Cr2O3 and Al2O3 complex gradient hydrogen resistant coating and preparation method and application thereof

A kind of Cr₂0₃And ΑΙ₂0₃Composite gradient hydrogen barrier coating and its preparation method and application technical field

[0001] The present invention relates to a Cr₂0₃And Α1₂0₃A composite gradient hydrogen barrier coating and a preparation method and application thereof. The coating can be applied to the hydrogen permeation barrier of high-temperature vacuum heat-collecting tubes.

Background technique

[0002] The aging of the heat-carrying fluid in the solar collector tube will produce free hydrogen. The hydrogen passes through the central tube by permeation and reaches the vacuum annular space between the central tube and the sleeve, causing the pressure in the annular space to rise, which in turn leads to The heat loss of the collector tube increases. In order to ensure the vacuum in the annular gap between the tubes, corresponding measures must be taken to reduce the amount of hydrogen in the vacuum annular space. Early solutions include the use of getter materials. The disadvantage of this method is that the capacity of the getter material is limited. When the capacity of the getter material is exhausted, the pressure in the annular space will rise again. Therefore, the use of absorption can only temporarily control but not fundamentally solve the problem. For this reason, the researchers proposed the use of a hydrogen barrier coating to prevent hydrogen penetration, thereby effectively controlling the pressure in the vacuum annular space of the collector tube and reducing the heat of the collector tube. loss.

[0003] The earliest hydrogen barrier coating is the use of Cr disclosed by CN1971168₂0₃As a hydrogen barrier material, it can prevent the penetration of hydrogen to a large extent, so that the absorption tube has less heat loss. However, there is a large mismatch between the thermal expansion coefficient of this type of hydrogen barrier material and the substrate. After a certain thermal shock, a large thermal stress occurs between the coating and the substrate, resulting in separation of the coating and the substrate, which seriously affects the hydrogen barrier performance of the coating. In order to solve the above problems, researchers are looking for other hydrogen barrier coatings that are well combined with the substrate and have a small thermal expansion coefficient. Representative patents are the patents of the hydrogen barrier coatings held by Nanjing University of Aeronautics and Astronautics, including glass powder and abrasives. CN101215709. CN101215710 and CN101230460 have simple coating preparation process and good combination with the substrate. Researchers have conducted a lot of screening of hydrogen barrier coating materials, including Al₂03>Y₂03>Er₂03>Si0₂-Cr₂0₃And other materials. Because of its relatively stable structure, AJO3 can form α -Α1 especially during the preparation process.₂0₃, It is of great help to the performance of the coating. Its insulation resistivity is relatively high, and the hydrogen barrier performance has been verified to be better. Therefore, it has become the most conventional material in the hydrogen barrier coating. Because the chemical vapor deposition method prepares α-Α12()3 at high temperature, it is easier to form large particles, which can often form brittle phases, which affects the reliability of the coating, and also affects the density and hydrogen barrier properties of the coating material. And Er₂0₃The hydrogen barrier coating has high insulation resistivity, good self-repair performance, and the preparation temperature is lower than α -Α1₂0₃The disadvantage is that the price is relatively high. Therefore, in order to overcome the shortcomings of the above two coatings, the Beijing Nonferrous Metals Research Institute provides two improved hydrogen barrier coatings, which are the barriers composed of alumina and oxidized bait disclosed by CN101469409. Hydrogen coating and the Fe-Er metal transition layer and Er disclosed in CN101469399₂0₃coating. While improving the reliability of the coating, it also reduces the preparation cost.

[0004] In view of the above, it is necessary to provide a composite gradient hydrogen barrier coating material that has a good combination with the substrate, a simple preparation process, and a low cost.

Summary of the invention

[0005] The object of the present invention is to provide a multilayer Cr₂0₃/Al₂0₃Composite gradient hydrogen barrier coating and preparation method thereof. Preparation of Cr by metal-organic chemical vapor deposition technology₂0₃-Al₂0₃Multi-layer composite gradient hydrogen barrier coating, the composite gradient coating can effectively reduce H₂In the permeability of stainless steel, so as to achieve the purpose of blocking hydrogen penetration.

[0006] A composite gradient hydrogen barrier coating consisting of 03 and AI2O3, the composite coating is composed of 03 and AI2O3, coated on stainless steel.

[0007] Preferably, Cr₂0₃/Al₂0₃Composite coating is Cr₂0₃Coating and Α1₂0₃Alternate coating structure, the total number of layers is greater than or equal to

4 layers; the innermost layer is Cr₂0₃Coating, the outermost layer is AI2O3 coating.

[0008] Preferably, Cr₂0₃/Al₂0₃The thickness of the composite coating is between 0.1 to 20 P m. Cr₂0₃/Al₂0₃The thickness of the composite coating is between 0.1 and lum to increase the hydrogen barrier performance by more than 100 times.

[0009] Preferably, the stainless steel is austenitic stainless steel or martensitic stainless steel.

[0010] The present invention also provides the aforementioned Cr₂0₃And Α1₂0₃A preparation method of a composite gradient hydrogen barrier coating. The composite coating can be prepared by metal organic chemical vapor deposition technology.

[0011] Cr₂0₃/Al₂0₃The specific preparation steps of the composite coating include:

[0012] (1) Polishing the stainless steel surface to a roughness of 0.1 1~2um;

[0013] (2) Using metal-organic chemical vapor deposition technology to prepare Cr on the surface of stainless steel₂0₃Coating; The specific process parameters are: the reaction source temperature is 50~200Ό; the carrier gas flow rate is 40~500ml/min;

[0014] (3) Preparation of A1 on the surface of stainless steel using metal-organic chemical vapor deposition technology₂0₃Coating, the specific process parameters are: reaction source temperature 50~200Ό; carrier gas flow rate 10~300ml/min;

[0015] (4) Repeat the above steps (2) and (3) to alternately prepare Cr₂0₃Coating and Α1₂0₃Coating; finally obtained a thickness of about 0. 1~20 μ m multilayer Cr₂0₃/Al₂0₃Composite gradient hydrogen barrier coating.

[0016] In view of the current situation that it is difficult to prepare a high-performance, uniform and stable hydrogen barrier coating on the inner surface of the high-temperature vacuum heat-collecting tube, the present invention also provides the application of the above-mentioned coating in the high-temperature vacuum heat-collecting tube, that is, on the inner surface of the high-temperature vacuum heat-collecting tube The first use of dual evaporation sources to prepare Cr in layers₂0₃-Al₂0₃Multi-layer composite gradient hydrogen barrier coating.

[0017] The high-temperature vacuum heat-collecting tube is composed of a stainless steel central tube with a spectrally selective absorption coating on the outer wall and an outer glass sleeve, where Cr₂0₃And Α1₂0₃The composite gradient hydrogen barrier coating is coated on the inner surface of the stainless steel central tube of the high-temperature vacuum heat-collecting tube.

[0018] The above-mentioned high-temperature vacuum heat collector tube uses spit 2.3 and A1₂0₃The preparation method of the composite gradient hydrogen barrier coating includes the following steps:

[0019] (1) Polishing the inner surface of the stainless steel central tube of the high-temperature vacuum heat-collecting tube to a roughness of 0.1~2um;

[0020] (2) Using metal-organic chemical vapor deposition technology to prepare Cr on the inner surface of the stainless steel tube₂0₃Coating; The specific process parameters are: the reaction source temperature is 50~200Ό; the carrier gas flow rate is 40~500ml/min;

[0021] (3) Preparation of A1 on the inner surface of the stainless steel tube using metal-organic chemical vapor deposition technology₂0₃Coating, the specific process parameters are: reaction source temperature 50~200Ό; carrier gas flow rate 10~300ml/min;

[0022] (4) Repeat the above steps (2) and (3) to alternately prepare Cr₂0₃Coating and Α1₂0₃Coating; finally obtained a thickness of about 0. 1~20 μ m multilayer Cr₂0₃/Al₂0₃Composite gradient hydrogen barrier coating.

[0023] The principle of the present invention is that when a thin film is grown, when the carrier gas is mainly passed through the container of the organometallic reaction source, the saturated vapor of the reaction source is brought into the reaction chamber and mixed with other reaction gases, and then on the heated substrate A chemical reaction takes place to promote the growth of the film.

[0024] Compared with the prior art, the present invention has the following advantages and outstanding results: for the first time to achieve the preparation of oxide and aluminum oxide mixed gradient hydrogen barrier coating on the inner wall of the high-temperature vacuum heat collector tube, and the Cr formed by the method₂0₃And Α1₂0₃The composite gradient hydrogen barrier coating has the characteristics of controllable thickness, high density, relatively uniform composition and excellent hydrogen barrier performance.

[0025] Multilayer Cr of the present invention₂0₃And Α1₂0₃The composite gradient hydrogen barrier coating can be used for the hydrogen permeation barrier of stainless steel structural parts, especially the hydrogen permeation barrier of the stainless steel tube in the inner tube of the solar high temperature vacuum heat collection tube. Cr₂0₃/Al₂0₃1~ The composite coating is prepared by a metal-organic chemical vapor deposition method, by repeatedly depositing aluminum oxide and oxide coatings to obtain a thickness of about 0.1~

um multilayer Cr₂0₃And Α1₂0₃Composite gradient hydrogen barrier coating; the coating is composed of a multilayer alternating structure with the innermost layer of oxide Luo and the outermost layer of aluminum oxide. The hydrogen barrier coating has high bonding strength with the substrate, simple preparation process and low cost, and the hydrogen barrier performance is improved by more than 100 times.

[0026] The present invention will be further described below with reference to the accompanying drawings and embodiments.

Description of the drawings

[0027] Figure 1 is a multilayer Cr₂0₃And Α1₂0₃Schematic diagram of composite gradient hydrogen barrier coating structure.

[0028] Main reference signs:

<td>[0029]</td><td>1&gt;Γ</td><td>Cr₂O₃coating</td>

<td>[0030]</td><td>3</td><td>stainless steel pipe</td>

<td>[0031]</td><td>5</td><td>Vacuum area</td>

2, 2'Α1₂0₃ Specific implementation of heat-absorbing coating of coated outer glass tube

[0032] Multilayer Cr₂O₃And Α1₂0₃The schematic diagram of the composite gradient hydrogen barrier coating used in the high-temperature vacuum collector tube is shown in Figure 1. The composite coating is made of Cr₂O₃Coating ΚΑ1₂0₃Coating 2, Cr₂0₃Coating 1'and AI2O3 coating 2'are alternately composited, the innermost layer is oxide coating, and the outermost layer is aluminum oxide coating. Among them, the innermost spit 2.3 coating 1 is covered on the inner surface of the stainless steel tube (stainless steel central tube) 3 of the high temperature vacuum heat collection tube. The high temperature vacuum heat collection tube is mainly composed of a stainless steel tube with a spectral selective absorption coating on the outer wall 3 and the outer glass tube (outer glass tube) 4, an annular vacuum area 5 is formed between the stainless steel tube 3 and the outer glass tube 4, and there is a heat-absorbing coating 6 on the outer wall of the stainless steel tube 3.

Example 1

[0034] (1) Polish the inner surface of the martensitic stainless steel tube 3 of the high-temperature vacuum collector tube to a roughness of 1 um;

[0035] (2) Using metal-organic chemical vapor deposition technology to prepare Cr on the inner surface of the stainless steel tube 3₂0₃Coating; The specific process parameters are: reaction source temperature 150Ό; carrier gas flow rate 200ml/min;

[0036] (3) A1 is prepared on the inner surface of the stainless steel tube 3 by using a metal-organic chemical vapor deposition technique₂0₃Coating; The specific process parameters are: the reaction source temperature is 100Ό; the carrier gas flow rate is 100ml/min;

[0037] (4) Repeat the above step (2);

[0038] (5) Repeat the above step (3);

[0039] Finally, a multilayer Cr with a thickness of about 0.5 pm is obtained₂O₃And A1₂O₃Composite gradient hydrogen barrier coating.

[0040] Determination of multi-layer Cr₂O₃And A1₂O₃Composite gradient hydrogen barrier coating at 400 Ό H₂Permeability, hydrogen barrier performance is increased by 100 times.

Example 2

[0042] (1) Polish the inner surface of the austenitic stainless steel tube 3 of the high-temperature vacuum collector tube to a roughness of 0.5 μm;

[0043] (2) Using metal-organic chemical vapor deposition technology to prepare Cr on the inner surface of the stainless steel tube 3₂O₃Coating; The specific process parameters are: reaction source temperature 180Ό; carrier gas flow rate 200ml/min;

[0044] (3) A1 is prepared on the inner surface of the stainless steel tube 3 using a metal-organic chemical vapor deposition technique₂O₃Coating; specific process parameters are: reaction source temperature 120Ό; carrier gas flow rate 150ml/min;

[0045] (4) Repeat the above step (2);

[0046] (5) Repeat the above step (3);

[0047] Finally, a multilayer Cr with a thickness of about 1 μm is obtained₂O₃And A1₂O₃Composite gradient hydrogen barrier coating.

[0048] Determination of multi-layer Cr₂0₃And Α1₂0₃Composite gradient hydrogen barrier coating at 400 Ό H₂The permeability and hydrogen barrier performance are increased by 200 times.

Example 3

[0050] (1) Polishing the inner surface of the austenitic stainless steel tube 3 of the high-temperature vacuum collector tube to a roughness of 0.3 μm;

[0051] (2) Using metal-organic chemical vapor deposition technology to prepare Cr on the inner surface of the stainless steel tube 3₂0₃Coating; the specific process parameters are: reaction source temperature 200Ό; carrier gas flow rate 200ml/min;

[0052] (3) Preparation of A1 on the inner surface of the stainless steel tube 3 using metal-organic chemical vapor deposition technology₂0₃Coating; the specific process parameters are: reaction source temperature 160°C; carrier gas flow rate 80ml/min;

[0053] (4) Repeat the above step (2);

[0054] (5) Repeat the above step (3);

[0055] The final thickness is about 0.8 P m multilayer Cr₂0₃And Α1₂0₃Composite gradient hydrogen barrier coating;

[0056] Determination of multi-layer Cr₂0₃And Α1₂0₃Composite gradient hydrogen barrier coating at 400 Ό H₂The permeability and hydrogen barrier performance are increased by 260 times.