JPH11293452A - Thermal insulation coating method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermal insulation coating method by which the peeling on the boundary between the surface of an undercoat layer and an Al2 O3 layer can be suppressed in the method for forming a ceramic shielding coating film by an electron beam physical deposition method (EB-PVD method), and a coating film excellent in heat cycle properties and improved in a service life can be obtd. SOLUTION: An undercoat layer 3 composed of an MCrAlY alloy layer (M: CoNi, NiCo, Ni, Co or Fe) is formed on a base material by a low pressure thermal spraying method, and thereafter, the formation of a thermal barrier coating film by an EB-PVD method is executed in a vacuum or in a nonoxidizing atmosphere in the initial stage and in a oxygen atmosphere after the coating of the surface of the undercoat layer with a ceramics layer 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal barrier coating method applied to members used in a high-temperature gas environment such as a gas turbine and a rocket engine.

[0002]

Conventionally, as a thermal barrier coating to members for use in a gas turbine, hot gas environment, such as a rocket engine, Y ₂ O ₃ stabilized ZrO ₂ (hereinafter, abbreviated as YSZ), MgO ₂ stable of ZrO _2, CeO ₂ stabilized ZrO ₂ thermal conductivity, such as small, have been used many methods of coating by thermal spraying a stable ceramic material at high temperatures. However, the coefficient of thermal expansion of ceramics such as YSZ is intended to form a high-temperature oxidation-resistant and high-temperature corrosion-resistant coating layer that is firmly fixed to a base material such as IN738LC (trade name of INCO, USA) or a base material. And YS
It is smaller than that of an undercoat material such as MCrAlY (M: CoNi, NiCo, Ni, Co or Fe) which is applied between a ceramic such as Z and a base material, and is generated when the member is heated or cooled. Ceramics were damaged by thermal stress caused by a difference in thermal expansion coefficient, and in the worst case, peeling occurred during use.

[0003] The problem due to such a difference in the coefficient of thermal expansion is addressed.
Therefore, as shown in FIG.
Electoron Beam Physical Vapor
Deposition: EB-PVD method)
Columnar 1 films have been proposed. In such a membrane
Indicates that each of the ceramic columnar crystals 1 is formed on the surface of the substrate 4.
Al on the undercoat layer 3 such as MCrAlY_TwoO
_ThreeAlthough firmly fixed through the layer 2, the adjacent ceramic
Since the bonding strength between the columnar crystals 1 is small, ceramic
Columnar crystal 1 can cope with expansion and contraction of undercoat layer 3
Therefore, the occurrence of thermal stress as described above is small,
It is said to be excellent. Such a thermal barrier coating
First, the MC film is formed on the substrate 4 by the EB-PVD method.
Y undercoat layer 3 is formed and hydrogen heat treatment or acid
Al treatment _TwoO_ThreeLayer 2 is formed and its Al_Two
O_ThreeTo form the ceramic columnar crystals 1 on the layer 2
Therefore, it is manufactured. Where Al_TwoO_ThreeLayer 2 is ceramic
The adhesion of the columnar crystals 1 to the undercoat layer 3
It is formed for the purpose.

YSZ commonly used for thermal barrier coatings
Of oxide ceramics such as
The coating is usually performed in an oxygen atmosphere to prevent oxygen deficiency.
Done in Coating under oxygen atmosphere
Simultaneously oxidizes the undercoat MCrAlY
This means that the most oxidizable Al among the components diffuses to the surface
And oxidize, resulting in undercoat and ceramic (Y
SZ etc.) between the layer _TwoO_ThreeIncrease the layer thickness
And Also, during preheating before film formation, Al_TwoO_Threelayer
May increase in thickness. Thus, the conventional E
Undercoat for coating layer by B-PVD method
The thickness of about 2 μm on the MCrAlY surface which is the layer 3
Al_TwoO_ThreeCeramic columnar crystal 1 is formed via layer 2
Because this Al_TwoO_ThreeHigh temperature oxidizing atmosphere when layer 2 is in use
Increased due to ambient air, as shown in FIG._TwoO_ThreeLayer 2 and
Peeling occurs at the interface of the undercoat layer (MCrAlY layer) 3
It has been reported that raw spot 6 occurs and peels off.
-Thermal barrier coating by PVD method ceramic columnar crystal 1
In the film, this Al_TwoO_ThreeLayer 2 and undercoat layer
(MCrAlY layer) Peeling at interface of 3 is weak point
ing.

[0005]

SUMMARY OF THE INVENTION In view of the above-mentioned circumstances of the prior art, the present invention relates to a method of forming a ceramic shielding coating film by an EB-PVD method, wherein a method for forming an interface between an undercoat layer surface and an Al ₂ O ₃ layer is provided. An object of the present invention is to provide a thermal barrier coating method capable of suppressing peeling, having excellent thermal cycling properties, and obtaining a coating film having an improved life.

[0006]

The present inventors have conducted various studies to solve the above-mentioned problems. As a result, the inventors have found that Al _2, which had conventionally required a certain thickness in order to improve the adhesion of the ceramic columnar crystals. The inventors have found that the O ₃ layer should be thinner (or better if not possible) to prevent breakage due to internal stress during use, and completed the present invention. The present invention relates to an MCrAlY alloy (M: CoNi, NiCo, N
i, Co or Fe), a method of forming a thermal barrier coating of ceramics on a surface of a substrate coated with electron beam physical vapor deposition (EB-PVD), wherein the MCrAlY alloy layer is formed on the substrate by low pressure spraying. After the formation of the thermal barrier coating film by the EB-PVD method, the initial stage is performed in a vacuum or a non-oxidizing atmosphere, and after the surface of the undercoat layer is covered with the ceramic layer, in an oxygen atmosphere. This is a method of performing thermal barrier coating on a substrate surface, which is performed. As a preferred embodiment of the present invention, there is a method of thermal barrier coating on a substrate surface on which a YSZ layer is formed as the ceramic layer.

[0007] In the method of the present invention, first, I is used in a high temperature gas environment such as a gas turbine or a rocket engine.
An MCrAlY alloy (M: CoNi, NiCo, Ni, C
o or Fe) by a low pressure spraying method (for example, 40 to 50).
(Torr, 500-800 ° C.). The thickness of the undercoat layer is 0.1 to 0.2 mm
Range. If the thickness is too small, the effect is small. If the thickness is too large, the formed Al ₂ O ₃ layer tends to be thick, and the undercoat layer and the Al ₂ O ₃ layer are easily separated. After forming the undercoat layer, if necessary, a vacuum heat treatment may be performed to improve the adhesion of the undercoat layer. In addition, IN738LC which is a typical base material is used.
Are as shown in Table 1.

[0008]

[Table 1]

Next, the substrate on which the undercoat layer is formed is placed in a vacuum atmosphere of 10 ^-4 Torr or less or 10 ^-3 Torr.
Preheating is performed at about 800 to 1000 ° C. in a non-oxidizing atmosphere such as Ar or H _{2 at} a low pressure of r or less. YSZ, Mg is applied to the pre-heated substrate surface by the EB-PVD method.
A thermal barrier coating film made of ceramics such as O ₂ -stabilized ZrO ₂ and CeO ₂ -stabilized ZrO ₂ is formed.
As a ceramic, YSZ has the best performance and is the most common. In the initial stage of formation of the thermal barrier coating film, in order to suppress the formation of an Al ₂ O ₃ layer between the undercoat layer and the ceramic layer, under a vacuum atmosphere of the order of 10 ⁻⁴ Torr or less or in the order of 10 ⁻³ Torr. A in the following low pressure condition
It is performed in a non-oxidizing atmosphere such as r or H ₂ .

Oxygen is supplied when the surface of the undercoat layer is coated with ceramics by the film formation in the vacuum atmosphere or the non-oxidizing atmosphere, and the risk of generation of Al ₂ O ₃ is reduced. Is formed in an oxygen atmosphere at a low pressure of 8 × 10 ⁻³ Torr or less. In this way, a thickness of 25 to 260 μm is formed on the surface of the undercoat layer.
A thermal barrier coating film made of m ceramics is formed. If the thickness of the thermal barrier coating film is less than 25 μm, the thermal barrier properties of the ceramics are not sufficient, and
If the thickness exceeds 0 μm, the adhesion of the ceramic layer is undesirably reduced.

By controlling the atmosphere during film formation by the EB-PVD method as described above, the undercoat layer
Al ₂ O _{3 at} the interface with the ceramic layer such as SZ
Can be suppressed, and the film forming method is EB-
Because the PVD method is used, the resulting ceramic layer such as YSZ becomes a columnar crystal, so that the generation of thermal stress due to the difference in the coefficient of thermal expansion between the ceramic such as YSZ and the base material is suppressed. It is possible to obtain a thermal barrier coating film having an improved life.

[0012]

The following examples further illustrate the method of the present invention.
However, the present invention is not limited to this embodiment.
is not. Undercoat layer and heat insulation by the method of the present invention
Al at the interface with the coating film _TwoO_ThreeSuppress layer formation
To form a thermal barrier coating film, using the conventional method
Performance comparison with the thermal barrier coating film was performed.

FIG. 1 shows the outline of the apparatus used in this embodiment.
Shown in FIGS. 1A, 1B, and 1C show the states of the initial film formation (film formation in a non-oxidizing atmosphere) and the main film formation (film formation in an oxygen atmosphere) during preheating, respectively. FIG. In FIG. 1, 4 is a substrate (test piece), 7 is a preheating furnace, 8 is a high-voltage EB gun that generates an electron beam 14, 9 is a water-cooled hollow crucible, 10 is a vacuum tank, and 15 is Ar
Gas inlet for introducing non-oxidizing gas 11 such as
The YSZ bar which is a source of SZ is shown. In this example, one gas inlet 15 is provided, and a non-oxidizing gas 11 or oxygen 13 is introduced by switching a valve (not shown) on the source stream side. Is also good. FIG. 2 shows a detailed view of the crucible 9 of FIG. Reference numeral 16 in FIG. 2 denotes a cooling water introduction pipe for supplying the cooling water 20. The outline of the film forming operation is as follows. First, FIG.
As shown in (a), a test piece (substrate) 4 is placed in a preheating furnace 7 in a vacuum atmosphere of 10 ⁻⁴ Torr or less in a vacuum chamber 10.
After heating and preheating by heating to about 800 to 1000 ° C., as shown in FIG.

The test piece 4 used had the shape and dimensions shown in FIG. 3 and had a coated surface 20 on an IN738LC substrate 19.
CoNiCrAlY alloy is sprayed at a low pressure to a thickness of 0.1
mm undercoat layer 18 is formed at 1120 ° C.
After the vacuum heat treatment for one hour, the one whose surface was polished to Ra = 3 was used.

As ceramics for thermal barrier coating, 7% Y ₂ O ₃ partially stabilized ZrO ₂ (YSZ) is used.
This YSZ rod (rod-shaped ingot) 12 is melted by an electron beam 14 from a high-voltage EB gun 8 and vaporized YS
Z is deposited on the rotating test piece (substrate) 4 to form a film.
In the initial stage of the film formation, as shown in FIG. 1B, the gas inlet 15 for suppressing the generation of Al ₂ O ₃ at the interface between the undercoat layer 18 on the surface of the substrate 19 and the thermal barrier coating film.
Introducing a non-oxidizing gas (Ar gas) 11, 10 ^-4 T
The film was formed under a non-oxidizing atmosphere at a pressure of orr.

The undercoat layer 18 is formed by forming the film for one minute.
Is coated with YSZ (the thickness of the YSZ layer is about 0.5 μm).
m), when the fear of producing Al ₂ O ₃ is reduced, as shown in FIG.
And the film formation was continued under an oxygen atmosphere at a pressure of 8 × 10 ⁻³ Torr to form a thermal barrier coating film having a thickness of about 250 μm. In this example, the thickness of the Al ₂ O ₃ layer generated at the interface between the undercoat layer 18 and the thermal barrier coating film was 0.2 μm.

As a comparative example simulating the conventional method, a test piece in which an Al ₂ O ₃ layer was previously formed on the surface of the undercoat layer 18 was used, and a pressure of 8 × 10 ⁻³ Torr was applied from the initial stage of film formation.
A YSZ film is formed in an oxygen atmosphere, and a 2 μm thick Al film is formed on the interface between the undercoat layer 18 and the thermal barrier coating film.
A thermal barrier coating film having a thickness of about 250 μm and having a ₂ O ₃ layer was formed. Table 2 shows the film forming conditions and the properties of the obtained thermal barrier coating film. (A) in Table 2 is a comparative example simulating the conventional method, and (b) is an example according to the method of the present invention.

In order to confirm the effects of the present invention, the results of an atmospheric oxidation test at 1000 ° C. for 1000 hours for the test pieces on which the above-mentioned thermal barrier coating films (a) and (b) were formed are shown in Table 3. Shown in From Table 3, an increase in Al ₂ O ₃ layer thickness is caused by the heating of 1000 hours at 1000 ° C. in a conventional manner, Al ₂ O ₃ which has been a weak conventionally
/ MCrAlY interface peeled off in less than 1000 hours. In contrast, in the case of the method of the present invention, Al
Although an increase in the ₂ O ₃ layer is observed, the initial Al ₂ O ₃
Since the layer is thin, the formed thickness is small and the layer has not been peeled off even at the stage of 1000 hours, which indicates that a long life has been achieved.

[0019]

[Table 2]

[0020]

[Table 3]

[0021]

According to the method of the present invention, MCrAlY is used for forming a thermal barrier coating film by the EB-PVD method.
The thickness of the Al ₂ O ₃ layer formed at the interface between the undercoat layer made of the alloy and the thermal barrier coating film can be reduced, and the life of the thermal barrier coating can be extended. It is effective when applied to a long member such as an industrial gas turbine.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing an outline of an apparatus used in an embodiment.

FIG. 2 is a detailed view of a crucible 9 in the apparatus of FIG.

FIG. 3 is an explanatory diagram showing properties of a test piece used in an example.

FIG. 4 is an explanatory diagram showing a state of a thermal barrier coating film formed by an EB-PVD method.

FIG. 5 is an explanatory view showing the state of occurrence of peeling in a thermal barrier coating film by the EB-PVD method.

[Explanation of symbols]

1 ceramic columnar crystals 2 Al ₂ O ₃ layer 3 undercoat layer 4 substrate 6 delamination occurrence point 7 preheating furnace 8 high-voltage type EB gun 9 crucible 10 vacuum tank 11 non-oxidizing gas 12 YSZ rod 13 oxygen 14 electron beam 15 Gas inlet 16 Cooling water inlet 17 Coated surface 18 Undercoat layer 19 Base material 20 Cooling water

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Risuke Nayama 2-1-1 Shinhama, Arai-cho, Takasago-shi, Hyogo Inside the Mitsubishi Heavy Industries, Ltd. Takasago Research Laboratory

Claims (2)

[Claims] 1. A method of forming a ceramic thermal barrier coating film on a surface of a base material coated with an MCrAlY alloy (M: CoNi, NiCo, Ni, Co or Fe) to be an undercoat layer by electron beam physical vapor deposition. After the MCrAlY alloy layer is formed on the base material by low pressure spraying, the formation of a thermal barrier coating film by electron beam physical vapor deposition is performed in a vacuum or in a non-oxidizing atmosphere in the initial stage, and the surface of the undercoat layer is formed. A method of performing thermal barrier coating on the surface of a substrate, wherein the method is performed in an oxygen atmosphere after the substrate is coated with a ceramic layer. 2. The method according to claim 1, wherein the ceramic is Y ₂ O ₃ stabilized Zr.
_{2. The method according} to claim 1, wherein the coating is O2.