A water-heat corrosion resistant coated yttrium aluminum garnet layer silicon carbide ceramic connector and its preparation method and application

Abstract

The application belongs to the technical field of ceramic welding, and discloses a water and heat corrosion resistant silicon carbide ceramic connecting piece coated with a yttrium aluminum garnet layer and a preparation method and application thereof. The connecting piece is formed by connecting two silicon carbide ceramic substrates through a silicon carbide based ceramic intermediate layer; a yttrium aluminum garnet layer is formed by coating yttrium aluminum garnet powder on the side surface of the silicon carbide ceramic connecting piece; the silicon carbide based ceramic intermediate layer takes silicon carbide powder, aluminum oxide powder, yttrium oxide powder, gadolinium oxide powder and zirconium oxide powder as connecting layer raw materials, is uniformly mixed and then coated between the two silicon carbide ceramic substrates, and is prepared through hot-pressing sintering or discharge plasma sintering; the coating material is coated on the side surface of the silicon carbide ceramic connecting piece, and is heat treated at 1400-1550 DEG C under a protective atmosphere to obtain the connecting piece. The silicon carbide ceramic connecting piece coated with the yttrium aluminum garnet layer has high connecting strength and excellent water and heat corrosion resistance, and can be applied in the field of nuclear energy.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of ceramic connection, and particularly relates to a water and heat corrosion resistant silicon carbide ceramic connecting piece coated with a yttrium aluminum garnet layer and a preparation method and application thereof. BACKGROUND

[0002] SiC ceramics have excellent properties such as high strength, large specific stiffness, corrosion resistance, high temperature performance, oxidation resistance, wear resistance, and high thermal conductivity, and are widely used in the fields of aviation, aerospace, metallurgy, etc. Due to the low neutron absorption cross section and radiation resistance of SiC ceramics, SiC ceramics have great application potential in nuclear reactors. However, it is difficult to directly sinter large-sized and complex-shaped SiC ceramic parts for nuclear use due to the high brittleness and low ductility of SiC ceramics. Therefore, it is of great significance to develop a SiC ceramic connection technology. Since the self-diffusion coefficients of silicon and carbon elements in SiC are low, an intermediate layer material is generally introduced to realize the welding of SiC ceramics.

[0003] At present, the welding technology of SiC ceramics mainly includes mechanical connection, metal brazing, diffusion welding, precursor method connection, glass welding, reaction connection, and nano-impregnated transient eutectic phase connection. In the field of nuclear energy, SiC ceramic connecting pieces are required to have sufficient connection strength and water and heat corrosion resistance. The nano-impregnated transient eutectic phase connection technology can obtain a connecting piece with high connection strength, and the connection layer has good radiation resistance and good water and heat corrosion resistance in the short term. However, due to the presence of sintering aids in the connection layer, the sintering aids in the connection layer will be corroded first when the connecting piece is exposed to a high temperature and high pressure water environment for a long time, resulting in the detachment of SiC grains in the connection layer, the degradation of the connection layer, and the significant decrease of the mechanical properties of the SiC ceramic connecting piece, which cannot meet the related nuclear requirements. SUMMARY

[0004] In order to solve the problem that the traditional nano-impregnated transient eutectic phase connection layer material is corroded and degraded when exposed to a water and heat corrosion environment for a long time and cannot meet the nuclear requirements, the application provides a water and heat corrosion resistant SiC ceramic connecting piece coated with a yttrium aluminum garnet layer.

[0005] Another object of the application is to provide a preparation method of the above-mentioned SiC ceramic connecting piece.

[0006] Still another object of the application is to provide an application of the above-mentioned SiC ceramic connecting piece.

[0007] The technical scheme adopted by the application to solve the technical problems is as follows:

[0008] The application discloses a water and hot corrosion resistant silicon carbide ceramic connector coated with a yttrium aluminum garnet layer, which is formed by connecting two silicon carbide ceramic substrates through a silicon carbide based ceramic intermediate layer, and then coating yttrium aluminum garnet powder on the side of the silicon carbide ceramic connector to form a yttrium aluminum garnet layer; the silicon carbide based ceramic intermediate layer is formed by taking silicon carbide powder, aluminum oxide powder, yttrium oxide powder, gadolinium oxide powder and zirconium oxide powder as connecting layer raw materials, uniformly mixing the raw materials and then coating the mixture between the two silicon carbide ceramic substrates, and then performing hot-pressing sintering or discharge plasma sintering under vacuum or a protective atmosphere at 1600-1950 DEG C and 5-50 MPa; the yttrium aluminum garnet powder is mixed with PVA to obtain coating material, the coating material is uniformly coated on the side of the silicon carbide ceramic connector, and then the sample is placed in a tube furnace and heat-treated at 1400-1550 DEG C under a protective atmosphere.

[0009] Preferably, the particle size of the silicon carbide powder is 100-1000 nm, the particle size of the aluminum oxide powder is 30-100 nm, the particle size of the yttrium oxide powder is 30-100 nm, the particle size of the gadolinium oxide powder is 30-100 nm, and the particle size of the zirconium oxide powder is 30-100 nm.

[0010] Preferably, the mass ratio of the silicon carbide powder, the aluminum oxide powder, the yttrium oxide powder, the gadolinium oxide powder and the zirconium oxide powder is (80-90):(8-16):(1.8-3):(0.1-0.5):(0.1-0.5).

[0011] Preferably, the protective atmosphere is nitrogen, argon or helium.

[0012] Preferably, the particle size of the yttrium aluminum garnet powder is 100-500 nm, the mass concentration of the PVA solution is 0.2-5 wt%, and the mass ratio of the yttrium aluminum garnet powder to the PVA solution is 1:(2-10).

[0013] Preferably, the thickness of the silicon carbide based ceramic intermediate layer is 10-300 microns, and the average thickness of the coating layer is 1-100 microns.

[0014] Preferably, the shear strength of the silicon carbide ceramic connector at room temperature is 120-160 MPa, the shear strength of the silicon carbide ceramic connector in an air atmosphere at 1200 DEG C is 100-150 MPa, and the average thickness loss rate of the coating layer after corrosion in high-purity water at 360 DEG C / 18.6 MPa for 3 days is 0-0.45 microns.

[0015] The preparation method of the water and hot corrosion resistant silicon carbide ceramic connector coated with a yttrium aluminum garnet layer comprises the following specific steps:

[0016] S1. Mix silicon carbide powder, aluminum oxide powder, yttrium oxide powder, gadolinium oxide powder and zirconium oxide powder, coat between two silicon carbide ceramic substrates to obtain a pre-connector;

[0017] S2. Connect the pre-connector by hot-pressing sintering or spark plasma sintering at 1600-1950 DEG C, 5-50 MPa for 5-30 min under vacuum or protective atmosphere to obtain a silicon carbide ceramic connector;

[0018] S3. Mix yttrium aluminum garnet powder and PVA to obtain a coating material, uniformly spray or brush the coating material on the side surface of the silicon carbide ceramic connector, then put the sample into a tube furnace, and heat treat at 1400-1550 DEG C for 30-120 min under a protective atmosphere to obtain a silicon carbide ceramic connector coated with a yttrium aluminum garnet layer.

[0019] The application of the silicon carbide ceramic connector coated with a yttrium aluminum garnet layer resistant to hydrothermal corrosion in the field of nuclear energy.

[0020] Preferably, the application environment of the nuclear energy is a hydrothermal environment of ≥330 DEG C, ≥15.5 MPa.

[0021] Compared with the prior art, the present application has the following beneficial effects:

[0022] 1. The present application first proposes a system taking nano silicon carbide powder, aluminum oxide powder, yttrium oxide powder, gadolinium oxide powder and zirconium oxide powder as the original material of the connecting layer, and the connecting layer prepared by the system has excellent mechanical strength and hydrothermal corrosion resistance;

[0023] 2. The present application first proposes a surface coating layer design for a silicon carbide ceramic connector prepared by a nano-impregnation transient eutectic phase method. Through fine design of the composition and process of the connecting layer and the coating layer, the connecting layer and the coating layer are not simply superimposed, but form a mutual protection and enhancement relationship between the two: during the heat treatment process of forming the coating layer, the silicon carbide ceramic connecting layer and the silicon carbide substrate will react with the coating layer to realize the close combination of the coating layer with the connecting layer and the substrate. At the same time, part of the elements and components of the connecting layer also enter the yttrium aluminum garnet coating layer to obtain a dense yttrium aluminum garnet-based coating layer structure with gradient characteristics. This design not only can alleviate the interface thermal mismatch problem between the substrate and the coating layer, but also can further improve the hydrothermal corrosion resistance of the coating layer. In turn, the dense coating layer fully protects the connecting layer from being eroded by high temperature and high pressure water, thereby improving the hydrothermal corrosion resistance of the silicon carbide ceramic connector. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 It is a schematic diagram of the present application for realizing the connection of two silicon carbide ceramic parts through the connecting layer material.

[0025] Figure 2 A schematic diagram of the present application for surface coating of the connected silicon carbide ceramic parts with a yttrium aluminum garnet coating layer. DETAILED DESCRIPTION

[0026] The present application is further described in conjunction with the specific examples, but should not be construed as limited thereto. If not specifically mentioned, the technical means used in the examples are the conventional means known to those skilled in the art. Unless specifically mentioned, the reagents, methods and equipment used in the present application are the conventional reagents, methods and equipment in the technical field.

[0027] Figure 1 A schematic diagram of the present application for connecting two silicon carbide ceramic parts through the connecting layer material. From the left side of the figure, Figure 1 It can be seen that the silicon carbide ceramic connecting piece is formed by connecting two silicon carbide ceramic substrates through the silicon carbide-based ceramic intermediate layer. Figure 2 A schematic diagram of the present application for surface coating of the connected silicon carbide ceramic parts with a yttrium aluminum garnet coating layer. From the left side of the figure, Figure 2 It can be seen that the yttrium aluminum garnet layer is formed by coating the yttrium aluminum garnet powder on the side of the silicon carbide ceramic connecting piece.

[0028] Example 1

[0029] 1. Mix silicon carbide (particle size 100 nm), aluminum oxide (particle size 30 nm), yttrium oxide (particle size 30 nm), gadolinium oxide (particle size 30 nm) and zirconium oxide (particle size 30 nm) in a mass ratio of 88:8:3:0.5:0.5, and coat them between two silicon carbide ceramic substrates to obtain a pre-connecting piece;

[0030] 2. Put the pre-connecting piece into a discharge plasma sintering device through a mold, and process connecting under the following conditions: argon atmosphere, 1900℃, axial pressure 30 MPa, and holding time 15 min, to obtain a silicon carbide ceramic connecting piece;

[0031] 3. Mix yttrium aluminum garnet powder (particle size 100 nm) with 0.2-5wt% polyvinyl alcohol (PVA) to obtain a coating material, uniformly spray the coating material on the side of the silicon carbide ceramic connecting piece, and then put the sample into a tube furnace, heat treat under argon atmosphere at 1500℃ for 60 min, to obtain a silicon carbide ceramic connecting piece coated with a yttrium aluminum garnet layer.

[0032] The thickness of the connection layer of the silicon carbide ceramic connector coated with yttrium aluminum garnet layer prepared in this example is 30 μm, the shear strength of the connector at room temperature is 160 MPa, and the high temperature shear strength at 1200°C is 145 MPa. The initial thickness of the coating layer is 20 μm. After 3 days of corrosion in high-purity water at 360°C / 18.6 MPa, the average thickness loss of the coating layer is 0.25 μm. After 30 days of hydrothermal corrosion, the room temperature strength of the silicon carbide ceramic connector does not change significantly.

[0033] Example 2

[0034] 1. Mix silicon carbide (particle size 250 nm), aluminum oxide (particle size 50 nm), yttrium oxide (particle size 50 nm), gadolinium oxide (particle size 50 nm), and zirconium oxide (particle size 50 nm) in a mass ratio of 85:11:3:0.5:0.5, and coat between two silicon carbide ceramic substrates to obtain a pre-connector;

[0035] 2. Put the pre-connector into a discharge plasma sintering device through a mold, connect under an argon atmosphere at 1850°C, an axial pressure of 50 MPa, and a holding time of 10 min to obtain a silicon carbide ceramic connector (without coating layer).

[0036] 3. Mix yttrium aluminum garnet powder (particle size 100 nm) with 0.2-5 wt% PVA to obtain a coating material, uniformly spray the coating material on the side surface of the silicon carbide ceramic connector, and then put the sample into a tube furnace and heat treat at 1550°C for 30 min under an argon atmosphere to obtain a silicon carbide ceramic connector coated with a yttrium aluminum garnet layer.

[0037] The thickness of the connection layer of the silicon carbide ceramic connector coated with yttrium aluminum garnet layer prepared in this example is 20 μm, the shear strength of the connector at room temperature is 130 MPa, and the high temperature shear strength at 1200°C is 115 MPa. The initial thickness of the coating layer is 10 μm. After 3 days of corrosion in high-purity water at 360°C / 18.6 MPa, the average thickness loss of the coating layer is 0.30 μm. After 30 days of hydrothermal corrosion, the room temperature strength of the silicon carbide ceramic connector does not change significantly.

[0038] Example 3

[0039] 1. Mix silicon carbide (particle size 500 nm), aluminum oxide (particle size 50 nm), yttrium oxide (particle size 50 nm), gadolinium oxide (particle size 30 nm), and zirconium oxide (particle size 30 nm) in a mass ratio of 85:10:1.5:3:0.25:0.25, and coat between two silicon carbide ceramic substrates to obtain a pre-connector;

[0040] 2. Put the pre-connector into the spark plasma sintering device through the mold, connect under argon atmosphere at 1950℃, axial pressure 50MPa, holding time 10min, to obtain the silicon carbide ceramic connector.

[0041] 3. Mix yttrium aluminum garnet powder (particle size 300nm) with 0.2-5wt% PVA to obtain coating material, uniformly spray the coating material on the side of the silicon carbide ceramic connector, then put the sample into the tube furnace, heat treatment under argon atmosphere at 1550℃ for 60min, to obtain the silicon carbide ceramic connector coated with yttrium aluminum garnet layer.

[0042] The silicon carbide ceramic connector coated with yttrium aluminum garnet layer prepared in this example has a connecting layer thickness of 20μm, the shear strength of the connector at room temperature is 140MPa, and the high-temperature shear strength at 1200℃ is 120MPa. The initial thickness of the coating layer is 15μm. After 3d of high-purity water corrosion at 360℃ / 18.6MPa, the average thickness loss of the coating layer is 0.25μm. After 30d of hydrothermal corrosion, the room temperature strength of the silicon carbide ceramic connector does not change significantly.

[0043] Example 4

[0044] 1. Mix silicon carbide (particle size 100nm), aluminum oxide (particle size 50nm), yttrium oxide (particle size 50nm), gadolinium oxide (particle size 30nm) and zirconium oxide (particle size 30nm) in a mass ratio of 90:5:1.5:3:0.25:0.25, coat between two silicon carbide ceramic substrates to obtain a pre-connector;

[0045] 2. Put the pre-connector into the spark plasma sintering device through the mold, connect under argon atmosphere at 1750℃, pressure 30MPa, holding time 10min, to obtain the silicon carbide ceramic connector (without coating layer).

[0046] 3. Mix yttrium aluminum garnet powder (particle size 100nm) with 0.2-5wt% PVA to obtain coating material, uniformly spray the coating material on the side of the silicon carbide ceramic connector, then put the sample into the tube furnace, heat treatment under argon atmosphere at 1450℃ for 120min, to obtain the silicon carbide ceramic connector coated with yttrium aluminum garnet layer.

[0047] The silicon carbide ceramic connector coated with yttrium aluminum garnet layer prepared in this example has a connecting layer thickness of 60μm, the shear strength of the connector at room temperature is 120MPa, and the high-temperature shear strength at 1200℃ is 100MPa. The initial thickness of the coating layer is 30μm. After 3d of high-purity water corrosion at 360℃ / 18.6MPa, the average thickness loss of the coating layer is 0.35μm. After 30d of hydrothermal corrosion, the room temperature strength of the silicon carbide ceramic connector does not change significantly.

[0048] Example 5

[0049] 1. Mix silicon carbide (particle size 1000 nm), alumina (particle size 50 nm), yttria (particle size 50 nm), gadolinia (particle size 50 nm) and zirconia (particle size 50 nm) in a mass ratio of 89:8:2.6:0.2:0.2, coat between two silicon carbide ceramic substrates to obtain a pre-connector;

[0050] 2. Put the pre-connector into a discharge plasma sintering device through a mold, connect under an argon atmosphere at 1800°C, axial pressure of 30 MPa, and heat preservation for 20 min to obtain a silicon carbide ceramic connector (without coating layer).

[0051] 3. Mix yttrium aluminum garnet powder (particle size 100 nm) with 0.2-5wt% PVA to obtain a coating material, uniformly spray the coating material on the side surface of the silicon carbide ceramic connector, then put the sample into a tube furnace, heat treat under an argon atmosphere at 1450°C for 30 min to obtain a silicon carbide ceramic connector coated with a yttrium aluminum garnet layer.

[0052] The thickness of the connecting layer of the silicon carbide ceramic connector coated with a yttrium aluminum garnet layer prepared in this example is 40 μm, the shear strength of the connector at room temperature is 125 MPa, and the high-temperature shear strength at 1200°C is 110 MPa. The initial thickness of the coating layer is 45 μm. After 3 days of high-purity water corrosion at 360°C / 18.6 MPa, the average thickness loss of the coating layer is 0.45 μm. After 30 days of hydrothermal corrosion, the room temperature strength of the silicon carbide ceramic connector does not change significantly.

[0053] The above examples are the preferred embodiments of the present application, but the embodiments of the present application are not limited by the above examples, and any changes, modifications, substitutions, combinations and simplifications made without departing from the spirit and principles of the present application should be equivalent replacement methods, and are included in the protection scope of the present application.

Claims

1. A water-heat-corrosion resistant, yttrium-aluminum-garnet-layer-coated silicon carbide ceramic fitting, characterized in that, The silicon carbide ceramic connector coated with yttrium aluminum garnet layer is formed by connecting two silicon carbide ceramic substrates through a silicon carbide-based ceramic intermediate layer, and then coating yttrium aluminum garnet powder on the side of the silicon carbide ceramic connector to form a yttrium aluminum garnet layer, wherein the silicon carbide-based ceramic intermediate layer is formed by taking silicon carbide powder, aluminum oxide powder, yttrium oxide powder, gadolinium oxide powder and zirconium oxide powder as the connecting layer raw materials, uniformly mixing the raw materials and then coating the mixture between the two silicon carbide ceramic substrates, and then performing hot-pressing sintering or discharge plasma sintering under vacuum or in a protective atmosphere at 1600-1950 DEG C and 5-50 MPa; the yttrium aluminum garnet powder is mixed with PVA to obtain coating material, the coating material is uniformly coated on the side of the silicon carbide ceramic connector, and then the sample is placed in a tube furnace and heat-treated at 1400-1550 DEG C in a protective atmosphere to obtain the silicon carbide ceramic connector coated with yttrium aluminum garnet layer. The particle size of the silicon carbide powder is 100-1000 nm, the particle size of the aluminum oxide powder is 30-100 nm, the particle size of the yttrium oxide powder is 30-100 nm, the particle size of the gadolinium oxide powder is 30-100 nm, and the particle size of the zirconium oxide powder is 30-100 nm; the mass ratio of the silicon carbide powder, the aluminum oxide powder, the yttrium oxide powder, the gadolinium oxide powder and the zirconium oxide powder is (80-90):(8-16):(1.8-3):(0.1-0.5):(0.1-0.5).

2. The water corrosion resistant, yttrium aluminum garnet coated silicon carbide ceramic fitting of claim 1, wherein, The protective atmosphere is nitrogen, argon or helium.

3. The hydrothermal corrosion resistant, yttrium aluminum garnet layer coated silicon carbide ceramic fitting of claim 1, wherein, The particle size of the yttrium aluminum garnet powder is 100-500 nm, the mass concentration of the PVA solution is 0.2-5 wt%, and the mass ratio of the yttrium aluminum garnet powder to the PVA solution is 1:(2-10).

4. The water corrosion resistant, yttrium-aluminum garnet coated silicon carbide ceramic fitting of claim 1, wherein, The thickness of the silicon carbide-based ceramic intermediate layer is 10-300 microns, and the average thickness of the coating layer is 1-100 microns.

5. The hydrothermal corrosion resistant, yttrium-aluminum garnet layer coated silicon carbide ceramic fitting of claim 1, wherein, The shear strength of the silicon carbide ceramic connector at room temperature is 120-160 MPa, the shear strength of the silicon carbide ceramic connector in an air atmosphere at 1200 DEG C is 100-150 MPa, and the average thickness loss rate of the coating layer after corrosion in high-purity water at 360 DEG C / 18.6 MPa for 3 days is 0-0.45 microns.

6. The method of producing a water corrosion resistant yttrium aluminum garnet coated silicon carbide ceramic fitting according to any one of claims 1 to 5, characterized in that, The method comprises the following specific steps: S1. mixing silicon carbide powder, aluminum oxide powder, yttrium oxide powder, gadolinium oxide powder and zirconium oxide powder, and coating the mixture between two silicon carbide ceramic substrates to obtain a pre-connector; S2. connecting the pre-connector by hot-pressing sintering or discharge plasma sintering at 1600-1950 DEG C and 5-50 MPa for 5-30 min under vacuum or in a protective atmosphere to obtain a silicon carbide ceramic connector; S3. mixing yttrium aluminum garnet powder with PVA to obtain coating material, uniformly spraying or brushing the coating material on the side of the silicon carbide ceramic connector, and then placing the sample in a tube furnace and heat-treating at 1400-1550 DEG C in a protective atmosphere for 30-120 min to obtain a silicon carbide ceramic connector coated with a yttrium aluminum garnet layer.

7. Use of the water corrosion resistant, yttrium-aluminum garnet layer coated silicon carbide ceramic fitting according to any one of claims 1 to 5 in the field of nuclear energy.

8. Use according to claim 7, characterized in that, The nuclear energy application environment is a hydrothermal environment of > 330 °C, > 15.5 MPa.

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