Super-wear-resistant composite coating for water cooling wall of circulating fluidized bed boiler and preparation method of super-wear-resistant composite coating

Abstract

The invention belongs to the field of high-temperature super-wear-resistant composite coatings for water-cooled walls of circulating fluidized beds, and particularly relates to a super-wear-resistant composite coating for a water-cooled wall of a circulating fluidized bed and a preparation method thereof. The composite coating comprises a nickel-chromium-titanium alloy coating and a nano ceramic coating, the nickel-chromium-titanium alloy coating is an electric arc spraying 45CT wire material; the particle spraying speed is larger than 386 m / s, the arc voltage is 32-34 V, the arc current is 160-200 A, the atomization air pressure is 0.5-0.6 Mp, the spraying distance is 150-200 mm, and the spraying angle is smaller than 45 degrees; the nano ceramic coating comprises colloid, nano ceramic powder and an additional auxiliary agent. The invention provides a method for combining a composite coating, a nickel-chromium-titanium alloy coating and a nano ceramic coating developed by the company, and the comprehensive protection of corrosion prevention of the inner layer and abrasion prevention of the outer layer is achieved.

Description

Technical Field

[0001] The present invention belongs to the field of high-temperature super wear-resistant composite coatings for the water-cooled walls of circulating fluidized bed boilers, and particularly relates to a super wear-resistant composite coating for the water-cooled walls of circulating fluidized bed boilers and a preparation method thereof. Background Art

[0002] Circulating fluidized bed boilers have the advantages of wide fuel adaptability (high-quality coal, high-sulfur coal, high-ash coal, high-ash high-sulfur coal, coal gangue, peat, etc.), high combustion efficiency (97.5% - 99.5%), high-efficiency desulfurization (>90%), low emissions of nitrogen oxides and other pollutants, wide load regulation range, and small furnace cross-sectional area. They are one of the economical and effective low-pollution combustion technologies. Due to the flow characteristics of the materials in the circulating fluidized bed boiler, the materials in the furnace are strongly back-mixed. While making the furnace heat load more uniform than that of pulverized coal boilers, it also causes a large amount of materials to erode the heating surface, resulting in serious wear of the metal parts of the circulating fluidized bed boiler. Especially in some special parts, the wear degree is extremely prominent, such as the transition zone between the water wall and the secondary air zone at the lower part of the furnace, the tube walls at the four corners of the furnace, elbows, through-wall tubes, irregular tube walls such as welds, and the area around the furnace flue outlet. The most serious wear can reach 5mm / 1000h. To solve the serious wear problem of circulating fluidized bed boilers, various surface technology methods are usually used to prevent wear of the boiler metal parts, such as nitriding or chromizing of furnace tubes, electroplating and hot dip plating, protective tiles, thermal spraying, spray welding, surfacing, etc. However, due to the porosity of the alloy coating, the corrosion resistance is seriously affected, and the coating falls off due to the spread of corrosion under the coating, losing the anti-corrosion and anti-wear effects. Nano-ceramic coatings have good wear resistance, but the bonding strength with the substrate is not strong. However, they bond firmly with the sprayed alloy. Nano-ceramic coatings can penetrate into the pores of the alloy, thus forming a firm rivet bond. Therefore, the present invention provides a method for combining an alloy coating and a nano-ceramic coating to obtain a composite coating, which plays a role in anti-wear and anti-corrosion. This technology is a very effective anti-wear and anti-corrosion method. Summary of the Invention

[0003] The purpose of the present invention is to effectively solve the problems that the water-cooled walls of circulating fluidized bed boilers are eroded and worn by corrosive media such as sulfur, resulting in wall thinning and tube explosion, thereby affecting the service life, and to provide a high-temperature anti-wear composite coating method for the water-cooled walls of circulating fluidized bed boilers.

[0004] In order to achieve the above purpose, the present invention adopts the following technical solutions: A super wear-resistant composite coating for the water-cooled walls of a circulating fluidized bed boiler, the composite coating comprising a nickel-chromium-titanium alloy coating and a nano-ceramic coating; The nickel-chromium-titanium alloy coating is an arc-sprayed 45CT wire; particle spraying speed: >386 m / s, arc voltage: 32 - 34 V, arc current: 160 - 200 A, atomizing air pressure: 0.5 - 0.6 Mp, spraying distance: 150 - 200 mm, spraying angle: <45°; The nano-ceramic coating contains colloid, nano-ceramic powder, and additional additives.

[0005] Furthermore, the colloid is: silica sol, with a solid content of 20% - 40 wt%; 1 - 5 wt% γ-methacryloxypropyltrimethoxysilane (KH-570) also needs to be added.

[0006] Furthermore, the composition of the nano-ceramic powder is: low-melting-point glass powder 20 - 35 wt%, calcined kaolin 10 - 30 wt%, corundum powder 10 - 20 wt%, zirconia powder 5 - 10 wt%, silica powder 10 - 20 wt%, bentonite 3 - 8 wt%, active magnesium oxide 1 - 3 wt%, yttrium oxide 1 - 3 wt%.

[0007] Furthermore, the composition of the additional additives is: surfactant 0.3 - 1 wt%, dispersant 0.3 - 1 wt%, defoamer 0.5 - 2 wt%, curing agent 0.5 - 2 wt%.

[0008] Furthermore, the low-melting-point glass powder is specifically as follows: ultra-low-temperature glass powder, initial melting temperature 280 °C, fineness: 1250 mesh, used to reduce the sintering temperature of the coating, form a limited solid solution with alumina, and most of these low-temperature glass powders contain variable-valence elements. The variable-valence effect enhances the lattice distortion, promotes the diffusion of particles or the movement of interfaces during the sintering process, activates the lattice, improves the sintering performance of the matrix, and makes the coating dense and ceramicized.

[0009] Furthermore, the preferred calcined kaolin is: fineness of 800 mesh; The preferred corundum powder is: with an Al2O3 content of more than 98% and a fineness of 400 mesh; The preferred zirconia is: nano-scale. By compounding with metal materials, nano-zirconia can improve the thermal conductivity, thermal shock resistance, and high-temperature oxidation resistance of metal materials; The preferred silica powder is: in silica fume, the fineness less than 1 micron accounts for more than 80%, and the average particle size is 0.1 - 0.2 microns; The preferred bentonite is: fineness of 600 mesh. This substance has good floating and dispersibility in water substances, making the coating not easy to deposit, not easy to stratify, with a uniform color, thus improving the stability of the coating mixture and having good brushing performance; The active magnesium oxide is preferably: fineness: 1000 mesh, having the advantages of large specific surface area, high surface energy and strong binding force; it can make the coating more densified after sintering; The yttrium oxide is preferably: the fineness of industrial grade yttrium oxide, used as a ceramic sintering aid, which can increase the sintering temperature and stability of ceramic materials, thereby increasing the hardness and toughness of ceramic materials. At the same time, yttrium oxide can also reduce the shrinkage and deformation of ceramic materials during sintering.

[0010] Furthermore, among the external additives: the surfactant is sodium dodecyl sulfonate, the dispersant is sodium carboxymethyl cellulose, the defoamer is a silicone ether copolymer type, and the curing agent is sodium fluorosilicate.

[0011] A method for preparing a high-temperature anti-wear composite coating for the water-cooled wall of a circulating fluidized bed boiler: The first step: Sandblasting and derusting the surface of the substrate to reach the sa2.5 level; The second step: Arc spraying 45CT wire, with a thickness of about 0.3 mm, spraying parameters: particle spraying speed: > 386 m / s, arc voltage: 32 - 34 V, arc current: 160 - 200 A, atomizing air pressure: 0.5 - 0.6 Mp, spraying distance: 150 - 200 mm, spraying angle: < 45°; The third step: 24 hours after the arc spraying is completed, spray the nano-ceramic coating, with a thickness of 0.4 - 0.5 mm.

[0012] The fourth step: The nano-ceramic coating is cured at room temperature and sintered with the furnace heating up to obtain a nickel-chromium-titanium alloy and nano-ceramic composite coating.

[0013] Furthermore, the preparation method of the sprayed nano-ceramic coating layer includes the following steps: S1. Weigh 95 - 99 parts by weight of acidic silica sol and add 1 - 5 parts of KH570, and fully stir and mix at room temperature with a magnetic stirrer to obtain a light blue semi-transparent or transparent sol, which is the A component of the organosilicon KH-570 modified hybrid silica sol; S2. Weigh the fillers by weight, 20 - 35 wt% of low melting point glass powder, 10 - 30 wt% of calcined kaolin, 10 - 20 wt% of corundum powder, 5 - 10 wt% of zirconia powder, 10 - 20 wt% of silica powder, 3 - 8 wt% of bentonite, 1 - 3 wt% of active magnesium oxide, 1 - 3 wt% of yttrium oxide; put them into a V-type mixer and stir for 30 - 60 min, with a stirring rate of 30 - 50 r / min. Obtain the mixed powder B component; S3. Weigh A:B = 5:5 by weight ratio, and add 0.3 - 1 wt% of surfactant, 0.3 - 1 wt% of dispersant, 0.5 - 2 wt% of defoamer, and 0.5 - 2 wt% of curing agent; after weighing, put them into a planetary ball mill and grind for 10 - 15 min at a ball milling speed of 200 r / min; obtain the nano-ceramic coating slurry.

[0014] Advantages of the present invention: The composite coating includes a nickel-chromium-titanium alloy coating and a nano-ceramic coating. A highly dense Cr2O3 oxide film can be formed on the surface of the nickel-chromium-titanium coating at high temperature, forming a corrosion-resistant surface layer of nickel-chromium alloy. The high chromium component endows it with the ability to resist high-temperature corrosion, including the ability to resist corrosion in fuel dust atmospheres containing sulfur and vanadium, and the anti-sulfide corrosion ability is 60 times that of carbon steel. However, there are inevitably many fine pores in the arc-sprayed nickel-chromium-titanium alloy coating. These pores are easily invaded by corrosive media and gradually spread at the interface with the substrate, resulting in coating peeling and loss of anti-corrosion and anti-wear effects. The nano-ceramic coating, through the synergistic effect of inorganic binder, nano-materials and hard fillers, has extremely high hardness after high-temperature sintering, that is, excellent anti-particle erosion and wear resistance. The gaps and surface unevenness of the nickel-chromium-titanium alloy coating itself will be filled by the nano-ceramic coating, forming a firm rivet structure, solving the problem of the adhesion of the ceramic coating to the water-cooled wall substrate.

[0015] The nano-ceramic coating undergoes hydrolysis and polycondensation under acidic conditions through γ-methacryloxypropyltrimethoxysilane (KH-570). The hydrolysis and polycondensation product of acidic silica sol and KH-570 forms an inorganic cross-linked network with organic groups on the surface of carbon steel through co-condensation reaction. The basic skeleton is composed of Si-O-Si with a large number of silanol groups. During the film-forming process, the silanol groups dehydrate and condense into a huge network structure, and then an extremely dense paint film is formed. Through the selected low-temperature glass powder, the coating can be sintered and densified at about 600 °C, and the shrinkage and deformation of the ceramic material during the sintering process are reduced by rare earth yttrium oxide. It well solves the problem of the large difference in thermal expansion coefficient from the metal. By adding nano-zirconia and compounding with metal materials, the thermal conductivity, thermal shock resistance and high-temperature oxidation resistance of the composite coating are improved. After the coating is sintered, it forms dense ceramization and covers the surface of the nickel-chromium-titanium alloy. This composite coating has both extremely strong sulfur corrosion resistance and erosion and wear resistance, achieving excellent effects for the protection of the water-cooled wall of the circulating fluidized bed. Description of the Drawings

[0016] Figure 1 Appearance morphology of the nickel-chromium-titanium alloy coating; In the figure: 1 - water-cooled wall substrate, 2 - nickel-chromium-titanium alloy coating, 3 - nano-ceramic coating. Detailed Embodiments

[0017] In order to make the purpose, technical solutions and advantages of this application clearer and more understandable, the following describes and explains this application in combination with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not used to limit this application. Based on the embodiments provided by this application, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of this application.

[0018] Obviously, the accompanying drawings in the following description are only some examples or embodiments of this application. For those of ordinary skill in the art, without creative efforts, this application can also be applied to other similar scenarios based on these drawings. In addition, it can also be understood that although the efforts made in this development process may be complex and lengthy, for those of ordinary skill in the art related to the content disclosed in this application, some design, manufacturing or production changes based on the technical content disclosed in this application are only conventional technical means and should not be understood as the content disclosed in this application being insufficient.

[0019] Referring to "embodiments" in this application means that the specific features, structures or characteristics described in combination with the embodiments can be included in at least one embodiment of this application. The appearance of this phrase in various positions in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those of ordinary skill in the art explicitly and implicitly understand that the embodiments described in this application can be combined with other embodiments without conflict.

[0020] A super wear-resistant composite coating for the water-cooled wall of a circulating fluidized bed. This coating includes a nickel-chromium-titanium alloy coating and a nano-ceramic coating; The nickel-chromium-titanium alloy coating is an alloy coating sprayed with 45CT wire by arc spraying, and the coating thickness is 0.3 mm; The nano-ceramic coating includes colloid, nano-powder and additives.

[0021] The components of the colloid include: acidic silica sol. The solid content of the acidic silica sol is 20% - 40 wt%. Add 1 - 5 wt% γ-methacryloxypropyltrimethoxysilane (KH-570).

[0022] The components of the powder are: low-melting glass powder 20 - 35 wt%, calcined kaolin 10 - 30 wt%, corundum powder 10 - 20 wt%, zirconia powder 5 - 10 wt%, silica powder 10 - 20 wt%, bentonite 3 - 8 wt%, active magnesium oxide 1 - 3 wt%, yttrium oxide 1 - 3 wt%; The composition of the external additive is as follows: surfactant 0.3 - 1 wt%, dispersant 0.3 - 1 wt%, defoamer 0.5 - 2 wt%, curing agent 0.5 - 2 wt%.

[0023] Furthermore, the solid content of the acidic silica sol is 20% - 40 wt%. The ultra-low temperature glass powder has an initial melting temperature of 280°C and a fineness of 1250 mesh. Its main function is to reduce the sintering temperature of the coating, connect the forces between each aggregate during the sintering and melting process, and make the coating dense and ceramized.

[0024] The calcined kaolin powder is characterized in that: preferably calcined kaolin, with a fineness of 800 mesh.

[0025] The corundum powder is characterized in that: preferably corundum powder, with an Al2O3 content of more than 98% and a fineness of 400 mesh.

[0026] The zirconia is characterized in that: it is nanoscale. By compounding with metal materials, nano-zirconia can improve the thermal conductivity, thermal shock resistance and high-temperature oxidation resistance of metal materials.

[0027] The silica fume is characterized in that: more than 80% of the silica fume has a fineness less than 1 micron, and the average particle size is 0.1 - 0.3 microns.

[0028] The bentonite: with a fineness of 600 mesh. This substance has good floating and dispersibility in water substances, making the coating not easy to deposit, not easy to stratify, with a uniform color, thus improving the stability of the coating mixture, and having good brushing performance.

[0029] The activated magnesia: with a fineness of 1000 mesh, has the advantages of large specific surface area, high surface energy and strong binding force, which can make the coating more densified after sintering.

[0030] The yttrium oxide, with a fineness of industrial grade, is used as a ceramic sintering aid. It can increase the sintering temperature and stability of ceramic materials, thereby increasing the hardness and toughness of ceramic materials. At the same time, yttrium oxide can also reduce the shrinkage and deformation of ceramic materials during sintering.

[0031] The external additive is characterized in that: the surfactant is sodium dodecyl sulfonate, the dispersant is sodium carboxymethyl cellulose, the defoamer is a silicone ether copolymer type, and the curing agent is sodium fluorosilicate.

[0032] A preparation method for an ultra-wear-resistant composite coating on the water-cooled wall of a circulating fluidized bed boiler includes the following steps: The first step: sandblast and derust the surface of the substrate to at least reach the sa2.5 level Step 2: Arc spray 45CT wire with a thickness of about 0.3 mm. Spraying parameters: particle spraying speed > 386 m / s, arc voltage 32 - 34 V, arc current 160 - 200 A, atomizing air pressure 0.5 - 0.6 Mp, spraying distance 150 - 200 mm, spraying angle < 45° Step 3: After 24 hours of arc spraying, spray the nano-ceramic coating developed by our company. Use air spraying, and control the spraying conditions at an inlet pressure of 0.3 mpa - 0.6 mpa, the distance between the spray gun and the coated surface is 20 cm - 30 cm. At this time, the spray width should be adjusted to 30 cm - 40 cm; keep the distance between the spray gun and the coated surface unchanged and spray evenly until the required wet film thickness is 0.4 - 0.5 mm.

[0033] Step 4: Cure the nano-ceramic coating at room temperature and sinter it by heating in the furnace to obtain a nickel-chromium-titanium alloy and nano-ceramic composite coating.

[0034] The preparation method of the nano-ceramic coating includes the following steps: ① Weigh 95 - 99 parts of acidic silica sol and 1 - 5 parts of KH570 by weight, and stir and mix them evenly with a magnetic stirrer at room temperature to obtain a light blue semi-transparent or transparent sol, which is the organosilicon KH-570 modified hybrid silica sol A; ② Weigh the fillers by weight, 20 - 35 parts of low-melting glass powder, 10 - 30 parts of calcined kaolin, 10 - 20 parts of corundum powder, 5 - 10 parts of zirconia powder%, 10 - 20 parts of silica powder, 3 - 8 parts of bentonite, 1 - 3 parts of active magnesium oxide, 1 - 3 parts of yttrium oxide, put them into a V-type mixer and stir for 30 - 60 min at a stirring rate of 30 - 50 r / min. Obtain the mixed powder B component; ③ Weigh A:B = 5:5 by weight ratio, and add 0.3 - 1 wt% of surfactant, 0.3 - 1 wt% of dispersant, 0.5 - 2 wt% of defoamer, 0.5 - 2 wt% of curing agent. After weighing, put them into a planetary ball mill and grind for 10 - 15 min at a ball mill speed of 200 r / min to obtain the nano-ceramic coating slurry. Example 1

[0035] Step 1: Sandblast and derust the surface of the substrate to at least reach sa2.5 level Step 2: Arc spray 45CT wire with a thickness of about 0.3 mm. Spraying parameters: particle spraying speed > 386 m / s, arc voltage 32 - 34 V, arc current 160 - 200 A, atomizing air pressure 0.5 - 0.6 Mp, spraying distance 150 - 200 mm, spraying angle < 45° Step 3: After 24 hours of arc spraying, apply the nano-ceramic coating developed by our company. Use air spraying, and control the spraying conditions at an inlet pressure of 0.3 mpa to 0.6 mpa, the distance between the spray gun and the coated surface is 20 cm to 30 cm. At this time, the spray width should be adjusted to 30 cm to 40 cm; keep the distance between the spray gun and the coated surface unchanged and spray evenly until the required wet film thickness is 0.4~0.5 mm.

[0036] Step 4: Curing the nano-ceramic coating at room temperature and sintering it with the furnace heating up to obtain a nickel-chromium-titanium alloy and nano-ceramic composite coating.

[0037] The preparation method of the nano-ceramic coating includes the following steps: ① Weigh 97 parts of acidic silica sol and 3 parts of KH570 by weight, and stir them evenly with a magnetic stirrer at room temperature to obtain a light blue translucent or transparent sol, which is the organosilicon KH-570 modified hybrid silica sol A; ② Weigh the fillers by weight, 26 parts of low-melting glass powder, 18 parts of calcined kaolin, 8 parts of zirconia, 22 parts of corundum powder, 15 parts of silica powder, 5 parts of bentonite, 2 parts of active magnesium oxide; 2 parts of yttrium oxide. Put them into a V-type mixer and stir for 30~60 min at a stirring rate of 30~50 r / min to obtain the mixed powder B component.

[0038] ③ Weigh A:B = 5:5 by weight ratio, and add 0.8 wt% of surfactant, 0.8 wt% of dispersant, 1 wt% of defoamer, and 0.6 wt% of curing agent. After weighing, put them into a planetary ball mill and grind for 10~15 min at a ball milling speed of 200 r / mi to obtain the nano-ceramic coating slurry. Example 2

[0039] Step 1: Sandblast and remove rust from the surface of the substrate to at least reach sa2.5 level Step 2: Arc spray 45CT wire, with a thickness of about 0.3 mm. The spraying parameters are particle spraying speed: >386 m / s, arc voltage: 32~34 V, arc current: 160~200 A, atomizing air pressure: 0.5~0.6 Mp, spraying distance: 150~200 mm, spraying angle: <45° Step 3: After 24 hours of arc spraying, apply the nano-ceramic coating developed by our company. Use air spraying, and control the spraying conditions at an inlet pressure of 0.3 mpa to 0.6 mpa, the distance between the spray gun and the coated surface is 20 cm to 30 cm. At this time, the spray width should be adjusted to 30 cm to 40 cm; keep the distance between the spray gun and the coated surface unchanged and spray evenly until the required wet film thickness is 0.4~0.5 mm.

[0040] Step 4: The nano-ceramic coating is cured at room temperature and sintered by heating with the furnace to obtain a nickel-chromium-titanium alloy and nano-ceramic composite coating.

[0041] A method for preparing a nano-ceramic coating, comprising the following steps: ① Weigh 95 parts of acidic silica sol and 5 parts of KH570 by weight, and fully stir and mix them evenly with a magnetic stirrer at room temperature to obtain a light blue translucent or transparent sol, which is the organosilicon KH-570 modified hybrid silica sol A; ② Weigh the fillers by weight, 26 parts of low-melting glass powder, 18 parts of calcined kaolin, 8 parts of zirconia, 22 parts of corundum powder, 15 parts of silica powder, 5 parts of bentonite, 2 parts of active magnesium oxide; 2 parts of yttrium oxide. Put them into a V-type mixer and stir for 30 - 60 min at a stirring rate of 30 - 50 r / min. Obtain the mixed powder B component; ③ Weigh A:B = 5:5 by weight ratio, and additionally add 1 wt% of surfactant, 1 wt% of dispersant, 0.8 wt% of defoamer, and 1 wt% of curing agent; After weighing, put them into a planetary ball mill and grind for 10 - 15 min at a ball mill rotation speed of 200 r / min; Obtain the nano-ceramic coating slurry.

[0042] Table 1: Performance comparison of experimental cases

[0043] Table 2: Composition of 45CT wire

[0044] The above experimental cases meet the anti-wear requirements of the circulating fluidized bed water-cooled wall boiler.

[0045] The present invention provides comprehensive protection for the anti-corrosion and anti-erosion of the water-cooled wall of a circulating fluidized bed boiler.

[0046] Figure 1 It is the appearance morphology of the substrate thermal sprayed with a metal alloy.

[0047] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0048] The above embodiments only represent several implementation manners of the present application. Their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several deformations and improvements can still be made, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims.

Claims

1. A super wear-resistant composite coating for the water-cooled wall of a circulating fluidized bed boiler, characterized in that: The composite coating includes a nickel-chromium-titanium alloy coating and a nano-ceramic coating; The nickel-chromium-titanium alloy coating is an arc-sprayed 45CT wire; Particle spraying speed: >386 m / s, arc voltage: 32 - 34 V, arc current: 160 - 200 A, atomizing air pressure: 0.5 - 0.6 Mp, spraying distance: 150 - 200 mm, spraying angle: <45°; The nano-ceramic coating contains a colloid, nano-ceramic powder, and an external additive.

2. The super wear-resistant composite coating for the water-cooled wall of a circulating fluidized bed boiler according to claim 1, wherein: The colloid is: silica sol, with a solid content of 20% - 40 wt%; 1 - 5 wt% γ-methacryloxypropyltrimethoxysilane (KH-570) also needs to be added.

3. The super wear-resistant composite coating for the water-cooled wall of a circulating fluidized bed boiler according to claim 1, wherein: The composition of the nano-ceramic powder is: low-melting glass powder 20 - 35 wt%, calcined kaolin 10 - 30 wt%, corundum powder 10 - 20 wt%, zirconia powder 5 - 10 wt%, silica powder 10 - 20 wt%, bentonite 3 - 8 wt%, active magnesium oxide 1 - 3 wt%, yttrium oxide 1 - 3 wt%.

4. The super wear-resistant composite coating for the water-cooled wall of a circulating fluidized bed boiler according to claim 1, wherein: The composition of the external additive is: surfactant 0.3 - 1 wt%, dispersant 0.3 - 1 wt%, defoamer 0.5 - 2 wt%, curing agent 0.5 - 2 wt%.

5. The super wear-resistant composite coating for the water wall of a circulating fluidized bed boiler according to claim 3, characterized in that: The specific low-melting glass powder is as follows: ultra-low-temperature glass powder, initial melting temperature 280 °C, fineness: 1250 mesh, used to reduce the sintering temperature of the coating, form a limited solid solution with alumina, and most of these low-temperature glass powders contain variable-valence elements. The variable-valence effect enhances lattice distortion, promotes the diffusion of particles or the movement of interfaces during the sintering process, activates the lattice, improves the sintering performance of the matrix, and makes the coating densified and ceramized.

6. The ultra-wear-resistant composite coating for the water-cooled wall of a circulating fluidized bed boiler according to claim 3, wherein: The preferred calcined kaolin is: fineness of 800 mesh; The preferred corundum powder is: with an Al2O3 content of more than 98% and a fineness of 400 mesh; The preferred zirconia is: nano-level. By compounding with metal materials, nano-zirconia can improve the thermal conductivity, thermal shock resistance, and high-temperature oxidation resistance of metal materials; The preferred silica powder is: the fineness of the silica powder in silica fume with a fineness less than 1 micron accounting for more than 80%, and the average particle size is 0.1 - 0.2 microns; The preferred bentonite is: fineness of 600 mesh. This substance has good floating and dispersibility in water substances, making the coating not easy to deposit or stratify, with a uniform color, thus improving the stability of the coating mixture and having good brushing performance; The preferred active magnesium oxide is: fineness: 1000 mesh, having the advantages of a large specific surface area, high surface energy, and strong binding force; it can make the coating more densified after sintering; The preferred yttrium oxide is: industrial-grade fineness of yttrium oxide. As a ceramic sintering aid, it can increase the sintering temperature and stability of ceramic materials, thereby increasing the hardness and toughness of ceramic materials. At the same time, yttrium oxide can also reduce the shrinkage and deformation of ceramic materials during sintering.

7. The ultra-wear-resistant composite coating for the water-cooled wall of a circulating fluidized bed boiler according to claim 4, wherein: Among the external additives: the surfactant is sodium dodecyl sulfonate, the dispersant is sodium carboxymethyl cellulose, the defoamer is a silicone-ether copolymer type, and the curing agent is sodium fluorosilicate.

8. A method for preparing a high-temperature anti-wear composite coating for the water-cooled wall of a circulating fluidized bed boiler as described in claims 1-8, characterized in that: The first step: sandblast and remove rust from the surface of the substrate to reach the sa2.5 level; The second step: arc spray 45CT wire, with a thickness of about 0.3 mm. The spraying parameters are as follows: particle spraying speed: >386 m / s, arc voltage: 32 - 34 V, arc current: 160 - 200 A, atomizing air pressure: 0.5 - 0.6 Mp, spraying distance: 150 - 200 mm, spraying angle: <45°; The third step: 24 hours after the arc spraying is completed, spray nano-ceramic coating with a thickness of 0.4 - 0.5 mm.

9. The fourth step: cure the nano-ceramic coating at room temperature and sinter it by heating in the furnace to obtain a nickel-chromium-titanium alloy and nano-ceramic composite coating.

10. According to the method for preparing a high-temperature anti-wear composite coating for the water-cooled wall of a circulating fluidized bed boiler as described in claim 9, characterized in that: The preparation method of the sprayed nano-ceramic coating layer includes the following steps: S1. Weigh 95 - 99 parts by weight of acidic silica sol and add 1 - 5 parts of KH570. Stir well at room temperature with a magnetic stirrer to obtain a light blue translucent or transparent sol, which is the A component of the organosilicon KH-570 modified hybrid silica sol; S2. Weigh the fillers by weight: 20 - 35 wt% of low-melting glass powder, 10 - 30 wt% of calcined kaolin, 10 - 20 wt% of corundum powder, 5 - 10 wt% of zirconia powder, 10 - 20 wt% of silica powder, 3 - 8 wt% of bentonite, 1 - 3 wt% of active magnesium oxide, 1 - 3 wt% of yttrium oxide; put them into a V-type mixer and stir for 30 - 60 min at a stirring rate of 30 - 50 r / min. Obtain the mixed powder B component; S3. Weigh A:B = 5:5 by weight ratio, and add 0.3 - 1 wt% of surfactant, 0.3 - 1 wt% of dispersant, 0.5 - 2 wt% of defoamer, and 0.5 - 2 wt% of curing agent; after weighing, put them into a planetary ball mill and grind for 10 - 15 min at a ball milling speed of 200 r / min; obtain the nano-ceramic coating slurry.

Images