WO2017017708A1

WO2017017708A1 - Method for producing cobalt-base alloy member

Info

Publication number: WO2017017708A1
Application number: PCT/JP2015/003741
Authority: WO
Inventors: 日野　武久; 今井　潔; 聡宮代; 斎藤　大蔵; 歴高久; 秀幸前田; 岩太郎佐藤; 国彦和田; 高橋　武雄
Original assignee: 株式会社東芝
Priority date: 2015-07-27
Filing date: 2015-07-27
Publication date: 2017-02-02
Also published as: JPWO2017017708A1

Abstract

Provided is a cobalt-base alloy member having improved oxidation resistance at high temperature. This method for producing a cobalt-base alloy member includes a step for preparing a cobalt-base alloy on which an aluminizing treatment has been performed, and a step for performing, at a degree of vacuum of 1×10^-5-1×10^-3 Pa, a heat treatment on the cobalt-base alloy on which the aluminizing treatment has been performed.

Description

Cobalt-based alloy member manufacturing method

Embodiment of this invention is related with the manufacturing method of a cobalt base alloy member.

In gas turbines, the combustion gas is being heated to improve its performance. For example, the temperature of the combustion gas near the inlet of the stationary blade was about 1100 ° C. in the 1990s, but is about 1300 to 1500 ° C. in the 2000s.

In recent years, development of a CO ₂ turbine having a higher temperature than that of a conventional gas turbine has been promoted. The CO ₂ turbine uses supercritical carbon dioxide as a medium. The CO ₂ turbine has excellent environmental characteristics because it can effectively use carbon dioxide from combustion and also suppresses emission of nitrogen oxides.

Conventionally, cobalt base alloys have been used for stationary blades in gas turbines for the following reasons. That is, since a stationary blade in a gas turbine is a stationary member, higher strength is not necessarily required compared to a rotating member such as a moving blade. On the other hand, the cobalt-based alloy is not necessarily high in strength as compared with a nickel-based alloy or the like, but is easy to repair because of its good weldability, and the price is low. For these reasons, a cobalt-based alloy is used for a stationary blade in a gas turbine.

Cobalt-based alloys usually contain chromium. When a cobalt-based alloy is used for a stationary blade in a gas turbine, chromium contained in the cobalt-based alloy is oxidized to chromium oxide (Cr ₂ O ₃ ). By forming such chromium oxide as a protective film on the surface of the stationary blade, the oxidation resistance of the stationary blade at high temperature is ensured.

However, it is expected that the surface temperature of the stationary blade exceeds 1000 ° C. due to the high temperature of the combustion gas in the gas turbine. In particular, in the CO ₂ turbine, the combustion gas is heated to a higher temperature than the conventional gas turbine, and the surface temperature of the stationary blade is expected to exceed 1000 ° C.

It is known that chromium oxide is sublimated as CrO _{3 at} about 1000 ° C. For this reason, there has been a problem in adopting a method for ensuring oxidation resistance by forming chromium oxide on the surface of a stationary blade whose surface temperature exceeds 1000 ° C.

International Publication No. 2013/061945 JP 2001-032061 A

Aluminizing treatment is known as a method for improving oxidation resistance at high temperatures. However, when the aluminizing treatment was performed on the cobalt-based alloy, the oxidation resistance was lowered at a high temperature exceeding 1000 ° C. as compared with the case where the aluminizing treatment was not performed.

The problem to be solved by the present invention is to provide a cobalt-based alloy member having improved oxidation resistance at high temperatures.

Method for producing a cobalt-based alloy of embodiment, a step of preparing a aluminizing is performed cobalt-based alloy, to the aluminizing is performed cobalt-based alloy, 1 × 10 -5 ^Pa ~ Heat treatment at a vacuum degree of 1 × 10 ⁻³ Pa.

According to the method for producing a cobalt-based alloy member of the embodiment, by performing a heat treatment at a vacuum degree of 1 × 10 ⁻⁵ Pa to 1 × 10 ⁻³ Pa on the cobalt-based alloy subjected to the aluminizing treatment, The oxidation resistance can be improved by increasing the content of aluminum oxide in the protective film.

It is sectional drawing which shows the to-be-processed object of embodiment. It is sectional drawing which shows the cobalt base alloy member of embodiment. It is a block diagram which shows the heat processing apparatus of embodiment. It is a procedure figure showing the heat treatment method of an embodiment. It is a lineblock diagram showing the power generation system of an embodiment. It is a sectional view showing a CO ₂ turbine embodiment.

Hereinafter, modes for carrying out the present invention will be described.
The method for producing a cobalt-based alloy member according to the embodiment includes a step of heat-treating a cobalt-based alloy that has undergone aluminizing treatment at a vacuum degree of 1 × 10 ⁻⁵ to 1 × 10 ⁻³ Pa (hereinafter referred to as heat treatment). Step).

The reason why the oxidation resistance is improved by the heat treatment is considered as follows.
When the aluminizing process is performed on the cobalt-based alloy, an aluminizing layer is formed on the surface of the main body made of the cobalt-based alloy. Usually, the aluminum concentration in the aluminizing layer is 30 mass% or more higher than that of the main body. When the concentration difference is large as described above, aluminum in the aluminizing layer is likely to diffuse to the main body side when exposed to a high-temperature oxidizing atmosphere.

If the heat treatment is performed after the aluminizing treatment, the concentration of aluminum in the aluminizing layer decreases. The decrease in concentration is achieved, for example, by increasing the thickness of the aluminizing layer. When the aluminum concentration in the aluminizing layer is lowered, the aluminum in the aluminizing layer is likely to diffuse to the surface side (the side opposite to the main body side) when the high-temperature oxidizing atmosphere is touched. Thereby, the content rate of the aluminum oxide in the protective film formed in the surface of an aluminizing layer becomes high, and oxidation resistance improves.

Further, when the degree of vacuum during heat treatment is 1 × 10 ⁻⁵ Pa to 1 × 10 ⁻³ Pa, metal oxides other than aluminum oxide are decomposed and decomposition of aluminum oxide is suppressed. Thereby, the content rate of the aluminum oxide in the protective film formed in the surface of an aluminizing layer becomes high, and oxidation resistance improves.

Hereinafter, the heat treatment process will be specifically described.

FIG. 1 is a cross-sectional view showing a cobalt-based alloy subjected to an aluminizing process used in a heat treatment process. Hereinafter, the cobalt-based alloy that has been subjected to the aluminizing process will be described as an object to be processed.

The object to be processed 1 is formed by, for example, a main body 2 made of a cobalt base alloy and the surface of the main body 2, and aluminum is diffused into the cobalt base alloy. And an aluminizing layer 3 having a high rate. In the aluminizing layer 3, for example, a constituent element of a cobalt base alloy and aluminum diffused in the cobalt base alloy react to form an intermetallic compound. Such a to-be-processed object 1 can be manufactured by performing an aluminizing process with respect to a cobalt base alloy.

The cobalt-based alloy used for the manufacture of the object 1 has a high cobalt content compared to other constituent elements in mass. The cobalt content in the cobalt-based alloy is preferably 30% by mass or more, and more preferably 35% by mass or more. Moreover, 70 mass% or less is preferable in a cobalt base alloy, and, as for content of cobalt, 65 mass% or less is more preferable.

The cobalt-based alloy preferably contains chromium. The content of chromium is preferably 10% by mass or more, and more preferably 15% by mass or more in the cobalt-based alloy. Further, the content of chromium is preferably 40% by mass or less, and more preferably 35% by mass or less in the cobalt-based alloy.

The cobalt-based alloy preferably contains at least one selected from nickel and tungsten. The cobalt-based alloy may contain only one selected from nickel and tungsten, or may contain two kinds of nickel and tungsten.

When nickel is contained, the content thereof is preferably 0.1% by mass or more, more preferably 1% by mass or more in the cobalt-based alloy. The content of nickel is preferably 30% by mass or less and more preferably 25% by mass or less in the cobalt-based alloy.

When tungsten is contained, the content thereof is preferably 1% by mass or more, more preferably 3% by mass or more in the cobalt-based alloy. The content of tungsten is preferably 25% by mass or less and more preferably 20% by mass or less in the cobalt-based alloy.

The cobalt-based alloy can contain elements other than those described above as necessary and within the limits not departing from the spirit of the present invention. Examples of such elements include various elements contained in commercially available cobalt-based alloys. For example, tantalum, molybdenum, titanium, boron, zirconium, carbon, iron, lanthanum, and the like can be given.

When tantalum is contained, the content thereof is preferably 1% by mass or more, and more preferably 2% by mass or more in the cobalt-based alloy. The content of tantalum is preferably 20% by mass or less and more preferably 15% by mass or less in the cobalt-based alloy.

When molybdenum is contained, its content is preferably 1% by mass or more, more preferably 2% by mass or more, in the cobalt-based alloy. The content of molybdenum is preferably 15% by mass or less, and more preferably 10% by mass or less in the cobalt-based alloy.

When titanium, boron, zirconium and carbon are contained, their content is preferably 1% by mass or less in the cobalt-based alloy. Further, the total content of titanium, boron, zirconium and carbon is preferably 3% by mass or less, more preferably 2% by mass or less in the cobalt-based alloy.

When iron is contained, its content is preferably 0.1% by mass or more, more preferably 0.5% by mass or more in the cobalt-based alloy. The content of iron is preferably 10% by mass or less, and more preferably 5% by mass or less in the cobalt-based alloy.

When lanthanum is contained, the content thereof is preferably 0.1% by mass or more, more preferably 0.5% by mass or more in the cobalt-based alloy. The content of lanthanum is preferably 5% by mass or less and more preferably 3% by mass or less in the cobalt-based alloy.

As the cobalt base alloy, a commercially available one can be used. Examples thereof include FSX-414, Stellite 21, Stellite 31, MarM302, MarM509, Haynes-188, and the like. Table 1 shows the compositions of these cobalt-based alloys.

The aluminizing treatment only needs to be able to diffuse aluminum into the cobalt-based alloy. A known method can be adopted as the aluminizing treatment. Such as Pack Aluminizing, Gas Aluminizing, Gas Aluminizing, Spray Aluminizing, Vacuum Aluminizing, Cladding, Electrolytic Coating , Hot dip aluminizing and the like.

Pack aluminizing is performed, for example, by placing a cobalt-based alloy to be aluminized in a container and heating aluminum or aluminum alloy powder. The heating temperature should just be able to diffuse aluminum in a cobalt base alloy. Usually, the heating temperature is preferably 900 to 1100 ° C. Pack aluminizing is preferable because it can process even complex shapes.

Gas aluminizing is performed, for example, by putting a cobalt base alloy to be aluminized in a container, 45 mass% aluminum (Al), 45 mass% aluminum oxide (Al ₂ O ₃ ), and 10 mass%. The mixture is heated by adding a mixture of aluminum chloride (AlCl ₃ ).

Spray aluminizing is performed, for example, by adhering aluminum or an aluminum alloy to the surface of a cobalt base alloy to be aluminized by spraying. In spray aluminizing, aluminum or an aluminum alloy may be adhered to the surface of a cobalt base alloy to be aluminized by thermal spraying.

Vacuum aluminizing is performed, for example, by depositing aluminum on the surface of a cobalt-based alloy to be aluminized at a degree of vacuum of about 0.001 to 0.1 Pa.

The cladding is performed, for example, by superimposing and rolling a cobalt base alloy to be aluminized and aluminum or an aluminum alloy.

Electroplating is performed, for example, by immersing a cobalt-based alloy to be aluminized in a molten electrolyte made of a molten salt of aluminum chloride or the like.

Hot dip aluminizing is performed by immersing a cobalt base alloy to be aluminized in aluminum or an aluminum alloy heated to 700 to 800 ° C. and melted.

The aluminizing treatment is preferably performed so that the thickness of the aluminizing layer 3 is 10 μm or more. When the thickness of the aluminizing layer 3 is 10 μm or more, the content of aluminum oxide in the protective film increases. The thickness of the aluminizing layer 3 is more preferably 30 μm or more, and further preferably 50 μm or more. In addition, from the viewpoint of shortening the time required for the aluminizing treatment, the thickness of the aluminizing layer 3 is preferably 200 μm or less, and more preferably 100 μm or less.

A heat treatment process is performed with respect to the above-mentioned to-be-processed object 1, ie, the cobalt base alloy in which the aluminizing process was performed. The heat treatment step is performed at a vacuum degree of 1 × 10 ⁻⁵ to 1 × 10 ⁻³ Pa.

By such a heat treatment step, for example, a cobalt-based alloy member 4 as shown in FIG. 2 is manufactured. The cobalt base alloy member 4 has, for example, a protective film 5 formed by oxidizing its constituent elements on the surface of the aluminizing layer 3.

When the degree of vacuum is 1 × 10 ⁻³ Pa or less, metal oxides other than aluminum oxide, for example, oxides such as cobalt and nickel, in the protective film 5 are decomposed, and the content of aluminum oxide increases. The degree of vacuum is preferably 5 × 10 ⁻⁴ Pa or less. In addition, it is thought that the said decomposition | disassembly is based on the reduction | restoration of the carbon monoxide or hydrogen produced | generated with decomposition | disassembly of the water | moisture content adsorbed by the to-be-processed object 1, or organic substance, for example.

Further, when the degree of vacuum is 1 × 10 ⁻⁵ Pa or more, the decomposition of the aluminum oxide in the protective film 5 is suppressed, and the content of aluminum oxide is increased. The degree of vacuum is preferably 5 × 10 ⁻⁵ Pa or more.

The heat treatment temperature is preferably 1000 ° C. or higher, more preferably 1100 ° C. or higher, and still more preferably 1200 ° C. or higher, from the viewpoint of increasing the aluminum oxide content in the protective film 5. The heat treatment temperature is preferably equal to or lower than the melting point of the cobalt base alloy from the viewpoint of maintaining the shape of the cobalt base alloy member 4 and the like. Usually, the heat treatment temperature is preferably 1300 ° C. or lower.

The heat treatment time is preferably 1 hour or longer, more preferably 2 hours or longer, and even more preferably 3 hours or longer from the viewpoint of increasing the content of aluminum oxide in the protective film 5. In addition, since productivity will fall when heat processing time increases, heat processing time is preferable 10 hours or less.

In the heat treatment step, it is preferable to introduce at least one gas selected from hydrogen gas, argon gas, and nitrogen gas while adjusting the degree of vacuum to 1 × 10 ⁻⁵ to 1 × 10 ⁻³ Pa. In addition, hydrogen gas, argon gas, and nitrogen gas may introduce only 1 type of gas, may introduce 2 types of gas, and may introduce all 3 types of gas. . By introducing at least one selected from hydrogen gas, argon gas, and nitrogen gas, the content of aluminum oxide in the protective film 5 is increased.

FIG. 3 shows an embodiment of a heat treatment apparatus used in the heat treatment step.
The heat treatment apparatus 10 includes, for example, a processing unit 11, a heating unit 12, a pressure adjustment unit 13, and a gas introduction unit 14.

In the processing unit 11, the heat treatment of the object 1 is performed. The processing unit 11 includes a processing chamber 111 in which the workpiece 1 is disposed. The processing unit 11 includes a vacuum heating furnace or the like.

The heating unit 12 is disposed, for example, in the vicinity of the processing chamber 111 and heats the object 1 to be processed. The heating unit 12 includes a heater whose temperature rises when energized, for example.

The pressure adjustment unit 13 includes, for example, a first pump 131 and a second pump 132. The first pump 131 is a rough reference pump capable of setting the degree of vacuum to about 1 × 10 ⁻³ Pa, and includes, for example, a rotary pump. The second pump 132 is a reference pump capable of making the degree of vacuum about 1 × 10 ⁻⁵ Pa, and includes an oil diffusion pump, a turbo pump, and the like.

The first pump 131 and the second pump 132 are connected by a first pipe 133. The second pump 132 and the processing unit 11 are connected by a second pipe 134. The first pipe 133 and the processing unit 11 are connected by a third pipe 135.

In the first pipe 133, a first main valve 136 is provided between a connection portion between the first pipe 133 and the third pipe 135 and the second pump 132. The second main valve 137 is provided in the second pipe 134. The third pipe 135 is provided with a roughing valve 138.

The gas introduction unit 14 includes a fifth pipe 141 for introducing gas into the processing chamber 111 and a sixth pipe 142 for discharging gas from the processing chamber 111. A gas introduction valve 143 is provided in the middle of the fifth pipe 141. A gas discharge valve 144 is provided in the middle of the sixth pipe 142. Note that the gas discharge valve 144 is connected to, for example, a sensor M that measures the degree of vacuum in the processing chamber 111, and is controlled so as to have a set degree of vacuum.

FIG. 4 is a diagram showing a specific heat treatment procedure when the heat treatment apparatus 10 as shown in FIG. 3 is used.

The heat treatment is preferably performed in the order of, for example, a step (S1) for placing the object 1 to be processed, an exhaust step (S2), a heating step (S3), a gas introduction step (S4), and a pressure adjustment step (S5).

In the step (S1) of disposing the object 1 to be processed, the object 1 is disposed in the processing chamber 111 of the processing unit 11.

In the exhaust step (S2), the air inside the processing unit 11 is exhausted. The exhaust step (S2) is preferably performed in the order of the roughing step and the main pulling step.

The roughing step is performed by, for example, driving the first pump 131 after closing the first main valve 136 and the second main valve 137 and opening the rough valve 138. The roughing step is performed, for example, until the degree of vacuum reaches about 1 × 10 ⁻³ Pa.

The main pulling step is performed, for example, by opening the first main pull valve 136 and the second main pull valve 137 and closing the rough pull valve 138 and driving the second pump 132. At this time, the first pump 131 may be driven or stopped. This pulling step is performed, for example, until the degree of vacuum reaches about 1 × 10 ⁻⁵ Pa.

The heating step (S3) energizes the heating unit 12 to heat the object 1 to be processed.

The gas introduction step (S4) is performed, for example, when the temperature of the workpiece 1 reaches a predetermined heat treatment temperature. The gas introduction step (S4) is performed, for example, by opening the gas introduction valve 143.

The pressure adjustment step (S5) is performed immediately after the start of the gas introduction step (S4), for example. The pressure adjustment step (S5) is performed, for example, by opening the gas discharge valve 144 so as to achieve a desired degree of vacuum.

Next, the cobalt base alloy member 4 manufactured by the manufacturing method of the embodiment will be described.
The cobalt-based alloy member 4 is preferably a gas turbine component, particularly a CO ₂ turbine component. Among such parts, a stationary blade generally using a cobalt-based alloy is preferable.

FIG. 5 is a configuration diagram illustrating an embodiment of a power generation system having a CO ₂ turbine.
The power generation system 30 generates power by rotating a CO ₂ turbine with high-temperature combustion gas generated by burning fuel such as natural gas, oxygen, and CO ₂ .

The power generation system 30 includes a generator 31 having a CO ₂ turbine. A combustor 32 that generates high-temperature gas is connected to the generator 31. The combustor 32 is connected to an oxygen production apparatus 33 that produces and supplies oxygen from air. The combustor 32 is connected to a fuel supply device (not shown) that supplies fuel such as natural gas. Further, a regenerative heat exchanger 34 that regenerates and supplies CO ₂ is connected to the combustor 32.

In the combustor 32, the fuel supplied from the fuel supply device, the oxygen supplied from the oxygen production device 33, and the carbon dioxide supplied from the regenerative heat exchanger 34 are mixed and burned to generate high-temperature combustion gas. . Electric power is generated by rotating the generator 31 with the combustion gas. The combustion gas containing carbon dioxide and steam discharged from the generator 31 is cooled by the cooler 35 through the regenerative heat exchanger 34, and then the moisture is separated by the moisture separator 36. Thereafter, the combustion gas from which moisture has been separated is compressed by a CO ₂ pump 37 that is a high-pressure pump. Most of the carbon dioxide is circulated to the combustor 32 via the regenerative heat exchanger 34, but a part of the carbon dioxide is recovered as it is.

According to the power generation system 30, carbon dioxide can be effectively used and nitrogen oxide emissions can be suppressed. For example, high-pressure carbon dioxide can be stored, or can be applied to EOR (Enhanced Oil Recovery) used at oil mining sites. EOR is a technique for increasing the amount of oil extracted by injecting high-pressure carbon dioxide at an old oil field. Therefore, the power generation system 30 is also useful from the viewpoint of protecting the global environment.

FIG. 6 is a cross-sectional view showing an embodiment of the CO ₂ turbine 40 constituting the generator 31.
The CO ₂ turbine 40 includes a rotor 42 and a moving blade 43 provided on the rotor 42 as a rotating system member 41. The CO ₂ turbine 40 includes a casing 45 and a stationary blade 46 that is supported by the casing 45 and disposed so as to face the moving blade 43 as the stationary member 44.

Hereinafter, examples will be described in more detail.

Example 1
Aluminizing treatment was performed on the trade name MarM509 as a cobalt-based alloy to produce a test piece as a workpiece. The aluminizing treatment was performed by pack aluminizing. The test piece has a shape of 15 mm × 10 mm × 2 mm, and has an aluminizing layer having a thickness of 50 μm on the surface.

Next, using the heat treatment apparatus as shown in FIG. 3, the test piece was heat-treated by the procedure as shown in FIG. That is, first, the test piece was placed in the processing chamber. Thereafter, the degree of vacuum was set to about 1 × 10 ⁻³ Pa using a rotary pump, and the degree of vacuum was set to about 1 × 10 ⁻⁵ Pa using an oil diffusion pump.

Thereafter, the test piece was heated by energizing the heating section. When the temperature of the test piece reached 1230 ° C., the gas introduction valve was opened to introduce argon gas. The amount of argon gas introduced was 20 cc / h. At this time, the degree of vacuum was adjusted to 1 × 10 ⁻⁴ Pa by opening the gas discharge valve. Thereafter, the temperature and the degree of vacuum were maintained for 6 hours, and the test piece was heat-treated.

(Example 2)
The degree of vacuum at the time of gas introduction was adjusted to 2 × 10 ⁻⁴ Pa, and heat treatment was performed in the same manner as in Example 1 except that hydrogen gas was introduced instead of argon gas.

(Example 3)
The degree of vacuum at the time of gas introduction was adjusted to 3 × 10 ⁻⁴ Pa, and heat treatment was performed in the same manner as in Example 1 except that nitrogen gas was introduced instead of argon gas.

Example 4
Heat treatment was performed in the same manner as in Example 1 except that a mixed gas composed of 50% by volume argon gas and 50% by volume hydrogen gas was introduced instead of argon gas.

(Example 5)
Example 1 except that the degree of vacuum at the time of gas introduction was adjusted to 2 × 10 ⁻⁴ Pa and a mixed gas composed of 50% by volume hydrogen gas and 50% by volume nitrogen gas was introduced instead of argon gas. Heat treatment was performed in the same manner as described above.

(Example 6)
Example 1 except that the degree of vacuum at the time of gas introduction was adjusted to 2 × 10 ⁻⁴ Pa, and a mixed gas composed of 50% by volume nitrogen gas and 50% by volume argon gas was introduced instead of argon gas. Heat treatment was performed in the same manner as described above.

(Example 7)
While adjusting the degree of vacuum at the time of gas introduction to 2 × 10 ⁻⁴ Pa, a mixed gas composed of 50% by volume argon gas, 25% by volume nitrogen gas, and 25% by volume hydrogen gas was used instead of argon gas. A heat treatment was performed in the same manner as in Example 1 except for the introduction.

(Comparative Example 1)
The degree of vacuum at the time of gas introduction was adjusted to 9 × 10 ⁻⁶ Pa, and heat treatment was performed in the same manner as in Example 1 except that hydrogen gas was introduced instead of argon gas.

(Comparative Example 2)
Example 1 except that the degree of vacuum at the time of gas introduction was adjusted to 1 × 10 ⁻¹ Pa and a mixed gas composed of 50% by volume argon gas and 50% by volume nitrogen gas was introduced instead of argon gas. In the same manner, heat treatment was performed.

Next, the protective coating formed on the surface of the aluminizing layer was observed by X-ray diffraction (XRD) for the test pieces subjected to the heat treatment of Examples and Comparative Examples. The results are shown in Table 2.

Table 2 shows the detected intensities of aluminum oxide (Al ₂ O ₃ ) and cobalt oxide (CoO) by XRD. In the table, “−” indicates that no detection is detected, “+” indicates that detection is performed but the detection intensity is low, “++” indicates that the detection intensity is high, and “++” indicates that the detection intensity is particularly high. It shows that.

As shown in Table 2, all of the test pieces of the examples subjected to the heat treatment with a degree of vacuum of 1 × 10 ⁻⁵ Pa to 1 × 10 ⁻³ Pa had high aluminum oxide detection strength, cobalt The detected intensity of oxide was lowered. That is, it can be seen that the test piece of the example has a high content of aluminum oxide in the protective coating and can ensure oxidation resistance even when used at a high temperature exceeding 1000 ° C.

On the other hand, for the test pieces of the comparative examples that were heat-treated with the degree of vacuum being less than 1 × 10 ⁻⁵ Pa or exceeding 1 × 10 ⁻³ Pa, aluminum oxide was detected, but the detected intensity was It became low. That is, about the test piece of a comparative example, the content rate of the aluminum oxide in a protective film is low, and there exists a possibility that sufficient oxidation resistance cannot be ensured in use at high temperature exceeding 1000 degreeC.

Although several embodiments of the invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

DESCRIPTION OF SYMBOLS 1 ... Cobalt base alloy (to-be-processed object) by which aluminizing process was performed, 2 ... Main body, 3 ... Aluminizing layer, 4 ... Cobalt base alloy member, 5 ... Protective film, 10 ... Heat processing apparatus, 11 ... Processing part, DESCRIPTION OF SYMBOLS 12 ... Heating part, 13 ... Pressure adjustment part, 14 ... Gas introduction part, 30 ... Electric power generation system, 31 ... Generator, 32 ... Combustor, 33 ... Oxygen production apparatus, 34 ... Regenerative heat exchanger, 35 ... Cooler, 36 ... moisture separator, 37 ... CO ₂ pumps, 40 ... CO ₂ turbine, 41 ... rotating system member, 42 ... rotor, 43 ... moving blades, 44 ... stationary system member, 45 ... casing, 46 ... stationary blade, 111 ... Processing chamber 131 ... first pump 132 ... second pump 133 ... first piping 134 ... second piping 135 ... third piping 136 ... first main valve 137 ... Second main valve, 138 ... Coarse valve, 141 ... Fifth Tube, 142 ... sixth pipe, 143 ... gas introduction valve, 144 ... gas discharge valve.

Claims

Preparing a cobalt-based alloy that has been aluminized;
Performing a heat treatment at a vacuum degree of 1 × 10 −5 Pa to 1 × 10 −3 Pa on the cobalt-based alloy subjected to the aluminizing treatment;
The manufacturing method of the cobalt base alloy member characterized by having.
The method for producing a cobalt-based alloy member according to claim 1, wherein at least one gas selected from argon gas, hydrogen gas, and nitrogen gas is introduced during the heat treatment.
The method for producing a cobalt-based alloy member according to claim 1 or 2, wherein the heat treatment is performed at a temperature of 1000 ° C or higher.
The method for producing a cobalt-based alloy member according to any one of claims 1 to 3, wherein the method is used for producing a stationary blade in a gas turbine.
The method for producing a cobalt-based alloy member according to claim 4, wherein the gas turbine is a CO 2 turbine.