JP2009280854A - Ceramic film and method of manufacturing the same and thermal barrier coating structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a ceramic film having excellent thermal barrier property, heat shock resistance, and oxygen barrier property, and favorable for thermal barrier coating structure. <P>SOLUTION: The method of manufacturing the ceramic film has a deposition step of colliding aerosolized raw ceramic powder on a film deposition base material to crush primary particles in the raw powder, and depositing the crushed raw powder on the film deposition base material. The deposition step is performed under the condition that a part of the primary particles 64P in the raw powder remains in crushed stuff 63 as aggregate 64 without being crushed. After the deposition step, the heat treatment step is preferably performed in which the aggregate 64 left in the crushed stuff 63 is sintered and contracted to form pores in the crushed stuff 63. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a ceramic film, a manufacturing method thereof, and a thermal barrier coating structure for protecting a metal substrate from heat.

  In aircraft jet engines, power generation gas turbines, and the like, the combustion gas temperature is being increased in order to improve thermal efficiency and output. Accordingly, along with a cooling technique for cooling a member used in a high-temperature environment and further a high-temperature and high-corrosion environment, a thermal barrier coating (TBC) technique for protecting the member from heat becomes important.

  The thermal barrier coating is applied on a metal base material composed of members such as a gas turbine combustor and a moving blade. Generally, its structure is a metal bonding layer (bond coat layer) excellent in environmental resistance, It has a laminated structure with a low thermal conductive ceramic thermal barrier layer (topcoat layer). By providing a ceramic heat shield layer with low thermal conductivity on the combustion gas flow path side, it is possible to extend the life without exposing the metal substrate to a high temperature. Conventionally, a porous ceramic film has been used as the ceramic heat shield layer because of its good heat shield and thermal shock resistance.

  As described in Patent Document 1 and the like, conventionally, a plasma sprayed coating has been widely used as a ceramic thermal barrier layer. FIG. 7 shows a cross-sectional photograph of the thermal barrier coating structure described in FIG. The thermal barrier coating structure 101 has a laminated structure of a metal bonding layer 112 formed on a metal substrate 111 and a ceramic thermal barrier layer 114 made of a sprayed coating.

On the other hand, as described in Non-Patent Document 1 and the like, in recent years, an EB-PVD (electron beam vapor deposition) film has been used as a ceramic thermal barrier layer for a turbine blade of a jet engine. FIG. 8 shows a cross-sectional photograph of the thermal barrier coating structure described in Non-Patent Document 1. This thermal barrier coating structure 102 has a laminated structure of a metal bonding layer 123 formed on a metal substrate 121 and a ceramic thermal barrier layer 124 made of an EB-PVD film. In the thermal barrier coating structure 102, a diffusion layer 122 is formed between the metal substrate 121 and the metal bonding layer 123.
Japanese Unexamined Patent Publication No. 2006-117975 Ishikawajima Harima Technical Report Vol.47 No.1 (2007-3)

  In the thermal spray coating described in Patent Document 1, a large number of pores exist in the coating, thereby exhibiting heat shielding properties and thermal shock resistance. However, many pores are often communicated with each other in the thermal spray coating, and a through-hole penetrating the thermal barrier layer is formed from the surface of the thermal barrier layer to the surface of the metal bonding layer as a base. Not a few.

  In FIG. 7, at first glance, it seems that many pores formed in the sprayed coating are independent from each other, but in reality, many fine pores are also formed in the portion that looks fine. In fact, if a laminated structure consisting of a metal substrate / metal bonding layer / sprayed coating is left immersed in water, rust will form on the surface of the metal bonding layer. Has been confirmed to be formed.

  In a structure in which a through hole that substantially penetrates the heat shield layer is formed, the metal bonding layer comes into contact with the outside air through the through hole, so that the heat shield effect is reduced accordingly. Further, since oxygen gas in the outside air reaches the surface of the metal bonding layer through the through hole, a metal oxide (TGO) is generated on the surface of the metal bonding layer, and this TGO grows, whereby the heat shielding layer. There is also a possibility that interfacial peeling occurs between the metal and the metal bonding layer.

In order to solve the above problem, in Patent Document 1, an oxygen barrier made of a dense Al ₂ O ₃ film or the like is formed between a metal bonding layer and a ceramic heat shield layer by a sol-gel method or a slurry method that is a wet method. It has been proposed to provide a layer (reference numeral 113 in FIG. 7). It is also conceivable to form the oxygen barrier layer by a normal vapor deposition method. However, in general, an oxygen barrier layer formed by a wet method such as a sol-gel method or a slurry method, or a normal vapor phase film formation method does not have good adhesion to the base, and can withstand repeated thermal shocks. There is a risk that interfacial peeling may occur.

  As shown in FIG. 8, the EB-PVD film described in Non-Patent Document 1 has a columnar structure composed of a large number of columnar crystals extending in a direction substantially perpendicular to the substrate surface. In such a structure, there are voids between the columnar crystals adjacent to each other, thereby exhibiting heat shielding properties and thermal shock resistance. However, this void is a through-hole penetrating the heat shield layer from the surface of the heat shield layer to the surface of the metal bonding layer as the base, and the situation is not different from that of the thermal spray coating.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a novel ceramic film having good heat shielding properties, thermal shock resistance, and oxygen barrier properties, and a method for producing the same.
Another object of the present invention is to provide a novel thermal barrier coating structure having good thermal barrier properties, thermal shock resistance, and oxygen barrier properties without providing an oxygen barrier layer.

In the method for producing a ceramic film of the present invention, an aerosolized ceramic raw material powder is collided with a film forming substrate to crush primary particles in the raw material powder, and the crushed material powder is used as the film forming substrate. In a method for producing a ceramic film having a deposition step of depositing on a ceramic film,
The deposition step is performed under the condition that some of the primary particles in the raw material powder remain in the crushed material as aggregates without being crushed.

  The method for producing a ceramic film of the present invention preferably further includes a heat treatment step of forming pores by sintering the aggregate remaining in the crushed material after the deposition step.

In the method for producing a ceramic film of the present invention, it is preferable that the method further includes a pre-powder treatment step for weakening the bonding force between primary particles in the raw material powder before the deposition step.
Examples of the pre-powder treatment step include a step of milling the raw material powder.

In the method for producing a ceramic film according to the present invention, the raw material powder having a composition adjusted so that the composition of the crushed material and the composition of the primary particles remaining as the aggregate in the crushed material are different from each other is used. Then, the deposition step may be performed.
In this case, as the raw material powder, using the powder whose composition is adjusted so that the melting point of the primary particles remaining as the aggregate in the crushed material is lower than the melting point of the crushed material, A process can be performed.

  The first ceramic film of the present invention is manufactured by the above-described method for manufacturing a ceramic film of the present invention.

The second ceramic film of the present invention is characterized in that the ceramic film has a plurality of pores whose internal pressure is less than atmospheric pressure.
According to the present invention, the second ceramic film of the present invention which is a porous film having a relative density of 50 to 95% can be provided.
“Relative density” represents the ratio of the actually measured density to the theoretical density, and is expressed by the following equation.
Relative density = (actual density / theoretical density) × 100 (%)
The actually measured density can be measured by the Archimedes method. As a measuring device, for example, SD200L manufactured by AlfaMirage can be used.

According to the present invention, it is possible to provide the second ceramic film of the present invention in which the plurality of pores have a disk shape in plan view.
The planar shape of the plurality of pores existing in the ceramic film can be analyzed by nondestructive shape inspection.

According to the present invention, it is possible to provide the second ceramic film of the present invention in which the plurality of pores are independent from each other.
When used for applications such as a thermal barrier coating structure, the ceramic film of the present invention preferably contains at least one oxide ceramic selected from the group consisting of Al ₂ O ₃ , HfO ₂ , CeO ₂ , and ZrO _2. .

The thermal barrier coating structure of the present invention is
In a thermal barrier coating structure for protecting a metal substrate from heat,
From the metal substrate side, a metal bonding layer and a heat shield layer made of the second ceramic film of the present invention are sequentially provided.

In the thermal barrier coating structure of the present invention,
The metal base material is mainly composed of an alloy containing at least one metal element selected from the group consisting of Co, Ni, and Fe,
The metal bonding layer is mainly composed of at least one alloy represented by the general formula MCrAlY (wherein M represents Ni and / or Co, Cr represents chromium, Al represents aluminum, and Y represents yttrium). It is preferable to do.
In this specification, the “main component” is defined as a component of 30% by mass or more.

According to the present invention, it is possible to provide a novel ceramic film having a good thermal barrier property, thermal shock resistance, and oxygen barrier property and suitable as a thermal barrier coating structure and a method for producing the same.
According to the present invention, it is possible to provide a novel thermal barrier coating structure with good thermal barrier properties, thermal shock resistance, and oxygen barrier properties without providing an oxygen barrier layer.

"Ceramic film and its manufacturing method, thermal barrier coating structure"
With reference to drawings, the ceramic film of embodiment which concerns on this invention, and the thermal-insulation coating structure provided with the same are demonstrated. The thermal barrier coating structure is used for protecting a metal base material from heat in, for example, an aircraft jet engine or a power generation gas turbine. FIG. 1 is a cross-sectional view of a metal substrate and a thermal barrier coating structure formed thereon. In order to facilitate visual recognition, the scale of the constituent elements is appropriately changed from the actual one.

  As shown in FIG. 1, the thermal barrier coating structure 1 has a laminated structure of a metal bonding layer (bond coat) 12 and a ceramic thermal barrier layer (top coat) 14 formed on a metal substrate 11. . By forming the ceramic heat shield layer 14 having a low thermal conductivity on the combustion gas flow path side, it is possible to extend the life without exposing the metal substrate 11 to a high temperature.

  The composition of the metal substrate 11 is not particularly limited, and in the above application, for example, an alloy containing at least one metal element selected from the group consisting of Co, Ni, and Fe (preferably a so-called “super heat-resistant alloy”). The main component is preferred.

“Super heat resistant alloy” refers to a group of advanced materials that can be used in a high temperature region of 1000 to 2000 ° C. under severe environments such as large stress, oxidation and corrosion. Specifically, as a super heat-resistant alloy, a ternary intermetallic compound of cobalt, aluminum, and tungsten (Co ₃ (Al, W)); an alloy mainly composed of nickel, copper, and iron (Ni: 66. 5% / Cu: 31.5% / Fe: 1.2%) and the like.

  The metal bonding layer 12 is a metal coating layer for the purpose of oxidation resistance of the metal substrate 11. The film thickness of the metal bonding layer 12 is not particularly limited, and is preferably 50 to 100 μm, for example.

The composition of the metal bonding layer 12 is not particularly limited. In the above application, the metal bonding layer 12 preferably contains Al, and more preferably contains Al and Pt.
Since higher corrosion resistance and oxidation resistance can be obtained, in the above application, the metal bonding layer 12 has a general formula MCrAlY (wherein M is Ni and / or Co, Cr is chromium, Al is aluminum, and Y is yttrium. It is more preferable to include an alloy represented by:

The metal bonding layer 12 can be formed by a known method described in Non-Patent Document 1 or the like.
Examples of the method for forming the metal bonding layer 12 containing Al include an Al diffusion coating method. For example, b-NiAl or the like is caused by causing a chemical reaction on the surface of the base material 11 by bringing an aluminum halide such as AlCl ₃ into contact with the surface of the metal base material 11 (Ni-based super heat-resistant alloy or the like) containing Ni. The metal bonding layer 12 containing can be formed. This process is called an aluminizing process.

  Prior to the aluminizing step, a Pt film having a thickness of, for example, about 5 to 10 μm is formed on the surface of the metal substrate 11, and Pt is diffused in the surface layer of the metal substrate 11, so that Al and Pt are dispersed. A metal bonding layer 12 can be formed. It is known that the oxidation resistance and life of the aluminized layer are improved by including Pt in the metal bonding layer 12. This coating method is called a Pt—Al coating method and is the most common method as a bond coat for an aircraft turbine blade.

  The metal bonding layer 12 including the alloy represented by the above general formula MCrAlY is formed by a low-pressure plasma spray (LPPS (VPS)) method or a high velocity gas flame spray (High Velocity Oxy-Fuel: HVOF). ) Method or the like. These methods are said to be higher in production cost than the Al diffusion coating method capable of performing a large amount of coating treatment at a time, but have an advantage that the degree of freedom in designing the coating composition is great.

The composition of the ceramic thermal barrier layer 14 is not particularly limited, and in the above application, for example, the ceramic thermal barrier layer 14 includes at least one oxide ceramic selected from the group of Al ₂ O ₃ , HfO ₂ , CeO ₂ , and ZrO _2. Those containing such a component as a main component are particularly preferable.
If the thermal barrier coating 14 comprises ZrO _2, the _{ZrO 2, Y 2 O 3,} CaO, and at least one added stabilizing agent partially stabilized moiety selected from the group such as MgO More preferably, ZrO ₂ is included in the form of stabilized zirconia.

The film thickness of the ceramic heat shield layer 14 is not particularly limited, and is preferably 10 to 300 μm, for example.
The relative density of the ceramic heat shield layer 14 is not particularly limited. Conventionally, it is considered that the ceramic heat shield layer is preferably a porous film having a relative density of 50 to 95% from the viewpoints of heat shield properties and thermal shock resistance, and the same applies to the ceramic heat shield layer 14 of the present embodiment. That is, the ceramic heat shield layer 14 of the present embodiment is particularly preferably a porous film having a relative density of 50 to 95%. However, when compared with the same relative density, in this embodiment, the ceramic heat shield layer 14 with improved heat shield and thermal shock resistance than the conventional method can be manufactured. Therefore, the ceramic heat shield layer 14 of the present embodiment can be used outside the range of the relative density of 50 to 95%.

  The ceramic heat shield layer 14 of the present embodiment is manufactured by a novel method for producing a ceramic film, and has a novel film structure. As shown in FIG. 4C and FIG. 6B, the ceramic heat shield layer 14 has a plurality of pores 66 in the form of a disk in plan view that are independent of each other and have an internal pressure of less than atmospheric pressure.

  In the present embodiment, the ceramic thermal barrier layer 14 is manufactured using an aerosol deposition (AD) method. The AD method is a method in which an aerosolized ceramic raw material powder is collided on a film forming substrate to crush primary particles in the raw material powder, and a crushed material powder is deposited on the film forming substrate to form a film. It is. In the production of the ceramic heat shield layer 14, the metal substrate 11 on which the metal bonding layer 12 is formed is the film forming substrate 13.

  “Aerosol” refers to solid or liquid particles suspended in a gas. The AD method is known as a method capable of forming a film of ceramics or the like at a relatively low temperature without requiring a sintering process. In the AD method, it is known that a very dense film is formed by crushed material generated by collision of raw material powder with an object. The AD method is also called a jet deposition method or a gas deposition method.

  In the present embodiment, the ceramic thermal barrier layer 14 is manufactured by using the AD method. However, by adding a new process to the conventional AD method, a ceramic film having a new film structure is realized.

(Deposition system)
Before describing in detail the manufacturing method of the ceramic thermal barrier layer 14, a configuration example of an AD film forming apparatus suitable for use in manufacturing the ceramic thermal barrier layer 14 will be described with reference to FIG.

  An AD film forming apparatus 2 shown in FIG. 2 includes an aerosol generating unit 20 that generates an aerosol, a film forming unit 40, an aerosol transport pipe 30 that connects the two, and a control unit 50 that controls the operation of each unit. And.

  The aerosol generation unit 20 includes an aerosol generation container 21, a vibration table 22, a hoisting gas nozzle 23, and a pressure adjusting gas nozzle 24. The raw material powder 61 is charged into the aerosol generation container 21, and generation of the aerosol is performed here. The aerosol generation container 21 is installed on a vibration table 22 that vibrates at a predetermined frequency in order to stir the raw material powder 61 and efficiently generate an aerosol.

  The hoisting gas nozzle 23 generates a cyclone flow by introducing a carrier gas supplied from an external gas cylinder into the aerosol generating container 21. Thereby, the raw material powder 61 in the aerosol generation container 21 is rolled up and dispersed, and an aerosol is generated. The pressure adjusting gas nozzle 24 adjusts the gas pressure in the aerosol generating container 21 by introducing a carrier gas supplied from an external gas cylinder into the aerosol generating container 21. Thereby, the difference between the pressure in the aerosol generation container 21 and the pressure in the film forming chamber 41 is adjusted.

The flow rate of the gas introduced by the hoisting gas nozzle 23 and the pressure adjusting gas nozzle 24 is adjusted by the flow rate adjusting units 23a and 24a. As the carrier gas supplied by the gas nozzles 23 and 24, He, O ₂ , N ₂ , Ar, a mixed gas thereof, dry air, or the like is used.

  The aerosol generated by the aerosol generating unit 20 is transported to the film forming unit 40 via the aerosol transport pipe 30. In the film forming chamber 41, the aerosol transport pipe 30 is connected to an injection nozzle 42 for injecting the aerosol.

  The film forming unit 40 includes a film forming chamber 41, an injection nozzle 42, a stage 48, and an exhaust pipe 49. The inside of the film forming chamber 41 can be evacuated by an exhaust pump connected to an exhaust pipe 49. During film formation, the inside of the film formation chamber 41 is maintained at a predetermined reduced pressure, preferably 100 Pa or less. The injection nozzle 42 has an opening of a predetermined shape and size, and injects the aerosol of the raw material powder supplied from the aerosol generation container 21 via the aerosol transport pipe 30 toward the film forming substrate 13. . The velocity of the aerosol ejected from the ejection nozzle 42 is determined by the pressure difference between the aerosol generation container 21 and the film forming chamber 41.

  The stage 48 to which the film forming substrate 13 is fixed is a stage that can be moved three-dimensionally to control the relative position and relative speed between the film forming substrate 13 and the injection nozzle 42. By adjusting this relative speed, the thickness of the film formed per reciprocation is controlled. In the present embodiment, the relative position between the injection nozzle 42 and the film forming substrate 13 is changed by moving the stage 48 side. However, the position of the film forming substrate 13 is fixed and the injection nozzle 42 side is fixed. May be moved.

  At the time of film formation, the raw material powder 61 is disposed in the aerosol generation container 21, and the film formation substrate 13 is disposed on the stage 48. When the film forming apparatus 2 is driven, the aerosol generated in the aerosol generating container 21 is introduced into the film forming chamber 41 through the aerosol transport pipe 30, sprayed from the spray nozzle 42, and sprayed onto the film forming substrate 13. The raw material powder 61 in the aerosol collides with the film forming substrate 13 and is crushed, and the crushed material is deposited on the film forming substrate 13. At that time, the stage 48 is moved at a predetermined speed under the control of the control unit 50, so that the stage 48 is moved at a rate corresponding to the moving speed of the stage 48 (relative speed between the spray nozzle 42 and the film forming substrate 13). A ceramic film 62 having the same composition as the raw material powder 61 is formed.

  Instead of the aerosol generation unit 20, an aerosol generation device 3 shown in FIG. 3 may be used. FIG. 3A is a cross-sectional view showing the configuration of the aerosol generating device, and FIG. 3B is a plan view showing the inside of the aerosol generating device.

  The aerosol generating apparatus 3 shown in FIGS. 3A and 3B includes a powder storage chamber 70 and an aerosol generating unit 80. The powder storage chamber 70 is a chamber for storing powder, and a powder supply port 70a is provided at the upper bottom thereof, and an opening 71 is formed at the lower bottom thereof. The powder storage chamber 70 and the aerosol generation unit 80 are connected via the opening 71.

  The powder storage chamber 70 is provided with a stirring blade 72 that rotates when driven by a motor. An O-ring 73 a is fitted on the rotating shaft 73 of the stirring blade 72, thereby ensuring airtightness in the powder storage chamber 70. The powder is stored in such a powder storage chamber 70, and the powder is stirred by the stirring blade 72. Thereby, the powder falls from the opening 71 and is led out to the aerosol generating unit 80. In addition, an assist gas introduction unit 74 is provided in the powder storage chamber 70 in order to assist or promote the powder being led out from the opening 71. The assist gas introduction unit 74 includes a pipe and a valve, and a gas cylinder, for example, is connected to the end of the pipe.

  The aerosol generating unit 80 includes a rotating disk 81 that rotates when driven by a motor. An O-ring 82 a is fitted on the rotation shaft 82 of the turntable 81, thereby ensuring airtightness in the aerosol generating unit 80. A groove 83 having a predetermined width and depth is formed in the turntable 81 along the circumference. The turntable 81 is arranged so that the groove 83 faces the opening 71 of the powder storage chamber 70. Such a rotating plate 81 conveys the powder at a certain ratio by rotating while receiving the powder dropped from the opening 71 through the groove 83.

Further, the aerosol generation unit 80 is provided with a dispersed gas introduction unit 84 and an aerosol supply pipe 85. The dispersed gas introduction part 84 includes a pipe and a valve, and a gas cylinder, for example, is connected to the end of the pipe. As the assist gas and the dispersion gas, N ₂ , O ₂ , He, Ar, a mixed gas thereof, dry air, or the like is used.

  As shown in FIG. 3A, the outlet of the dispersed gas introduced into the aerosol generating unit 80 by the dispersed gas introducing unit 84 is provided so as to face the groove 83 of the rotating plate 81. The aerosol supply pipe 85 is a pipe disposed so that the opening at the tip thereof faces the groove 83, and the other end is connected to the aerosol carrying pipe 30 shown in FIG. 2 via a pipe formed of, for example, a flexible material. Connected to.

  In such an aerosol generating device 3, the desired powder is stored in the powder storage chamber 70 and the stirring blade 72 is driven, and the rotating plate 81 is rotated in the aerosol generating unit 80, and the groove 83 of the rotating plate 81 is inserted. A dispersion gas is sprayed on the surface. The powder stored in the powder storage chamber 70 falls into the groove 83 through the opening 71 while being stirred by the stirring blade 72. At that time, an air flow is formed in the opening 71 by introducing an assist gas into the powder storage chamber 70. This airflow acts as a driving force that assists or accelerates the derivation of the powder. Thereby, the powder falls from the opening 71 into the groove 83 more smoothly. The powder that has fallen into the groove 83 is deposited and conveyed in accordance with the rotational speed of the turntable 82. The introduction of the assist gas may be continuous or intermittent.

  On the other hand, in the groove 83 of the turntable 82, the dispersed gas blown there flows along the groove 83 to form an air flow. This dispersed gas flows into the aerosol supply pipe 85 from the opening at the tip thereof. At that time, a suction force toward the inside of the aerosol supply pipe 85 is generated around the aerosol supply pipe 85. Due to this suction force, the powder accumulated in the groove 83 flows into the aerosol supply pipe 85 together with the dispersion gas. The aerosol generated in this way is supplied from the aerosol supply pipe 85 to the aerosol transport pipe 30 (FIG. 2) and is introduced into the film forming unit 40 via the aerosol transport pipe 30.

(One Embodiment of Manufacturing Method of Ceramic Film)
Hereinafter, an embodiment of a method for producing a ceramic film according to the present invention will be described. In the present embodiment, the production of the ceramic heat shield layer 14 will be described. However, the production method of the present embodiment can be applied to a ceramic film for any use other than the ceramic heat shield layer 14.

<Preparation of raw material powder>
First, ceramic raw material powder is prepared. In the AD method, primary particles in the raw material powder are crushed by the collision energy of the raw material powder against the film-forming substrate. If the other AD conditions such as the aerosol injection speed are the same, the larger the primary particle diameter of the raw material powder, the larger the kinetic energy, so the collision energy against the film-forming substrate tends to increase. The average primary particle diameter of the raw material powder is not particularly limited, and is preferably 0.1 to 1.0 μm, for example.

<Pre-flouring process>
The raw material powder produced by the solid phase method is very rarely dispersed in the form of primary particles, and usually a large number of secondary particles in which a plurality of primary particles are strongly aggregated by necking are dispersed. In the present embodiment, prior to the film formation by the AD method, a pre-powder treatment step for weakening the bonding force between the primary particles in the raw material powder is performed. By performing film formation by the AD method after performing this pretreatment, at least a part of the aggregated particles is trapped in the film without being crushed. This can weaken the necking between the primary particles in the raw powder by the pre-powder treatment, and the primary particles can be brought into a state of agglomerated softly, and the impact of the agglomerated particles upon collision with the substrate is absorbed. It is thought to be done. In the case of the normal AD method in which the pretreatment is not performed, the aggregated particles in the aerosol are crushed and scattered simultaneously with the base material collision, and are not trapped as aggregates in the film.

  As the pre-powder treatment for weakening the bonding force between the primary particles in the raw material powder, mechanical treatment such as mill treatment is preferable. The mill treatment can be performed using an automatic mortar or a ball mill. By adjusting the milling time and the stress applied to the raw material powder during the milling process, the binding force between the primary particles in the raw material powder after the milling process can be controlled. Although it is difficult to control the bonding force between the primary particles in the raw material powder after milling, manual milling using a mortar or the like may be performed.

  As a method for preparing a raw material powder containing an aggregate in which primary particles are softly bonded, a process of adding a liquid such as water or an organic binder to the raw material powder and granulating it can also be mentioned. In such a treatment, it is preferable to adjust the addition amount to be small in consideration of the fact that the liquid component added in the ceramic film undergoes vaporization and expansion in the subsequent heat treatment step.

<Deposition process>
Using the raw powder subjected to the above-mentioned pre-powder treatment, film formation by the AD method is performed using an apparatus as shown in FIG. 2 or FIG. That is, the raw powder subjected to the above-mentioned pre-powder treatment is aerosolized and collides with the film-forming substrate to crush primary particles in the raw material powder, and the crushed material powder is deposited on the film-forming substrate. A deposition step is performed.

  In the present embodiment, this deposition step is performed under the condition that some of the primary particles in the raw material powder remain in the crushed material as aggregates without being crushed. In the normal AD method, the purpose is to form a dense film, so it is not preferable that the primary particles in the raw material powder remain in the crushed material without being crushed. There was no idea of actively remaining.

  FIG. 4A is a diagram schematically showing an enlarged cross-sectional view of the ceramic film 62 formed after this step, and FIG. 6A is a SEM cross-sectional photograph of the ceramic film formed after this step in Example 1 described later. FIG. 5 is an explanatory diagram of the trap / crash model proposed by the present inventor.

  As shown in the left diagram of FIG. 5, the normal raw material powder is in a state where a large number of aggregates 64 (secondary particles) in which a plurality of primary particles 64P are aggregated are dispersed. The left diagram in FIG. 5 shows a state in which one aggregate 64 is about to collide with the film forming substrate 13.

  In the normal AD method, the aerosol containing the raw material powder collides with the film forming substrate with a large kinetic energy. At this time, many primary particles are crushed to become crushed material having a finer particle diameter and deposited on the film forming substrate. The fine particle group in FIG. 4A is a pulverized product 63 of primary particles.

  In the present embodiment, since the pre-powder treatment for weakening the bonding force between the primary particles is performed, as shown in the lower right diagram (b) of FIG. It can remain in the crushed material 63 as an aggregate 64 (trap phenomenon). Although this mechanism is not necessarily clear, the present inventor believes that this phenomenon is due to the fact that the collision energy to the film-forming substrate is absorbed by the weak binding force between the primary particles.

  In the state where the binding force between the primary particles in the raw material powder is strong, the collision energy to the film forming substrate easily propagates to the plurality of primary particles 64P forming the aggregate 64, and the upper right diagram (a) in FIG. As shown, the aggregates 64 are crushed and the primary particles 64P are disconnected from each other (crash phenomenon). These primary particles 64P do not contribute to the film formation and are not trapped in the crushed material 63, but collide with the film forming substrate 13 again, and become a crushed material 63 having a finer particle diameter. It is considered that the film is deposited on the film forming substrate 13.

  Since the agglomerates 64 collide with the film forming substrate 13 in an energy-stable, relatively sphere-like shape, as shown in the lower right view (b) of FIG. 4A and FIG. 5 and FIG. 6A. The aggregate 64 remaining in the crushed material 63 becomes a disk shape.

  In FIG. 4A, it is considered that some voids exist between the primary particles 64P of the aggregate 64 taken into the crushed material 63. Since the AD method is carried out in a reduced pressure state less than atmospheric pressure, preferably in a reduced pressure state of 100 Pa or less, the pressure in the gap is equivalent to the pressure in the film formation chamber of the AD method.

  After this step, a ceramic film 62 having a film structure in which a plurality of aggregates 64 are incorporated in the dense crushed material 63 is obtained. In the present embodiment, heat treatment is further performed in a later process, but the intermediate product film 62 after this process is also novel. The relative density of the intermediate product film 62 is, for example, 50 to 95%.

<Heat treatment process>
A heat treatment is performed on the ceramic film 62 after the deposition step. FIG. 4C schematically shows a ceramic film after heat treatment at a temperature equal to or higher than the sintering temperature of the aggregate 64 remaining in the crushed material 63, and FIG. 4B shows a ceramic film at an intermediate temperature from FIG. 4A to FIG. 4C. Is shown. FIG. 6B is a SEM cross-sectional photograph of the ceramic film formed after this step in Example 1 described later.

  For example, in the case of an alumina film or a YSZ (yttria stabilized zirconia) film, the intermediate state shown in FIG. 4B is obtained by heat treatment at about 1200 ° C., and the state shown in FIG. 4C is obtained by heat treatment at 1500 ° C. or higher.

  When heat treatment is performed on the ceramic film 62, the crushed material 63 grows and crystal grains 65 having a larger particle diameter are generated and densified. On the other hand, the aggregate 64 remaining in the crushed material 63 is sintered and contracted to form pores 66. The shape of the pores 66 inherits the shape of the aggregates 64 remaining in the crushed material 63 and becomes a disk shape.

  In the present embodiment, as shown in FIG. 6B, a film in which a plurality of disc-shaped pores 66 exist independently in a dense ceramic made up of a large number of crystal grains 65 produced by grain growth of crushed material 63. A ceramic film 14 having a structure is obtained.

  The number and size of the pores 66 correlate with the number and size of the aggregates 64 remaining in the crushed material 63, and therefore can be controlled by controlling the pre-powder treatment process and the deposition process.

  It has been described that the ceramic thermal barrier layer 14 is preferably a porous film having a relative density of 50 to 95%, for example, but the relative density can be controlled within a preferable range by controlling the pre-powder treatment step and the deposition step. . It is also possible to control the relative density outside the range of 50 to 95%.

  In FIG. 4A before the heat treatment, it is considered that there are some voids between the primary particles 64P of the aggregate 64 taken into the crushed material 63, and the pressure of the voids is the same level as the pressure in the film formation chamber of the AD method. I mentioned earlier.

The agglomerates 64 taken into the crushed material 63 and the voids somewhat present between the primary particles 64P of the agglomerates 64 are a group of dense crushed materials 63 existing around them or crystal grains 65 from which the grains have grown. Due to the presence of the group, the film is cut off from the outside of the film, so that the internal pressure of the pores 66 generated after this step is equal to or lower than the pressure in the film forming chamber of the AD method. That is, pores 66 having an internal pressure of less than atmospheric pressure, for example, 10 ⁴ Pa or less are generated. Since the pores 66 are independent of the external environment, the internal pressure of the pores 66 does not depend on the pressure of the external environment.

  The heat treatment temperature may be a temperature at which the pores 66 are generated. If heat treatment is performed at a temperature higher than the sintering temperature of the aggregate 64 taken into the crushed material 63, the pores 66 are reliably generated. Even at an intermediate temperature lower than that, pores 66 are generated as shown in FIG.

  When the heat treatment temperature at which the pores 66 are generated is higher than the heat resistance temperature of the metal bonding layer 12 that is the base, the heat effect on the base is relatively reduced, such as heating from the surface side of the ceramic film 62. There is a need to.

  The manufacturing method of this embodiment is applicable to arbitrary uses other than a ceramic thermal barrier layer. For example, in the case of ceramics such as PZT (lead zirconate titanate), the sintering temperature is lower than that of ceramics for the ceramic heat shield layer, and the pores 66 can be generated at a relatively low temperature. In such a case, it is not indispensable to devise a heat treatment because the thermal influence on the base can be reduced.

  As described in the section “Problems to be Solved by the Invention”, in the plasma spraying method and the EB-PVD (electron beam deposition) method, which are the conventional methods for producing a ceramic thermal barrier layer, the generated pores are in the external environment. Therefore, the pressure inside the pores is atmospheric pressure under normal atmospheric pressure use conditions. That is, the ceramic film itself having a plurality of pores whose internal pressure is less than atmospheric pressure is novel.

  Whether or not the pores communicate with the external environment can be evaluated by, for example, a BET adsorption test. Compared with the same composition and the same porosity, the pores generated in the ceramic film by the conventional plasma spraying method and EB-PVD method are in communication with the external environment, whereas the BET specific surface area is greatly increased. Even if a large number of pores 66 are formed in the ceramic film obtained in this embodiment, the BET specific surface area is not so large because they are independent of the external environment.

  According to this embodiment, it is possible to provide the ceramic heat shield layer 14 which is preferably a porous film having a relative density of 50 to 95%. Since the ceramic heat shield layer 14 has a porous structure, the heat shield property and the thermal shock resistance are good.

  According to this embodiment, the ceramic heat shield layer 14 having a plurality of pores 66 independent of the external environment can be manufactured. In the conventional ceramic heat shield layer having pores communicating with the external environment, high-temperature combustion gas or the like easily enters the pores. However, in the ceramic heat shield layer 14 of the present embodiment, this is not the case. Thermal insulation and thermal shock resistance are further improved.

Furthermore, according to this embodiment, the ceramic heat shield layer 14 having a plurality of pores 66 whose internal pressure is less than atmospheric pressure can be manufactured, and the ceramic heat shield layer 14 having a plurality of pores 66 whose internal pressure is 10 ⁴ Pa or less. Can also be manufactured. As can be understood from the term of so-called vacuum insulation, the lower the internal pressure of the pores 66, the higher the heat shielding property.

  According to this embodiment, the ceramic heat shield layer 14 having a plurality of pores 66 independent of the external environment can be manufactured. Unlike the conventional ceramic thermal barrier layer having pores communicating with the external environment, the ceramic thermal barrier layer 14 has good oxygen barrier properties. Therefore, in the thermal barrier coating structure 1 of the present embodiment, the generation of metal oxide (TGO) on the surface of the metal bonding layer 12 and the ceramic thermal barrier by this, without providing an oxygen barrier layer separately as in the conventional method. Interfacial peeling between the layer 14 and the metal bonding layer 12 is suppressed.

  An oxygen barrier layer formed by a wet method or a normal vapor deposition method does not have good adhesion to the base, cannot withstand repeated thermal shocks, and may cause interface peeling. In this embodiment, since it is not necessary to provide an oxygen barrier layer, such a problem does not occur.

  In the thermal barrier coating structure 1 of the present embodiment, a good thermal barrier property / thermal shock resistance / oxygen barrier property can be obtained by the ceramic thermal barrier layer 14 alone, so that layers other than the metal bonding layer 12 and the ceramic thermal barrier layer 14 are provided. There is no need. However, other layers may be provided as necessary.

(Modification example of ceramic film manufacturing method)
In the above embodiment, the case where the raw material powder has a uniform composition has been described. In this case, the composition of the crushed material 63 and the composition of the primary particles 64P remaining as aggregates 64 in the crushed material 63 are the same.

  As the raw material powder, the deposition process may be performed using a powder whose composition is adjusted so that the composition of the crushed material 63 and the composition of the primary particles 64P remaining as aggregates 64 in the crushed material 63 are different. . Also by this method, a ceramic film having the same pore structure and effect as described above can be produced.

  In this case, the raw material powder A having the composition of the crushed material 63 and the raw material powder B having the composition of the aggregate 64 remaining in the crushed material 63 are prepared, respectively, and only the raw material powder B is subjected to the milling or the like. It is preferable to mix the raw material powder A and the raw material powder B after carrying out the powder treatment to weaken the bonding force between the primary particles in the raw material powder B, and to carry out the deposition step using this mixture as the raw material powder. .

  An aerosol containing the raw material powder A and an aerosol containing the raw material powder B may be separately generated, and these aerosols may be simultaneously injected onto the film-forming substrate to perform the deposition step. In this case, the aerosol containing the raw material powder A and the aerosol containing the raw material powder B, which are separately generated, may be sprayed from different spray nozzles to the film-forming substrate, respectively, before the spray nozzle, etc. The aerosol containing the generated raw material powder A and the aerosol containing the raw material powder B may be merged and then injected from the same injection nozzle onto the film forming substrate.

  It is particularly preferable to use a raw material powder whose composition is adjusted so that the melting point of the primary particles 64P remaining as aggregates 64 in the crushed material 63 is lower than the melting point of the crushed material 63. In this case, since the heat treatment temperature generated by the pores 66 can be relatively lowered, the thermal influence on the base can be reduced.

For example, the composition of the crushed material 63 is an oxide ceramic containing at least one selected from the group of Al ₂ O ₃ , HfO ₂ , CeO ₂ , and ZrO ₂ , and is left as an aggregate 64 in the crushed material 63. A combination of the primary particles 64P having a relatively low melting point composition such as PZT is conceivable.

  Embodiments according to the present invention will be described.

Example 1
A PZT powder (lead zirconate titanate, trade name PZT-L9) manufactured by Sakai Chemical Co., Ltd. was prepared. The particle size data was measured and found to be as follows. This raw powder was milled for 1 hour using an automatic mortar with dry-box (MND-01, AS ONE, Osaka, Japan).
Average primary particle diameter observed with a scanning electron microscope (FE-SEM, S-4100, Hitachi, Tokyo, Japan): 0.3 μm,
Average particle size measured with a particle size distribution meter (Microtrac MT3300, Nikkiso, Tokyo, Japan) (particle size measured with a particle size distribution meter is mainly a secondary particle size): about 1 μm.

A 300 μm thick PZT film was formed on a stainless steel substrate using the AD film forming apparatus shown in FIG. The film forming conditions were as follows.
The flow rate of gas introduced into the aerosol generation container by the hoisting gas nozzle and the pressure adjusting gas nozzle: 7 L / min,
Deposition substrate temperature: room temperature (27 ° C.)
Pressure of aerosol generation container: 50 kPa,
Deposition chamber pressure: 50 Pa.

  A SEM cross-sectional photograph of the ceramic film formed after this step is shown in FIG. 6A. As shown in the drawing, it was confirmed that a PZT film having a film structure in which a plurality of aggregates were taken in a disk-like form in a dense crushed material was obtained. The diameter of the aggregate was about 3 to 10 μm.

  After the film formation, the stainless steel substrate was removed by etching from the back side of the stainless steel substrate, and only the PZT film was taken out. On the other hand, heat treatment was performed in an air atmosphere at 1000 ° C. for 3 hours (this heat treatment temperature is equal to or higher than the sintering temperature of PZT). FIG. 6B shows a SEM cross-sectional photograph of the PZT film formed after this step.

  As shown in the figure, the crushed material is grown to produce crystal grains having a larger particle diameter, and the aggregate remaining in the crushed material is sintered and contracted to form disk-like pores. It was confirmed. That is, according to the present example, a PZT film having a film structure in which a plurality of disk-like pores exist independently in a dense ceramic made up of a large number of crystal grains generated by grain growth of crushed material is obtained. It was. The relative density of the obtained film was 80 to 90%, and the pore diameter was about 3 to 10 μm.

(Example 2)
Commercially available YSZ powder (yttria-stabilized zirconia) was prepared and milled for 1 hour using the same automatic mortar as in Example 1. A 300 μm-thick YSZ film was formed using the AD film forming apparatus shown in FIG. As the film forming substrate, a metal bonding layer made of an alloy represented by the general formula NiCrAlY was formed on a Ni-based superalloy alloy substrate by a low pressure plasma spraying method.

The deposition conditions for the YSZ film were as follows.
The flow rate of gas introduced into the aerosol generation container by the hoisting gas nozzle and the pressure adjusting gas nozzle: 7 L / min,
Deposition substrate temperature: room temperature (27 ° C.)
Pressure of aerosol generation container: 50 kPa,
Deposition chamber pressure: 50 Pa.

As a result of SEM observation, as in Example 1, it was confirmed that a YSZ film having a film structure in which a plurality of aggregates were taken in a disk-like form in a dense crushed material was confirmed.
After the film formation, heat treatment was performed in an air atmosphere at 1500 ° C. for 3 hours (this heat treatment temperature is equal to or higher than the sintering temperature of YSZ). When SEM observation was carried out, as in Example 1, the crushed material was grown and crystal grains having a larger particle diameter were generated, and the aggregate remaining in the crushed material was sintered and contracted. It was confirmed that disk-like pores were formed. Also according to this example, a YSZ film having a film structure in which a plurality of disk-like pores exist independently in a dense ceramic made up of a large number of crystal grains generated by the growth of crushed particles was obtained.

  The ceramic film of the present invention can be preferably used for a thermal barrier coating structure for protecting a member used in a high temperature environment from heat.

Sectional drawing which shows typically the thermal barrier coating structure of embodiment which concerns on this invention The figure which shows the structural example of AD film-forming apparatus Diagram showing an example of design change of the deposition system Diagram showing an example of design change of the deposition system Schematic diagram showing the mechanism of pore generation Schematic diagram showing the mechanism of pore generation Schematic diagram showing the mechanism of pore generation Explanatory diagram of the trap / crash model proposed by the present inventor SEM cross-sectional photograph of PZT film before firing in Example 1 SEM cross-sectional photograph of PZT film after firing at 1000 ° C. in Example 1 Thermal barrier coating structure described in Patent Document 1 Thermal barrier coating structure described in Non-Patent Document 1

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Thermal barrier coating structure 11 Metal base material 12 Metal bonding layer 13 Film-forming base material 14 Ceramic thermal barrier layer 61 Ceramic raw material powder 62 Ceramic film before baking 63 Crushed material 64 Aggregate 64P Primary particle which comprises aggregate 65 Crystal grain 66 pores

Claims (14)

A ceramic film having a deposition step of causing aerosolized ceramic raw material powder to collide with a film forming substrate to crush primary particles in the raw material powder, and depositing the crushed material powder on the film forming substrate. In the manufacturing method of
A method for producing a ceramic film, wherein the deposition step is carried out under a condition that a part of primary particles in the raw material powder remains in the crushed material as an aggregate without being crushed.   The method for producing a ceramic film according to claim 1, further comprising a heat treatment step of forming pores by sintering and shrinking the aggregate remaining in the crushed material after the deposition step.   The method for producing a ceramic film according to claim 1 or 2, further comprising a pre-powder treatment step for weakening the bonding force between primary particles in the raw material powder before the deposition step.   The method for producing a ceramic film according to claim 3, wherein the pre-powder treatment step is a step of milling the raw material powder.   The raw material powder is subjected to the deposition step using a powder whose composition is adjusted so that the composition of the crushed material and the composition of the primary particles remaining as the aggregate in the crushed material are different. The method for producing a ceramic film according to any one of claims 1 to 4.   The deposition step is performed using the raw material powder whose composition is adjusted so that the melting point of the primary particles remaining as aggregates in the crushed material is lower than the melting point of the crushed material. The method for producing a ceramic film according to claim 5.   A ceramic film produced by the method for producing a ceramic film according to claim 1.   A ceramic film having a plurality of pores having an internal pressure of less than atmospheric pressure in the ceramic film.   The ceramic film according to claim 8, which is a porous film having a relative density of 50 to 95%.   The ceramic film according to claim 8 or 9, wherein the plurality of pores have a disk shape in plan view.   The ceramic film according to claim 8, wherein the plurality of pores are independent of each other. 12. The ceramic film according to claim 8, comprising at least one oxide ceramic selected from the group consisting of Al ₂ O ₃ , HfO ₂ , CeO ₂ , and ZrO ₂ . In a thermal barrier coating structure for protecting a metal substrate from heat,
A thermal barrier coating structure comprising a metal bonding layer and a thermal barrier layer made of the ceramic film according to any one of claims 8 to 12 in order from the metal substrate side. The metal base material is mainly composed of an alloy containing at least one metal element selected from the group consisting of Co, Ni, and Fe,
The metal bonding layer is mainly composed of at least one alloy represented by the general formula MCrAlY (wherein M represents Ni and / or Co, Cr represents chromium, Al represents aluminum, and Y represents yttrium). The thermal barrier coating structure according to claim 13.