Preparation method of self-propagating anti-corrosion and wear-resistant coating for boiler water-cooled wall

Abstract

The present invention relates to a preparation method of a self-propagating anti-corrosion and wear-resistant coating for a boiler water wall, belonging to the technical field of high-temperature protective coatings. The preparation steps are as follows: (1) Aluminum powder, iron(III) oxide powder, chromium oxide powder, zirconia fine powder, alumina fiber, heat-conducting filler and flux are ball-milled and mixed to obtain a mixed powder; (2) The mixed powder and sodium silicate binder are mixed evenly to obtain a suspension slurry; (3) The surface of the boiler water wall is treated by sandblasting; (4) A precoating is made on the surface of the boiler water wall; (5) A sodium silicate layer is made on the precoating; (6) A magnesium strip is ignited to initiate a self-propagating reaction to obtain a protective layer; (7) The protective layer is removed to obtain a self-propagating anti-corrosion and wear-resistant coating on the surface of the boiler water wall. The sodium silicate used as the binder obtains a dense self-propagating anti-corrosion and wear-resistant coating, and the self-propagating anti-corrosion and wear-resistant coating has good thermal conductivity, uniform thickness, excellent mechanical wear resistance and good corrosion resistance.

Description

Technical Field

[0001] The present invention relates to the technical field of high-temperature protective coatings, and particularly relates to a self-propagating anti-corrosion and wear-resistant coating for a boiler water wall and a preparation method thereof. Background Art

[0002] For power station boilers such as waste incinerators, fluidized bed boilers, and pulverized coal boilers, the water wall heating surface of the boiler not only has to withstand the high-temperature scouring effect of fly ash solid particles, but also has to withstand the severe high-temperature corrosion effect of flue gas. The combined action of high-temperature corrosion and thermal erosion wear causes the wall thickness of the water wall tubes and superheater tubes to become thinner and the strength to decline, resulting in unplanned shutdowns such as tube bursts.

[0003] At present, spraying a coating on the water wall heating surface is an important method to alleviate the above problems. For example, the commonly used Inconel 625 in thermal spraying has poor wear resistance, there are a certain number of pores in the coating, and the density is poor. On the other hand, its process cost is extremely expensive, which results in a short service life of the thermal spraying coating. The shutdown of the boiler to replace the coating seriously affects the safe operation of the power plant and significantly increases the operating cost of the power plant.

[0004] In summary, the existing methods for overcoming the corrosion problem of the boiler heating surface still have high costs and unsatisfactory effects. Compared with other surface coating technologies, the self-propagating coating technology has the characteristics of high production efficiency and low cost. At the same time, the coating contains alumina hard phases, which improves the wear resistance of the coating. The present invention prepares a self-propagating anti-corrosion and wear-resistant coating to solve the problems of high-temperature corrosion and erosion wear on the surface of the boiler water wall. Summary of the Invention

[0005] In order to achieve the long-term use of the boiler water wall, the present invention provides a preparation method for a self-propagating anti-corrosion and wear-resistant coating for the boiler water wall.

[0006] The preparation operation steps of a self-propagating anti-corrosion and wear-resistant coating for the boiler water wall are as follows:

[0007] (1) Prepare the mixed powder

[0008] Mix 40 - 60 parts by mass of aluminum powder, 200 - 240 parts by mass of ferric oxide powder, 80 - 100 parts by mass of chromium oxide powder, and 20 - 40 parts by mass of zirconia fine powder, and ball mill for 1 h - 2 h under the condition of a rotation speed of 500 r / min - 600 r / min in a ball mill; add 30 - 50 parts by mass of alumina fiber, 40 - 70 parts by mass of heat-conducting filler, and 120 - 150 parts by mass of flux, and ball mill for 24 h - 48 h under the condition of a rotation speed of 100 r / min - 200 r / min to obtain the mixed powder;

[0009] (2) Prepare the suspension slurry

[0010] Add 140 - 180 parts by mass of sodium silicate binder to the mixed powder, stir evenly to obtain a suspension slurry, and the viscosity of the suspension slurry is 400 - 700 Pa·s;

[0011] (3)Sandblast the surface of the boiler water wall

[0012] Sandblast the surface of the boiler water wall to be sprayed so that the cleanliness of the sandblasted boiler water wall surface reaches above Sa3.0 level, and the surface roughness reaches 15 - 25 µm;

[0013] (4)Prepare a pre - coating

[0014] Uniformly pre - coat the suspension slurry on the sandblasted surface of the boiler water wall to obtain a pre - coating with a thickness of 1 - 2 mm, let it stand, and air - dry. The pre - coating is as Figure 1 shown;

[0015] (5)Prepare a sodium silicate layer

[0016] Mix 80 - 100 parts by mass of alumina fiber and 40 - 60 parts by mass of sodium silicate binder and stir for 2 h, then uniformly coat it on the pre - coating to obtain a sodium silicate layer with a thickness of 1 - 2 mm, let it stand, and air - dry. The sodium silicate layer is as Figure 1 shown;

[0017] (6)Prepare a protective layer

[0018] Insert magnesium strips evenly around the circumference of the pre - coating, and ignite the magnesium strips evenly distributed in the circumference at the same time. The distribution of the magnesium strips is as Figure 1 shown. The burning magnesium strips cause a self - propagating reaction of the pre - coating from top to bottom to form a self - propagating anti - corrosion and wear - resistant coating; a large amount of welding slag generated by the welding flux combines with the sodium silicate layer to form a protective layer on the surface of the self - propagating anti - corrosion and wear - resistant coating. The self - propagating anti - corrosion and wear - resistant coating and the protective layer are as Figure 2 shown;

[0019] (7)Prepare a self - propagating anti - corrosion and wear - resistant coating

[0020] Remove all protective layers to obtain a self - propagating anti - corrosion and wear - resistant coating with a thickness of 500 - 700 µm on the surface of the boiler water wall.

[0021] The further defined technical solutions are as follows:

[0022] In step (1), the average particle size of the aluminum powder is 40 - 70 μm, the average particle sizes of the ferric oxide powder and the chromium oxide powder are both 1 μm, and the average particle size of the zirconia micropowder is 20 - 40 μm.

[0023] In steps (1) and (5), the alumina content in the alumina fiber is above 95%, the fiber diameter is 5 - 10 μm, and the density is 2 - 5 g / cm 3 .

[0024] In step (1), the heat-conducting filler is at least one of boron nitride, silicon carbide, and aluminum nitride, and the average particle size of the heat-conducting filler is 30 - 50 μm.

[0025] In step (1), the soldering flux is at least two of silicon dioxide, magnesium oxide, and calcium fluoride.

[0026] In step (1), the first ball milling conditions are: ball milling time of 1 h - 2 h under the condition of a rotation speed of 500 r / min - 600 r / min; the second ball milling conditions are: ball milling time of 24 h - 48 h under the condition of a rotation speed of 100 r / min - 200 r / min.

[0027] In steps (2) and (5), the water glass binder is sodium silicate water glass or potassium silicate water glass, and the modulus of the water glass is 3.1 - 3.6.

[0028] In steps (4) and (5), the standing time is 24 h - 48 h.

[0029] In step (6), the length of the magnesium strip is 10 - 15 cm, the distance between adjacent magnesium strips is 21 cm, and before use, it is polished with 1000 - 1500 mesh sandpaper.

[0030] In step (7), the bonding strength of the self-propagating anti-corrosion and wear-resistant coating is 21.2 - 28.6 Mpa, the high-temperature corrosion resistance index is 0.216 - 0.458 mg / mm 2 , the thermal conductivity is 15.5 - 35.6 W / m·K, and the thermal shock resistance of the self-propagating anti-corrosion and wear-resistant coating is 7 - 15 times.

[0031] The beneficial technical effects of the present invention are embodied in the following aspects:

[0032] 1. The self-propagating anti-corrosion and wear-resistant coating for the boiler water wall prepared by the present invention uses the self-propagating coating technology. The self-propagating combustion process is relatively simple, the process time is short, the production efficiency is high, and the cost is low. During the coating preparation process, a heat-conducting filler is added, which greatly improves the heat transfer efficiency of the ceramic coating. Using water glass as a binder, the heat generated by the self-propagating combustion reaction is used to cure the binder, making the coating firmly bonded to the substrate and not easy to fall off and crack. The prepared coating has good comprehensive performance, combining excellent mechanical wear resistance and good corrosion resistance.

[0033] 2. During the preparation process of the self-propagating anti-corrosion and wear-resistant coating of the present invention, at least two of silicon dioxide, magnesium oxide, and calcium fluoride are added as fluxes. When the magnesium strip is ignited and a self-propagating reaction occurs, the heat released by the reaction cures the water glass layer. A large amount of welding slag generated by the fluxes and the water glass layer form a protective layer on the outside. At the same time, due to the relatively large frictional resistance of the alumina fibers, the liquid metal flows uniformly on the alumina fibers, and the molten metal liquid in the shell flows uniformly downward, avoiding the phenomenon of sagging and ensuring the thickness uniformity of the coating during the preparation process. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a structural diagram before the ignition of the magnesium strip and the distribution of the magnesium strip during the preparation process of the self-propagating anti-corrosion and wear-resistant coating of the present invention.

[0035] Figure 2 It is a structural diagram after the ignition of the magnesium strip during the preparation process of the self-propagating anti-corrosion and wear-resistant coating of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0036] In order to better understand the technical solution of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0037] Embodiment 1

[0038] The boiler in this Embodiment 1 is a waste incinerator boiler.

[0039] The preparation operation steps of a self-propagating anti-corrosion and wear-resistant coating for the water-cooled wall of a boiler are as follows:

[0040] (1) Mix 50 g of aluminum powder, 224 g of ferric oxide powder, 91 g of chromium oxide powder, and 35 g of zirconia micropowder, and ball mill for the first time for 2 h at a rotation speed of 500 r / min in a ball mill; add 45 g of alumina fibers, 25 g of boron nitride, 35 g of silicon nitride, 60 g of silicon dioxide, 30 g of magnesium oxide, and 30 g of calcium fluoride, and ball mill for the second time for 48 h at a rotation speed of 150 r / min to obtain a mixed powder.

[0041] The average particle size of the aluminum powder is 60 μm, the average particle sizes of the ferric oxide powder and the chromium oxide powder are both 1 μm, and the average particle size of the zirconia micropowder is 35 μm.

[0042] The alumina content in the alumina fibers is more than 95%, the fiber diameter is 10 μm, and the density is 5 g / cm 3 .

[0043] Among them, boron nitride and silicon nitride are heat-conducting fillers, and the average particle size of the heat-conducting fillers is 30 μm.

[0044] Among them, silicon dioxide, magnesium oxide, and calcium fluoride are fluxes.

[0045] (2) Add 150 g of sodium silicate binder to 625 g of the mixed powder and stir evenly to obtain a suspension slurry with a viscosity of 600 mPa·s.

[0046] The sodium silicate binder is sodium silicate water glass, and the modulus of the water glass is 3.2.

[0047] (3) Sandblast the surface of the boiler water wall to be sprayed so that the cleanliness of the sandblasted boiler water wall surface reaches above Sa3.0 level, and the surface roughness reaches 15 - 25 µm.

[0048] (4) Uniformly pre - coat the suspension slurry on the sandblasted surface of the boiler water wall to obtain a pre - coating layer with a thickness of 1.5 mm, let it stand for 24 h, and dry it in the shade.

[0049] (5) Mix 90 g of alumina fiber and 50 g of sodium silicate binder and stir for 2 h, then uniformly coat it on the pre - coating layer to obtain a sodium silicate layer with a thickness of 1.5 mm, let it stand for 24 h, and dry it in the shade.

[0050] The sodium silicate binder is sodium silicate water glass, and the modulus of the water glass is 3.2.

[0051] (6) Insert magnesium strips evenly around the circumference of the pre - fabricated coating, with a spacing of 21 cm between adjacent magnesium strips. At the same time, ignite the magnesium strips evenly distributed in the circumference. The burning magnesium strips cause a self - propagating reaction of the pre - coating layer from top to bottom to form a self - propagating anti - corrosion and wear - resistant coating; a large amount of welding slag generated by the welding flux combines with the sodium silicate layer to form a protective layer on the surface of the self - propagating anti - corrosion and wear - resistant coating.

[0052] The length of the magnesium strip is 12 cm. Before use, polish it with 1200 - mesh sandpaper.

[0053] (7) Remove all the protective layers to obtain a self - propagating anti - corrosion and wear - resistant coating with a thickness of 600 µm on the surface of the boiler water wall.

[0054] The thickness of the self - propagating anti - corrosion and wear - resistant coating of this Example 1 is measured by scanning electron microscope to be 600 µm; the bonding strength of the composite ceramic coating is detected by GB / T 8642 - 2002 to be 26.2 Mpa; the thermal conductivity of the coating is 34.6 W / m·K; the high - temperature corrosion resistance of the composite ceramic coating is detected by keeping it at 650 °C for 60 hours in a mixed salt of 3 mg / cm 2 of KCl and Na₂SO₄, and the mass change is 0.216 mg / mm 2 ; Heat the self - propagating anti - corrosion and wear - resistant coating to 800 °C, keep it warm for 15 min, cool it to 20 °C in water, and cycle 14 times. Cracks or spalling occur on the self - propagating anti - corrosion and wear - resistant coating, that is, the thermal shock resistance of the self - propagating anti - corrosion and wear - resistant coating is 14 times.

[0055] Example 2

[0056] The boiler in this Embodiment 2 is a waste incineration furnace boiler.

[0057] The preparation operation steps of a self-propagating anti-corrosion and wear-resistant coating for the boiler water wall are as follows:

[0058] (1) Mix 50 g of aluminum powder, 235 g of iron(III) oxide powder, 80 g of chromium oxide powder, and 20 g of zirconia fine powder, and conduct the first ball milling for 1 h in a ball mill under the condition of a rotation speed of 550 r / min; add 30 g of alumina fiber, 60 g of boron nitride, 90 g of silicon dioxide, and 40 g of magnesium oxide, and conduct the second ball milling for 36 h under the condition of a rotation speed of 150 r / min to obtain a mixed powder.

[0059] The average particle size of the aluminum powder is 60 μm, the average particle sizes of the iron(III) oxide powder and the chromium oxide powder are both 1 μm, and the average particle size of the zirconia fine powder is 20 μm.

[0060] The alumina content in the alumina fiber is more than 95%, the fiber diameter is 6 μm, and the density is 5 g / cm 3 .

[0061] Among them, boron nitride is a heat-conducting filler, and the average particle size of the heat-conducting filler is 30 μm.

[0062] Among them, silicon dioxide and magnesium oxide are fluxes.

[0063] (2) Add 170 g of sodium silicate binder to 605 g of the mixed powder, stir evenly to obtain a suspension slurry, and the viscosity of the suspension slurry is 520 mPa·s;

[0064] The sodium silicate binder is sodium silicate water glass, and the modulus of the water glass is 3.5.

[0065] (3) Conduct sandblasting treatment on the surface of the boiler water wall to be sprayed, so that the cleanliness of the sandblasted boiler water wall surface reaches above Sa3.0 level, and the surface roughness reaches 15 - 25 µm.

[0066] (4) Uniformly pre-coat the suspension slurry on the surface of the sandblasted boiler water wall to obtain a pre-coated layer with a thickness of 1.5 mm, let it stand for 36 h, and air-dry it.

[0067] (5) Mix 100 g of alumina fiber and 50 g of sodium silicate binder and stir for 2 h, and uniformly coat it on the pre-coated layer to obtain a sodium silicate layer with a thickness of 1.5 mm, let it stand for 36 h, and air-dry it.

[0068] The sodium silicate binder is sodium silicate water glass, and the modulus of the water glass is 3.5.

[0069] (6) Magnesium strips are evenly inserted around the circumference of the prefabricated coating, with a spacing of 21 cm between adjacent magnesium strips. At the same time, the magnesium strips evenly distributed around the circumference are ignited, and the burning magnesium strips cause a self-propagating reaction of the pre-coated coating from top to bottom to form a self-propagating anti-corrosion and wear-resistant coating; a large amount of welding slag generated by the welding flux combines with the water glass layer to form a protective layer on the surface of the self-propagating anti-corrosion and wear-resistant coating.

[0070] The length of the magnesium strip is 15 cm. Before use, it is polished with 1200-mesh sandpaper.

[0071] (7) Remove all protective layers to obtain a self-propagating anti-corrosion and wear-resistant coating with a thickness of 650 µm on the surface of the boiler water wall.

[0072] The thickness of the self-propagating anti-corrosion and wear-resistant coating in this Example 2 was measured by scanning electron microscope to be 650 µm; the bonding strength of the composite ceramic coating was detected by GB / T 8642-2002 to be 24.3 Mpa; the thermal conductivity of the coating was 15.5 W / m·K; the high-temperature corrosion resistance of the composite ceramic coating was detected by incubating with a mixed salt of KCl and Na2SO4 at 3 mg / cm 2 at 650 °C for 60 hours, and the mass change was 0.338 mg / mm 2 ; the self-propagating anti-corrosion and wear-resistant coating was heated to 800 °C, held for 15 min, water-cooled to 20 °C, and cycled 8 times. Cracks or spalling occurred in the self-propagating anti-corrosion and wear-resistant coating, and the thermal shock resistance of the self-propagating anti-corrosion and wear-resistant coating was obtained as 8 times.

[0073] Example 3

[0074] The boiler in this Example 3 is a waste incinerator boiler.

[0075] The preparation operation steps of a self-propagating anti-corrosion and wear-resistant coating for a boiler water wall are as follows:

[0076] (1) Mix 60 g of aluminum powder, 224 g of iron oxide powder, 91 g of chromium oxide powder, and 30 g of zirconia fine powder, and ball-mill for the first time for 2 h at a rotation speed of 600 r / min in a ball mill; add 45 g of alumina fiber, 10 g of boron nitride, 20 g of silicon carbide, 30 g of silicon nitride, 90 g of silicon dioxide, and 40 g of calcium fluoride, and ball-mill for the second time for 48 h at a rotation speed of 200 r / min to obtain a mixed powder.

[0077] The average particle size of the aluminum powder is 40 µm, the average particle sizes of the iron oxide powder and the chromium oxide powder are both 1 µm, and the average particle size of the zirconia fine powder is 35 µm.

[0078] The alumina content in the alumina fiber is more than 95%, the fiber diameter is 6 µm, and the density is 5 g / cm 3 .

[0079] Among them, boron nitride, silicon carbide, and silicon nitride are thermal conductive fillers, and the average particle size of the thermal conductive fillers is 50 μm.

[0080] Among them, silicon dioxide and calcium fluoride are fluxes.

[0081] (2) Add 150 g of sodium silicate binder to 640 g of the mixed powder and stir evenly to obtain a suspension slurry with a viscosity of 580 mPa·s.

[0082] The sodium silicate binder is potassium silicate sodium silicate, and the modulus of the sodium silicate is 3.2.

[0083] (3) Sandblast the surface of the boiler water wall to be sprayed so that the cleanliness of the sandblasted boiler water wall surface reaches above Sa3.0 level, and the surface roughness reaches 15 - 25 µm.

[0084] (4) Uniformly pre - coat the suspension slurry on the sandblasted surface of the boiler water wall to obtain a pre - coating layer with a thickness of 1.5 mm, let it stand for 24 h, and dry it in the shade.

[0085] (5) Mix 90 g of alumina fiber and 60 g of sodium silicate binder and stir for 2 h, then uniformly coat it on the pre - coating layer to obtain a sodium silicate layer with a thickness of 1.5 mm, let it stand for 24 h, and dry it in the shade.

[0086] The sodium silicate binder is potassium silicate sodium silicate, and the modulus of the sodium silicate is 3.2.

[0087] (6) Insert magnesium strips evenly around the circumference of the pre - fabricated coating, with a spacing of 21 cm between adjacent magnesium strips. At the same time, ignite the magnesium strips evenly distributed in the circumference. The burning magnesium strips cause a self - propagating reaction of the pre - coating layer from top to bottom to form a self - propagating anti - corrosion and wear - resistant coating; A large amount of welding slag generated by the flux combines with the sodium silicate layer to form a protective layer on the surface of the self - propagating anti - corrosion and wear - resistant coating.

[0088] The length of the magnesium strip is 15 cm. Before use, it is polished with 1400 - mesh sandpaper.

[0089] (7) Remove all protective layers to obtain a self - propagating anti - corrosion and wear - resistant coating with a thickness of 600 µm on the surface of the boiler water wall.

[0090] The thickness of the self - propagating anti - corrosion and wear - resistant coating in this Example 3 is measured by scanning electron microscope to be 600 μm; The bonding strength of the composite ceramic coating is detected by GB / T 8642 - 2002 to be 25.9 Mpa; The thermal conductivity of the coating is 29.1 W / m·K; The high - temperature corrosion resistance of the composite ceramic coating is detected by keeping it in a mixture of 3 mg / cm 2 of KCl and Na2SO4 at 650 °C for 60 hours, and the mass change is 0.285 mg / mm 2;Heat the self-propagating anti-corrosion and wear-resistant coating to 800 °C, keep it at this temperature for 15 minutes, then cool it to 20 °C with water, and repeat this cycle 10 times. When cracks or spalling appear on the self-propagating anti-corrosion and wear-resistant coating, the thermal shock resistance of the self-propagating anti-corrosion and wear-resistant coating is 10 times.

[0091] Example 4

[0092] The boiler in this Example 4 is a waste incinerator boiler.

[0093] The preparation operation steps of a self-propagating anti-corrosion and wear-resistant coating for the water-cooled wall of a boiler are as follows:

[0094] (1) Mix 50 g of aluminum powder, 224 g of iron(III) oxide powder, 91 g of chromium oxide powder and 30 g of zirconia fine powder, and perform the first ball milling for 2 h in a ball mill at a rotational speed of 500 r / min; add 30 g of alumina fiber, 60 g of silicon carbide, 60 g of silicon dioxide, 30 g of magnesium oxide and 30 g of calcium fluoride, and perform the second ball milling for 48 h at a rotational speed of 200 r / min to obtain a mixed powder.

[0095] The average particle size of the aluminum powder is 50 μm, the average particle sizes of the iron(III) oxide powder and the chromium oxide powder are both 1 μm, and the average particle size of the zirconia fine powder is 30 μm.

[0096] The alumina content in the alumina fiber is more than 95%, the fiber diameter is 10 μm, and the density is 3 g / cm 3 .

[0097] Among them, silicon carbide is a thermal conductivity filler, and the average particle size of the thermal conductivity filler is 30 μm.

[0098] Among them, silicon dioxide, magnesium oxide, and calcium fluoride are fluxes.

[0099] (2) Add 140 g of sodium silicate binder to 605 g of the mixed powder and stir evenly to obtain a suspension slurry, and the viscosity of the suspension slurry is 550 mPa·s;

[0100] The sodium silicate binder is sodium silicate water glass, and the modulus of the water glass is 3.1.

[0101] (3) Perform sandblasting treatment on the surface of the water-cooled wall of the boiler to be sprayed, so that the cleanliness of the sandblasted surface of the water-cooled wall of the boiler reaches Sa3.0 or above, and the surface roughness reaches 15 - 25 µm.

[0102] (4) Uniformly pre-coat the suspension slurry on the surface of the sandblasted water-cooled wall of the boiler to obtain a pre-coated layer with a thickness of 2 mm, let it stand for 36 h, and dry it in the shade.

[0103] (5) Mix 90 g of alumina fibers and 50 g of sodium silicate binder and stir for 2 h. Uniformly coat the pre-coated layer to obtain a sodium silicate layer with a thickness of 2 mm. Let it stand for 36 h and air-dry.

[0104] The sodium silicate binder is sodium silicate water glass, and the modulus of the water glass is 3.1.

[0105] (6) Insert magnesium strips evenly around the circumference of the prefabricated coating. The distance between adjacent magnesium strips is 21 cm. At the same time, ignite the magnesium strips evenly distributed in the circumference. The burning magnesium strips cause a self-propagating reaction of the pre-coated layer from top to bottom to form a self-propagating anti-corrosion and wear-resistant coating; a large amount of welding slag generated by the welding flux combines with the sodium silicate layer to form a protective layer on the surface of the self-propagating anti-corrosion and wear-resistant coating;

[0106] The length of the magnesium strip is 15 cm. Before use, polish it with 1200-mesh sandpaper.

[0107] (7) Remove all protective layers to obtain a self-propagating anti-corrosion and wear-resistant coating with a thickness of 600 µm on the surface of the boiler water wall.

[0108] The thickness of the self-propagating anti-corrosion and wear-resistant coating of this Example 4 is measured by scanning electron microscope to be 600 µm; the bonding strength of the composite ceramic coating is detected to be 22.1 Mpa by GB / T 8642-2002; the thermal conductivity of the coating is 33.1 W / m·K; the high-temperature corrosion resistance of the composite ceramic coating is detected by keeping it at 650 °C for 60 hours in a mixed salt of 3 mg / cm 2 of KCl and Na2SO4, and the mass change is 0.258 mg / mm 2 ; Heat the self-propagating anti-corrosion and wear-resistant coating to 800 °C, keep it warm for 15 min, cool it to 20 °C in water, and cycle 12 times. Cracks or spalling occur in the self-propagating anti-corrosion and wear-resistant coating, that is, the thermal shock resistance of the self-propagating anti-corrosion and wear-resistant coating is 12 times.

[0109] Example 5

[0110] The boiler in this Example 1 is a waste incinerator boiler.

[0111] The preparation operation steps of a self-propagating anti-corrosion and wear-resistant coating for a boiler water wall are as follows:

[0112] (1) Mix 50 g of aluminum powder, 224 g of ferric oxide powder, 91 g of chromium oxide powder and 30 g of zirconia fine powder. In a ball mill, under the condition of a rotation speed of 600 r / min, the first ball milling time is 1 h; add 30 g of alumina fibers, 25 g of boron nitride, 35 g of silicon nitride, 60 g of silicon dioxide, 30 g of magnesium oxide and 30 g of calcium fluoride, and under the condition of a rotation speed of 200 r / min, the second ball milling time is 36 h to obtain a mixed powder.

[0113] The average particle size of the aluminum powder is 50 μm, the average particle sizes of the iron(III) oxide powder and the chromium oxide powder are both 1 μm, and the average particle size of the zirconia fine powder is 30 μm.

[0114] The alumina content in the alumina fiber is above 95%, the fiber diameter is 10 μm, and the density is 3 g / cm 3 。

[0115] Among them, boron nitride and silicon nitride are heat-conducting fillers, and the average particle size of the heat-conducting fillers is 30 μm.

[0116] Among them, silicon dioxide, magnesium oxide, and calcium fluoride are fluxes.

[0117] (2) Add 150 g of sodium silicate binder to 605 g of the mixed powder and stir evenly to obtain a suspension slurry. The viscosity of the suspension slurry is 600 mPa·s;

[0118] The sodium silicate binder is potassium silicate sodium silicate, and the modulus of the sodium silicate is 3.5.

[0119] (3) Perform sandblasting treatment on the surface of the boiler water wall to be sprayed, so that the cleanliness of the surface of the sandblasted boiler water wall reaches above Sa3.0 level, and the surface roughness reaches 15 - 25 µm.

[0120] (4) Uniformly pre-coat the suspension slurry on the surface of the sandblasted boiler water wall to obtain a pre-coated layer with a thickness of 1.5 mm, let it stand for 24 h, and dry it in the shade.

[0121] (5) Mix 90 g of alumina fiber and 50 g of sodium silicate binder and stir for 2 h, then uniformly coat it on the pre-coated layer to obtain a sodium silicate layer with a thickness of 1.5 mm, let it stand for 24 h, and dry it in the shade.

[0122] The sodium silicate binder is potassium silicate sodium silicate, and the modulus of the sodium silicate is 3.5.

[0123] (6) Insert magnesium strips evenly around the circumference of the prefabricated coating, and the distance between adjacent magnesium strips is 21 cm. At the same time, ignite the magnesium strips evenly distributed in the circumference. The burning magnesium strips cause a self-propagating reaction of the pre-coated layer from top to bottom to form a self-propagating anti-corrosion and wear-resistant coating; A large amount of welding slag generated by the flux combines with the sodium silicate layer to form a protective layer on the surface of the self-propagating anti-corrosion and wear-resistant coating;

[0124] The length of the magnesium strip is 12 cm. Before use, it is polished with 1400-mesh sandpaper.

[0125] (7) Remove all the protective layers to obtain a self-propagating anti-corrosion and wear-resistant coating with a thickness of 560 µm on the surface of the boiler water wall.

[0126] The thickness of the self-propagating anti-corrosion and wear-resistant coating of Example 5 was measured by scanning electron microscopy to be 560 μm; the bonding strength of the composite ceramic coating was 25.2 MPa as measured by GB / T 8642-2002; the thermal conductivity of the coating was 34.7 W / m·K; and the thermal conductivity of the composite ceramic coating was 3 mg / cm 2 The high temperature corrosion resistance of the composite ceramic coating was tested by keeping the mixed salt of KCl and Na2SO4 for 60 hours, and the mass change was 0.279 mg / mm 2 The self-propagating anti-corrosion and wear-resistant coating is heated to 800°C, kept warm for 15 minutes, water-cooled to 20°C, and cycled 11 times. Cracks or peeling appear on the self-propagating anti-corrosion and wear-resistant coating, indicating that the thermal shock resistance of the self-propagating anti-corrosion and wear-resistant coating is 11 times.

Claims

1. A preparation method of a self-propagating anti-corrosion and wear-resistant coating for a boiler water wall, characterized in that, The operation steps are as follows: (1)Prepare the mixed powder Mix 40 - 60 parts by mass of aluminum powder, 200 - 240 parts by mass of iron(III) oxide powder, 80 - 100 parts by mass of chromium oxide powder, and 20 - 40 parts by mass of zirconia micropowder, and conduct the first ball milling in a ball mill; add 30 - 50 parts by mass of alumina fiber, 40 - 70 parts by mass of heat-conducting filler, and 120 - 150 parts by mass of flux, and conduct the second ball milling to obtain the mixed powder; (2)Prepare the suspension slurry Add 140 - 180 parts by mass of sodium silicate binder to the mixed powder and stir evenly to obtain the suspension slurry, and the viscosity of the suspension slurry is 400 - 700 Pa·s; (3)Sandblast the surface of the boiler water wall Sandblast the surface of the boiler water wall to be sprayed so that the cleanliness of the sandblasted boiler water wall surface reaches above Sa3.0 level, and the surface roughness reaches 15 - 25 µm; (4)Make the precoating Evenly precoat the suspension slurry on the sandblasted surface of the boiler water wall to obtain a precoating with a thickness of 1 - 2 mm, let it stand, and air-dry it; (5)Make the sodium silicate layer Mix 80 - 100 parts by mass of alumina fiber and 40 - 60 parts by mass of sodium silicate binder and stir for 2 h, and evenly coat it on the precoating to obtain a sodium silicate layer with a thickness of 1 - 2 mm, let it stand, and air-dry it; (6)Make the protective layer Insert magnesium strips evenly around the circumference of the prefabricated coating, and ignite the magnesium strips evenly distributed around the circumference at the same time. The burning magnesium strips cause a self-propagating reaction of the precoating from top to bottom to form a self-propagating anti-corrosion and wear-resistant coating; a large amount of welding slag generated by the flux combines with the sodium silicate layer to form a protective layer on the surface of the self-propagating anti-corrosion and wear-resistant coating; (7)Prepare the self-propagating anti-corrosion and wear-resistant coating Remove all the protective layers to obtain a self-propagating anti-corrosion and wear-resistant coating with a thickness of 500 - 700 µm on the surface of the boiler water wall.

2. The preparation method of a self-propagating anti-corrosion and wear-resistant coating for a boiler water wall according to claim 1, characterized in that: In step (1), the average particle size of the aluminum powder is 40 - 70 μm, the average particle sizes of the iron(III) oxide powder and the chromium oxide powder are both 1 μm, and the average particle size of the zirconia micropowder is 20 - 40 μm.

3. The preparation method of a self-propagating anti-corrosion and wear-resistant coating for a boiler water wall according to claim 1, characterized in that: In steps (1) and (5), the alumina content in the alumina fiber is more than 95%, the fiber diameter is 5 - 10 μm, and the density is 2 - 5 g / cm 3 .

4. The preparation method of a self-propagating anti-corrosion and wear-resistant coating for a boiler water wall according to claim 1, characterized in that: In step (1), the heat-conducting filler is at least one of boron nitride, silicon carbide, and aluminum nitride, and the average particle size of the heat-conducting filler is 30 - 50 μm.

5. The preparation method of a self-propagating anti-corrosion and wear-resistant coating for a boiler water wall according to claim 1, characterized in that: In step (1), the flux is at least two of silicon dioxide, magnesium oxide, and calcium fluoride.

6. The preparation method of a self-propagating anti-corrosion and wear-resistant coating for a boiler water wall according to claim 1, characterized in that: In step (1), the conditions for the first ball milling are: ball milling time of 1 h - 2 h under the condition of a rotation speed of 500 r / min - 600 r / min; the conditions for the second ball milling are: ball milling time of 24 h - 48 h under the condition of a rotation speed of 100 r / min - 200 r / min.

7. The preparation method of a self-propagating anti-corrosion and wear-resistant coating for a boiler water wall according to claim 1, characterized in that: In steps (2) and (5), the sodium silicate binder is sodium silicate water glass or potassium silicate water glass, and the modulus of the sodium silicate is 3.1 - 3.

6.

8. The preparation method of a self-propagating anti-corrosion and wear-resistant coating for a boiler water wall according to claim 1, characterized in that: In steps (4) and (5), the standing time is 24 h - 48 h.

9. The preparation method of a self-propagating anti-corrosion and wear-resistant coating for a boiler water wall according to claim 1, characterized in that: In step (6), the length of the magnesium strip is 10 - 15 cm, the distance between adjacent magnesium strips is 21 cm, and before use, it is polished with 1000 - 1500 mesh sandpaper.

10. The preparation method of a self-propagating anti-corrosion and wear-resistant coating for a boiler water wall according to claim 1, characterized in that: In step (7), the bonding strength of the self-propagating anti-corrosion and wear-resistant coating is 21.2 to 28.6 Mpa, the high-temperature corrosion resistance index is 0.216 to 0.458 mg / mm 2 , the thermal conductivity is 15.5 to 35.6 W / m·K, and the thermal shock resistance of the self-propagating anti-corrosion and wear-resistant coating is 7 to 15 times.

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