Method for preparing long-aging anti-oxidation high-emissivity aluminum oxide-silicon dioxide double-layer structure coating through pre-oxidation method

Abstract

The invention discloses a method for preparing a long-aging anti-oxidation high-emissivity aluminum oxide-silicon dioxide double-layer structure coating through a pre-oxidation method, and belongs to the technical field of coating surface modification. The invention aims to solve the problems of uncontrollable coating structure and insufficient high-temperature resistance and oxidation resistance in the high-temperature long-time service process of the existing coating. The prepared long-aging anti-oxidation high-emissivity double-layer structure coating comprises an aluminum-series inner layer and a silicon-series outer layer, and the coating forms a double-layer structure with the inner layer being Al2O3 and the outer layer being SiO2 as the main in-situ mode in the pre-oxidation process. The coating with the double-layer structure has good bonding performance, the bonding strength reaches 13 MPa or above, the emissivity reaches 0.9, the double-layer structure of inner Al2O3 and outer SiO2 is kept after oxidation is conducted for 50 h in high-temperature static air at the temperature of 1150 DEG C, the coating is kept complete and free of the falling-off phenomenon, and the coating has application potential in a long-time-efficiency anti-oxidation radiant heat protection system of a high-speed aircraft.

Description

Technical Field

[0001] The present invention belongs to the technical field of coating surface modification, and particularly relates to a method for preparing a long-term aging antioxidant high-emissivity alumina-silica double-layer structure coating by a pre-oxidation method. Background Technique

[0002] Driven by the pursuit of higher speeds, longer ranges, and stronger performance in the aerospace field, high-speed aircraft will inevitably encounter extremely harsh thermal environments and oxidation conditions during flight, which pose more stringent requirements for the long-term aging high-temperature resistance and oxidation resistance of key components of the aircraft. Superalloys play a crucial role in the hot-end components of high-speed aircraft due to their excellent high-temperature strength, creep resistance, and corrosion resistance. However, superalloys mainly rely on the spontaneous formation of oxide films on the surface by active elements such as chromium and aluminum contained in the alloy to resist oxidation attacks. The above oxide films are extremely prone to cracking and peeling, and cannot provide effective protection. Therefore, it is of great significance to design and prepare a long-term high-temperature resistant and antioxidant coating to ensure the stable and reliable operation of key components of high-speed aircraft in extreme environments.

[0003] The published patent (CN 113278968 B) prepared an Al and Si composite-added modified nickel-based superalloy coating with high-temperature oxidation resistance by using plasma cladding technology. This coating improves the antioxidant ability by increasing the content of Al element to rapidly generate a dense alumina protective film during high-temperature oxidation, and promotes the formation of Cr 2 O 3 by introducing Si, and generates a SiO 2 O 3 interlayer between the metal and Cr 2 to absorb vacancies, prevent the generation of voids at the interface, and improve the antioxidant and hot corrosion resistance of the coating. However, after the coating is oxidized, the oxide films formed at various temperatures are all Al 2 O 3The single layer has limited oxidation protection effect. The published patent (CN 116463589 A) discloses a Pt-Si co-modified aluminide coating and its preparation method. By adjusting the contents of platinum and silicon, platinum is used to improve the tissue stability of the coating, and silicon enhances the hot corrosion resistance of the coating, thereby improving the problem of insufficient high-temperature oxidation resistance of a single aluminide coating. The results of high-temperature oxidation experiments show that the Pt-Si co-modified aluminide coating has self-healing properties during high-temperature oxidation, significantly enhancing its high-temperature oxidation resistance. However, this coating is prepared by magnetron sputtering-thermal dipping, and the obtained coating fails to achieve a double-layer coating structure. Only by adding Si and Pt to the aluminide coating to improve its oxidation resistance, the oxidation improvement effect is limited, and the long-term oxidation resistance at temperatures above 1000 °C remains questionable. Therefore, how to prepare a thermal protection coating with long-term high-temperature oxidation resistance on the surface of superalloys through a simple process still needs to be further explored to meet the further requirements of key components of high-speed aircraft for the long-term high-temperature oxidation resistance of thermal protection coatings. Summary of the Invention

[0004] The object of the present invention is to solve the problems of uncontrollable coating structure and insufficient high-temperature oxidation resistance during the long-term service of existing coatings at high temperatures, and to provide a method for preparing a long-term oxidation-resistant and high-emissivity alumina-silica double-layer structure coating by pre-oxidation.

[0005] A method for preparing a long-term oxidation-resistant and high-emissivity alumina-silica double-layer structure coating by pre-oxidation. The long-term oxidation-resistant and high-emissivity double-layer structure coating includes an aluminum-based inner layer and a silicon-based outer layer. During the pre-oxidation process of the coating, a double-layer structure with the inner layer mainly composed of Al 2 O 3 and the outer layer mainly composed of SiO 2 is formed in-situ;

[0006] The specific method is completed according to the following steps:

[0007] I. Pretreatment of the substrate:

[0008] First, use SiC sandpaper to polish the surface of the superalloy substrate until it is flat, and then remove the oil stain on the surface of the superalloy substrate to obtain a pretreated superalloy substrate;

[0009] II. Preparation of a long-term oxidation-resistant and high-emissivity aluminum-based inner layer:

[0010] Make a slurry from a high-temperature oxidation-resistant component providing an aluminum source and a low-temperature polymerized inorganic precursor binder, and then coat it on one or two surfaces of the pretreated superalloy substrate to obtain a substrate to be formed with an aluminum-based inner layer;

[0011] III. Preparation of a long-term oxidation-resistant and high-emissivity silicon-based outer layer:

[0012] A slurry is prepared from a high-temperature resistant and oxidation-resistant component providing a silicon source and a low-temperature polymerizable inorganic precursor binder, and then coated on the surface of a substrate to be formed with an aluminum-based inner layer, obtaining a substrate to be formed with an aluminum-based inner layer and a silicon-based outer layer;

[0013] IV. Coating pre-oxidation treatment:

[0014] The substrate to be formed with an aluminum-based inner layer and a silicon-based outer layer is placed in a muffle furnace and pre-oxidized at 900 °C to 1100 °C for a period of time, and the coating is cured to obtain a double-layer structure with Al 2 O 3 as the inner layer and SiO 2 as the main component of the outer layer, that is, a long-term aging oxidation-resistant and high-emissivity Al 2 O 3 -SiO 2 double-layer structure coating.

[0015] Principle of the present invention:

[0016] The present invention proposes a method for preparing a long-term aging oxidation-resistant and high-emissivity Al 2 O 3 -SiO 2 double-layer structure coating by a pre-oxidation method. The aluminum-based inner layer and the silicon-based outer layer are respectively prepared by an inorganic precursor low-temperature polymerization conversion method, and a double-layer structure mainly composed of "inner layer Al 2 O 3 -outer layer SiO 2 " is formed in-situ through pre-oxidation. The synergistic design strategy of this double-layer structure for strengthening the mechanism of long-term aging oxidation-resistant radiation heat protection of a superalloy substrate is mainly reflected in:

[0017] (1). The outer layer SiO 2 cooperatively plays the roles of infrared radiation heat dissipation and oxygen diffusion barrier: After pre-oxidation, the main component of the outer layer is SiO 2 , which has good infrared radiation characteristics and can effectively reduce the heat load on the coating surface through radiation heat dissipation; The continuous and dense SiO 2 outer layer can serve as the first oxygen diffusion barrier to effectively prevent oxidizing gases such as oxygen from further diffusing into the coating interior; The high-temperature resistant and oxidation-resistant component providing the silicon source in the outer layer can continuously oxidize to generate a SiO 2 oxide layer to play an antioxidant role; The SiO 2 with fluidity at high temperature can heal defects such as cracks and pores generated during the antioxidant process, prevent the further expansion of cracks, and extend the service life of the coating;

[0018] (2). The inner layer Al 2 O 3 acts as the second oxygen shielding layer: Al2 O 3 It also has good compactness and can further hinder oxygen diffusion. After a long-term oxidation process, oxygen penetrates through the outer SiO 2 barrier to reach the inner layer, and the high-temperature oxidation-resistant component that provides the aluminum source in the inner layer continuously generates Al 2 O 3 oxygen shielding layer, which can provide more reliable protection for the substrate.

[0019] The present invention has the following beneficial effects:

[0020] First, the present invention prepares an in-situ long-ageing oxidation-resistant high-emissivity Al 2 O 3 -SiO 2 double-layer structure coating by the pre-oxidation method. The outer SiO 2 plays the role of infrared radiation heat dissipation and the first oxygen diffusion barrier, and the inner Al 2 O 3 acts as the second oxygen shielding layer to prevent oxygen penetration. The dual barriers work together to improve the long-ageing oxidation-resistant radiation heat protection performance of the coating.

[0021] Second, the long-ageing oxidation-resistant high-emissivity Al 2 O 3 -SiO 2 double-layer structure coating prepared by the pre-oxidation method of the present invention has a bonding strength above 13 MPa; the coating has excellent infrared radiation heat dissipation characteristics, and the emissivity value reaches 0.9; the coating thickness and structure are controllable, the coating thickness is 50 μm to 500 μm, and after oxidizing in static air at 1150 °C for 50 h, it maintains the "inner Al 2 O 3 -outer SiO 2 " double-layer structure, the coating remains intact without peeling, and has application potential in the long-ageing oxidation-resistant radiation heat protection system of high-speed aircraft. Description of the Drawings

[0022] Figure 1 is the XRD pattern of the long-ageing oxidation-resistant high-emissivity Al 2 O 3 -SiO 2 double-layer structure coating prepared by the pre-oxidation method in Example 1 of the present invention;

[0023] Figure 2 is the macroscopic and microscopic morphology photos of the long-ageing oxidation-resistant high-emissivity Al 2 O 3 -SiO 2 double-layer structure coating prepared by the pre-oxidation method in Example 1 of the present invention;

[0024] Figure 3 For the long-term aging antioxidant and high emissivity Al 2 O 3 -SiO 2 double-layer structure coating prepared by the pre-oxidation method in Example 1 of the present invention; a cross-sectional microscopic morphology photograph

[0025] Figure 4 For the stress-strain curve of the long-term aging antioxidant and high emissivity Al 2 O 3 -SiO 2 double-layer structure coating prepared by the tensile test method in Example 1 of the present invention

[0026] Figure 5 For the emissivity spectra of the long-term aging antioxidant and high emissivity Al 2 O 3 -SiO 2 double-layer structure coating prepared by the pre-oxidation method in Example 1 of the present invention and the nickel-based superalloy GH4061 in Comparative Example 1

[0027] Figure 6 For the XRD spectra of the specimens' surfaces after static oxidation at 1150°C for 50 h of the long-term aging antioxidant and high emissivity Al 2 O 3 -SiO 2 double-layer structure coatings prepared by the pre-oxidation method in Examples 1 to 3 of the present invention and the nickel-based superalloy GH4061 in Comparative Example 1

[0028] Figure 7 For the cross-sectional microscopic morphology photograph and EDS energy spectrum pictures of the long-term aging antioxidant and high emissivity Al 2 O 3 -SiO 2 double-layer structure coating after static oxidation at 1150°C for 50 h prepared by the pre-oxidation method in Example 1 of the present invention

[0029] Figure 8 For the oxidation weight gain curves of the long-term aging antioxidant and high emissivity Al 2 O 3 -SiO 2 double-layer structure coating prepared by the pre-oxidation method in Example 1 of the present invention and the nickel-based superalloy GH4061 in the comparative example Detailed implementation manners

[0030] The following examples further illustrate the content of the present invention, but should not be construed as limiting the present invention. Without departing from the essence of the present invention, modifications and substitutions made to the methods, steps or conditions of the present invention all fall within the scope of the present invention.

[0031] Embodiment 1: A method for preparing a long-term aging antioxidant and high emissivity alumina-silica double-layer structure coating by pre-oxidation. The long-term aging antioxidant and high emissivity double-layer structure coating includes an aluminum-based inner layer and a silicon-based outer layer. During the pre-oxidation process of the coating, a double-layer structure with Al 2 O 3 as the inner layer and SiO 2 as the outer layer is formed in-situ;

[0032] The specific method is completed according to the following steps:

[0033] I. Pretreatment of the substrate:

[0034] First, use SiC sandpaper to polish the surface of the superalloy substrate until it is flat, and then remove the oil stain on the surface of the superalloy substrate to obtain the pretreated superalloy substrate;

[0035] II. Preparation of the long-term aging antioxidant and high emissivity aluminum-based inner layer:

[0036] Make a slurry from the high-temperature resistant antioxidant component providing the aluminum source and the low-temperature polymerizable inorganic precursor binder, and then coat it on one or two surfaces of the pretreated superalloy substrate to obtain the substrate to be formed with the aluminum-based inner layer;

[0037] III. Preparation of the long-term aging antioxidant and high emissivity silicon-based outer layer:

[0038] Make a slurry from the high-temperature resistant antioxidant component providing the silicon source and the low-temperature polymerizable inorganic precursor binder, and then coat it on the surface of the substrate to be formed with the aluminum-based inner layer to obtain the substrate to be formed with the aluminum-based inner layer and the silicon-based outer layer;

[0039] IV. Coating pre-oxidation treatment:

[0040] Place the substrate to be formed with the aluminum-based inner layer and the silicon-based outer layer in a muffle furnace and pre-oxidize it at 900 °C to 1100 °C for a period of time. The coating is cured to obtain a double-layer structure with Al 2 O 3 as the inner layer and SiO 2 as the outer layer, which is the long-term aging antioxidant and high emissivity Al 2 O 3 -SiO 2 double-layer structure coating.

[0041] Embodiment 2: The difference between this embodiment and Embodiment 1 is that: in step I, the superalloy substrate is a superalloy; the superalloy is a ferrous-based alloy, a nickel-based alloy or a cobalt-based alloy. Other steps are the same as those in Embodiment 1.

[0042] Specific Embodiment 3: The difference between this embodiment and one of Specific Embodiments 1 or 2 is that: in Step 1, the superalloy substrate is polished successively with 400#, 600#, 800#, and 1000# sandpapers, and then anhydrous ethanol is used to remove the oil stains on the surface, obtaining the pretreated superalloy substrate. Other steps are the same as those in Specific Embodiment 1 or 2.

[0043] Specific Embodiment 4: The difference between this embodiment and one of Specific Embodiments 1 to 3 is that: the high-temperature resistant and oxidation-resistant component providing the aluminum source in Step 2 is one or a mixture of several of Al, NiAl, AlSi, MCrAlY, and NiCrAlBSi powders. Other steps are the same as those in Specific Embodiments 1 to 3.

[0044] Specific Embodiment 5: The difference between this embodiment and one of Specific Embodiments 1 to 4 is that: the preparation method of the slurry in Step 2 is as follows: the high-temperature resistant and oxidation-resistant component providing the aluminum source and the low-temperature polymerizable inorganic precursor binder are put into a ball milling tank, zirconia balls are added, and ball milling is carried out for 12h to 24h under the condition of a ball milling speed of 60r / min to 100r / min, and the ball-to-material ratio is (2 to 4):1 to obtain a homogeneous slurry; the mass ratio of the high-temperature resistant and oxidation-resistant component providing the aluminum source to the low-temperature polymerizable inorganic precursor binder is 1:(1 to 4). Other steps are the same as those in Specific Embodiments 1 to 4.

[0045] Specific Embodiment 6: The difference between this embodiment and one of Specific Embodiments 1 to 5 is that: the high-temperature resistant and oxidation-resistant component providing the silicon source in Step 3 is one or a mixture of several of Si, SiC, ZrSi 2 , NbSi 2 , TaSi 2 , Cr 3 , SiB 4 , SiB 6 and the like. Other steps are the same as those in Specific Embodiments 1 to 5.

[0046] Specific Embodiment 7: The difference between this embodiment and one of Specific Embodiments 1 to 6 is that: the preparation method of the slurry in Step 3 is as follows: the high-temperature resistant and oxidation-resistant component providing the silicon source and the low-temperature polymerizable inorganic precursor binder are put into a ball milling tank, zirconia balls are added, and ball milling is carried out for 12h to 24h under the condition of a ball milling speed of 60r / min to 100r / min, and the ball-to-material ratio is (2 to 4):1 to obtain a homogeneous slurry; the mass ratio of the high-temperature resistant and oxidation-resistant component providing the silicon source to the low-temperature polymerizable inorganic precursor binder is 1:(1 to 4). Other steps are the same as those in Specific Embodiments 1 to 6.

[0047] Embodiment 8: The difference between this embodiment and any one of Embodiments 1 to 7 is as follows: The coating method described in Steps 2 and 3 is one or several of spraying, dipping, brushing, and painting. The number of coating times is one or more to control the thickness of the coating. The low-temperature polymerized inorganic precursor binder described in Steps 2 and 3 is a phosphate binder. The preparation method of the phosphate binder is specifically completed according to the following steps:

[0048] Weigh and mix a phosphoric acid solution with a mass fraction of 85% and deionized water in a volume ratio of (1-2):1, and then heat it in a water bath at 60°C - 100°C and continuously stir for 20 min - 60 min. Then, weigh and add aluminum hydroxide powder according to the ratio of P:Al of 3:(1-2), keep the temperature of the water bath heating at 60°C - 100°C, heat and stir for 1 h - 3 h to obtain a mixed solution. Add a curing agent to the mixed solution, and the mass ratio of the curing agent to the volume of the mixed solution is (1 g - 10 g):100 mL. Heat and stir at 60°C - 100°C for 1 h - 3 h, and then adjust the pH value of the solution to 2 - 6 to obtain the phosphate binder. The curing agent is one or a mixture of several of MgO, ZnO, CuO, CrO 3 in the mixture. Other steps are the same as those in Embodiments 1 to 7.

[0049] Embodiment 9: The difference between this embodiment and any one of Embodiments 1 to 8 is as follows: The time of the pre-oxidation treatment described in Step 4 is 10 min - 30 min. The thickness of the inner layer of the long-term aging oxidation-resistant and high-emissivity Al 2 O 3 -SiO 2 double-layer structure coating is 10 μm - 200 μm, and the thickness of the outer layer is 50 μm - 300 μm. Other steps are the same as those in Embodiments 1 to 8.

[0050] Embodiment 10: The difference between this embodiment and any one of Embodiments 1 to 9 is as follows: The bonding strength of the long-term aging oxidation-resistant and high-emissivity Al 2 O 3 -SiO 2 double-layer structure coating reaches above 13 MPa; the coating has excellent infrared radiation heat dissipation characteristics, and the emissivity value reaches 0.9. The coating thickness is 50 μm - 500 μm. After oxidizing in static air at 1150°C for 50 h, it maintains the "inner layer Al 2 O 3 - outer layer SiO 2 " double-layer structure, and the coating remains intact without peeling. Other steps are the same as those in Embodiments 1 to 9.

[0051] The beneficial effects of the present invention are verified by the following examples:

[0052] Example 1: A method for preparing a long-term aging antioxidant and high emissivity Al 2 O 3 -SiO 2 double-layer structure coating. The long-term aging antioxidant and high emissivity double-layer structure coating includes an aluminum-based inner layer and a silicon-based outer layer. During the pre-oxidation process, a double-layer structure mainly composed of Al 2 O 3 in the inner layer and SiO 2 in the outer layer is formed in-situ;

[0053] The method is specifically completed according to the following steps:

[0054] I. Pretreatment of the substrate:

[0055] The superalloy substrate is polished successively with 400#, 600#, 800#, and 1000# sandpapers, and then the surface oil stain is removed with anhydrous ethanol to obtain the pretreated superalloy substrate;

[0056] The superalloy substrate described in step I is nickel-based superalloy GH4061;

[0057] II. Preparation of the long-term aging antioxidant and high emissivity aluminum-based inner layer:

[0058] A heat-resistant antioxidant component providing an aluminum source and a low-temperature polymerizable inorganic precursor binder are made into a slurry, and then coated on the two surfaces of the pretreated superalloy substrate to obtain a substrate to be formed with an aluminum-based inner layer;

[0059] The heat-resistant antioxidant component providing an aluminum source described in step II is Al;

[0060] The preparation method of the slurry described in step II is: putting the heat-resistant antioxidant component providing an aluminum source and the low-temperature polymerizable inorganic precursor binder into a ball mill tank, adding zirconia balls, and ball milling for 12 h under the condition of a ball milling speed of 80 r / min and a ball-to-material ratio of 4:1 to obtain a uniform slurry; the mass ratio of the heat-resistant antioxidant component providing an aluminum source to the low-temperature polymerizable inorganic precursor binder is 1:2;

[0061] The coating method described in step II is brush coating, and the number of coating times is multiple times to control the thickness of the coating;

[0062] III. Preparation of the long-term aging antioxidant and high emissivity silicon-based outer layer:

[0063] A heat-resistant antioxidant component providing a silicon source and a low-temperature polymerizable inorganic precursor binder are made into a slurry, and then coated on the surface of the substrate to be formed with an aluminum-based inner layer to obtain a substrate to be formed with an aluminum-based inner layer and a silicon-based outer layer;

[0064] The high-temperature resistant and oxidation-resistant component providing the silicon source in Step 3 is SiC;

[0065] The preparation method of the slurry described in Step 3 is as follows: Put the high-temperature resistant and oxidation-resistant component providing the silicon source and the low-temperature polymerizable inorganic precursor binder into a ball mill tank, add zirconia balls, and ball mill for 12 h under the condition of a ball milling speed of 80 r / min, with a ball-to-material ratio of 4:1 to obtain a homogeneous slurry; the mass ratio of the high-temperature resistant and oxidation-resistant component providing the silicon source to the low-temperature polymerizable inorganic precursor binder is 1:2;

[0066] The coating method described in Step 3 is brush coating, and the number of coating times is multiple times to control the thickness of the coating;

[0067] The low-temperature polymerizable inorganic precursor binder described in Step 2 and Step 3 is a phosphate binder; the preparation method of the phosphate binder is specifically completed according to the following steps:

[0068] Weigh and mix the phosphoric acid solution with a mass fraction of 85% and deionized water according to a volume ratio of 2:1, and then heat in a water bath at 80 °C and continuously stir for 30 min; then weigh and add aluminum hydroxide powder according to the ratio of P:Al of 3:1, keep the temperature of the water bath heating at 80 °C, heat and stir for 2 h to obtain a mixed solution; add a curing agent to the mixed solution, and the mass ratio of the curing agent to the volume of the mixed solution is 10 g:100 mL, heat and stir at 80 °C for 3 h, and then adjust the pH value of the solution to 2 to obtain the phosphate binder; the curing agent is ZnO;

[0069] IV. Coating pre-oxidation treatment:

[0070] Place the substrate to be formed with an aluminum-based inner layer and a silicon-based outer layer in a muffle furnace, and pre-oxidize at 900 °C to 1100 °C for a period of time, and the coating is cured to obtain a double-layer structure with an inner layer of Al 2 O 3 and an outer layer of SiO 2 as the main component, that is, a long-term aging oxidation-resistant and high-emissivity Al 2 O 3 -SiO 2 double-layer structure coating.

[0071] The thickness of the inner layer in the long-term aging oxidation-resistant and high-emissivity Al 2 O 3 -SiO 2 double-layer structure coating described in Step 4 is 50 μm, and the thickness of the outer layer is 50 μm.

[0072] Figure 1 This is the long-term aging oxidation-resistant and high-emissivity Al prepared by the pre-oxidation method in Example 1 of the present invention2 O 3 -SiO 2 XRD pattern of the double-layer structure coating;

[0073] From Figure 1 it can be seen that after pre-oxidation, the coating surface mainly includes the binder phase and the SiO 2 phase after pre-oxidation of the silicon-based outer layer, indicating that an in-situ outer layer SiO 2 structure is obtained on the coating surface after pre-oxidation. However, due to the limited depth of X-ray testing, the inner layer Al 2 O 3 phase is not detected.

[0074] Figure 2 This is the macroscopic and microscopic morphology photos of the long-term aging antioxidant and high emissivity Al 2 O 3 -SiO 2 double-layer structure coating prepared by the pre-oxidation method in Example 1 of the present invention;

[0075] Figure 3 This is the microscopic morphology photo of a cross-section of the long-term aging antioxidant and high emissivity Al 2 O 3 -SiO 2 double-layer structure coating prepared by the pre-oxidation method in Example 1 of the present invention;

[0076] From Figures 2 to 3 it can be seen that after the coating is pre-oxidized, the filler is oxidized to form a continuous coating, and in addition, some of the P-O-Al macromolecular network skeletons extend and grow at high temperatures; the cross-sectional morphology of the coating shows that the finally obtained double-layer structure coating includes an aluminum-based inner layer with a thickness of about 50 μm and a silicon-based outer layer with a thickness of 50 μm, and the total thickness of the coating is about 100 μm.

[0077] Figure 4 This is the stress-strain curve of the long-term aging antioxidant and high emissivity Al 2 O 3 -SiO 2 double-layer structure coating prepared in Example 1 of the present invention tested by the tensile test method;

[0078] From Figure 4 it can be seen that the bonding strength of the long-term aging antioxidant and high emissivity Al 2 O 3 -SiO 2 double-layer structure coating prepared by the pre-oxidation method in Example 1 of the present invention reaches above 13 MPa, having good bonding performance.

[0079] Example 2: A method for preparing a long-term aging antioxidant and high emissivity Al 2 O 3-SiO 2 Method for a double-layer structure coating. The long-term aging oxidation-resistant and high-emissivity double-layer structure coating includes an aluminum-based inner layer and a silicon-based outer layer. During the pre-oxidation process of the coating, a double-layer structure is formed in-situ with the inner layer being Al 2 O 3 and the outer layer being mainly SiO 2 ;

[0080] The method described above is specifically completed according to the following steps:

[0081] I. Pretreatment of the substrate:

[0082] The superalloy substrate is polished successively with 400#, 600#, 800#, and 1000# sandpapers, and then the surface oil is removed using anhydrous ethanol to obtain the pretreated superalloy substrate;

[0083] The superalloy substrate described in step I is nickel-based superalloy GH4061;

[0084] II. Preparation of the long-term aging oxidation-resistant and high-emissivity aluminum-based inner layer:

[0085] The high-temperature oxidation-resistant component providing the aluminum source and the low-temperature polymerizable inorganic precursor binder are made into a slurry, which is then coated on the two surfaces of the pretreated superalloy substrate to obtain the substrate to be formed with the aluminum-based inner layer;

[0086] The high-temperature oxidation-resistant component providing the aluminum source described in step II is NiAl;

[0087] The preparation method of the slurry described in step II is as follows: The high-temperature oxidation-resistant component providing the aluminum source and the low-temperature polymerizable inorganic precursor binder are placed in a ball milling tank, zirconia balls are added, and ball milling is carried out for 18 h at a ball milling speed of 60 r / min with a ball-to-material ratio of 3:1 to obtain a homogeneous slurry; the mass ratio of the high-temperature oxidation-resistant component providing the aluminum source to the low-temperature polymerizable inorganic precursor binder is 1:1;

[0088] The coating method described in step II is brush coating, and the number of coating times is multiple times to control the thickness of the coating;

[0089] III. Preparation of the long-term aging oxidation-resistant and high-emissivity silicon-based outer layer:

[0090] The high-temperature oxidation-resistant component providing the silicon source and the low-temperature polymerizable inorganic precursor binder are made into a slurry, which is then coated on the surface of the substrate to be formed with the aluminum-based inner layer to obtain the substrate to be formed with the aluminum-based inner layer and the silicon-based outer layer;

[0091] The high-temperature oxidation-resistant component providing the silicon source described in step III is ZrSi 2 ;

[0092] The preparation method of the slurry described in Step 3 is as follows: Put the high-temperature resistant and antioxidant component providing silicon source and the low-temperature polymerizable inorganic precursor binder into a ball milling tank, add zirconia balls, and ball mill for 18 h under the condition of a ball milling speed of 60 r / min and a ball-to-material ratio of 3:1 to obtain a uniform slurry; the mass ratio of the high-temperature resistant and antioxidant component providing silicon source to the low-temperature polymerizable inorganic precursor binder is 1:1.

[0093] The coating method described in Step 3 is brush coating, and the number of coating times is multiple times to control the thickness of the coating.

[0094] The low-temperature polymerizable inorganic precursor binder described in Step 2 and Step 3 is a phosphate binder; the preparation method of the phosphate binder is specifically completed according to the following steps:

[0095] Weigh and mix the phosphoric acid solution with a mass fraction of 85% and deionized water in a volume ratio of 3:2 and mix them evenly, then heat them in a water bath at 90 °C and continuously stir for 20 min; then weigh and add aluminum hydroxide powder according to the ratio of P:Al of 2:1, keep the temperature of the water bath heating at 90 °C, heat and stir for 1 h to obtain a mixed solution; add a curing agent to the mixed solution, and the mass-to-volume ratio of the curing agent to the mixed solution is 5 g:100 mL, heat and stir at 90 °C for 2 h, and then adjust the pH value of the solution to 4 to obtain the phosphate binder; the curing agent is CuO.

[0096] IV. Coating pre-oxidation treatment:

[0097] Place the substrate to be formed with an aluminum-based inner layer and a silicon-based outer layer in a muffle furnace, and perform pre-oxidation treatment at 900 °C to 1100 °C for a period of time, and the coating is cured to obtain a double-layer structure with an inner layer mainly composed of Al 2 O 3 and an outer layer mainly composed of SiO 2 , that is, a long-term aging antioxidant and high emissivity Al 2 O 3 -SiO 2 double-layer structure coating.

[0098] After testing, the long-term aging antioxidant and high emissivity Al 2 O 3 -SiO 2 double-layer structure coating prepared by the pre-oxidation method in this example includes an aluminum-based inner layer with a thickness of 100 μm and a silicon-based outer layer with a thickness of about 100 μm, and the total thickness of the coating is about 200 μm.

[0099] Example 3: A long-term aging antioxidant and high emissivity Al 2 O 3 -SiO 2Method for double-layer structure coating. The long-term aging oxidation-resistant and high-emissivity double-layer structure coating includes an aluminum-based inner layer and a silicon-based outer layer. During the pre-oxidation process of the coating, a double-layer structure with the inner layer being Al 2 O 3 and the outer layer being SiO 2 is formed in-situ;

[0100] The method described above is specifically completed according to the following steps:

[0101] I. Pretreatment of the substrate:

[0102] The superalloy substrate is polished successively with 400#, 600#, 800#, and 1000# sandpapers, and then the surface oil stain is removed with anhydrous ethanol to obtain the pretreated superalloy substrate;

[0103] The superalloy substrate described in step I is nickel-based superalloy GH4061;

[0104] II. Preparation of the long-term aging oxidation-resistant and high-emissivity aluminum-based inner layer:

[0105] The high-temperature oxidation-resistant component providing aluminum source and the low-temperature polymerized inorganic precursor binder are made into a slurry, and then coated on the two surfaces of the pretreated superalloy substrate to obtain the substrate to be formed with the aluminum-based inner layer;

[0106] The high-temperature oxidation-resistant component providing aluminum source described in step II is NiCrAlBSi;

[0107] The preparation method of the slurry described in step II is: putting the high-temperature oxidation-resistant component providing aluminum source and the low-temperature polymerized inorganic precursor binder into a ball mill tank, adding zirconia balls, ball milling for 24 h under the condition of a ball milling speed of 100 r / min, and the ball-to-material ratio is 2:1 to obtain a homogeneous slurry; the mass ratio of the high-temperature oxidation-resistant component providing aluminum source to the low-temperature polymerized inorganic precursor binder is 1:3;

[0108] The coating method described in step II is brush coating, and the number of coating times is multiple times to control the thickness of the coating;

[0109] III. Preparation of the long-term aging oxidation-resistant and high-emissivity silicon-based outer layer:

[0110] The high-temperature oxidation-resistant component providing silicon source and the low-temperature polymerized inorganic precursor binder are made into a slurry, and then coated on the surface of the substrate to be formed with the aluminum-based inner layer to obtain the substrate to be formed with the aluminum-based inner layer and the silicon-based outer layer;

[0111] The high-temperature oxidation-resistant component providing silicon source described in step III is SiB 4 ;

[0112] The preparation method of the slurry described in Step 3 is as follows: Put the high-temperature resistant and oxidation-resistant component providing silicon source and the low-temperature polymerizable inorganic precursor binder into a ball mill tank, add zirconia balls, and ball mill for 24 hours under the condition of a ball mill speed of 100 r / min, with a ball-to-material ratio of 2:1, to obtain a homogeneous slurry; the mass ratio of the high-temperature resistant and oxidation-resistant component providing silicon source to the low-temperature polymerizable inorganic precursor binder is 1:3;

[0113] The coating method described in Step 3 is brush coating, and the number of coating times is multiple times to control the thickness of the coating;

[0114] The low-temperature polymerizable inorganic precursor binder described in Step 2 and Step 3 is a phosphate binder; the preparation method of the phosphate binder is specifically completed according to the following steps:

[0115] Weigh and mix the phosphoric acid solution with a mass fraction of 85% and deionized water in a volume ratio of 1:1, and then heat in a water bath at 60 °C and continuously stir for 60 min; then weigh and add aluminum hydroxide powder according to the ratio of P:Al of 3:2, keep the temperature of the water bath heating at 60 °C, heat and stir for 3 h to obtain a mixed solution; add a curing agent to the mixed solution, and the mass ratio of the curing agent to the volume of the mixed solution is 2 g:100 mL, heat and stir at 60 °C for 1 h, and then adjust the pH value of the solution to 6 to obtain the phosphate binder; the curing agent is MgO;

[0116] IV. Coating pre-oxidation treatment:

[0117] Place the substrate to be formed with an aluminum-based inner layer and a silicon-based outer layer in a muffle furnace, and perform pre-oxidation treatment at 900 °C - 1100 °C for a period of time, and the coating is cured to obtain a double-layer structure with an inner layer mainly composed of Al 2 O 3 and an outer layer mainly composed of SiO 2 , that is, a long-term aging oxidation-resistant and high-emissivity Al 2 O 3 -SiO 2 double-layer structure coating.

[0118] After testing, the long-term aging oxidation-resistant and high-emissivity Al 2 O 3 -SiO 2 double-layer structure coating prepared by the pre-oxidation method in this example includes an aluminum-based inner layer with a thickness of 10 μm and a silicon-based outer layer with a thickness of about 50 μm, and the total thickness of the coating is about 60 μm.

[0119] Comparative Example 1:

[0120] This comparative example selects the nickel-based superalloy GH4061.

[0121] Test Example:

[0122] The emissivity performance tests and 1150 °C static high-temperature oxidation tests were respectively carried out on the long-ageing antioxidant high-emissivity Al 2 O 3 -SiO 2 double-layer structure coatings prepared by the pre-oxidation method in Examples 1 to 3 and the nickel-based superalloy GH4061 of Comparative Example 1. The detection methods are as follows:

[0123] (1) Use an emissivity test device to test the emissivity of the long-ageing antioxidant high-emissivity Al 2 O 3 -SiO 2 double-layer structure coating prepared by the pre-oxidation method in Example 1 and the nickel-based superalloy GH4061 of the comparative example;

[0124] (2) Use a high-temperature muffle furnace to respectively carry out 1150 °C static high-temperature oxidation tests on the long-ageing antioxidant high-emissivity Al 2 O 3 -SiO 2 double-layer structure coatings prepared by the pre-oxidation method in Examples 1 to 3 and the nickel-based superalloy GH4061 of Comparative Example 1 to evaluate their high-temperature oxidation resistance;

[0125] Figure 5 The emissivity spectra of the long-ageing antioxidant high-emissivity Al 2 O 3 -SiO 2 double-layer structure coating prepared by the pre-oxidation method in Example 1 of the present invention and the nickel-based superalloy GH4061 of Comparative Example 1.

[0126] From Figure 5 it can be seen that the emissivity value of the nickel-based superalloy GH4061 of Comparative Example 1 is about 0.3, while the emissivity value of the long-ageing antioxidant high-emissivity Al 2 O 3 -SiO 2 double-layer structure coating prepared by the pre-oxidation method in Example 1 of the present invention is as high as 0.9, and the emissivity value is increased by 3 times, indicating that the long-ageing antioxidant high-emissivity Al 2 O 3 -SiO 2 double-layer structure coating has good infrared radiation heat dissipation characteristics and can play an effective radiation heat dissipation role.

[0127] The XRD patterns of the specimens' surfaces after Examples 1 to 3 and Comparative Example 1 were statically oxidized at 1150 °C for 50 h are as Figure 6 shown. From Figure 6 it can be seen that the surface of the nickel-based superalloy GH4061 of Comparative Example 1 mainly includes the γ-Ni phase and the oxidation products NiO, Cr2 O 3 、Al 2 O 3 phase; The long-term aging antioxidant and high emissivity Al 2 O 3 -SiO 2 double-layer structure coating mainly includes SiO 2 phase on the surface after oxidation, which can play a good role in blocking oxygen diffusion and provide effective high-temperature oxidation protection for the substrate.

[0128] Figure 7 This is the long-term aging antioxidant and high emissivity Al 2 O 3 -SiO 2 double-layer structure coating prepared by the pre-oxidation method in Example 1 of the present invention; cross-sectional microscopic morphology photograph and EDS energy spectrum picture after static oxidation at 1150 °C for 50 h.

[0129] It can be seen from Figure 7 that after high-temperature oxidation, the coating maintains the "inner layer Al 2 O 3 - outer layer SiO 2 " double-layer structure. This double-layer structure plays a synergistic role during high-temperature oxidation. The double oxygen diffusion barriers can block the diffusion of oxygen and have excellent long-term aging antioxidant and radiative heat protection performance.

[0130] The weight gain curves of high-temperature oxidation with time for Example 1 and the comparative example are plotted as Figure 8 shown;

[0131] Figure 8 This is the long-term aging antioxidant and high emissivity Al 2 O 3 -SiO 2 double-layer structure coating and the oxidation weight gain curve of the comparative example nickel-based superalloy GH4061;

[0132] It can be seen from Figure 8 that the long-term aging antioxidant and high emissivity Al 2 O 3 -SiO 2 double-layer structure coating prepared by the pre-oxidation method in Example 1 of the present invention and the comparative example nickel-based superalloy GH4061 both show segmented oxidation behavior during the entire oxidation process, but the oxidation rates are significantly different. The long-term aging antioxidant and high emissivity Al 2 O 3 -SiO 2The double-layer structure coating has a relatively fast oxidation weight gain within 0 - 1 h, indicating that the high-temperature oxidation-resistant components in the coating react with oxygen at the initial stage of oxidation. The oxidation weight gain curve significantly slows down within 2 - 50 h, and the oxidation rate of the coating is slow, indicating that the "inner layer Al 2 O 3 - outer layer SiO 2 " structure acts as an oxygen diffusion barrier, blocking the diffusion of the oxidation atmosphere into the interior of the coating, thus delaying the oxidation rate of the coating. After 50 h of oxidation, the weight gain of the sample is 2.197 mg / cm 2 ; while for the comparative nickel-based superalloy GH4061, the oxidation rate is relatively large within the range of 0 - 50 h, and the oxidation weight gain is obvious. After 50 h of oxidation, the weight gain of the sample is 2.461 mg / cm 2 , indicating serious oxidation of the matrix, and the high-temperature oxidation products NiO, Cr 2 O 3 cannot provide effective thermal protection for the matrix.

Claims

1. A method for preparing a long-term oxidation-resistant and high-emissivity aluminum oxide-silicon dioxide double-layer structure coating by a pre-oxidation method, characterized in that The long-term oxidation-resistant high-emissivity double-layer structure coating comprises an aluminum inner layer and a silicon outer layer, and the coating forms a double-layer structure mainly composed of an inner layer of Al2O3 and an outer layer of SiO2 in situ during the pre-oxidation process; The method is specifically completed according to the following steps:

1. Pretreatment of substrate: Firstly, SiC sandpaper is used to grind the surface of the high-temperature alloy substrate flat, and then oil stains on the surface of the high-temperature alloy substrate are removed to obtain a pretreated high-temperature alloy substrate; 2. Preparation of long-term anti-oxidation and high-emissivity aluminum inner layer: A high temperature resistant and anti-oxidation component providing an aluminum source and a low temperature polymerized inorganic precursor binder are made into a slurry, and then coated onto one or two surfaces of a pretreated high temperature alloy substrate to obtain a substrate on which an aluminum inner layer is to be formed; 3. Preparation of long-lasting anti-oxidation and high-emissivity silicon outer layer: A high temperature resistant and anti-oxidation component providing a silicon source and a low temperature polymerized inorganic precursor binder are made into a slurry, and then coated onto the surface of a substrate to be formed with an aluminum inner layer, to obtain a substrate to be formed with an aluminum inner layer and a silicon outer layer; 4. Pre-oxidation treatment of coating: The substrate to be formed with an aluminum inner layer and a silicon outer layer is placed in a muffle furnace and pre-oxidized at 900°C to 1100°C for a period of time. The coating is cured to obtain a double-layer structure with an inner layer of Al2O3 and an outer layer mainly of SiO2, that is, a long-term anti-oxidation and high-emissivity Al2O3-SiO2 double-layer structure coating.

2. The method for preparing a long-term antioxidant high-emissivity aluminum oxide-silicon dioxide double-layer structure coating by a pre-oxidation method according to claim 1, characterized in that The high-temperature alloy substrate described in step 1 is a high-temperature alloy; the high-temperature alloy is an iron-based alloy, a nickel-based alloy or a cobalt-based alloy.

3. The method for preparing a long-term antioxidant high-emissivity aluminum oxide-silicon dioxide double-layer structure coating by a pre-oxidation method according to claim 1, characterized in that In step 1, the high-temperature alloy substrate is polished using 400#, 600#, 800#, and 1000# sandpapers in sequence, and then the oil stains on the surface are removed using anhydrous ethanol to obtain a pretreated high-temperature alloy substrate.

4. The method for preparing a long-term antioxidant high-emissivity aluminum oxide-silicon dioxide double-layer structure coating by a pre-oxidation method according to claim 1, characterized in that The high temperature resistant and anti-oxidation component providing the aluminum source in step 2 is one of Al, NiAl, AlSi, MCrAlY, NiCrAlBSi powders or a mixture of several of them.

5. The method for preparing a long-term oxidation-resistant and high-emissivity aluminum oxide-silicon dioxide double-layer structure coating by a pre-oxidation method according to claim 1, characterized in that The preparation method of the slurry described in step 2 is: put the high temperature resistant and antioxidant component providing the aluminum source and the low temperature polymerization inorganic precursor binder into a ball mill, add zirconium oxide balls, and ball mill for 12h to 24h at a ball milling speed of 60r / min to 100r / min, with a ball-to-material ratio of (2 to 4):1, to obtain a uniform slurry; the mass ratio of the high temperature resistant and antioxidant component providing the aluminum source to the low temperature polymerization inorganic precursor binder is 1:(1 to 4).

6. The method for preparing a long-term oxidation-resistant and high-emissivity aluminum oxide-silicon dioxide double-layer structure coating by a pre-oxidation method according to claim 1, characterized in that The high temperature resistant and anti-oxidation component providing the silicon source described in step three is one of Si, SiC, ZrSi2, NbSi2, TaSi2, Cr3Si, SiB4, SiB6 or a mixture of several of them.

7. The method for preparing a long-term antioxidant high-emissivity aluminum oxide-silicon dioxide double-layer structure coating by a pre-oxidation method according to claim 1, characterized in that The preparation method of the slurry described in step three is: put the high temperature resistant antioxidant component providing a silicon source and the low temperature polymerization inorganic precursor binder into a ball mill, add zirconium oxide balls, and ball mill for 12h to 24h at a ball milling speed of 60r / min to 100r / min, with a ball-to-material ratio of (2 to 4):1, to obtain a uniform slurry; the mass ratio of the high temperature resistant antioxidant component providing a silicon source to the low temperature polymerization inorganic precursor binder is 1:(1 to 4).

8. The method for preparing a long-term oxidation-resistant and high-emissivity aluminum oxide-silicon dioxide double-layer structure coating by a pre-oxidation method according to claim 1, characterized in that The coating method described in step 2 and step 3 is one or more of spraying, dipping, brushing and dipping, and the number of coatings is one or more, so as to achieve the regulation of the coating thickness; the low-temperature polymerization inorganic precursor binder described in step 2 and step 3 is a phosphate binder; the preparation method of the phosphate binder is specifically completed according to the following steps: A phosphoric acid solution with a mass fraction of 85% and deionized water are weighed and mixed uniformly in a volume ratio of (1-2):1, and then heated in a water bath at 60°C-100°C and continuously stirred for 20min-60min; aluminum hydroxide powder is weighed and added in a ratio of P:Al of 3:(1-2), the water bath heating temperature is maintained at 60°C-100°C, and heated and stirred for 1h-3h to obtain a mixed solution; a curing agent is added to the mixed solution, the mass ratio of the curing agent to the volume ratio of the mixed solution is (1g-10g):100mL, heated and stirred at 60°C-100°C for 1h-3h, and then the pH value of the solution is adjusted to 2-6 to obtain a phosphate binder; the curing agent is one of MgO, ZnO, CuO, CrO3 or a mixture of several thereof.

9. The method for preparing a long-term antioxidant high-emissivity aluminum oxide-silicon dioxide double-layer structure coating by a pre-oxidation method according to claim 1, characterized in that The pre-oxidation treatment time described in step 4 is 10min to 30min; the thickness of the inner layer of the long-term anti-oxidation and high-emissivity Al2O3-SiO2 double-layer structure coating described in step 4 is 10μm to 200μm, and the thickness of the outer layer is 50μm to 300μm.

10. The method for preparing a long-term oxidation-resistant and high-emissivity aluminum oxide-silicon dioxide double-layer structure coating by a pre-oxidation method according to claim 1, characterized in that The bonding strength of the long-term anti-oxidation and high-emissivity Al2O3-SiO2 double-layer structure coating described in step 4 reaches above 13MPa; the coating has excellent infrared radiation heat dissipation characteristics, the emissivity value reaches 0.9, the coating thickness is 50μm~500μm, and after oxidation in high-temperature static air at 1150℃ for 50h, it maintains the "inner layer Al2O3-outer layer SiO2" double-layer structure, and the coating remains intact without falling off.

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