Anti-corrosion and wear-resistant coating for boiler heating surface and preparation method of anti-corrosion and wear-resistant coating

Abstract

The invention provides a corrosion-resistant and wear-resistant coating for a boiler heating surface and a preparation method, the corrosion-resistant and wear-resistant coating comprises a base material, a gradient hard wear-resistant phase, a corrosion-resistant reinforcement phase, a toughening system and a functional auxiliary agent, the base material comprises the following raw materials by weight: 80-100 parts of a potassium silicate binder; 15 to 20 parts of yttrium stabilized zirconium oxide powder 3Y-ZrO2; and 8 to 12 parts of nano boehmite colloid AlOOH. According to the invention, a kaliophilite KAlSiO4 network is generated by the potassium silicate binder and the nano boehmite colloid under high-temperature stepped curing, and the thermal shock resistance is improved by cooperating with the yttria-stabilized zirconia; the tungsten carbide micro powder is used as a rigid framework, the zirconium oxide toughened ceramic balls absorb energy in a phase change mode, the abrasion resistance, corrosion resistance and high-temperature stability of the boiler surface can be improved when the ceramic balls are applied to the boiler surface, and the service life of the boiler heating surface is prolonged.

Description

TECHNICAL FIELD

[0001] The embodiment of the present application relates to the technical field of anti-corrosion and wear-resistant coating, in particular to an anti-corrosion and wear-resistant coating for a boiler heating surface and a preparation method thereof. BACKGROUND

[0002] The boiler is a key component of the core equipment in the flue gas desulfurization system of the power plant, and its main function is to efficiently transfer heat and ensure the full contact of the flue gas and the limestone slurry under the complex working conditions of high temperature, strong corrosion and high wear, so as to promote the smooth completion of the sulfur dioxide absorption reaction. Since the boiler heating surface is exposed to a strong acidic environment with a pH value of 2-5 for a long time, and at the same time, it is subjected to the scouring of high-temperature flue gas (300-400℃) and slurry containing 15%-20% of gypsum particles and chlorine ions, its surface is subjected to the triple damage of chemical corrosion, high-temperature oxidation and mechanical wear. If there is no effective protection, the heating surface will quickly cause pitting corrosion perforation, scaling blockage or thermal fatigue cracking, resulting in a sharp decrease in heat transfer efficiency, an increase in system energy consumption, and even causing unplanned shutdown, which directly affects the stability of the desulfurization system and the compliance of the power plant environmental emission indicators.

[0003] The traditional boiler protection technology for the heating surface mainly adopts high-temperature alloy base material matched with thermal spraying ceramic coating or aluminizing / chromizing process. Among them, the ceramic coating has good high-temperature resistance and wear resistance, but the thermal expansion coefficient is greatly different from the metal matrix material, which is easy to crack and peel off in the cold and hot cycle; the corrosion resistance of the infiltration layer process is limited, and it cannot repair local damage. In addition, the existing technologies cannot simultaneously consider high-temperature oxidation resistance, slurry corrosion resistance and particle scouring resistance, resulting in an average service life of the heating surface of less than 2 years and high maintenance costs. SUMMARY

[0004] The embodiment of the present application aims to at least solve one of the technical problems existing in the prior art, and provides an anti-corrosion and wear-resistant coating for a boiler heating surface and a preparation method thereof.

[0005] In a first aspect, the embodiment of the present application provides an anti-corrosion and wear-resistant coating for a boiler heating surface, which comprises a base material, a gradient hard and wear-resistant phase, a corrosion-resistant reinforcing phase, a toughening system and a functional additive, The base material is composed of the following raw materials in parts by weight: potassium silicate binder: 80-100 parts; yttrium stabilized zirconia powder 3Y-ZrO2: 15-20 parts; nano boehmite colloid AlOOH: 8-12 parts; The gradient hard and wear-resistant phase is composed of the following raw materials in parts by weight: tungsten carbide powder WC: 25-40 parts; hexagonal boron nitride microparticle h-BN: 5-8 parts; zirconia toughening ceramic ball: 10-15 parts; The corrosion-resistant reinforcing phase is composed of the following raw materials in parts by weight: borosilicate glass flakes: 12 to 18 parts; chromium III oxide nanopowder: 8 to 12 parts; The toughening system is composed of the following raw materials in parts by weight: silicon carbide whiskers: 8 to 15 parts; pre-oxidized polyacrylonitrile fiber: 8 to 12 parts; The functional additives are composed of the following raw materials in parts by weight: lithium saponite rheology modifier: 0.5 to 1.2 parts; silane coupling agent: 1.5 to 2.5 parts; zirconate coupling agent: 0.8 to 1.5 parts.

[0006] In some possible embodiments, the particle size range of the tungsten carbide micro powder WC is 5μm~15μm, and the tungsten carbide micro powder is prepared by reacting quartz sand and petroleum coke at a mass ratio of 1:1.2 in an electric arc furnace at 2200℃ for 6 hours, followed by acid washing with 15% hydrofluoric acid and air classification. The thickness of the hexagonal boron nitride microsheet h-BN ranges from 0.5 μm to 2 μm, and the hexagonal boron nitride microsheet is prepared by pyrolyzing ammonia borane at 1100 °C for 2 hours in an ammonia atmosphere and then ultrasonically exfoliating it with N-methylpyrrolidone for 45 minutes. The zirconia toughened ceramic spheres are 3 mol% yttrium oxide stabilized zirconia with a diameter range of 20 μm to 50 μm, and are formed by sintering a spray granulation precursor at 1550°C for 1.5 hours.

[0007] In some possible embodiments, the borosilicate glass flakes have an aspect ratio ≥15, a composition of 72%~78% SiO2, 12%~15% B2O3, 5%~8% Al2O3, and a softening point ≥700℃. The chromium III oxide nanopowder has an average particle size of 40 nm and is prepared by reduction decomposition of ammonium dichromate in a 1:9 hydrogen-argon mixture at 450 °C for 1 hour. The surface hydroxyl density is ≥3 hydroxyl groups / nm. 2 ; The mass ratio of glass flakes to chromium III oxide is (1.2~1.5):1, and Cr2O3 nanoparticles are embedded between the flake layers to form a labyrinthine barrier structure.

[0008] In some possible embodiments, the silicon carbide whiskers have a diameter range of 0.2 μm to 0.5 μm and an aspect ratio of 30 to 50, and the silicon carbide whiskers are grown by vapor deposition of SiO2 and carbon black at 1:3 molar ratio under argon at 1550 °C. The pre-oxidized polyacrylonitrile fiber has a core-shell structure. The core layer is acrylonitrile-butadiene copolymer latex with a diameter ranging from 8 μm to 10 μm, and the shell layer is polyglycidyl methacrylate with a thickness of 150 nm. The core-shell mass ratio is 7:3.

[0009] In some possible embodiments, the zirconate coupling agent is methacryloxypropyltrimethoxyzirconium salt, which is prepared by oxidative polymerization of aniline monomer in 0.5 mol / L hydrochloric acid with ammonium persulfate for 12 hours; The mass ratio of the silane coupling agent to the zirconate coupling agent is (1~2.0):1, which synergistically acts on the ceramic-metal interface; The lithium saponite rheology modifier has a particle size ≤1μm, the interlayer spacing of the layered silicate sheets is 1.2nm~1.5nm, and the slurry zeta potential is ≥35mV.

[0010] Secondly, embodiments of the present invention provide a method for preparing a corrosion-resistant and wear-resistant coating for boiler heating surfaces as described above, comprising the following steps: Step S1. Sandblast the boiler heating surface substrate using 60-mesh brown corundum abrasive, sandblasting angle 70°, surface roughness Ra=6.5μm~7.5μm, immerse in aluminum-titanium phosphating solution for 10 minutes to form a 3μm phosphating film, and dehydrate and cure at 120℃ for 20 minutes. Step S2. Spray a phosphate-based inorganic coating primer containing 20% ​​aluminum powder onto the surface with a wet film thickness of 0.20 mm, let it stand for 15 minutes to defoam, and cure at 80°C for 30 minutes to form a 25 μm base coating. Step S3. Gradient dispersion of functional slurry: Stage 1: Add 80-100 parts of potassium silicate binder, 0.8-1.5 parts of zirconate coupling agent, and 8-12 parts of nano-boehmite colloid into a mixing tank and mix at 1000 rpm for 5 minutes; Stage 2: Add 15-20 parts of yttrium-stabilized zirconia powder, 25-40 parts of tungsten carbide micro powder, and 10-15 parts of zirconia toughened ceramic balls. Switch to -0.09MPa vacuum mode and disperse at 1200rpm for 20 minutes. Phase 3: Inject 12-18 parts of borosilicate glass flakes and 8-12 parts of chromium III oxide nanoparticles, and mix at 600 rpm for 10 minutes; Stage 4: Add 5-8 parts of hexagonal boron nitride micron sheets, 8-15 parts of silicon carbide whiskers, 8-12 parts of pre-oxidized polyacrylonitrile fiber, and 0.5-1.2 parts of lithium saponite rheology modifier, and disperse at a low speed of 400 rpm for 15 minutes. Phase 5: Grind the slurry twice in a sand mill until the fineness is ≤15μm; Step S4. Electrostatic spraying, nozzle diameter 1.2mm, atomization pressure 0.5MPa, spray distance 200mm, gun speed 400mm / s: first layer 80μm~100μm → surface dry for 10 minutes → second layer 80μm~100μm → surface dry for 15 minutes → third layer to total thickness 300μm~350μm; Step S5. Stepped curing: Step 1: Hold at 120℃ for 2 hours; Step 2: Increase temperature to 400℃ at 5℃ / min and hold for 2 hours; Step 3: Increase temperature to 600℃ at 3℃ / min and hold for 1 hour; Step 4: Cool in the furnace to 100℃ and remove from the furnace, with argon gas supplied throughout the process; Step S6. Laser scanning is used to check the thickness uniformity, cross-cut adhesion is tested, and 50μm aluminum phosphate sealant is sprayed on the edge and cured at 400℃ for 30 minutes.

[0011] In some possible embodiments, in step S3: Stage 2 vacuum dispersion with a shear rate ≥1200 s⁻¹ -1 The apparent viscosity of the slurry was controlled at 4500 mPa·s to 6000 mPa·s. During the third stage of glass flake injection, a vortex guide tube is used, with a guide tube diameter / tank diameter ratio of 0.3-0.4 and a Reynolds number Re≥10. 4 ; In the fourth stage, a 0.5T~1.0T axial static magnetic field is applied at a low speed to cause the silicon carbide whiskers to align in the direction of the magnetic field.

[0012] In some possible embodiments, in step S5: When the temperature is increased to 400℃ in step two, the boehmite colloid is dehydrated and transformed into γ-Al2O3, with a volume shrinkage rate of 18%~22%.

[0013] In some possible embodiments, potassium silicate reacts with γ-Al2O3 to form potassium nepheline KAlSiO4 when the temperature is increased to 600°C in a stepwise manner. Argon flow rate 2 L / min~3 L / min, oxygen partial pressure ≤10 ppm, to suppress high-temperature oxidation of tungsten carbide.

[0014] In some possible embodiments, in step S6: The aluminum phosphate sealant is prepared by mixing aluminum dihydrogen phosphate solution and α-Al2O3 micro powder at a mass ratio of 1:1.2, and after curing, it forms an AlPO4-Al2O3 multiphase structure.

[0015] In some possible embodiments, the coefficient of thermal expansion of the sealant is 8.5 × 10⁻⁶. -6 / K~9.0×10 -6 / K, with coating substrate ΔCTE≤1.5×10 -6 / K; After curing at 400℃, the edge sealing area forms a gradient transition layer, with the Al / P atomic ratio gradually changing from 1:1 to 1:0.3 in the thickness direction.

[0016] Compared with the prior art, the present invention has at least the following beneficial effects: This invention utilizes potassium silicate binder and nano-boehmite colloid to generate a potassium nepheline KAlSiO4 network through stepped curing at 600℃, achieving a breakthrough in thermal shock resistance (>150 cycles) in conjunction with yttrium-stabilized zirconia; using tungsten carbide microparticles as a rigid framework and zirconia-toughened ceramic spheres for phase transformation energy absorption, wear resistance is improved by 60% (ASTM G65 weight loss ≤12.8mg); through the synergy of borosilicate glass flake layered barrier and chromium(III) oxide nanoparticle passivation film, Cl... - Penetration rate suppressed to 1.2×10 - 11 g / (m 2 •s), salt spray life >3000 hours; combined with the directional toughening of silicon carbide whiskers (magnetic field orientation deviation ≤8°), high-temperature carbonization network of pre-oxidized polyacrylonitrile fibers, and interface strengthening with zirconate / silane coupling agent, the bonding strength reaches 28.7MPa (ΔCTE≤0.5×10). -6 / K), which improves wear resistance, corrosion resistance and high-temperature stability, extends the service life of boiler heating surfaces and reduces maintenance costs. Detailed Implementation

[0017] To enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described in detail below with reference to specific embodiments. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the described embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] Unless otherwise specifically stated, the technical or scientific terms used in the embodiments of this invention should be understood in their ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains. The terms "comprising" or "including," as used in the embodiments of this invention, do not limit the shapes, numbers, steps, actions, operations, components, elements, and / or groups thereof mentioned, nor do they exclude the appearance or addition of one or more other different shapes, numbers, steps, actions, operations, components, elements, and / or groups thereof, or the inclusion of these.

[0019] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of the invention. Techniques, methods, and apparatus known to those skilled in the art may not be discussed in detail, but where appropriate, the illustrated techniques, methods, and apparatus should be considered part of the specification. In all examples shown and discussed herein, any other specific example may have different values.

[0020] In the description of the embodiments of the present invention, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In the embodiments of the present invention, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in a suitable manner in any one or more embodiments or examples. Furthermore, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in the embodiments of the present invention, as well as the features of different embodiments or examples.

[0021] The following will describe in detail exemplary embodiments according to the present invention. Obviously, the described embodiments are merely some embodiments of the present invention, and not all embodiments of the present invention. It should be understood that the present invention is not limited to the exemplary embodiments described herein.

[0022] This invention provides a corrosion-resistant and wear-resistant coating for boiler heating surfaces, comprising a substrate material, a gradient hard wear-resistant phase, a corrosion-resistant reinforcing phase, a toughening system, and functional additives.

[0023] In some other preferred embodiments, the matrix material is composed of the following raw materials in parts by weight: potassium silicate binder: 80 to 100 parts; yttrium-stabilized zirconia powder 3Y-ZrO2: 15 to 20 parts; nano-boehmite colloid AlOOH: 8 to 12 parts; In some other preferred embodiments, the gradient hard wear-resistant phase is composed of the following raw materials in parts by weight: tungsten carbide micro powder WC: 25 parts to 40 parts; hexagonal boron nitride microsheets h-BN: 5 parts to 8 parts; zirconia toughened ceramic balls: 10 parts to 15 parts; In some other preferred embodiments, the corrosion-resistant reinforcing phase is composed of the following raw materials in parts by weight: borosilicate glass flakes: 12 to 18 parts; chromium III oxide nanopowder: 8 to 12 parts; In some other preferred embodiments, the toughening system is composed of the following raw materials in parts by weight: silicon carbide whiskers: 8 to 15 parts; pre-oxidized polyacrylonitrile fibers: 8 to 12 parts; In some other preferred embodiments, the functional additives are composed of the following raw materials in parts by weight: lithium saponite rheology modifier: 0.5 to 1.2 parts; silane coupling agent: 1.5 to 2.5 parts; zirconate coupling agent: 0.8 to 1.5 parts.

[0024] In some other preferred embodiments, the tungsten carbide micro powder WC has a particle size range of 5μm to 15μm, and is prepared by reacting quartz sand and petroleum coke at a mass ratio of 1:1.2 in an electric arc furnace at 2200℃ for 6 hours, and the tungsten carbide micro powder WC is obtained by acid washing with 15% hydrofluoric acid and air classification.

[0025] In some other preferred embodiments, the thickness of the hexagonal boron nitride microsheet h-BN ranges from 0.5 μm to 2 μm. The hexagonal boron nitride microsheet h-BN is prepared by pyrolysis of ammonia borane at 1100 °C for 2 hours in an ammonia atmosphere, followed by ultrasonic exfoliation with N-methylpyrrolidone for 45 minutes.

[0026] In some other preferred embodiments, the zirconia toughened ceramic spheres are 3 mol% yttrium oxide stabilized zirconia with a diameter ranging from 20 μm to 50 μm, and are formed by sintering a spray granulation precursor at 1550°C for 1.5 hours.

[0027] In some other preferred embodiments, the borosilicate glass flakes have an aspect ratio ≥15, a composition of 72%~78% SiO2, 12%~15% B2O3, and 5%~8% Al2O3, and a softening point ≥700℃.

[0028] In other preferred embodiments, the chromium III oxide nanoparticles have an average particle size of 40 nm and are prepared by reduction decomposition of ammonium dichromate in a 1:9 hydrogen-argon mixture at 450 °C for 1 hour, with a surface hydroxyl density ≥ 3 / nm. 2 .

[0029] In some other preferred embodiments, the mass ratio of glass flakes to chromium III oxide is (1.2~1.5):1, and Cr2O3 nanoparticles are embedded between the flake layers to form a labyrinthine barrier structure.

[0030] In some other preferred embodiments, the silicon carbide whiskers have a diameter range of 0.2 μm to 0.5 μm and an aspect ratio of 30 to 50, and are grown by vapor deposition at 1550 °C under argon atmosphere using a 1:3 molar ratio of SiO2 to carbon black.

[0031] In some other preferred embodiments, the pre-oxidized polyacrylonitrile fiber has a core-shell structure, with the core layer being acrylonitrile-butadiene copolymer latex with a diameter ranging from 8 μm to 10 μm, and the shell layer being polyglycidyl methacrylate with a thickness of 150 nm, and the core-shell mass ratio being 7:3.

[0032] In some other preferred embodiments, the zirconate coupling agent is methacryloxypropyltrimethoxyzirconium salt, which is prepared by oxidative polymerization of aniline monomer in 0.5 mol / L hydrochloric acid with ammonium persulfate for 12 hours.

[0033] In some other preferred embodiments, the mass ratio of silane coupling agent to zirconate ester coupling agent is (1~2.0):1, for example, (1.6-2.0):1 is preferred, and the two work synergistically at the ceramic-metal interface.

[0034] In some other preferred embodiments, the lithium saponite rheology modifier has a particle size ≤1μm, the interlayer spacing of the layered silicate sheets is 1.2nm~1.5nm, and the slurry zeta potential is ≥35mV.

[0035] Based on the same inventive concept, embodiments of the present invention also provide a method for preparing the corrosion-resistant and wear-resistant coating for boiler heating surfaces as described above, comprising the following steps: Step S1. Sandblast the boiler heating surface substrate using 60-mesh brown corundum abrasive, sandblasting angle 70°, surface roughness Ra=6.5μm~7.5μm, immerse in aluminum-titanium phosphating solution for 10 minutes to form a 3μm phosphating film, and dehydrate and cure at 120℃ for 20 minutes.

[0036] Step S2. Spray a phosphate-based inorganic coating primer containing 20% ​​aluminum powder onto the surface with a wet film thickness of 0.20 mm, let it flow and stand for 15 minutes to defoam, and cure at 80°C for 30 minutes to form a 25 μm base coating.

[0037] Step S3. Gradient dispersion of functional slurry: Stage 1: Add 80-100 parts of potassium silicate binder, 0.8-1.5 parts of zirconate coupling agent, and 8-12 parts of nano-boehmite colloid into a mixing tank and mix at 1000 rpm for 5 minutes; Stage 2: Add 15-20 parts of yttrium-stabilized zirconia powder, 25-40 parts of tungsten carbide micro powder, and 10-15 parts of zirconia toughened ceramic balls. Switch to -0.09MPa vacuum mode and disperse at 1200rpm for 20 minutes. Phase 3: Inject 12-18 parts of borosilicate glass flakes and 8-12 parts of chromium III oxide nanoparticles, and mix at 600 rpm for 10 minutes; Stage 4: Add 5-8 parts of hexagonal boron nitride micron sheets, 8-15 parts of silicon carbide whiskers, 8-12 parts of pre-oxidized polyacrylonitrile fiber, and 0.5-1.2 parts of lithium saponite rheology modifier, and disperse at a low speed of 400 rpm for 15 minutes. Phase 5: Grind the slurry twice in a sand mill until the fineness is ≤15μm.

[0038] Step S4. Electrostatic spraying, nozzle diameter 1.2mm, atomization pressure 0.5MPa, spray distance 200mm, gun speed 400mm / s: first layer 80μm~100μm → surface dry for 10 minutes → second layer 80μm~100μm → surface dry for 15 minutes → third layer to total thickness 300μm~350μm.

[0039] Step S5. Stepped curing: Step 1: Hold at 120℃ for 2 hours; Step 2: Increase temperature to 400℃ at 5℃ / min and hold for 2 hours; Step 3: Increase temperature to 600℃ at 3℃ / min and hold for 1 hour; Step 4: Cool furnace to 100℃ and remove from furnace, with argon gas supplied throughout the process.

[0040] Step S6. Laser scanning is used to check the thickness uniformity, cross-cut adhesion is tested, and 50μm aluminum phosphate sealant is sprayed on the edge and cured at 400℃ for 30 minutes.

[0041] In some embodiments, in step S3: Stage 2 vacuum dispersion with a shear rate ≥1200 s⁻¹ -1 The apparent viscosity of the slurry is controlled between 4500 mPa·s and 6000 mPa·s. A vortex guide tube is used during the third stage of glass flake injection, with a guide tube diameter / tank diameter ratio of 0.3-0.4 and a Reynolds number Re≥10. 4 In stage four, a 0.5T~1.0T axial static magnetic field is applied at low speed to cause the silicon carbide whiskers to align in the direction of the magnetic field.

[0042] In some embodiments, in step S5: In step two, heating to 400℃ dehydrates boehmite colloid into γ-Al₂O₃, with a volume shrinkage rate of 18%–22%. In step three, heating to 600℃ causes potassium silicate to react with γ-Al₂O₃ to form potassium nepheline (KAlSiO₄). Argon flow rate is 2–3 L / min, and oxygen partial pressure is ≤10 ppm to suppress high-temperature oxidation of tungsten carbide.

[0043] In some embodiments, in step S6: The aluminum phosphate sealant is prepared by mixing aluminum dihydrogen phosphate solution and α-Al₂O₃ micro powder at a mass ratio of 1:1.2, and after curing, it forms an AlPO₄-Al₂O₃ multiphase structure. The sealant has a coefficient of thermal expansion of 8.5 × 10⁻⁶. -6 / K~9.0×10 -6 / K, with coating substrate ΔCTE≤1.5×10 -6 / K. After curing at 400℃, the edge sealing area forms a gradient transition layer, with the Al / P atomic ratio gradually changing from 1:1 to 1:0.3 in the thickness direction.

[0044] The following sections will provide a detailed description of the corrosion-resistant and wear-resistant coating for boiler heating surfaces and its preparation method, using several specific embodiments.

[0045] Example 1 In this embodiment, the coating process is carried out according to the following parts by weight: 90 parts potassium silicate binder, 18 parts yttrium stabilized zirconia powder (3Y-ZrO2), 10 parts nano boehmite colloid (AlOOH), 35 parts tungsten carbide micro powder (WC), 6 parts hexagonal boron nitride microsheets (h-BN), 12 parts zirconia toughened ceramic spheres, 15 parts borosilicate glass flakes, 10 parts chromium (III) oxide nanoparticles, 12 parts silicon carbide whiskers, 10 parts pre-oxidized polyacrylonitrile fiber, 0.8 parts lithium saponite rheology modifier, 2.0 parts silane coupling agent, and 1.0 part zirconate ester coupling agent. The process flow is as follows: 1. Matrix pretreatment Sandblasting: 60-mesh brown fused alumina abrasive, compressed air pressure 0.7MPa, spray gun angle 70°, spray distance 150mm, to achieve a surface roughness Ra=7.0±0.2μm; Phosphating treatment: Immerse in aluminum-titanium phosphating solution (total acidity 23 points, temperature 50℃) for 10 minutes to generate a 3.0μm phosphating film; Dehydration and curing: Curing in a 120℃ hot air circulating oven for 20 minutes.

[0046] 2. Primer application Spraying: Phosphate-based inorganic primer (containing 20% ​​aluminum powder) is applied using an HVLP spray gun (1.3mm nozzle) with a wet film thickness of 0.20mm; Leveling and defoaming: Let stand on a constant temperature flow platform at 25℃ for 15 minutes; Curing: Curing with hot air in an 80℃ oven for 30 minutes to form a dense 25μm base coating.

[0047] 3. Preparation of functional slurry Stage 1: Add 90 parts of potassium silicate binder, 1.0 part of zirconate coupling agent, and 10 parts of nano-boehmite colloid into a high-speed dispersion kettle (50L volume) and stir at 1000rpm for 5 minutes. Stage 2: Add 18 parts of yttrium-stabilized zirconia powder, 35 parts of tungsten carbide micro powder, and 12 parts of zirconia toughened ceramic balls. Switch to vacuum mode (-0.09MPa) and disperse at high speed of 1200rpm for 20 minutes (shear rate ≥1500s). -1 (Slurry viscosity 5500 mPa·s) Phase 3: Inject 15 parts of borosilicate glass flakes and 10 parts of chromium (III) oxide nanoparticles through a vortex guide tube (diameter / tank diameter ratio 0.35) and mix at a medium speed of 600 rpm for 10 minutes (Reynolds number Re = 1.2 × 10⁻⁶). 4 ); Stage 4: Add 6 parts of hexagonal boron nitride microsheets, 12 parts of silicon carbide whiskers, 10 parts of pre-oxidized polyacrylonitrile fiber, and 0.8 parts of lithium saponite rheology modulator. Apply an axial static magnetic field of 0.8T and disperse at a low speed of 400rpm for 15 minutes (whisker orientation angle deviation ≤8°). Stage 5: The slurry is circulated and ground twice using a pin mill (zirconia beads with a particle size of 0.4 mm). The outlet slurry temperature is ≤40℃ and the fineness D50 is 12.5μm.

[0048] 4. Electrostatic spraying Parameter settings: Spraying voltage 70kV, atomization pressure 0.5MPa, spray gun nozzle diameter 1.2mm, gun travel speed 400mm / s, spray distance 200mm; Layered construction: First coat: 100μm thickness → Surface dry at 25℃ for 10 minutes; Second layer: Spray coating thickness 100μm → Surface dry in 15 minutes; Third layer: Spray coating thickness 150μm → Total thickness 350μm.

[0049] 5. Stepped curing Step 1: Incubate at 120℃ for 2 hours (potassium silicate initial cross-linking); Step 2: Increase the temperature to 400℃ at a rate of 5℃ / min and hold for 2 hours (boehmite dehydrates and is converted to γ-Al2O3, with a volume shrinkage rate of 20%). Step 3: Increase the temperature to 600℃ at 3℃ / min and hold for 1 hour (to generate potassium nepheline KAlSiO4, lattice constant a=1.37nm). Step 4: The furnace is cooled to 100°C, and argon gas is supplied throughout the process (flow rate 2.5L / min, oxygen partial pressure ≤8ppm).

[0050] 6. Post-processing Laser scanning inspection: thickness uniformity deviation ≤ ±5%; Cross-cut adhesion test: ASTM D3359 standard, 1mm spacing cross-cut, adhesion grade 0 (no peeling). Edge sealing: Spray aluminum phosphate sealant (aluminum dihydrogen phosphate: α-Al2O3=1:1.2) 50μm, and cure at 400℃ for 30 minutes (to generate an AlPO4-Al2O3 gradient layer).

[0051] Example 2 In this embodiment, 90 parts of potassium silicate binder, 15 parts of yttrium-stabilized zirconia powder (3Y-ZrO2), 8 parts of nano-boehmite colloid (AlOOH), 30 parts of tungsten carbide micropowder (WC), 5 parts of hexagonal boron nitride microsheets (h-BN), 10 parts of zirconia toughened ceramic spheres, 12 parts of borosilicate glass flakes, 8 parts of chromium(III) oxide nanopowder, 10 parts of silicon carbide whiskers, 8 parts of pre-oxidized polyacrylonitrile fiber, 0.5 parts of lithium saponite rheology modifier, 1.5 parts of silane coupling agent, and 0.8 parts of zirconate ester coupling agent are used. Other components and process parameters are the same as in Example 1.

[0052] Example 3 In this embodiment, 90 parts of potassium silicate binder, 20 parts of yttrium-stabilized zirconia powder (3Y-ZrO2), 12 parts of nano-boehmite colloid (AlOOH), 40 parts of tungsten carbide micropowder (WC), 8 parts of hexagonal boron nitride microsheets (h-BN), 15 parts of zirconia toughened ceramic spheres, 18 parts of borosilicate glass flakes, 12 parts of chromium (III) oxide nanopowder, 15 parts of silicon carbide whiskers, 12 parts of pre-oxidized polyacrylonitrile fiber, 1.2 parts of lithium saponite rheology modifier, 2.5 parts of silane coupling agent, and 1.5 parts of zirconate ester coupling agent are used. Other components and process parameters are the same as in Example 1.

[0053] Example 4 In this embodiment, the silicon carbide whiskers are 8 parts, the pre-oxidized polyacrylonitrile fiber is 12 parts, and the other components and process parameters are the same as in Example 1.

[0054] Example 5 In this embodiment, 25 parts of tungsten carbide micro powder (WC) and 15 parts of zirconia toughened ceramic balls were used, and other components and process parameters were the same as in Example 1.

[0055] Example 6 In this embodiment, the zirconate coupling agent is 1.5 parts, the silane coupling agent is 1.5 parts, and the other components and process parameters are the same as in Example 1.

[0056] Example 7 In this embodiment, the functional slurry dispersion stage adopts a low-speed process: stage two 600 rpm, stage three 300 rpm, stage four 200 rpm, and other components and process parameters are the same as in Example 1.

[0057] Example 8 In this embodiment, the functional slurry dispersion stage adopts a medium-high speed process: stage two 1000 rpm, stage three 450 rpm, stage four 350 rpm, and other components and process parameters are the same as in Example 1.

[0058] Example 9 In this embodiment, the layered spraying thickness adopts a thin coating process: the first layer is 80μm, the second layer is 80μm, the third layer is 140μm, and the total thickness is 300μm. Other components and process parameters are the same as in Example 1.

[0059] Example 10 In this embodiment, the layered spraying thickness adopts a medium-thickness coating process: the first layer is 90μm, the second layer is 90μm, the third layer is 145μm, and the total thickness is 325μm. Other components and process parameters are the same as in Example 1.

[0060] The material formulations for the examples are shown in Table 1: Table 1: Material Formulation Table for Examples

[0061] Comparative Example 1 In this comparative example, 90 parts of potassium silicate binder, 12 parts of yttrium-stabilized zirconia powder (3Y-ZrO2), 22 parts of tungsten carbide micropowder (WC), 3 parts of hexagonal boron nitride microsheets (h-BN), 8 parts of zirconia toughened ceramic spheres, 10 parts of borosilicate glass flakes, 5 parts of chromium(III) oxide nanopowder, 6 parts of silicon carbide whiskers, 5 parts of pre-oxidized polyacrylonitrile fiber, 0.3 parts of lithium saponite rheology modifier, 1.0 part of silane coupling agent, and 0.5 parts of zirconate ester coupling agent were used. Other process parameters were the same as in Example 1.

[0062] Comparative Example 2 In this comparative example, 90 parts of potassium silicate binder, 22 parts of yttrium-stabilized zirconia powder (3Y-ZrO2), 45 parts of tungsten carbide micropowder (WC), 10 parts of hexagonal boron nitride microsheets (h-BN), 18 parts of zirconia toughened ceramic spheres, 22 parts of borosilicate glass flakes, 15 parts of chromium(III) oxide nanopowder, 18 parts of silicon carbide whiskers, 15 parts of pre-oxidized polyacrylonitrile fiber, 1.5 parts of lithium saponite rheology modifier, 3.0 parts of silane coupling agent, and 2.0 parts of zirconate ester coupling agent were used. Other process parameters were the same as in Example 1.

[0063] Comparative Example 3 In this comparative example, the silane coupling agent was 1.0 part, and other process parameters were the same as in Example 1.

[0064] Comparative Example 4 In this comparative example, 15 parts of pre-oxidized polyacrylonitrile fiber were used, and other process parameters were the same as in Example 1.

[0065] Comparative Example 5 In this comparative example, 90 parts of potassium silicate binder and 22 parts of yttrium-stabilized zirconia powder (3Y-ZrO2) were used, and other process parameters were the same as in Example 1.

[0066] Comparative material formulations are shown in Table 2: Table 2: Comparative Example Material Formulation Table

[0067] III. Performance Testing: The coatings were prepared according to the process parameters in the examples and comparative examples, and the following performance tests were performed on the completed coatings: a. Abrasion resistance: ASTM G65 method, load 10N, revolutions 1000 rpm; b. Bond strength: ASTM D4541 hydraulic pull-out method; c. Salt spray test: ISO9227 neutral salt spray, 3000h; d. Cavitation test: ASTM G32 vibration cavitation test, amplitude 50μm × 4h; Record the performance test data and analyze the performance data due to differences in material composition in the examples, as shown in Table 3: Table 3: Material Composition and Sample Performance Data of Examples 1-6

[0068] The performance data due to differences in process parameters in the examples are shown in Table 4: Table 4: Process Parameters and Sample Performance Data of Examples 7-10

[0069] Comparative performance data are shown in Table 5: Table 5: Comparative Performance Data Table

[0070] IV. Data Analysis: The wear resistance weight loss of Examples 1-6 (12.8-16.3 mg) was significantly lower than that of the comparative examples (19.8-38.5 mg), mainly because the tungsten carbide micro powder (WC) formed a continuous rigid skeleton (non-silicon carbide) in the range of 30-40 parts, and its high hardness (Hv≥2200) resisted particle erosion. Zirconia-toughened ceramic spheres (10-15 parts) absorb impact energy and inhibit crack propagation through a phase transformation toughening mechanism (t→m phase transformation). (Comparative Example 2: Excess WC causes embrittlement, increasing the cavitation rate to 2.87 mm). 3 / h).

[0071] The bonding strength of the examples is all >22MPa (maximum 28.7MPa), which is higher than that of comparative examples 1 and 5 (only 14.7-16.2MPa). This may be due to the synergistic effect of potassium silicate binder (80-100 parts) and zirconate coupling agent (0.8-1.5 parts) to form -Si-O-Zr- covalent bonds at the metal-ceramic interface (non-polyurethane system). In contrast, Comparative Example 1 may have insufficient yttrium-stabilized zirconium oxide, resulting in insufficient ceramicization of the matrix and a sharp drop in bonding strength.

[0072] The example showed no failure after 3000 hours of salt spray, while Comparative Examples 1 / 2 / 5 showed rust / peeling. This may be due to the formation of a Cr2O3 / Fe2O3 composite passivation film by chromium(III) oxide nanopowder (8-12 parts) in an acidic environment. Borosilicate glass flakes (12-18 parts) are layered and stacked (aspect ratio ≥15), forming a labyrinthine barrier structure with Cr2O3, Cl - Permeability ≤ 1.2 × 10 -11 g / (m 2 ·s); Comparative Example 2 may have been caused by excessive glass flakes (22 parts), leading to interlayer stress concentration and subsequent peeling after salt spraying.

[0073] Example 7 (low speed) abrasion weight loss 14.5mg > Example 8 (13.2mg), possibly because high shear dispersion at 1200rpm (stage two) is key to eliminating WC agglomeration; Example 9 (thin coating 300 μm) edge corrosion may be due to weakened edge protection (reduced borosilicate flake coverage) because the coating thickness <350 μm. The optimized process in Example 1 (static magnetic field orientation + step-by-step curing) resulted in oriented whisker alignment (deviation angle ≤ 8°) and a low cavitation rate of 0.82 mm. 3 / h.

[0074] Comparative Example 3 (1.0 part of silane coupling agent) had a bonding strength of 27.1 MPa, which was close to that of the Example, but its wear resistance weight loss of 25.7 mg was significantly deteriorated, proving that the silane / zirconate mass ratio (1.6-2.0):1 is the critical point for interface optimization.

[0075] It is understood that the above embodiments are merely exemplary implementations used to illustrate the principles of the present invention, and the present invention is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A corrosion-resistant and wear-resistant coating for boiler heating surfaces, comprising a substrate material, a gradient hard wear-resistant phase, a corrosion-resistant reinforcing phase, a toughening system, and functional additives, characterized in that, The matrix material includes: potassium silicate binder: 80-100 parts; yttrium-stabilized zirconia powder: 15-20 parts; nano-boehmite colloid: 8-12 parts; The gradient hard wear-resistant phase comprises: tungsten carbide micro powder: 25-40 parts; hexagonal boron nitride micro flakes: 5-8 parts; and zirconia toughened ceramic spheres: 10-15 parts. The corrosion-resistant reinforcing phase comprises: borosilicate glass flakes: 12 to 18 parts; chromium III oxide nanopowder: 8 to 12 parts; The toughening system comprises: silicon carbide whiskers: 8 to 15 parts; pre-oxidized polyacrylonitrile fibers: 8 to 12 parts; The functional additives include: lithium saponite rheology modifier: 0.5 to 1.2 parts; silane coupling agent: 1.5 to 2.5 parts; zirconate coupling agent: 0.8 to 1.5 parts.

2. The corrosion-resistant and wear-resistant coating for boiler heating surfaces according to claim 1, characterized in that, The particle size range of the tungsten carbide micro powder is 5μm~15μm, and the tungsten carbide micro powder is prepared by reacting quartz sand and petroleum coke at a mass ratio of 1:1.2 in an electric arc furnace at 2200℃ for 6 hours, followed by acid washing with 15% hydrofluoric acid and air classification. The thickness of the hexagonal boron nitride microsheets ranges from 0.5 μm to 2 μm, and the hexagonal boron nitride microsheets are prepared by pyrolyzing ammonia borane at 1100 °C for 2 hours in an ammonia atmosphere and then ultrasonically exfoliating them with N-methylpyrrolidone for 45 minutes. The zirconia toughened ceramic spheres are 3 mol% yttrium oxide stabilized zirconia with a diameter range of 20 μm to 50 μm, and are formed by sintering a spray granulation precursor at 1550°C for 1.5 hours.

3. The corrosion-resistant and wear-resistant coating for boiler heating surfaces according to claim 2, characterized in that, The borosilicate glass flakes have an aspect ratio ≥15, a composition of 72%~78% SiO2, 12%~15% B2O3, and 5%~8% Al2O3, and a softening point ≥700℃; The chromium III oxide nanopowder has an average particle size of 40 nm and is prepared by reduction decomposition of ammonium dichromate in a 1:9 hydrogen-argon mixture at 450 °C for 1 hour. The surface hydroxyl density is ≥3 hydroxyl groups / nm. 2 ; The mass ratio of the borosilicate glass flakes to the chromium III oxide nanopowder is (1.2~1.5):1, and Cr2O3 nanoparticles are embedded between the flake layers to form a labyrinthine barrier structure.

4. The corrosion-resistant and wear-resistant coating for boiler heating surfaces according to any one of claims 1 to 3, characterized in that, The silicon carbide whiskers have a diameter range of 0.2μm to 0.5μm and an aspect ratio of 30 to 50. The silicon carbide whiskers are grown by vapor deposition of SiO2 and carbon black at 1550℃ under argon atmosphere through a 1:3 molar ratio. The pre-oxidized polyacrylonitrile fiber has a core-shell structure. The core layer is acrylonitrile-butadiene copolymer latex with a diameter ranging from 8 μm to 10 μm, and the shell layer is polyglycidyl methacrylate with a thickness of 150 nm. The core-shell mass ratio is 7:

3.

5. The corrosion-resistant and wear-resistant coating for boiler heating surfaces according to any one of claims 1 to 3, characterized in that, The zirconate coupling agent is methacryloxypropyltrimethoxyzirconium salt, which is prepared by oxidative polymerization of aniline monomer in 0.5 mol / L hydrochloric acid with ammonium persulfate for 12 hours; The mass ratio of the silane coupling agent to the zirconate coupling agent is (1~2.0):1, which synergistically acts on the ceramic-metal interface; The lithium saponite rheology modifier has a particle size ≤1μm, a layered silicate sheet interlayer spacing of 1.2nm~1.5nm, and a slurry zeta potential ≥35mV.

6. A method for preparing a corrosion-resistant and wear-resistant coating for boiler heating surfaces as described in any one of claims 1 to 5, characterized in that, The method includes the following steps: Step S1. Sandblast the boiler heating surface substrate using 60-mesh brown corundum abrasive, sandblasting angle 70°, surface roughness Ra=6.5μm~7.5μm, immerse in aluminum-titanium phosphating solution for 10 minutes to form a 3μm phosphating film, and dehydrate and cure at 120℃ for 20 minutes. Step S2. Spray a phosphate-based inorganic coating primer containing 20% ​​aluminum powder onto the surface with a wet film thickness of 0.20 mm, let it stand for 15 minutes to defoam, and cure at 80°C for 30 minutes to form a 25 μm base coating. Step S3. Gradient dispersion of functional slurry: Stage 1: Add 80-100 parts of potassium silicate binder, 0.8-1.5 parts of zirconate coupling agent, and 8-12 parts of nano-boehmite colloid into a mixing tank and mix at 1000 rpm for 5 minutes; Stage 2: Add 15-20 parts of yttrium-stabilized zirconia powder, 25-40 parts of tungsten carbide micro powder, and 10-15 parts of zirconia toughened ceramic balls. Switch to -0.09MPa vacuum mode and disperse at 1200rpm for 20 minutes. Phase 3: Inject 12-18 parts of borosilicate glass flakes and 8-12 parts of chromium III oxide nanoparticles, and mix at 600 rpm for 10 minutes; Stage 4: Add 5-8 parts of hexagonal boron nitride micron sheets, 8-15 parts of silicon carbide whiskers, 8-12 parts of pre-oxidized polyacrylonitrile fiber, and 0.5-1.2 parts of lithium saponite rheology modifier, and disperse at a low speed of 400 rpm for 15 minutes. Phase 5: Grind the slurry twice in a sand mill until the fineness is ≤15μm; Step S4. Electrostatic spraying, nozzle diameter 1.2mm, atomization pressure 0.5MPa, spray distance 200mm, gun speed 400mm / s: first layer 80μm~100μm → surface dry for 10 minutes → second layer 80μm~100μm → surface dry for 15 minutes → third layer to total thickness 300μm~350μm; Step S5. Stepped curing: Step 1: Hold at 120℃ for 2 hours; Step 2: Increase temperature to 400℃ at 5℃ / min and hold for 2 hours; Step 3: Increase temperature to 600℃ at 3℃ / min and hold for 1 hour; Step 4: Cool in the furnace to 100℃ and remove from the furnace, with argon gas supplied throughout the process; Step S6. Laser scanning is used to check the thickness uniformity, cross-cut adhesion is tested, and 50μm aluminum phosphate sealant is sprayed on the edge and cured at 400℃ for 30 minutes.

7. The method according to claim 6, characterized in that, In step S3: Stage 2 vacuum dispersion with a shear rate ≥1200 s⁻¹ -1 The apparent viscosity of the slurry was controlled at 4500 mPa·s to 6000 mPa·s. During the third stage of injection of borosilicate glass flakes, a vortex guide tube is used, with a guide tube diameter / tank diameter ratio of 0.3-0.4 and a Reynolds number Re≥10. 4 ; In the fourth stage, a 0.5T~1.0T axial static magnetic field is applied at a low speed to cause the silicon carbide whiskers to align in the direction of the magnetic field.

8. The method according to claim 6, characterized in that, In step S5: When the temperature is increased to 400℃ in step two, the boehmite colloid dehydrates and transforms into γ-Al2O3, with a volume shrinkage rate of 18%~22%; When the temperature is increased to 600℃ in a stepwise manner, potassium silicate binder reacts with γ-Al2O3 to generate potassium nepheline KAlSiO4. Argon flow rate 2 L / min~3 L / min, oxygen partial pressure ≤10 ppm, to suppress high-temperature oxidation of tungsten carbide.

9. The method according to claim 6, characterized in that, In step S6: The aluminum phosphate sealant is prepared by mixing aluminum dihydrogen phosphate solution and α-Al2O3 micro powder at a mass ratio of 1:1.2, and after curing, it forms an AlPO4-Al2O3 multiphase structure.

10. The method according to claim 9, characterized in that, The aluminum phosphate sealant has a coefficient of thermal expansion of 8.5 × 10⁻⁶. -6 / K~9.0×10 -6 / K, with coating substrate ΔCTE≤1.5×10 -6 / K; After curing at 400℃, the edge sealing area forms a gradient transition layer, with the Al / P atomic ratio gradually changing from 1:1 to 1:0.3 in the thickness direction.

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