing. In addition, no defects such as voids were observed by cross-sectional observation, and it was confirmed that the interface had good adhesion.

[0061]

As described above, according to the present invention,
It is possible to provide a high-temperature heat receiving body made of a joined body of a high melting point metal W and a dissimilar material having a large difference in thermal expansion coefficient such as Cu.

Further, according to the present invention, it is possible to provide a high-temperature heat receiving body comprising a joined body having excellent adhesion strength between different materials such as W and Cu or Ni having a large difference in thermal expansion coefficient.

Further, according to the present invention, it is possible to provide a high-temperature heat receiving body comprising a high-efficiency, high-adhesion thick-film joined body by forming a W thick film on a Cu base material by the CVD method.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a high-temperature heat receiving body according to an embodiment of the present invention.

2 (a), 2 (b) and 2 (c) are cross-sectional views showing various examples of the groove shape of the base material of the high-temperature heat receiving body of FIG.

FIG. 3A is a plan view showing an example of the arrangement of the base material in FIG. (B) is sectional drawing of the base material of (a).

FIG. 4A is a plan view showing another example of the groove arrangement of the base material in FIG. (B) is sectional drawing of the base material of (a).

[Explanation of symbols]

 1, 1a, 1b, 1c Processing groove 2, 2 'Base material 3 W film formation layer (thick film) 10 High temperature heat receiving body

Claims (6)

[Claims] 1. A high-temperature heat receiving body characterized in that a dense tungsten thick film is directly joined to at least a part of a base material having a larger thermal expansion coefficient than tungsten without an intermediate layer by a CVD method. 2. The high temperature heat receiver according to claim 1, wherein said tungsten thick film has a thickness of at least 1 mm. 3. The high-temperature heat receiving body according to claim 1, wherein said base material is substantially made of copper or a copper alloy. 4. The high-temperature heat receiving body according to claim 1, wherein a groove is formed on a bonding surface of said base material with said tungsten thick film. 5. The high-temperature heat receiving body according to claim 4, wherein a cross section of the groove formed by the groove processing of the base has a trapezoidal shape that opens outward. 6. The high-temperature heat receiving body according to claim 5, wherein the width of the opening of the groove having a trapezoidal cross section formed by processing the groove of the base material is equal to or greater than the depth of the groove. Heat receiver.