JP5104575B2 - Aluminum coating method and apparatus - Google Patents

Description

  The present invention relates to an aluminum coating method and apparatus for use in jet engine turbine blades, vehicle supercharger turbine blades, and the like.

  Turbines used in jet engines and superchargers for vehicles tend to have higher inlet temperatures due to higher efficiency and higher output. For this reason, turbine blades are required to have high heat resistance that can withstand harsh environments, corrosion resistance to combustion gases, and oxidation resistance.

  For turbine blades, nickel-based or cobalt-based heat-resistant superalloys are generally used, but there is a limit to cope with harsh environments using only these base materials, and high temperature corrosion resistant materials such as alumina are coated. Has been implemented.

  In the case of coating alumina, it is common to first coat the turbine blade substrate with aluminum and then oxidize the aluminum coating to obtain alumina.

  Conventionally, as a method of coating the turbine blades with aluminum, for example, a powder pack (Pack Management) or a VPA (Vapor Phase Aluminizing) can be cited.

In the aluminum coating method using a powder pack, as shown in FIG. 8, first, a mixed powder in which an aluminum alloy powder, a halogen compound (eg, AlF ₃ , NH ₄ Cl, etc.), and a sintering inhibitor are mixed in a heating furnace 81. 82 is accommodated, and a coated member 83 such as a turbine blade is embedded in the mixed powder.

Thereafter, the aluminum alloy of the mixed powder 82 and the halogen compound are reacted at a high temperature to produce aluminum halide (for example, AlF _x , AlCl _x ), and aluminum is formed on the surface of the coated member 83 by gas diffusion of the aluminum halide. In addition, the aluminum halide is reduced on the surface of the coated member 83 to precipitate aluminum, and the deposited aluminum and the elements of the coated member 83 are interdiffused to form an Al alloy layer. ing.

On the other hand, in the aluminum coating method by VPA, as shown in FIG. 9, a granular (or powder or lump) metal aluminum-containing alloy 92 (for example, CrAl, FeAl, TiAl, etc.) is accommodated in a heating furnace 91. An activator (halogen compounds: NH ₄ Cl, NH ₄ F, NaCl, etc.) and a sintering inhibitor (alumina, kaolin, etc.) are added to the metal aluminum-containing alloy 92 and heated in a heating furnace 91.

  As a result, the metal-aluminum-containing alloy 92 is decomposed to produce aluminum halide, and an aluminum coating film is formed on the surface of the member to be coated 93 in the same manner as the powder pack method.

  As another aluminum coating method, there is a method of performing aluminum coating by flowing an aluminum-based carry gas over the surface of a turbine blade by a chemical process such as CVD (Chemical Vapor Deposition) (for example, Patent Document 1).

JP 09-195049 A Japanese Patent Laid-Open No. 08-225958 JP 2002-155380 A

  However, conventional aluminum coating methods such as powder packs and VPA have the problem that the used aluminum alloy becomes industrial waste, and further, because fluoride (halogen compound) is used as an activator. There are also safety issues.

  In the conventional aluminum coating method, an aluminum alloy is decomposed to produce aluminum halide, and the aluminum halide is reduced and coated. In addition, there is a problem that it is difficult to control the film thickness and state of the coating.

  Furthermore, after aluminum is removed from the aluminum alloy surface layer, which is an aluminum gas supply source, the coating ability will drop, the metal residue contained in the aluminum alloy will remain in the coating, and the aluminum When powder is used as an alloy, there is also a problem that particles are easily seized during the reaction (fused with aluminum).

  In addition, the aluminum coating method by CVD increases the equipment cost due to the complicated structure of the apparatus, and further increases the product price because the kind of aluminum carry gas is limited and an expensive one must be used. There is a problem.

  Therefore, the object of the present invention is to solve the above-mentioned problems, industrial waste does not occur, coating film thickness and change in state is small, coating capacity deterioration with time, adhesion between particles, metal residue, etc. An object of the present invention is to provide an aluminum coating method and apparatus capable of solving workability problems caused by a metal which is an aluminum generation source.

  The present invention has been devised to achieve the above object, and the invention of claim 1 is an aluminum coating method for coating aluminum on the surface of a member to be coated in a vacuum, and in contact with carbon in the vacuum. In this state, the alumina is heated to 1300 ° C. or higher to decompose the alumina, and the generated aluminum gas is coated on the surface of the member to be coated.

The invention of claim 2, wherein the carbon is a carbon heater, the alumina was disposed on the carbon heater, an aluminum coating process according to claim 1, wherein heating the alumina at the carbon heater.

A third aspect of the present invention is the aluminum coating method according to the first or second aspect, wherein the vacuum pressure is 10 ⁻⁴ Pa or less .

  According to a fourth aspect of the present invention, there is provided an aluminum coating apparatus for coating aluminum on a surface of a member to be coated in a vacuum furnace, wherein the vacuum coating furnace is in contact with carbon and an aluminum coating portion for housing the member to be coated. This is an aluminum coating apparatus provided with an aluminum gas generator for heating the alumina.

  According to a fifth aspect of the present invention, the heating chamber for accommodating the aluminum coating portion is formed in the vacuum furnace, and the strong heating portion for accommodating the aluminum gas generating portion is formed in the heating chamber. It is an aluminum coating device.

  According to a sixth aspect of the present invention, a heating chamber for accommodating the aluminum coating portion is formed in the vacuum furnace, and a strong heating chamber for accommodating the aluminum gas generation portion is formed, and the coating portion is downstream of the vacuum exhaust. The aluminum coating apparatus according to claim 4, wherein a flow path is formed between the heating chambers so that the aluminum gas generating portion is upstream of the vacuum exhaust.

  The invention according to claim 7 is the aluminum coating apparatus according to claim 6, wherein a preliminary exhaust chamber for taking the member to be coated in and out of the heating chamber in the vacuum furnace is connected to the vacuum furnace via a gate valve.

  According to the present invention, alumina is heated to be decomposed into aluminum gas and oxygen, and the coated member is coated with the aluminum gas, so that no industrial waste is generated during coating, and the coating thickness and state change. In addition, it is possible to solve workability problems caused by the metal that is the source of aluminum, such as deterioration of coating ability over time, fusion of particles, metal residue, etc., improving quality stability and workability. Can be improved.

  Preferred embodiments of the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 is a schematic cross-sectional view of an aluminum coating apparatus according to this embodiment.

As shown in FIG. 1, an aluminum coating apparatus 1 is for coating aluminum on the surface of a member to be coated 3 in a vacuum furnace 2, and an aluminum coating that accommodates the member to be coated 3 in the vacuum furnace 2. A heating chamber 7 composed of a part 4 is provided, and a strong heating part 8 composed of an aluminum gas generation unit 6 that heats alumina (Al ₂ O ₃ ) 5 in contact with carbon is provided below the heating chamber 7. Is. The heating chamber 7 is provided with a heater (not shown) for heating the inside of the heating chamber 7.

  The member 3 to be coated is a base material (such as a nickel-base superalloy or a cobalt-base superalloy) such as a jet engine turbine blade or a supercharger turbine blade for a vehicle.

  The aluminum gas generator 6 is configured by arranging alumina 5 on a carbon heater 9. In the present embodiment, a plate-shaped carbon heater 9 is used, and the alumina 5 made of a cylindrical sintered body is disposed on the carbon heater 9. For example, α-alumina (corundum type) may be used as the alumina 5.

An exhaust port 10 is provided in the upper part of the vacuum furnace 2, and a vacuum pump or the like (not shown) for reducing the vacuum furnace 2 to a vacuum degree of 10 ⁻⁴ Pa or higher is connected to the exhaust port 10. The

  Next, an aluminum coating method according to this embodiment will be described.

  First, the member 3 to be coated is set in the heating chamber 7 of the vacuum furnace 2 and the alumina 5 is disposed on the carbon heater 9 so that the carbon heater 9 and the alumina 5 are brought into contact with each other.

Thereafter, the inside of the vacuum furnace 2 is reduced to a vacuum degree of 10 ⁻⁴ Pa or more by a vacuum pump or the like, the alumina 5 is heated by a heater and a carbon heater 9 (not shown), and the strong heating unit 8 (or the entire heating chamber 7) is heated. The temperature is set to 1300 ° C. or higher, preferably 1300 to 1400 ° C.

When the degree of vacuum in the heating chamber 7 is 10 ⁻⁴ Pa or more and the temperature is 1300 ° C. or more, the alumina 5 is reduced by the carbon of the carbon heater 9 and the alumina 5 is decomposed into aluminum gas and oxygen.

  The generated aluminum gas diffuses into the heating chamber 7, contacts the member to be coated 3 set in the heating chamber 7, and interdiffuses with the elements constituting the member to be coated 3, thereby forming a coating layer. .

  The oxygen generated by the decomposition of the alumina 5 reacts with the carbon of the carbon heater 9 to become carbon monoxide or carbon dioxide, or is discharged as it is from the exhaust port 10 as oxygen.

  In other words, in this embodiment, the alumina 5 is decomposed into aluminum gas and oxygen, the aluminum gas is used for coating, and oxygen is discharged as carbon monoxide, carbon dioxide, or oxygen. Therefore, an ideal process that does not generate industrial waste. It becomes.

  The time for performing the aluminum coating is 1 to 10 hours, preferably about 4 hours.

  After the completion of the aluminum coating, the obtained coated member is subjected to a firing treatment to oxidize the aluminum in the coating layer, whereby an alumina-coated product is obtained.

  Here, the decomposition reaction of alumina will be described in detail.

  FIG. 2 shows a phase diagram (vapor pressure) of temperature and pressure of alumina.

As shown in FIG. 2, alumina decomposes into aluminum gas and oxygen at a temperature of 1600 ° C. when the degree of vacuum is 10 ⁻⁴ Pa. Under normal pressure, a temperature of 2000 ° C. or higher is required to decompose alumina.

  Alumina does not contain any metal other than aluminum like aluminum alloy, so it solves workability problems caused by the metal that is the source of aluminum, such as deterioration of coating ability over time, fusion of particles, metal residue, etc. This is a promising source of aluminum gas.

  However, if the temperature in the heating chamber 7 is set to a high temperature of 1600 ° C. or higher in order to decompose alumina, it is difficult to use alumina as an aluminum gas generation source because the coated member 3 is affected by the high temperature. Although the decomposition temperature of alumina can be lowered by further increasing the degree of vacuum, if the degree of vacuum is increased, it takes time to reduce the pressure with a vacuum pump or the like, resulting in a problem that productivity is lowered.

Therefore, the present inventors have intensively studied the possibility of using alumina as an aluminum gas generation source. As a result, by bringing alumina into contact with carbon, the degree of vacuum is 10 ⁻⁴ Pa or higher and 1300 ° C. or higher. It has been found that alumina can be decomposed into aluminum gas and oxygen (Al ₂ O ₃ → 2Al ↑ + 3 / 2O ₂ ↑).

That is, when the degree of vacuum is 10 ⁻⁴ Pa or higher and the temperature is 1300 ° C. or higher in a state where alumina and carbon are in contact with each other, the alumina is reduced by carbon and aluminum gas can be generated.

  FIG. 3A shows the result of measuring the partial pressure of each component when the heat treatment is performed in a state where alumina and carbon are brought into contact (at the time of aluminum coating) with a simple partial pressure measuring device (mass spectrometer). For comparison, FIG. 3B shows the partial pressure of each component when heat treatment is performed without contacting alumina and carbon under the same conditions.

  Comparing FIG. 3 (a) and FIG. 3 (b), in FIG. 3 (a) according to the present invention, the partial pressure of aluminum is about one digit higher than that in FIG. 3 (b). It can be seen that the partial pressure of carbon oxide is also increased. This is probably because alumina is reduced by carbon to generate aluminum gas, and oxygen generated by decomposition of alumina further reacts with carbon to generate carbon monoxide.

  Furthermore, the change in Al-based vapor pressure at 1300 ° C. was determined by thermodynamic calculation. The calculation results are shown in FIG.

  As shown in FIG. 4, it can be seen that when alumina and carbon coexist (contact) at 1300 ° C., the vapor pressure of aluminum (Al) occupies most at a total pressure of 1 Pa or less.

  Moreover, the optical microscope photograph of the to-be-coated member 3 cross section coated with the aluminum by the aluminum coating apparatus 1 is shown in FIG.

  As shown in FIG. 5, an outer diffusion layer 52 in which an element constituting the member to be coated 3 is diffused is formed on the inner side of the coating layer 51, and the inner side of the original surface S of the member to be coated 3 is formed. It can be seen that the inner diffusion layer 53 is formed by diffusing the aluminum of the coating layer 51. That is, the coated aluminum and the elements constituting the member to be coated 3 are interdiffused to form an aluminum alloy. In FIG. 5, 54 is an embedding resin.

  The thickness and state of the formed coating layer 51 were constant, and there was no metal residue as in the case where an aluminum alloy was used as the aluminum gas generation source.

  As described above, in the aluminum coating method according to the present embodiment, the alumina 5 is decomposed by heating the alumina 5 to 1300 ° C. or higher in the vacuum furnace 2 in contact with the carbon, and the generated aluminum gas. Is coated on the surface of the member 3 to be coated.

  Alumina 5 is decomposed into aluminum gas and oxygen, and the generated aluminum gas is used for coating. Oxygen reacts with carbon and is discharged as carbon monoxide, carbon dioxide, or oxygen as it is. Things do not occur.

  In addition, the present embodiment does not include a complicated process of generating an aluminum halide from an aluminum alloy and reducing the aluminum halide to form a coating layer as in the conventional method. The state can be easily controlled, and changes in coating thickness and state can be reduced.

  Further, since alumina 5 does not contain any metal other than aluminum like the aluminum alloy that has been used as an aluminum gas generation source in the past, it is an aluminum generation source such as coating capacity deterioration with time, adhesion between particles, metal residue, etc. There is no workability problem caused by a certain metal, and quality stability and workability can be greatly improved.

  Next, another embodiment of the present invention will be described.

  As shown in FIG. 6, the aluminum coating apparatus 61 forms a heating chamber 63 that accommodates the aluminum coating portion 4 in the vacuum furnace 62 and also forms a strong heating chamber 64 that accommodates the aluminum gas generation portion 6, and heats it. A flow path 65 is formed between the chamber 63 and the strong heating chamber 64.

  In the aluminum coating apparatus 61, the aluminum gas generated in the aluminum gas generating section 6 of the strong heating chamber 64 is sucked by a vacuum pump or the like (not shown) connected to an exhaust port 66 provided in the vacuum furnace 62. Is moved to the heating chamber 63 side through the flow path 65 and brought into contact with the member to be coated 3 to perform aluminum coating.

  The aluminum coating apparatus 61 is complicated compared to the aluminum coating apparatus 1 of FIG. 1, but the heating chamber 63 in which the member to be coated 3 is arranged and the strong heating chamber 64 in which the alumina 5 is heated are separated. The temperature of the heating chamber 63 can be set separately from the temperature of the strong heating chamber 64, and the temperature (coating temperature) of the heating chamber 63 can be controlled more precisely.

  The aluminum coating apparatus 71 shown in FIG. 7 is the same as the aluminum coating apparatus 61 shown in FIG. 6 except that the first preliminary exhaust chamber 72 and the second preliminary exhaust chamber 72 are provided in the vacuum furnace 62 and the heating chamber 63 in the vacuum furnace 62. The preliminary exhaust chamber 73 is connected through gate valves 74 and 75. A gate valve 76 is provided in the flow path 65 between the heating chamber 63 and the strong heating chamber 64 in order to control the coating time.

  When aluminum coating is performed by the aluminum coating apparatus 71, first, the inside of the vacuum furnace 2 is depressurized, and the alumina 5 is heated by the carbon heater 9 to generate aluminum gas.

  Thereafter, the member to be coated 3 is set in the first preliminary exhaust chamber 72, and the inside of the first preliminary exhaust chamber 72 is depressurized to the same degree of vacuum as the vacuum furnace 2.

  After depressurizing the inside of the first preliminary exhaust chamber 72, the gate valve 74 is opened to move the member to be coated 3 into the heating chamber 63, the gate valve 74 is closed, and the coated member 3 is coated with aluminum.

  In parallel with the aluminum coating, the member 3 to be coated is set in the second preliminary exhaust chamber 73, and the inside of the second preliminary exhaust chamber 73 is decompressed to the same degree of vacuum as the vacuum furnace 2.

  After aluminum coating with a predetermined film thickness is performed, the gate valve 74 is opened to move the aluminum-coated member 3 to be moved to the first preliminary exhaust chamber 72, the gate valve 74 is closed, and the first preliminary exhaust chamber 72 is closed. The coated member 3 is taken out from

  At the same time, the gate valve 75 is opened to move the member to be coated 3 from the second preliminary exhaust chamber 73 into the heating chamber 63, the gate valve 75 is closed, and the coated member 3 is coated with aluminum.

  By repeating this, the coated member 3 is continuously coated with aluminum.

  According to the aluminum coating apparatus 71, time for evacuation (decompression) can be saved, and aluminum coating can be performed continuously on the member to be coated 3, so that the processing capacity (productivity) can be improved. .

  Although the case where the coated member 3 set in the first preliminary exhaust chamber 72 is taken out from the first preliminary exhaust chamber 72 after coating has been described here, for example, the first preliminary exhaust chamber 72 is used as the coated member insertion port, The two preliminary exhaust chambers 73 may be used as the coated member outlet.

  In addition, this invention is not limited to these embodiment, It cannot be overemphasized that other various embodiment is assumed.

It is a schematic sectional drawing of the aluminum coating apparatus of this invention. It is a state diagram of temperature and pressure of alumina. FIG. 3 (a) is a diagram showing the partial pressure of each component during the aluminum coating of the present invention, and FIG. 3 (b) is a diagram showing the partial pressure of each component when heat-treated without contacting alumina and carbon. It is. In this invention, it is a figure which shows the change of Al type vapor pressure in 1300 degreeC. 2 is an electron micrograph of a cross-section of a member to be coated that has been aluminum-coated by the aluminum coating apparatus of FIG. It is a schematic sectional drawing of the aluminum coating apparatus which concerns on other embodiment of this invention. It is a schematic sectional drawing of the aluminum coating apparatus which concerns on other embodiment of this invention. It is a schematic sectional drawing of the conventional aluminum coating apparatus. It is a schematic sectional drawing of the conventional aluminum coating apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Aluminum coating apparatus 2 Vacuum furnace 3 Coated member 5 Alumina 9 Carbon heater

Claims (7)

  In the aluminum coating method of coating aluminum on the surface of the member to be coated in a vacuum, the alumina is decomposed by heating the alumina to 1300 ° C. or higher in the vacuum while being in contact with carbon, and the generated aluminum gas is An aluminum coating method comprising coating the surface of the member to be coated. The carbon is a carbon heater;
The alumina was disposed on the carbon heater, aluminum coating method according to claim 1, wherein heating the alumina at the carbon heater. The aluminum coating method according to claim 1 or 2, wherein the vacuum pressure is 10 ^-4 Pa or less .   In an aluminum coating apparatus that coats aluminum on the surface of a member to be coated in a vacuum furnace, an aluminum gas that heats alumina in a state where it is in contact with carbon, and an aluminum coating portion that houses the member to be coated in the vacuum furnace An aluminum coating apparatus comprising a generator.   The aluminum coating apparatus according to claim 4, wherein a heating chamber that accommodates the aluminum coating portion is formed in the vacuum furnace, and a strong heating portion that accommodates the aluminum gas generation portion is formed in the heating chamber.   A heating chamber for accommodating the aluminum coating portion is formed in the vacuum furnace, and a strong heating chamber for accommodating the aluminum gas generation portion is formed, and a flow path is provided between the heating chamber and the strong heating chamber. The aluminum coating apparatus according to claim 4 formed.   The aluminum coating apparatus according to claim 6, wherein a preliminary exhaust chamber for inserting and removing the member to be coated into and out of the heating chamber in the vacuum furnace is connected to the vacuum furnace via a gate valve.

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