KR20200075355A - Non oxide substrate comprising densified top coating and method of forming thereof - Google Patents

Abstract

The present invention relates to a non-oxide substrate including a densified top coating, and also relates to a method for manufacturing the non-oxide substrate including the densified top coating. In the present invention, provided is a substrate including a densified coating layer by densifying the coating of a substrate (a base material), thereby providing a shielding coating layer with improved high temperature chemical stability.

Description

Non-oxide substrate including densified top coating and its manufacturing method {NON OXIDE SUBSTRATE COMPRISING DENSIFIED TOP COATING AND METHOD OF FORMING THEREOF}

The present invention relates to a non-oxide substrate comprising a densified top coating, and also to a method for producing a non-oxide substrate comprising such a densified top coating.

Materials applied to the defense industry, aerospace, and high-tech industries are representative materials exposed to extreme use environments such as high temperature, high pressure, and chemical deterioration. Therefore, the development of composite materials with heat resistance, light weight, and corrosion resistance for core component materials such as turbine engines and peripheral devices, and the technology to maintain and protect the materials are required. Among these composite materials, ceramic matrix composites (CMC) based on silicon carbide (SiC), which is durable and has high temperature stability, is used for various applications such as gas turbine engines and peripheral parts as materials for ultra-high temperature environments. It is attracting attention as a material.

However, in the case of SiC, it is known that chemical deterioration such as erosion and oxidation may be accelerated in an environment repeatedly exposed to CMAS (calcium-magnesium aluminosilicate) or moisture in a high temperature environment of 1300°C or higher. Therefore, research on environmental shielding coating technology (EBC) is being conducted to suppress chemical deterioration at high temperatures and to protect Si-based CMC substrates from high temperature, moisture, high pressure fuel, and other oxidation and erosion environments.

Materials such as SiC and Si ₃ N ₄ are used as materials for aircraft turbine engines and generator turbines, and these materials are very vulnerable to moisture and oxygen, and require chemical resistance at high temperatures. Since the use temperature is 1200 to 1800℃, chemical resistance (preventing chemical deterioration) at high temperature is necessary.

At present, research on coatings exhibiting heat resistance and chemical resistance at high temperatures has been continuously conducted.

In the present invention, to provide a method for densifying the coating to secure the heat resistance and chemical resistance of the substrate (base material) at a high temperature, and to provide a substrate having the densified coating layer.

A method of forming a densified top coating on a non-oxide substrate according to an embodiment of the present invention comprises: preparing a non-oxide substrate; Forming a bond coating layer on the substrate; Forming a top coating layer made of yttrium silicate or rare earth silicate on the bond coating layer; And densifying the top coating layer.

The non-oxide substrate is a silicon-based non-oxide substrate.

The bond coating layer is made of a silicon-based material.

Forming a top coating layer made of yttrium silicate or rare earth silicate on the bond coating layer comprises: preparing a suspension in which calcined yttrium silicate or calcined lanthanum rare earth silicate raw powder is dispersed; Coating the suspension by spraying the suspension onto a base material using a Suspension Plasma Spray (SPS) method; And heat-treating the coated coating film.

The rare earth silicate is a lanthanide rare earth silicate. The lanthanide rare earth elements are La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu.

The step of densifying the top coating layer includes: preparing a coating solution for densification; Dipping the substrate in which the top coating layer is formed in the coating solution; And drying the substrate and then heat-treating it.

The coating solution for densification includes liquefying any one or more of rare earth oxides, Al ₂ O ₃ , SiO ₂ , and ZrO ₂ .

The coating solution for densification is controlled according to the temperature of use of the substrate.

A method of forming a densified top coating on a non-oxide substrate according to a further embodiment of the present invention includes preparing a silicon-based non-oxide substrate; Forming a silicon-based bond coating layer on the substrate; Forming a top coating layer made of yttrium silicate or rare earth silicate on the bond coating layer; And densifying the top coating layer, and densifying the top coating layer comprises: preparing a coating solution for densification; Dipping the substrate in which the top coating layer is formed in the coating solution; And drying the substrate and then heat-treating it.

The coating solution for densification includes liquefying any one or more of rare earth oxides, Al ₂ O ₃ , SiO ₂ , and ZrO ₂ .

The coating solution for densification is controlled according to the temperature of use of the substrate.

The present invention provides a substrate including a densified coating layer by densifying the coating of the substrate (base material), thereby providing a shielding coating layer having improved high-temperature chemical stability.

1 shows a flow chart of a method of forming a densified top coating on a non-oxide substrate according to an embodiment of the present invention.
2 is a flowchart illustrating a method of forming a top coating on a non-oxide substrate according to an embodiment of the present invention.
Figure 3 shows a flow chart of a method for densifying the top coating according to an embodiment of the present invention.
4A and 4B respectively show schematic views of a substrate on which the densification process is not performed and a substrate on which the densification process is performed.
5 is a schematic diagram for performing a densification process according to an embodiment of the present invention.
6A and 6B show SEM images of a substrate on which densification is not performed and a substrate on which densification is performed, respectively.
Various embodiments are now described with reference to the drawings, and like reference numbers throughout the drawings are used to indicate similar elements. For purposes of illustration, various descriptions are presented to provide an understanding of the invention. However, it is apparent that these embodiments can be practiced without these specific details. In other instances, well-known structures and devices are presented in block diagram form in order to facilitate describing the embodiments.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The present invention may be variously modified and may have various forms, and specific embodiments will be illustrated in the drawings and described in detail in the text. However, this is not intended to limit the present invention to a specific disclosure form, and it should be understood that all modifications, equivalents, and substitutes included in the spirit and scope of the present invention are included. In describing each drawing, similar reference numerals are used for similar components.

The terms used in the present application are only used to describe specific embodiments and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this application, the terms "comprises" or "have" are intended to indicate the presence of features, steps, acts, components, parts or combinations thereof described in the specification, one or more other features or steps. It should be understood that it does not preclude the existence or addition possibility of the operation, components, parts or combinations thereof.

1 shows a flow chart of a method of forming a densified top coating on a non-oxide substrate according to an embodiment of the present invention.

As shown in Figure 1, a method of forming a densified top coating on a non-oxide substrate according to an embodiment of the present invention, preparing a non-oxide substrate (S 110); Forming a bond coating layer on the substrate (S 120); Forming a top coating layer made of yttrium silicate or rare earth silicate on the bond coating layer (S 130); And densifying the top coating layer (S 140).

In step S 110, a non-oxide substrate is prepared. As the non-oxide substrate, a silicon-based non-oxide substrate is used. SiC or Si ₃ N ₄ may be used as the substrate (base material) on which the coating is made, and these substrates are used for defense applications, aerospace, and high-tech industries, such as ultra-high temperature, high pressure, and chemical degradation. These are representative materials to be exposed. It is used as core parts such as turbine engine and peripheral equipment.

In step S 120, a bond coating layer is formed on the substrate. The bond coating layer may be made of a silicon-based material, and other bonding materials may be used. The bond coating layer serves to connect each other between the substrate and the top coating, and also serves as a substrate protection barrier. It is preferable to use a material that is in a value between the coefficient of thermal expansion of each of the materials of the substrate and the top coating layer as the bond coating layer. This minimizes the rate of change due to thermal expansion due to temperature change so that the top coating layer is well maintained.

In step S 130, a top coating layer made of yttrium silicate or rare earth silicate is formed on the bond coating layer. The base material of the coating film is coated on a base material such as a turbine or a generator as described above. The base material is made of SiC or Si ₃ N ₄ . The coating film ultimately improves the reliability of the base material by inhibiting moisture or oxygen from penetrating the base material. In the present invention, heat resistance and chemical resistance are secured at a higher temperature by additionally passing through a top coating and a densification coating step described later.

2 is a flowchart illustrating a method of forming a top coating on a non-oxide substrate according to an embodiment of the present invention. A method of forming a top coating includes preparing a suspension in which calcined yttrium silicate or calcined lanthanum rare earth silicate raw material powder is dispersed (S 210); Spraying and coating the suspension on the base material using a suspension plasma spray (SPS) method (S 220); And heat-treating the coated coating film (S 230).

In step S 210, a suspension in which calcined yttrium silicate or calcined lanthanum rare earth silicate raw material powder is dispersed is prepared. After mixing the raw powders in a certain ratio, mixing them through a ball mill, etc., calcining them at a high temperature to prepare the powders, and using this to prepare a suspension. Lanthanum rare earth elements are used from La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu. Ethanol and distilled water may be used as solvents in preparing the suspension.

In step S 220, the suspension may be coated by spraying the suspension on a base material using a suspension plasma spray (SPS) method. In this case, a general thermal spray coating or air plasma spray (APS) is also possible. In the case of using a conventional thermal spray coating, coating is performed using a granulated powder raw material instead of a suspension. In addition, in the case of using a general thermal spray coating, in step S 210, a process of preparing granule powder according to a target composition is performed. In addition, in the case of a general thermal spray coating, coating is performed by spraying the base material using a granulated powder raw material. Suspension plasma spray (SPS) method uses a small-sized particle material in the form of droplets, compared to atmospheric plasma sprays using powdered raw materials, and the particle size of the sprayed droplets is as small as a few microns, resulting in atmospheric plasma spraying. Compared to this, a denser and higher density coating layer can be obtained. He, Ar, N ₂ and H ₂ are used as the plasma forming gas.

In step S 230, the coated coating film is heat treated. The heat treatment may be performed in various ways depending on the use and condition, and typically, a fusion method by flame or a heating method by a lamp after forming a coating layer may be used, but is not limited thereto. The heat treatment of step S 230 is not an essential step and can be applied only when necessary, and such a heat treatment is not an essential process even in the case of a general thermal spray coating, but can be used as needed.

In step S 140, the step of densifying the top coating layer is performed. Figure 3 shows a flow chart of a method for densifying the top coating according to an embodiment of the present invention.

As shown in Figure 3, the step of densifying the top coating layer, the step of preparing a coating solution for densification (S 310); Dipping the substrate in which the top coating layer is formed in a coating solution (S 320); And drying and heat-treating the substrate (S330).

In the present invention, when only the top coating was performed, it was confirmed that pores or cracks were observed, and the heat resistance and chemical resistance were further enhanced by performing a densification coating to densify these pores or cracks. These pores or cracks are usually several tens of nm to mm in size, and through these pores or cracks, an external gas may cause oxidation or erosion, and thus a densification process to reduce the size of the pores or cracks is required.

As the coating liquid for densification, a liquid obtained by liquefying any one or more of rare earth oxides, Al ₂ O ₃ , SiO ₂ , and ZrO ₂ is used. It may be available as long as it is a liquefied rare earth oxide.

The coating solution for densification can be controlled according to the temperature of use of the substrate. That is, a rare earth-based oxide having good high-temperature durability may be used depending on the use temperature of the substrate (base material), or one of Al ₂ O ₃ , SiO ₂ , and ZrO ₂ may be used if the use temperature is not very high. That is, the coating material for densification can be controlled differently according to the use temperature. The manufacturing, coating, and heat treatment processes of the specific coating solution will be further described in the following examples.

The non-oxide substrate including the densified top coating prepared according to the method of the present invention described so far exhibits high temperature heat resistance and chemical resistance at high temperature. Thus, these non-oxide substrates can be used in chemical plants, aircraft engines, nuclear power plants, and aerospace materials.

The contents of the present invention have been described so far, and the contents of the present invention will be further described below with specific examples.

As the coating substrate, a coin-shaped sintered silicon carbide (Silicon carbide, SiC, 99.9%, MAX-TECH, Korea) substrate having a thickness of 3 mm and a diameter of 1 inch was used. To increase the adhesion between the substrate material and the coating layer, the surface of the substrate was treated by sand blasting before coating. Then, after 30 minutes of ultrasonic cleaning with acetone, dried and sprayed.

The coating layer was prepared by a double layer structure consisting of a bond coating and a top coating. Si (99.9%, Vesta, Sweden) powder was used as the bond coating material, and Ytterbium disilicate (Yb ₂ Si ₂ O ₇ ) powder was used as the top coating. Yb ₂ Si ₂ O ₇ raw material powder for manufacturing top coat is Yb ₂ O ₃ (99.9%, Materion, USA, 4μm) and SiO ₂ (99.9%, kojundo chemical, Japan, 4μm) powder 1:2( mol. ratio) and mixed for 6 hours through a ball mill, calcined at 1500°C for 12 hours, Yb ₂ Si ₂ O ₇ The powder was prepared. The calcination condition was heat-treated at a heating rate of 5° C./min for 12 hours, and then 1500° C. conditions were selected and applied to the suspension preparation. A suspension having a particle size of about 4 μm was prepared by a ball mill method using zirconia balls for 24 hours by adding 0.5 wt% of dibuthyl phosphate as a dispersant to 10 wt% of Yb ₂ Si ₂ O ₇ and ethanol solvent 900 ml. The suspension for the manufacture of the bond coating was prepared by preparing 10 wt% of Si powder in 900 ml of ethanol solvent, and at this time, 0.5 wt% of dibuthyl phosphate was added as a dispersant. The suspension for bond coating was prepared through ball milling for 4 hours. At this time, the particle size was observed at a level of about 3 μm.

In the plasma spray coating process, the substrate was fixed to a rotating table, and rotated at 250 RPM to spray the suspension to prepare a coating layer. Before preparing the bond coating and the top coating, the mixture was preheated through plasma irradiation for 70 times under a mixed condition of Ar and N ₂ gas (Ar:N ₂ =80:20). At this time, the surface temperature of the substrate material was 270°C. In order to deposit the bond coating on the surface of the substrate material, a Si bond coat layer was prepared by plasma spraying under conditions such as preheating. The top coating was intended to prepare a coating layer composed of a composition of Yb ₂ Si ₂ O ₇ using a suspension made of 1500°C calcined powder. At this time, Ar 60-80% of gas conditions, 10-20% of N _{2, and} 10-20% of H ₂ were flowed at 45 ml per minute, and coating was performed under the current condition of 230A.

The schematic diagram of the substrate having the bond coating and the top coating thus produced is illustrated in FIG. 4A.

Thereafter, the process of densification is performed. 5 shows a schematic diagram of performing a densification process according to an embodiment of the present invention, and FIG. 4B shows a schematic diagram of a densification process for the substrate of FIG. 4A.

The densification process is performed as follows. First, a coating solution is prepared. The coating solution was stirred by adding 2 mol of Ytterbium(III) Nitrate pentahydrate (N ₃ O ₃ Yb·5H ₂ O) + 2 mol of Tetraethyl orthosilicate (C ₈ H ₂₀ O ₄ Si) to 100 ml of ethanol. Top-coated (Yb-Si-O (Yb ₂ SiO ₅ , Yb ₂ Si ₂ O ₇ )) is immersed in the prepared coating solution as shown in Figure 4a, defoamed (bubble removed) and dried (vacuum oven, 60 After drying at 1 C for 1 hour), heat treatment was performed at 1400 C for 5 hours at normal pressure.

6A and 6B show SEM images of a substrate on which densification is not performed and a substrate on which densification is performed, respectively.

6A and 6B, as shown in the SEM images of the substrates after which the densification process was not performed and the substrates after the densification process, respectively, the pores or cracks were much seen before densification, but were rapidly reduced after densification.

The images below of FIGS. 6A and 6B respectively show weight changes after a wet oxidation test for a substrate on which the densification process is not performed and a substrate on which the densification process is performed. The wet oxidation resistance evaluation was conducted in an atmosphere of H ₂ O 90% + O ₂ 10% for 100 hrs at a temperature of 1400°C. If the support which have a densification process was conducted, the weight change is 0.08mg / cm ² h after wet oxidation test, when the densification process is a wet oxidation comprising the weight change 0.0014mg / cm was ² h after test. Through this, it was confirmed that when the densification process was performed, the wet oxidation resistance of about 80 times or more was improved.

The description of the presented embodiments is provided to enable any person of ordinary skill in the art to use or practice the present invention. Various modifications to these embodiments will be apparent to those skilled in the art of the present invention, and the general principles defined herein can be applied to other embodiments without departing from the scope of the present invention. Thus, the present invention should not be limited to the embodiments presented herein, but should be interpreted in the broadest scope consistent with the principles and novel features presented herein.

Claims (14)

Preparing a non-oxide substrate;
Forming a bond coating layer on the substrate;
Forming a top coating layer made of yttrium silicate or rare earth silicate on the bond coating layer; And
Comprising the step of densifying the top coating layer,
A method of forming a densified top coating on a non-oxide substrate.
According to claim 1,
The non-oxide substrate is a silicon-based non-oxide substrate,
A method of forming a densified top coating on a non-oxide substrate.
According to claim 1,
The bond coating layer is made of a silicon-based material,
A method of forming a densified top coating on a non-oxide substrate.
According to claim 1,
The step of forming a top coating layer made of yttrium silicate or rare earth silicate on the bond coating layer,
Preparing a suspension in which calcined yttrium silicate or calcined lanthanide rare earth silicate raw powder is dispersed;
Coating the suspension by spraying the suspension onto a base material using a Suspension Plasma Spray (SPS) method; And
Comprising the step of heat-treating the coated coating film,
A method of forming a densified top coating on a non-oxide substrate.
According to claim 1,
The rare earth silicate is a lanthanide rare earth silicate,
A method of forming a densified top coating on a non-oxide substrate.
The method of claim 5,
The lanthanide rare earth elements are La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu phosphorus,
A method of forming a densified top coating on a non-oxide substrate.
According to claim 1,
The step of densifying the top coating layer,
Preparing a coating solution for densification;
Dipping the substrate in which the top coating layer is formed in the coating solution; And
Comprising the step of heat treatment after drying the substrate,
A method of forming a densified top coating on a non-oxide substrate.
The method of claim 7,
The coating solution for densification comprises liquefying any one or more of rare earth oxides, Al ₂ O ₃ , SiO ₂ , and ZrO ₂ ,
A method of forming a densified top coating on a non-oxide substrate.
The method of claim 7,
The coating solution for densification is controlled according to the temperature of use of the substrate,
A method of forming a densified top coating on a non-oxide substrate.
Preparing a silicon-based non-oxide substrate;
Forming a silicon-based bond coating layer on the substrate;
Forming a top coating layer made of yttrium silicate or rare earth silicate on the bond coating layer; And
Comprising the step of densifying the top coating layer,
The step of densifying the top coating layer,
Preparing a coating solution for densification;
Dipping the substrate in which the top coating layer is formed in the coating solution; And
Comprising the step of heat treatment after drying the substrate,
A method of forming a densified top coating on a non-oxide substrate.
The method of claim 10,
The coating solution for densification comprises liquefying any one or more of rare earth oxides, Al ₂ O ₃ , SiO ₂ , and ZrO ₂ ,
A method of forming a densified top coating on a non-oxide substrate.
The method of claim 10,
The coating solution for densification is controlled according to the temperature of use of the substrate,
A method of forming a densified top coating on a non-oxide substrate.
It is prepared according to the method of any one of claims 1 to 12,
Chemical resistance at high temperature,
Non-oxide substrate with densified top coating.
The method of claim 13,
The non-oxide substrate can be used as a chemical plant, aircraft engine, nuclear power plant, aerospace material,
Non-oxide substrate with densified top coating.

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