A coating for the water-cooled wall surface of a coal-fired boiler and a preparation method and application thereof

Abstract

The present application relates to a special coating for water-cooled wall surface of coal-fired boiler, in particular to a coating for water-cooled wall surface of coal-fired boiler, a preparation method and application thereof. The coating comprises nano-tungsten powder, tungsten carbide, rare earth compound, sodium borate, potassium chromate, rock asphalt, binder, modifier, dispersant, defoaming agent, curing agent and solvent. The coating is fused on the water-cooled wall surface of coal-fired boiler, the obtained coating has good interface bonding with the water-cooled wall base material, low porosity, avoids the penetration of corrosive gas and liquid, solves the corrosion problem of water-cooled wall, and also avoids the reduction of coating hardness and wear resistance; the coating is not easy to wear and damage in long-term use, can improve the high-temperature resistance, hardness, corrosion resistance and wear resistance of the water-cooled wall surface of boiler, effectively prolongs the service life of the water-cooled wall surface of boiler, and further ensures the safe and stable operation of coal-fired boiler.

Description

TECHNICAL FIELD

[0001] The present application relates to a special coating for the water-cooled wall surface of a coal-fired boiler, in particular to a coating for the water-cooled wall surface of a coal-fired boiler, a preparation method and application thereof. BACKGROUND

[0002] Coal-fired power generation occupies an important position in power production in China. In order to improve coal combustion efficiency, reduce environmental pollution and save energy, low-nitrogen combustion technology is widely promoted in power plants. As the ballast and stabilizer of the power industry, thermal power generating units play an increasingly prominent role in low-load operation regulation, flexibility deep peak shaving modification and other aspects. However, rapid load deep adjustment will have a certain impact on the safety, stability and economy of the coal-fired boiler.

[0003] Based on the demand for deep peak shaving and flexibility modification of thermal power generating units, along with the popularization of low-nitrogen combustion technology, higher requirements are put forward for the material of the water-cooled wall surface of the coal-fired power plant boiler. Under the above background, the water-cooled wall surface of the boiler is prone to burst pipe safety accidents caused by high-temperature corrosion, ash deposition and slagging, stress concentration and other factors, and more seriously, it will lead to the shutdown of the boiler, which seriously affects the safe operation of the boiler and brings serious economic losses to the unit. The hardness of the original matrix material of the water-cooled wall of the boiler is not enough, and the corrosion resistance and wear resistance are poor. Therefore, in the prior art, a ceramic coating is coated on the water-cooled wall surface of the coal-fired boiler to improve the hardness, corrosion resistance and wear resistance of the matrix material. On the one hand, the effect of the ceramic coating on improving the hardness and wear resistance of the water-cooled wall surface is limited, and the ceramic coating is easy to wear and damage in the long-term use; on the other hand, the ceramic coating has poor compactness and has pores, so that corrosive gases and liquids can easily penetrate, leading to corrosion of the water-cooled wall surface and also leading to reduction of the hardness and wear resistance of the coating.

[0004] Therefore, it is urgent to develop a new coating material to protect the matrix material of the water-cooled wall surface of the boiler. SUMMARY

[0005] In view of the above technical problems, the present application provides a coating for the water-cooled wall surface of a coal-fired boiler, a preparation method and application thereof. The coating is cladded on the water-cooled wall surface of the coal-fired boiler, and the obtained coating has good interface bonding with the matrix material of the water-cooled wall, low porosity, can avoid the penetration of corrosive gases and liquids, solves the corrosion problem of the water-cooled wall, and also avoids the reduction of the hardness and wear resistance of the coating; the coating is not easy to wear and damage in the long-term use, can improve the comprehensive performance such as high-temperature resistance, hardness and wear resistance of the water-cooled wall surface of the boiler, can effectively prolong the service life of the water-cooled wall surface of the boiler, and further ensure the safe and stable operation of the coal-fired boiler.

[0006] To solve the above technical problems, the present application adopts the following technical scheme:

[0007] The present application provides a coating for the water-cooled wall surface of a coal-fired boiler, comprising the following components in the following proportions by weight: 10-30 parts of nano-tungsten powder, 5-10 parts of tungsten carbide, 2-3 parts of a rare earth compound, 10-15 parts of sodium borate, 2-6 parts of potassium chromate, 2-3 parts of rock asphalt, 10-20 parts of a binder, 2-5 parts of a modifier, 0.5-1.5 parts of a dispersing agent, 1.0-1.5 parts of an antifoaming agent, 1.0-1.5 parts of a curing agent, and 30-34 parts of a solvent.

[0008] Compared with the prior art, the coating of the present application has a hardness of 910-938 HV, a corrosion rate of 1.5-1.7 mg / cm 2 , a wear loss of 19-22 mg, and can withstand a high temperature of 3000°C or above, and has excellent high-temperature resistance, high hardness, corrosion resistance and wear resistance. After the coating is fused onto the water-cooled wall surface of the coal-fired boiler, the obtained coating has good interfacial bonding with the base material of the water-cooled wall, low porosity, and can avoid the penetration of corrosive gases and liquids, thereby solving the corrosion problem of the water-cooled wall and avoiding the reduction of the hardness and wear resistance of the coating. The coating is not prone to wear and damage during long-term use, and improves the high-temperature resistance, high hardness, corrosion resistance and wear resistance of the water-cooled wall surface of the boiler, thereby effectively prolonging the service life of the water-cooled wall surface of the boiler and ensuring the safe and stable operation of the coal-fired boiler.

[0009] The melting points of the nano-tungsten powder and the tungsten carbide are 3400 DEG C and 2800 DEG C respectively, and the Mohs hardnesses are 7.5 and 9.0 respectively, so that the coating has the characteristics of high temperature resistance and high hardness; the synergistic effect between the metal elements provided by the nano-tungsten powder, the tungsten carbide, the sodium borate and the potassium chromate makes the coating have excellent corrosion resistance and wear resistance, meanwhile, the sodium borate and the potassium chromate can further improve the dispersion uniformity of each component in the coating and further improve the high temperature resistance and hardness of the coating; the rare earth elements can further enhance the comprehensive performance of the coating, such as high temperature resistance, high hardness, corrosion resistance and wear resistance, and can also neutralize part of the low-melting-point harmful impurities in the coating, avoid the increase of the porosity of the coating caused by the impurities, and further avoid the reduction of the comprehensive performance of the coating, such as hardness, corrosion resistance and wear resistance; the rock asphalt has good adhesion and anti-peeling between other components in the coating preparation stage, and can be used as an active activator of the coating material, and in the coating preparation stage, the rock asphalt has cross-linking effect with the curing agent, the modifier, the binder and other raw materials; the rock asphalt will volatilize at high temperature, and under the high-temperature laser cladding in the coating preparation stage, the rock asphalt will volatilize with the remaining low-melting-point impurities in the coating, thereby improving the cross-linking reaction degree between the curing agent, the modifier, the binder and other raw materials in the coating, and obviously improving the comprehensive performance of the coating, such as hardness, high temperature corrosion resistance and wear resistance; the solvent acts as a medium for full contact of each raw material, and plays a role of dissolution and stability. The synergistic effect of each component under the above ratio gives the coating excellent high temperature resistance, high hardness, corrosion resistance and wear resistance.

[0010] The low-melting-point impurities in the coating are impurities introduced by the nano-tungsten powder, the sodium borate, the tungsten carbide, the potassium chromate and other raw materials, which will make the porosity of the coating larger, and further affect the comprehensive performance of the coating, such as hardness, corrosion resistance and wear resistance. The addition of 2-3 parts of rock asphalt can completely volatilize and remove the impurities in the coating, and the content of the rock asphalt is less than 2 parts, which cannot remove more impurities, and the content of the rock asphalt is more than 3 parts, which will cause the residue of the impurities.

[0011] Preferably, the particle size of the nano-tungsten powder is 50-100 nm.

[0012] The particle size of the tungsten carbide is 100-200 μm.

[0013] The rare earth compound is lanthanum and cerium with a mass ratio of 2-3:1.

[0014] Preferably, the binder is water glass, polyvinyl alcohol and carboxymethyl cellulose with a mass ratio of (1-2):(1-2):1.

[0015] Preferably, the modifier is kaolin and glass fiber with a mass ratio of 1:(1-2).

[0016] Preferably, the dispersant is triethylhexylphosphoric acid and sodium dodecyl sulfate in a mass ratio of (1-2):3.

[0017] Preferably, the defoamer is ammonium sulfate and aluminum silicate in a mass ratio of (1-2):1.

[0018] Preferably, the curing agent is hexamethylenediamine, triethylenetetramine, and diethylaminopropylamine in a mass ratio of (1-2):(2-1):1.

[0019] Preferably, the solvent is ethanol with a volume concentration of 5% to 15%.

[0020] Secondly, the present invention also provides a method for preparing the above-mentioned coating, comprising:

[0021] Weigh each component according to the designed ratio, add sodium borate, potassium chromate, tungsten carbide, binder, modifier and dispersant to the solvent and stir evenly; then add rare earth composite, rock pitch and defoamer and stir evenly; then add nano tungsten powder and curing agent and stir evenly to obtain a mixture; finally, dry the mixture at 105-110℃ and grind it to a particle size of 20-60μm to obtain the final product.

[0022] The coating preparation method provided by this invention is simple and easy to operate, and is suitable for large-scale production.

[0023] Thirdly, the present invention also provides a method for preparing a coating for a water-cooled wall of a coal-fired boiler using the above-mentioned coating or the coating obtained by the above-mentioned preparation method, wherein the coating is obtained by laser cladding process to clad the coating onto the surface of a substrate material.

[0024] This invention utilizes laser cladding technology to prepare boiler water-cooled wall coatings with dense structure, ultra-high hardness, high temperature resistance, corrosion resistance, and wear resistance. The laser cladding process can be performed under the following conditions: spot diameter of 3.5 mm, laser power of 2.5 kW, scanning speed of 300 mm / min, powder feeding speed of 5 g / min, and protective gas of 5 L / min neon gas. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the preparation process of a coating for a water-cooled wall surface of a coal-fired boiler according to Embodiment 1 of the present invention;

[0026] Figure 2 The image shows the SEM microstructure of a coating used for a water-cooled wall surface of a coal-fired boiler according to Embodiment 1 of the present invention.

[0027] Figure 3 The results are microhardness test results (from the coating surface to the interior of the water-cooled wall substrate material) of the coating used for water-cooled walls of coal-fired boilers according to Embodiments 1 to 3 of the present invention.

[0028] Figure 4 is a curve diagram of the corrosion rate of the coating of the coating material for the water-cooled wall surface of the coal-fired boiler according to the present application, and the water-cooled wall surface changing with time;

[0029] Figure 5 is a curve diagram of the wear amount of the coating of the coating material for the water-cooled wall surface of the coal-fired boiler according to the present application, and the water-cooled wall surface changing with time;

[0030] Figure 6 is a contrast column diagram of the microhardness of the coating of the coating material under different rock asphalt contents;

[0031] Figure 7 is a contrast column diagram of the corrosion rate of the coating of the coating material under different rock asphalt contents (60h);

[0032] Figure 8 is a contrast column diagram of the wear amount of the coating of the coating material under different rock asphalt contents (60min). DETAILED DESCRIPTION

[0033] In order to make the purpose, technical scheme and advantages of the present application more clear, the present application is further described in detail below in combination with specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application, and are not used to limit the present application.

[0034] Embodiment 1

[0035] The present application provides a coating material for the water-cooled wall surface of a coal-fired boiler, which comprises the following components in parts by weight: 15 parts of nano-tungsten powder, 9 parts of tungsten carbide, 3 parts of rare earth compound, 14 parts of sodium borate, 2 parts of potassium chromate, 2 parts of rock asphalt, 16 parts of binder, 4 parts of modifier, 0.8 parts of dispersing agent, 1.2 parts of defoaming agent, 1.1 parts of curing agent, and 31.9 parts of ethanol solvent; wherein the particle size of the nano-tungsten powder is 50-100 nm;

[0036] The particle size of the tungsten carbide is 100-200 μm;

[0037] The rare earth compound is lanthanum and cerium in a mass ratio of 2:1;

[0038] The binder is water glass, polyvinyl alcohol and carboxymethyl cellulose in a mass ratio of 1:1:1;

[0039] The modifier is kaolin and glass fiber in a mass ratio of 1:1;

[0040] The dispersing agent is triethylhexyl phosphoric acid and sodium dodecyl sulfate in a mass ratio of 1:3;

[0041] The defoaming agent is ammonium sulfate and aluminum silicate in a mass ratio of 1:1;

[0042] The curing agent is hexanediamine, triethylenetetramine and diethylaminopropylamine with a mass ratio of 1:2:1;

[0043] The solvent is ethanol with a volume concentration of 15%.

[0044] The preparation method of the coating is as follows:

[0045] According to the designed proportion, each component is weighed, sodium borate, potassium chromate, tungsten carbide, binder, modifier and dispersant are added into ethanol, and stirred at 300 r / min for 20 minutes; then, rare earth compound, rock asphalt and defoaming agent are added, and stirred at 600 r / min for 20 minutes; then, nano tungsten powder and curing agent are added, and stirred for 800 minutes to obtain a mixture; finally, the mixture is dried at 110℃ for 12 hours, ground to a particle size of 20μm, and the coating is obtained.

[0046] The coating is used for preparing a water-cooled wall surface coating of a coal-fired boiler, which comprises the following steps:

[0047] 1. Base treatment

[0048] The water-cooled wall surface base material is first subjected to oil removal treatment with acetone; then, the surface of the base material is subjected to sandblasting treatment with brown corundum sand, and the sandblasting treatment is performed under the following conditions: the particle size of the brown corundum sand is 400μm, the air pressure is 0.9Mpa, the sandblasting distance is 150μm, and the sandblasting angle is 80°; finally, the surface of the water-cooled wall surface base material after sandblasting treatment is cleaned with analytical pure ethanol, and is covered with a protective film, and after natural drying for 24 hours, the base treatment is completed.

[0049] 2. Coating preparation

[0050] The prepared coating is laser cladded on the surface of the water-cooled wall surface base material to form a dense coating with a thickness of about 350μm, and the conditions of the laser cladding process are as follows: the spot diameter is 3.5mm, the laser power is 2.5kW, the scanning speed is 300mm / min, the powder feeding speed is 5g / min, and the protective gas is neon with a flow rate of 5L / min.

[0051] The coating sample is subjected to SEM micro-morphology observation.

[0052] Figure 2 The SEM micro-morphology of the coating for the water-cooled wall surface of a coal-fired boiler according to the embodiment 1 of the present application is shown in the figure. Figure 2 As can be seen from the figure, a dense cladding layer coating structure is formed on the surface of the water-cooled wall surface base material.

[0053] Embodiment 2

[0054] The present application provides a kind of paint for coal-fired boiler water-cooled wall surface, comprising the following weight parts of the following components: 20 parts of nano tungsten powder, 9 parts of tungsten carbide, 3 parts of rare earth complex, 13 parts of sodium borate, 2 parts of potassium chromate, 2 parts of rock asphalt, 16 parts of binder, 4 parts of modifier, 0.8 parts of dispersing agent, 1.2 parts of defoaming agent, 1.1 parts of curing agent, 31.9 parts of solvent;Wherein, the particle size of nano tungsten powder is 50-100nm;

[0055] The particle size of tungsten carbide is 100-200 μm;

[0056] The rare earth complex is lanthanum and cerium with a mass ratio of 2.5:1;

[0057] The binder is water glass, polyvinyl alcohol and carboxymethyl cellulose with a mass ratio of 1:1:1;

[0058] The modifier is kaolin and glass fiber with a mass ratio of 1:1.5;

[0059] The dispersing agent is triethylhexylphosphoric acid and sodium dodecyl sulfate with a mass ratio of 1.5:3;

[0060] The defoaming agent is ammonium sulfate and aluminum silicate with a mass ratio of 1.5:1;

[0061] The curing agent is hexanediamine, triethylenetetramine and diethylaminopropylamine with a mass ratio of 1:1.5:1;

[0062] The solvent is ethanol with a volume concentration of 10%.

[0063] The preparation method of the above-mentioned paint is as follows:

[0064] According to the designed ratio, each component is weighed, sodium borate, potassium chromate, tungsten carbide, binder, modifier and dispersing agent are added to ethanol, and stirred at 400 r / min for 25 minutes;Rare earth complex, rock asphalt and defoaming agent are added, and stirred at 700 r / min for 25 minutes;Nano tungsten powder and curing agent are added, and stirred at 700 r / min for 25 minutes to obtain a mixture;Finally, the mixture is dried at 105℃ for 15h, and ground to a particle size of 40 μm.

[0065] The above-mentioned paint is used for the preparation of coal-fired boiler water-cooled wall surface coating.

[0066] Example 3

[0067] The present application provides a kind of paint for coal-fired boiler water-cooled wall surface, comprising the following weight parts of the following components: 25 parts of nano tungsten powder, 5 parts of tungsten carbide, 3 parts of rare earth complex, 11 parts of sodium borate, 4 parts of potassium chromate, 2 parts of rock asphalt, 11 parts of binder, 3 parts of modifier, 1.3 parts of dispersant, 1.3 parts of defoaming agent, 1.3 parts of curing agent, 33.1 parts of solvent;Wherein, the particle size of nano tungsten powder is 50-100nm;

[0068] The particle size of tungsten carbide is 100-200 μm;

[0069] The rare earth complex is lanthanum and cerium with a mass ratio of 3:1;

[0070] The binder is water glass, polyvinyl alcohol and carboxymethyl cellulose with a mass ratio of 2:1:1;

[0071] The modifier is kaolin and glass fiber with a mass ratio of 1:2;

[0072] The dispersant is triethylhexylphosphoric acid and sodium dodecyl sulfate with a mass ratio of 2:3;

[0073] The defoaming agent is ammonium sulfate and aluminum silicate with a mass ratio of 2:1;

[0074] The curing agent is hexanediamine, triethylenetetramine and diethylaminopropylamine with a mass ratio of 1:1:1;

[0075] The solvent is ethanol with a volume concentration of 5%.

[0076] The preparation method of the above-mentioned paint is:

[0077] According to the design ratio, each component is weighed, sodium borate, potassium chromate, tungsten carbide, binder, modifier and dispersant are added to ethanol, and stirred at 500 r / min for 20 minutes;Rare earth complex, rock asphalt and defoaming agent are added, and stirred at 800 r / min for 20 minutes;Nano tungsten powder and curing agent are added, and stirred at 800 r / min for 2 minutes to obtain a mixture;Finally, the mixture is dried at 110℃ for 12h, and ground to a particle size of 60 μm.

[0078] The above-mentioned paint is used for the application in the preparation of coal-fired boiler water-cooled wall surface coating, which is the same as example 1.

[0079] Example 4

[0080] The present application provides a kind of paint for coal-fired boiler water-cooled wall surface, comprising the following weight parts of the following components: 10 parts of nano tungsten powder, 5 parts of tungsten carbide, 2 parts of rare earth complex, 10 parts of sodium borate, 2 parts of potassium chromate, 2 parts of rock asphalt, 10 parts of binder, 2 parts of modifier, 0.5 parts of dispersing agent, 1 part of defoaming agent, 1 part of curing agent, 30 parts of solvent;Wherein, the particle size of nano tungsten powder is 50-100nm;

[0081] The particle size of tungsten carbide is 100-200 μm;

[0082] The rare earth complex is lanthanum and cerium with a mass ratio of 3:1;

[0083] The binder is water glass, polyvinyl alcohol and carboxymethyl cellulose with a mass ratio of 2:1:1;

[0084] The modifier is kaolin and glass fiber with a mass ratio of 1:2;

[0085] The dispersing agent is triethylhexylphosphoric acid and sodium dodecyl sulfate with a mass ratio of 2:3;

[0086] The defoaming agent is ammonium sulfate and aluminum silicate with a mass ratio of 2:1;

[0087] The curing agent is hexanediamine, triethylenetetramine and diethylaminopropylamine with a mass ratio of 1:1:1;

[0088] The solvent is ethanol with a volume concentration of 5%.

[0089] The preparation method of the above-mentioned paint is:

[0090] According to the designed ratio, each component is weighed, sodium borate, potassium chromate, tungsten carbide, binder, modifier and dispersing agent are added into ethanol, and stirred at 500 r / min for 20 minutes;Rare earth complex, rock asphalt and defoaming agent are added, and stirred at 800 r / min for 20 minutes;Nano tungsten powder and curing agent are added, and stirred at 800 r / min for 2 minutes to obtain a mixture;Finally, the mixture is dried at 110℃ for 12h, and ground to a particle size of 60 μm.

[0091] The above-mentioned paint is used for the preparation of coal-fired boiler water-cooled wall surface coating.

[0092] Example 5

[0093] This invention provides a coating for water-cooled walls of coal-fired boilers, comprising the following components in parts by weight: 30 parts of nano-tungsten powder, 10 parts of tungsten carbide, 3 parts of rare earth composite, 15 parts of sodium borate, 6 parts of potassium chromate, 3 parts of rock pitch, 20 parts of binder, 5 parts of modifier, 1.5 parts of dispersant, 1.5 parts of defoamer, 1.5 parts of curing agent, and 34 parts of solvent; wherein the nano-tungsten powder has a particle size of 50-100 nm.

[0094] The particle size of tungsten carbide is 100–200 μm;

[0095] The rare earth complex is composed of lanthanum and cerium in a mass ratio of 3:1;

[0096] The binder is water glass, polyvinyl alcohol and carboxymethyl cellulose in a mass ratio of 2:1:1;

[0097] The modifier is kaolin and glass fiber in a mass ratio of 1:2;

[0098] The dispersant is triethylhexylphosphoric acid and sodium dodecyl sulfate in a mass ratio of 2:3;

[0099] The defoamer is ammonium sulfate and aluminum silicate in a mass ratio of 2:1;

[0100] The curing agent is hexamethylenediamine, triethylenetetramine, and diethylaminopropylamine in a mass ratio of 1:1:1;

[0101] The solvent is ethanol with a volume concentration of 5%.

[0102] The preparation method of the above coating is as follows:

[0103] Weigh each component according to the designed ratio, add sodium borate, potassium chromate, tungsten carbide, binder, modifier and dispersant to ethanol, and stir at 500 r / min for 20 minutes; then add rare earth composite, rock pitch and defoamer, and stir at 800 r / min for 20 minutes; then add nano tungsten powder and curing agent, and stir at 800 r / min for 2 minutes to obtain a mixture; finally, dry the mixture at 110℃ for 12 h, and grind it to a particle size of 60 μm to obtain the final product.

[0104] The application of the above coating in the preparation of water-cooled wall coatings for coal-fired boilers is the same as in Example 1.

[0105] Comparative Example 1

[0106] Sodium borate and potassium chromate were removed from Example 1, while the remaining components, proportions, and preparation methods were the same as in Example 1.

[0107] Comparative Example 2

[0108] The rock bitumen in Example 1 was removed, and the remaining components, proportions, and preparation methods were the same as in Example 1.

[0109] Example 1

[0110] 1. Porosity test

[0111] The porosities of the coating layers prepared in Examples 1-3 were tested according to GB / T 17721-1999 (Porosity Test of Metal Coating Layer), and the results are shown in Table 1.

[0112] Table 1. Porosity test results of the coating layers prepared in Examples 1-3 (%)

[0113] Coating Example 1 Example 2 Example 3 Porosity (%) 0.58 0.63 0.61

[0114] As shown in Table 1, the coating layers prepared in Examples 1-3 can form excellent interface bonding with the water-cooled wall base material, and the porosities of the coating layers are low, and the internal porosities of the coating layers are almost negligible.

[0115] 2. Comprehensive performance test

[0116] The coating layers prepared in Examples 1-3 and Comparative Examples 1-2 and the water-cooled wall base material were subjected to microhardness, high-temperature resistance, corrosion resistance and wear resistance performance tests, and the results are shown in Table 2.

[0117] The microhardness test method was as follows: an HV-1000 microhardness tester was used to measure the microhardness of the coating layer at intervals of 50 μm along the coating layer direction, the experimental load was 1.961 N, and the load holding time was 15 s.

[0118] The corrosion resistance test method was as follows: the coating layer sample was placed in a salt spray chamber, the humidity in the chamber was in the range of 65%-90%, the temperature was 35±1°C, the medium was a 20% dilute sulfuric acid solution, the dry-wet alternating time was 45 min of heating per hour, the spraying time was 15 min, and the test was performed for 100 h.

[0119] The wear resistance test method was as follows: a BHM-50 reciprocating friction and wear tester was used to perform wear test on the coating layer, and the test conditions were as follows: the counter-abrasive was GCr15 steel with a hardness of 65 HRC, the external load was 80 N, the rotation speed was 120 r / min, and there was no lubrication. After each wear test for 20 min, the coating layer was taken out of the tester and dried, and then the mass of the coating layer was measured by an analytical balance, and the wear loss of the coating layer was recorded according to the mass difference before and after the test.

[0120] Table 2. Performance test results of Examples 1-3 and Comparative Examples 1-2

[0121]

[0122] From Table 2, it can be seen that the coating layers prepared in Examples 1-3 have excellent hardness, high-temperature resistance, corrosion resistance and wear resistance. The coating layers prepared in Comparative Examples 1-2 are all inferior to those prepared in Examples 1-3.

[0123] Figure 3 are the microhardness test results of the coating layers of the water-cooled wall surface of the coal-fired boiler prepared according to Examples 1-3 of the present application (from the surface of the coating layer to the inside of the substrate material of the water-cooled wall surface); from Figure 3 it can be seen that the microhardness of the coating layers prepared in Examples 1-3 are all between 910 and 938 HV, and the hardness of the same working condition will have a small fluctuation, which is probably caused by the process characteristics and measurement error. When the distance reaches 350 μm, the hardness decreases obviously, which is the hardness of the substrate material of the water-cooled wall surface, and the overall hardness is between 259 and 287 HV, and the change is also not too large. The above hardness test results fully show that the dense coating layer with a thickness of about 350 μm is successfully prepared by the laser cladding process, and the microhardness of the coating layer is much higher than that of the substrate material of the water-cooled wall surface.

[0124] Figure 4 are the corrosion rate-time curves of the coating layers of the water-cooled wall surface of the coal-fired boiler prepared according to Examples 1-3 of the present application; from Figure 4 it can be seen that with the change of time, the corrosion rate of the coating layers prepared in Examples 1-3 increases slowly, while the corrosion rate of the water-cooled wall surface is much higher than that of the coating layer. After 10 h, the corrosion rate of the water-cooled wall surface is about 18.2 mg / cm 2 , while the corrosion rate of the coating layers of Examples 1-3 is between 1.5 and 1.7 mg / cm 2 , which shows that the coating layer prepared from the coating of the present application can slow down the corrosion rate of the water-cooled wall surface by more than 10 times.

[0125] Figure 5 are the wear loss-time curves of the coating layers of the water-cooled wall surface of the coal-fired boiler prepared according to Examples 1-3 of the present application; from Figure 5 it can be seen that with the increase of the wear time, the wear loss of the water-cooled wall surface is surprisingly 526 mg after 160 min, while the wear loss of the coating layers of Examples 1-3 is much lower than that of the water-cooled wall surface, and is about between 19 and 22 mg, which shows that the wear resistance of the coating layer of the present application is much higher than that of the substrate material of the water-cooled wall surface.

[0126] Verification Example 2

[0127] The effects of different bitumen contents on the microhardness, corrosion rate and wear loss of the coating layer are further verified. The composition and preparation method of the coating, and the preparation method of the water-cooled wall surface of the coal-fired boiler are the same as those in Example 1, and the difference lies in the different amounts of rock bitumen.

[0128] Figure 6 This is a bar chart comparing the microhardness of coatings with different rock bitumen contents; from Figure 6 It can be seen that when the rock asphalt content is 2 to 3 parts, the microhardness of the coating is above 910 HV. When the rock asphalt content is 1 part and 2 parts, the microhardness of the coating is below 800 HV and 900 HV, respectively. When the rock asphalt content is greater than 3 parts, the microhardness of the coating also shows a slow decreasing trend.

[0129] Figure 7 This is a bar chart comparing the corrosion rates of coatings with different rock bitumen contents (60h); from Figure 7 It can be seen that when the rock bitumen content is between 2 and 3 parts, the corrosion rate of the coating after 60 hours is 1.3 mg / cm³. 2 The corrosion rate of the coating was approximately 3.5 mg / cm³ when the rock bitumen content was 1 part and 2 parts, respectively. 2 2.6 mg / cm 2 When the content of rock asphalt is greater than 3 parts, the corrosion rate of the coating also increases, and the trend of increasing increases.

[0130] Figure 8 This is a bar chart comparing the wear of coatings with different rock bitumen contents (60 min); from Figure 8 It is known that when the rock asphalt content is 2 to 3 parts, the wear amount of the coating after 60 minutes is approximately 7.4 to 8.1 mg. When the content is 1 or 2 parts, the wear amount exceeds 13 mg, and when the content exceeds 3 parts, the wear amount also exceeds 11 mg, showing an increasing trend. Therefore, rock asphalt plays a significant role in activating the coating material. Furthermore, with changes in its content, the overall performance of the coating does not increase or decrease linearly, but rather exhibits a relatively optimal range. Experimental test results show that when the rock asphalt content is 2 to 3 parts, it has the best effect on improving the coating's hardness, high-temperature corrosion resistance, and wear resistance.

[0131] This may be because: on the one hand, rock asphalt exhibits good adhesion and anti-peel properties with other components during the coating preparation stage, serving as an active activator for the coating material. During coating preparation, it undergoes chemical cross-linking with raw materials such as curing agents, modifiers, and adhesives. On the other hand, rock asphalt also has high viscosity and volatilizes at high temperatures. Under high-temperature laser cladding in coating preparation, rock asphalt will volatilize and carry away the remaining low-melting-point impurities in the coating, thereby increasing the degree of chemical cross-linking reaction between raw materials such as curing agents, modifiers, and adhesives in the coating, significantly improving the overall performance of the coating, such as hardness, high-temperature corrosion resistance, and wear resistance.

[0132] The coating prepared by the coating material has high temperature resistance of above 3000 DEG C, hardness of 910-938HV, corrosion rate of 1.5-1.7mg / cm 2 , wear amount of 19-22mg, and excellent high temperature resistance, high hardness, corrosion resistance and wear resistance. The coating material is cladded on the water cooled wall surface of a coal-fired boiler, and the obtained coating has good interface bonding with the water cooled wall base material, low porosity, high melting degree of coating particles, good heat conduction performance and high thermal stability; the coating is not easy to wear and damage during long-term use of the water cooled wall surface of the boiler, and can improve the high temperature resistance, high hardness, corrosion resistance and wear resistance of the water cooled wall surface of the boiler, effectively prolong the service life of the water cooled wall surface of the boiler, and further ensure the safe and stable operation of the coal-fired boiler.

[0133] The above merely describes preferred embodiments of the present application, but should not be used to limit the present application, and any modification, equivalent replacement or improvement within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. A coating, characterized in that, The tungsten nanopowder has a particle size of 50-100 nm, and the rare earth compound is lanthanum and cerium.

2. The coating of claim 1, wherein, The tungsten carbide has a particle size of 100-200 mu m; and / or The rare earth compound is lanthanum and cerium in a mass ratio of 2-3:

1.

3. The coating of claim 1, wherein, The binder is water glass, polyvinyl alcohol and carboxymethyl cellulose in a mass ratio of (1-2):(1-2):

1.

4. The coating of claim 1, wherein, The modifier is kaolin and glass fiber in a mass ratio of 1:(1-2).

5. The coating of claim 1, wherein, The dispersant is triethylhexyl phosphate and sodium dodecyl sulfate in a mass ratio of (1-2):

3.

6. The coating of claim 1, wherein, The defoaming agent is ammonium sulfate and aluminum silicate in a mass ratio of (1-2):

1.

7. The coating of claim 1, wherein, The curing agent is hexanediamine, triethylenetetramine and diethylaminopropylamine in a mass ratio of (1-2):(2-1):

1.

8. The coating of claim 1, wherein, The solvent is ethanol with a volume concentration of 5-15%.

9. Process for the preparation of the coating according to any one of claims 1 to 8, characterized in that, The method comprises the following steps: The components are weighed according to the design ratio, the sodium borate, potassium chromate, tungsten carbide, binder, modifier and dispersant are added into the solvent and stirred uniformly, the rare earth compound, rock asphalt and defoaming agent are added and stirred uniformly, the tungsten nanopowder and curing agent are added and stirred uniformly to obtain a mixture, and finally the mixture is dried at 105-110 DEG C and ground to a particle size of 20-60 mu m.

10. A method for preparing a coating for the water-cooled walls of a coal-fired boiler with the coating material according to any one of claims 1 to 8 or the coating material obtained by the method according to claim 9, characterized in that The coating is obtained by laser cladding process.

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