JPH0772352B2 - Chemical vapor deposition apparatus and chemical vapor deposition method - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to an aluminum (Al) coating on the inner surface of a hollow article, and more particularly to a chemical vapor deposition (hereinafter referred to as CVD) coating apparatus.

[Background of the Invention]

Al coatings improve the corrosion resistance of alloys containing, for example, Cr, Fe, Ni or Co as major constituents, and of Ni-based and Co-based superalloys used especially in high temperature environments such as gas turbine blades and nozzles. It is well known in the art to improve properties. Normal
In the Al pack coating method, the part to be coated with Al is a coating material (Al or Al compound), a carrier or an activator (usually an ammonium halide or an alkali metal halide), and an inert material such as Al ₂ O ₃ . It is embedded in a pack powder containing a filler. This member is embedded in such a packing powder, and 750 to 125
Although heated to 0 ° C., the thickness of the coating layer depends on the time and temperature of this heat treatment. In such an Al coating method, the halide is transferred from the Al source to the member.
Acts as a carrier or activator to facilitate the transfer of Al. Representative patent publications disclosing such a packing method include JP-A-55-82764, 55-82770, and 55-82764.
There are 115963 and 58-177456 publications.

When attempting to coat the internal passages using the packing method, in many cases very small internal passages must be filled with packing powder, and after processing such internal passages will remove residual packing powder. Faced with difficulties, because they have to be cleaned. Furthermore, such diffusion and penetration methods are affected by the ratio of pack powder to coating area. Therefore, the geometry of the inner member affects the coating layer thickness.

As a method of coating the internal passage, the gas phase coating method (Gas Ph
ase Deposition, hereinafter abbreviated as GPD method). There is an enclosure consisting of a lower chamber and an upper chamber which are connected to each other by a tube, and a coating material such as Al and NaAl is contained in the lower chamber.
Powdered in the form of F ₂ and filled with a mixed powder containing a catalyst, while the hollow part of the article to be coated is attached to the tube member in the upper chamber so that the hollow portion communicates with the tube. Then, the enclosure is placed in a furnace or other suitable heating device to heat the packing powder and the article to be coated, and the carrier gas introduced from one end in the lower chamber is vaporized from the packing powder through the tube. Are transported into the hollow part of the article, thereby coating the inner surface of the hollow article. The heating temperature is usually 982 ° to 1204 ° C. Representative patent publications disclosing such a GPD method include Japanese Patent Publication No. 59-19988 and US Pat. No. 4,148,275.

If the internal passages are coated by the GPD method, the treatment temperature is too high, which may impair the mechanical properties of the substrate or limit the heat treatment of the substrate. For example, in Ni-based superalloys, the precipitation aging temperature is around 850 ° C, and a lower coating treatment temperature is desired. The thickness of the coating layer depends on the treatment temperature and time, and if it is desired to increase the concentration of vaporized gas from the pack powder, the treatment temperature must be increased, and the treatment temperature should be adjusted considering the influence on the substrate. The lower the length, the longer the coating treatment time. Also, since this method is simply a method of sending the vaporized gas into the hollow portion of the article to be coated with a carrier gas such as Ar,
In the case of an article including a very small internal passage, there is a portion where the flow deteriorates depending on the location, which is disadvantageous in forming a uniform film thickness. Further
In the GPD method, the gas passes through the hollow article heated to a constant temperature, so if the internal passage becomes long, the concentration of the supplied gas is high at the gas inlet side and is exhausted as it goes to the outlet side. The concentration becomes higher. Therefore, the coating film layer is thick on the inlet side and tends to be thin toward the outlet side.
It becomes difficult to obtain a uniform film thickness.

Disproportionation reaction of trivalent aluminum halide (dispropo
The CVD method utilizing rtionation) is a known method, and a typical patent publication disclosing this method is Australian Patent No. 182024. According to this patent, a CVD method utilizing a disproportionation reaction is mainly disclosed based on an example in which the surface of a wire or the like is coated with Al. In addition, there is a patent publication which discloses the above-mentioned CVD method as a method for forming a thin film of a wiring material for an electric material by limiting it to a low temperature range, and its representative example is JP-B-59-48952. In any case, for example, as the main component, Cr, Fe, Ni or
There is no patent publication disclosing a device for rapid coating on the inner surface of a hollow article such as an alloy containing Co by a CVD method utilizing a disproportionation reaction, at a low temperature, with a uniform film thickness distribution, and the development of such a device. Was desired.

[Object of the Invention]

The object of the present invention utilizes the disproportionation reaction of halogen compounds.
An object of the present invention is to provide a device and a method for rapidly coating the inner surface of a hollow article having a complicated internal passage by a CVD coating method at a low temperature with a uniform film thickness.

[Outline of Invention]

Briefly describing the present invention, the present invention relates to a CVD apparatus, which is a gas shift chamber for producing a monovalent aluminum halide by a reaction between a trivalent aluminum halide and a metal Al under a pressure below atmospheric pressure. And a CVD reaction in which the monovalent aluminum halide is decomposed into trivalent aluminum halide and metallic Al, and the metallic Al is deposited on the inner surface of a hollow article kept in a temperature range of 1000 ° C. or lower and simultaneously diffused and permeated. In a CVD apparatus including a chamber, the chambers are independent of each other, the hollow portion of the article is arranged to communicate with the gas shift chamber by a tube member, and the chambers are independent of each other. It is characterized in that temperature control equipment is provided.

The present invention is also an invention relating to a method for coating a hollow article with aluminum, which comprises a gas conversion step of producing monovalent aluminum halide by the reaction of trivalent aluminum halide and metal Al under a pressure of atmospheric pressure or less, A step of decomposing the monovalent aluminum halide into trivalent aluminum halide and metal Al, and 800 to 1000
It is characterized in that it includes a chemical vapor deposition reaction step of depositing on the inner surface of the hollow article kept at a high temperature of ° C, and at the same time diffusing and permeating.

The reaction formula in the disproportionation reaction of a halogen compound is shown in the following formula (1).

AlX ₃ + 2Al3AlX (1) (where AlX ₃ is trivalent aluminum halide and AlX is monovalent aluminum halide) Hereinafter, the case where X = Cl will be described. For example, if aluminum chloride (AlCl ₃ ) and metallic Al are used as the raw materials for the inner surface coating of hollow articles, in the reaction between Al and AlCl ₃ , the disproportionation reaction shown in the formula (1) proceeds to the right is an endothermic reaction. Since it is a reaction, AlCl is actively produced at high temperature and reduced pressure.

On the other hand, in the low temperature region, the reaction proceeds to the left side, AlCl releases Al, and AlCl ₃ becomes a stable state, so the released Al forms a film on the inner surface of the hollow article.

In order to efficiently form a film without mixing AlX made by the reaction in the right direction and AlX ₃ made by the reaction in the left direction here,
A gas conversion chamber that reacts the source gas AlX ₃ with metallic Al,
AlCl releases Al due to the reverse reaction of equation (1), and stable AlCl
_It was isolated and sealed from the CVD reaction chamber ( ₃ ).

In the equation (1), the reaction in the right direction is performed at a high temperature, and the reaction in the left direction is performed at a low temperature. Therefore, a dedicated heat source separate from the CVD reaction chamber is used for the gas shift chamber where AlX is formed. I was there. The above is the main point of the device of the present invention.

Further, in the device of the present invention, it is preferable to provide the following facilities.

Since the Al precipitation reaction is carried out at a low temperature, and in the inner surface coating of the hollow article having a relatively long internal passage, AlX is thick on the inlet side, AlX is small on the contrary on the outlet side, and AlX _{3 in} the exhaust gas is large. Along the passage of this hollow article, there is a structure in which there is a temperature gradient in the longitudinal direction, and a gas collection port is provided in the hollow article near the gas outlet side, and a structure for exhausting with a pump is provided. The gas flow is controlled to make the film thickness distribution in the internal passage uniform.

Next, CVD using such disproportionation reaction of halogen compounds
However, if the tube that connects the gas shift chamber and the CVD reaction chamber that performs Al precipitation is too long, AlX formed at high temperature may return to AlX ₃ in the middle tube, so both chambers may They are placed close to each other in a vertical positional relationship, and the gas shift chamber has a large chamber volume to increase the amount of AlX produced, and the produced AlX is transported uniformly to the CVD reaction chamber quickly with a short tube length. In order to achieve this, the hollow article and / or the support base of the article is structured to have a ring-shaped chamber on the same normal line. Although it is easy to obtain the film thickness distribution, when the hollow article becomes a return flow type, some ingenuity is required to provide a temperature gradient along the internal passage. For example, (i) If electricity is applied to the hollow article itself and an electric heating method is used, a desired temperature gradient can be provided by increasing the number of electrodes or controlling the cross-sectional wall thickness of the hollow article. For example, if the temperature can be easily detected over the entire length of the tube, it is possible to control the electric current flow with a minicomputer or the like.

(Ii) In addition, if there are many articles to be coated, it is possible to create a dedicated heating element that matches the shape. In any case of (i) and (ii), it is not technically difficult to form a temperature gradient along the internal passage.

Hereinafter, the device of the present invention will be specifically described with reference to the drawings.

FIG. 1 is a sectional view of an example of the device of the present invention.

Gas controller 1 apparatus shown in Figure 1 is to control Kiyariagasu Ar or H ₂ flow, container 2 of AlCl ₃ to gasification, melting Al @ 3, AlCl ₃ and is reacted Al gas shift chamber 4 to create AlCl, Hollow article 5 to be coated,
Support 6 for supporting hollow articles, exhaust gas collection port 7, vacuum pump 8, electric furnace 9 for gas shift chamber, multi-stage electric furnace 10, matsufuru 11, CVD reaction chamber 12, gas shift chamber and communication between hollow article inner surface And a tube 13 that

Conventionally melted Al at high temperature (H) inside a horizontal quartz tube
The sample to be coated is placed in the low temperature part (L), the source gas AlCl ₃ is transported by the carrier gas from one end on the H side of the quartz tube, and the molten Al is melted in the high temperature part.
Was reacted with to form AlCl, and this gas was introduced onto the sample in the low temperature portion to precipitate Al. In this method, the source and exhaust gas AlCl ₃ and the CVD reaction gas AlCl are mixed,
I couldn't do efficient CVD. In the present invention, the gas shift chamber is
This defect was ameliorated by separating and sealing from the VD reaction chamber. The temperature of the gas shift chamber was controlled separately from that of the CVD reaction chamber, and the CVD reaction chamber was heated and controlled by a multi-stage electric furnace to provide a temperature gradient in the longitudinal direction of the article to be coated. In addition, a gas collection port was provided near the exhaust gas outlet of the hollow article, and the gas was exhausted by a vacuum pump to control the gas flow in the hollow article. This made the coating film thickness distribution uniform.

Example of Invention

Hereinafter, the present invention will be described in more detail with reference to Examples.
The present invention is not limited to this.

Example 1 FIG. 2 shows an example of the film thickness distribution in the case of coating using the apparatus shown in FIG. That is, Fig. 2 shows the distribution of the Al coating film thickness (deposition plus diffusion layer) on the cross section of the tube when the tube length of the hollow article is about 90 to 150 mm, the distance from the gas inlet (mm, horizontal axis) and the film thickness (μm) and Pipe temperature (℃)
It is a graph shown in relation to (vertical axis).

Carrier gas Ar was used on the inner surface of the Ni-Cr alloy tube with an inner diameter of about 5 mmφ, and gasified AlCl ₃ was sent to the gas shift chamber heated to 1000 ° C, and the sample temperature was changed to 840 to 930 ° C and the inner surface of the tube was changed.
Al was CVD-deposited and simultaneously diffused and permeated. Evacuation was done with a rotary pump and kept at 10 torr in the CVD reaction chamber. As a result, the coating thickness (deposition plus diffusion layer) is 60 tubes long.
In mm, it was in the range of 10 ± 1 μm. The temperature gradient is low in the gas upstream and high in the gas downstream.

〔The invention's effect〕

As described above, according to the present invention, a uniform film thickness distribution can be obtained even in a relatively long internal passage. Then, by expanding the gas shift chamber and increasing the number of tubes that communicate the gas shift chamber with the hollow articles, the inner surfaces of many hollow articles are coated at one time without impairing the uniform film thickness distribution. can do. Moreover, the utilization efficiency of AlX, which is a CVD reaction gas, is increased, and the remarkable effect that the CVD rate is increased can be achieved.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an example of the device of the present invention, and FIG. 2 is a hollow article having a tube length of about 90 to 150 mm, which is formed by the device shown in FIG.
The distribution of the Al coating thickness of the cross section of the pipe when VD is performed,
6 is a graph showing a relationship between a flow direction of a reaction gas and a temperature gradient of a tube. 1: Gas controller, 2: AlCl ₃ container, 3: Al, 4: Gas shift chamber, 5: Hollow article, 6: Support base, 7: Exhaust gas collection port, 8: Vacuum pump, 9: Electric furnace, 10: Multi-stage electric furnace, 11: Matsufuru, 12: C
VD reaction chamber, 13: tube

Claims (8)

[Claims] 1. A gas shift chamber for producing monovalent aluminum halide by the reaction of trivalent aluminum halide and metallic aluminum under a pressure below atmospheric pressure, and the monovalent aluminum halide is converted into trivalent aluminum halide. Decomposes into aluminum halide and metallic aluminum.
In a chemical vapor deposition apparatus including a chemical vapor deposition reaction chamber which is deposited on the inner surface of a hollow article held in a temperature range of 00 ° C. or lower and simultaneously diffuses and permeates, both chambers are independent, and the hollow portion of the article is A chemical vapor deposition device, which is arranged so as to communicate with a gas shift chamber by a tube member, and both chambers are provided with independent temperature control equipment. 2. The chemical vapor deposition apparatus according to claim 1, wherein the temperature control equipment in the chemical vapor deposition reaction chamber is equipment capable of fine temperature control along the longitudinal direction of the article. 3. The chemical vapor deposition apparatus according to claim 1, wherein the chemical vapor deposition reaction chamber is provided with a reduced pressure exhaust gas collecting facility. 4. The chemical vapor deposition apparatus according to claim 1, wherein the two chambers have a vertical positional relationship. 5. The chemical vapor deposition apparatus according to claim 4, wherein the hollow article is above the gas shift chamber. 6. The chemical vapor deposition apparatus according to claim 4, wherein the hollow article is below the gas shift chamber. 7. The gas shift chamber is a chamber having a ring-shaped structure which is arranged on the same normal line as the hollow article and / or the hollow article support base, and the gas shift chamber has a ring-shaped structure. The chemical vapor deposition apparatus described. 8. A gas conversion step for producing monovalent aluminum halide by the reaction of trivalent aluminum halide and metallic aluminum under a pressure of atmospheric pressure or less, wherein the monovalent aluminum halide is trivalent halogen. Hollow article characterized by including a step of decomposing into aluminum oxide and metallic aluminum, and a chemical vapor deposition reaction step of precipitating the metallic aluminum on the inner surface of the hollow article held at a high temperature of 800 to 1000 ° C. and simultaneously diffusing and permeating it. Aluminum coating method.