High-temperature-resistant insulating paint and preparation method thereof

Abstract

The invention provides a high-temperature-resistant insulating paint and a preparation method thereof, and belongs to the technical field of paints.The high-temperature-resistant insulating paint is prepared from, by weight, 58-72 parts of high-temperature-resistant aggregate, 3-8 parts of aluminum silicate whisker fiber, 3-8 parts of nickel-chromium-aluminum Y alloy, 0.5-2 parts of molybdenum disulfide, 20-30 parts of silica sol and 0.5-2 parts of rheological additive; the high-temperature-resistant aggregate comprises 15-25 parts by weight of silicon carbide, 10-15 parts by weight of zirconium dioxide, 5-10 parts by weight of high-frequency porcelain, 10-15 parts by weight of aluminum oxide and 8-12 parts by weight of silicon dioxide. According to the technical scheme provided by the invention, the high-temperature-resistant insulating paint and the preparation method thereof are provided, so that the purposes of high-strength adhesion, excellent thermal shock resistance and convenience in construction are achieved at the same time.

Description

Technical Field

[0001] This invention relates to the field of coating technology, and in particular to a high-temperature resistant insulating coating and its preparation method. Background Technology

[0002] In high-temperature industrial fields such as metallurgy, chemical engineering, and aerospace, metal equipment often needs to operate in extreme environments of 1500°C and above. Existing high-temperature protective coatings are often limited by the difficulty in balancing application performance and final performance. Liquid coatings are prone to sagging and are difficult to apply in a single thick coat; powder coatings require specialized equipment and have poor coating uniformity.

[0003] Chinese patent document CN115418121A, entitled "An Iron-Based Waterborne High-Temperature Resistant Insulating Coating and Its Preparation Method and Application," discloses an iron-based waterborne high-temperature resistant insulating coating composed of the following components: 30-50 parts of low-melting-point glass powder, 5-20 parts of inorganic aggregate, 0.5-5 parts of binder, 0.2-5 parts of dispersant, 0-5 parts of organosilicon film-forming aid, 0.5-5 parts of silica sol, and 35-60 parts of deionized water. The application involves coating the iron-based waterborne high-temperature resistant insulating coating onto a steel surface, followed by curing at three temperature levels: dehydration at 60-120℃ for 30 minutes, holding at 240-300℃ for 5-10 minutes, and curing at 540-620℃ for 5-15 minutes, followed by cooling. The beneficial effects are: the preparation method using only water as the dispersion medium and without volatile solvents is green and environmentally friendly; the sintering temperature is low (540-620℃), which causes little damage to the substrate; and the organic components are few, avoiding problems such as coating powdering, decreased adhesion, and coating peeling caused by the decomposition of organic matter at high temperatures.

[0004] However, the high-temperature resistance, adhesion, thermal shock resistance, and ease of construction of the above-mentioned technical solutions and existing technologies still have considerable room for improvement. Developing a coating that can withstand ultra-high temperatures of 1500℃ through the synergistic effect of multiple materials, and simultaneously achieve high-strength adhesion and excellent thermal shock resistance, has become an urgent need in this field. Summary of the Invention

[0005] In view of this, the present invention provides a high-temperature resistant insulating coating and its preparation method, which achieves the purpose of simultaneously possessing high adhesion strength, excellent thermal shock resistance and easy construction.

[0006] To achieve the above objectives, the present invention provides a high-temperature resistant insulating coating, which is made from raw materials comprising the following parts by weight: 58-72 parts of high-temperature resistant aggregate, 3-8 parts of aluminum silicate whisker fiber, 3-8 parts of nickel-chromium-aluminum Y alloy, 0.5-2 parts of molybdenum disulfide, 20-30 parts of silica sol and 0.5-2 parts of rheology modifier; The high-temperature resistant aggregate comprises 15-25 parts by weight of silicon carbide, 10-15 parts by weight of zirconium dioxide, 5-10 parts by weight of high-frequency ceramic material, 10-15 parts by weight of alumina and 8-12 parts by weight of silicon dioxide.

[0007] Optionally, the nickel-chromium-aluminum Y alloy powder comprises the following components by weight percentage: Cr 15-25wt%, Al 5-15wt%, Y 0.1-1.0wt%; the nickel-chromium-aluminum Y alloy is a powder with a particle size D50 = 5-15μm.

[0008] Optionally, the molybdenum disulfide has a purity of ≥99%, and the molybdenum disulfide is in powder form with a particle size D50 of 1-5 μm.

[0009] Optionally, the rheology modifier is a modified cellulose or fumed silica; the amount of the rheology modifier is 0.5-2% of the total weight of the raw materials.

[0010] Rheology modifiers are used to stabilize the state of paste and prevent sedimentation and sagging.

[0011] Optionally, the raw materials of the high-temperature resistant insulating coating may also include a solvent, and the viscosity of the high-temperature resistant insulating coating is 60,000-100,000 cP.

[0012] Optionally, the purity of silicon carbide is ≥99%, and the particle size D50 is 5~20μm.

[0013] The SiC phase serves as the main high-temperature resistant framework, providing excellent high-temperature strength, wear resistance, and thermal shock stability.

[0014] Optionally, the zirconium dioxide has a purity of ≥99.5% and a particle size D50 of 0.5~3μm.

[0015] Yttrium-stabilized zirconium oxide is used to improve the toughness of the coating and inhibit crack propagation by utilizing its phase transformation toughening effect.

[0016] Optionally, the main components of the high-frequency ceramic material are Al2O3, TiO2, MgO, and particle size D50 = 1~5μm.

[0017] High-frequency ceramic materials offer excellent high-temperature insulation and dielectric properties.

[0018] Optionally, the alumina purity is ≥99% and the particle size D50 is 1~8μm.

[0019] Alumina has extremely stable chemical properties, which improves the hardness and corrosion resistance of coatings.

[0020] Optionally, the silica is amorphous SiO2 with a purity ≥99.8% and a particle size D50 = 0.5~2μm.

[0021] Silica also acts as a high-temperature sintering aid, promoting coating densification.

[0022] Optionally, the aluminum silicate whisker fibers are needle-shaped, with a diameter of 0.1~1.0μm and a length of 10~50μm, and are of the mullite phase.

[0023] Alumina silicate whisker fibers form a three-dimensional network structure in the coating, which plays a significant role in toughening, crack resistance, and thickening and suspension in the slurry.

[0024] Optionally, the silica sol contains 30±2% SiO2, has a particle size of 10~20nm, and a pH of 9~10.

[0025] Silica sol acts as an inorganic binder, forming a siloxane network at high temperatures that firmly bonds the filler.

[0026] To achieve the above objectives, the present invention also provides a method for preparing a high-temperature resistant insulating coating, comprising the following steps: 1) Mix the high-temperature resistant aggregate with molybdenum disulfide evenly; then add aluminum silicate whisker fibers and nickel-chromium-aluminum Y alloy, mix evenly; then add silica sol and rheology modifier, mix evenly to obtain the base material; 2) Mix the base material obtained in step 1) with the solvent evenly and adjust the viscosity to obtain the final product.

[0027] Optionally, the high-temperature resistant aggregate, molybdenum disulfide, aluminum silicate whisker fiber, and nickel-chromium-aluminum Y alloy are all dried at 110-130℃ for 3-5 hours before use.

[0028] Optionally, in step 1), the high-temperature resistant aggregate and molybdenum disulfide are mixed evenly by dry mixing, using a planetary mixer at a speed of 280-350 rpm and a mixing time of 15-30 min.

[0029] Optionally, in step 1), after adding aluminum silicate whisker fibers and nickel-chromium-aluminum Y alloy, the mixture is mixed at a speed of 400-600 rpm for 10-20 minutes.

[0030] Optionally, in step 1), after adding silica sol and rheology modifier, the stirring speed after mixing is 280-350 rpm and the stirring time is 15-30 min.

[0031] Optionally, during the above stirring process, the mixture gradually changes from a powder to a paste-like base material with uniform viscosity and no obvious particle feel. The resulting paste-like base material is the coating material that can be applied by scraping or brushing.

[0032] Optionally, the base material may be diluted with 3-10% by weight of solvent to a viscosity of 2,000-5,000 cP to facilitate spray application.

[0033] The above-described technical solution of the present invention has at least the following beneficial effects: The base material prepared by this invention can withstand high temperatures of 1500℃. During preparation, silicon carbide, zirconium dioxide, high-frequency ceramic material, alumina, and silicon dioxide are used as high-temperature resistant aggregates, needle-like aluminosilicate whisker fibers are used as reinforcing agents, and silica sol is used as a binder. Molybdenum disulfide and nickel-chromium-aluminum (NiCrAlY) alloy are introduced for toughening, and NiCrAlY alloy powder and molybdenum disulfide are added simultaneously. Their synergistic effect significantly improves the coating's thermal shock resistance and high-temperature adhesion durability. The paste-like base material formed by this coating can be brushed or diluted and sprayed. After high-temperature sintering, it can form a protective layer with excellent comprehensive performance on a metal substrate.

[0034] Furthermore, through a specific process of stepwise feeding and stirring, a paste-like mixture with controllable viscosity is formed. After high-temperature sintering on a metal substrate, this coating exhibits strong adhesion (≥12MPa), high Mohs hardness (≥8), and good insulation (≥10 at 800℃). 8 It is a robust protective layer that can withstand high temperatures of 1500℃ for a long time. It is especially suitable for industrial equipment with stringent requirements for heat protection, insulation and corrosion resistance, as well as for insulating and corrosion-resistant robust coatings. It solves the problems of poor construction performance, weak adhesion and uneven coating of traditional high temperature coatings.

[0035] The high-temperature insulating coating of this invention has a scientifically formulated and technologically stable formula. It can be applied by brushing for local repairs or diluted and sprayed for large-area, efficient construction, ultimately forming a high-performance, high-temperature resistant protective layer on the metal surface.

[0036] The core technology of this invention lies in the introduction of NiCrAlY alloy powder and molybdenum disulfide, which generates multiple synergistic effects with the components: The synergistic toughening and self-healing mechanism of NiCrAlY alloy powder: The synergistic targets are zirconium dioxide (ZrO2), alumina (Al2O3), and silicon dioxide (SiO2). The phase transformation toughening effect of zirconium dioxide combines with the metal toughening mechanisms such as crack pinning, deflection, and bridging introduced by NiCrAlY particles to form multiple anti-crack propagation barriers. In a high-temperature oxidizing environment, Al and Cr in NiCrAlY preferentially oxidize, forming a dense Al2O3 and Cr2O3 protective film in situ, effectively blocking oxygen infiltration. The newly formed oxides can fill and heal microcracks in the coating, significantly improving the long-term high-temperature stability of the coating. High-temperature conversion and lubrication enhancement mechanism of molybdenum disulfide: Synergistic partners are silicon carbide (SiC), silicon dioxide (SiO2), and NiCrAlY. Mechanism of action: Molybdenum disulfide acts as a solid lubricant below 450℃, transforming into MoO3 at higher temperatures, while still providing lubrication and acting as a liquid-phase sintering aid. MoO3 reacts with SiO2 and Al2O3 in the coating to form molybdate complex salts with higher thermal stability, significantly improving corrosion resistance.

[0037] Needle-shaped aluminum silicate whisker fibers, NiCrAlY particles, and various aggregates form a three-dimensional network in which rigid particles, flexible fibers, and metal toughening phases intertwine, effectively transferring and dispersing stress and providing sufficient interfaces for in-situ reactions. Attached Figure Description

[0038] Figure 1 The image shows the actual effect of applying the coating prepared in Example 1. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following will be described in conjunction with the accompanying drawings of the embodiments of the present invention. Figure 1 The technical solutions of the embodiments of the present invention will be clearly and completely described herein. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention are within the scope of protection of the present invention. Example

[0040] The high-temperature resistant insulating coating of this embodiment comprises the following components in parts by weight: The mixture contains 62 parts of high-temperature resistant aggregate, 5 parts of needle-shaped aluminum silicate whisker fibers, 5 parts of nickel-chromium-aluminum Y alloy powder, 1 part of molybdenum disulfide powder, 25 parts of silica sol, and 11 parts of rheology modifier. The rheology modifier is fumed silica, and the amount of rheology modifier is 1% of the total weight of the raw materials. The high-temperature resistant aggregate consists of 18 parts silicon carbide, 12 parts zirconium dioxide, 8 parts high-frequency ceramic material, 13 parts alumina, and 11 parts silicon dioxide.

[0041] The aluminum silicate whisker fibers are needle-shaped, with a diameter of 0.1~1.0μm and a length of 10~50μm, and are of the mullite phase; the nickel-chromium-aluminum (NiChA) alloy powder comprises the following components by weight percentage: Cr 15-25wt%, Al 5-15wt%, Y 0.1-1.0wt%; the NiChA alloy is in powder form with a particle size D50=5-15μm; the molybdenum disulfide has a purity ≥99%, and is in powder form with a particle size D50=1-5μm; the silica sol contains 30±2% SiO2, has a particle size of 10~20nm, and a pH of 9~10.

[0042] Silicon carbide has a purity ≥99% and a particle size D50 of 5~20μm; zirconium dioxide has a purity ≥99.5% and a particle size D50 of 0.5~3μm; the main components of high-frequency ceramic material are Al2O3, TiO2, MgO, and a particle size D50 of 1~5μm; alumina has a purity ≥99% and a particle size D50 of 1~8μm; silicon dioxide is amorphous SiO2 with a purity ≥99.8% and a particle size D50 of 0.5~2μm. The various raw materials of the coating are mixed to form a paste-like base with a viscosity of 60,000-100,000 cP.

[0043] The preparation method of the high-temperature resistant insulating coating in this embodiment includes the following steps: 1) Dry all powder raw materials and fiber raw materials at 120℃ for 4 hours, and then weigh them accurately according to the design ratio; 2) Add the weighed high-temperature resistant aggregate and molybdenum disulfide powder to a planetary mixer and dry mix at 300 rpm for 20 minutes; then add the mixture of needle-shaped aluminosilicate whisker fibers and nickel-chromium-aluminum Y alloy powder evenly in three portions, increase the speed to 450 rpm, and mix for 15 minutes until evenly mixed. Then add silica sol and rheology modifier to the mixer, adjust the speed to 300 rpm, stir for 30 minutes, and mix evenly. At this time, the mixture gradually changes from powder to a paste-like base material with uniform viscosity and no obvious particle feel. The resulting paste-like base material is the coating material that can be applied by scraping or brushing.

[0044] The formulations of each component (raw material) in Examples 2-5 and the comparative examples are shown in Table 1 below. Table 1. Formulation ratios of Examples 1-5 and Comparative Examples The preparation methods in Examples 1-4 are the same as in Example 1.

[0045] In Example 5, after adding silica sol and rheology modifier to the mixer, the speed was adjusted to 200 rpm and the mixture was stirred for 30 minutes. Everything else was the same as in Example 1.

[0046] The coatings prepared in Examples 1-5 above are suitable for scraping or brushing. If it is necessary to prepare coatings suitable for spraying, 3-10% of deionized water or organic solvent, accounting for 3% of the total weight of the raw materials, can be slowly added to the paste-like base material prepared in Examples 4 and 5. Stir at 150 rpm for 10 minutes, pass through an 80-mesh sieve, adjust the viscosity, seal and let stand for 24 hours to stabilize its chemical and rheological properties.

[0047] The coatings prepared in Examples 1-5 and the comparative examples were subjected to performance tests according to the following methods. The test results are shown in Table 2 below.

[0048] During coating, the coating prepared according to the above method is applied to a 304 stainless steel test plate, and the dry film thickness is controlled at 1000±10μm.

[0049] The adhesion test was conducted according to the pull-off method of GB / T 5210-2006.

[0050] The high-temperature strength was tested using a Mohs hardness pen after heat treatment at 1500℃ for 2 hours.

[0051] Insulation resistance was tested using a ZC-90G high resistance meter, 500VDC, at a temperature of 800℃.

[0052] The aging resistance time is the time it takes for the coating to lose 5% of its weight or peel off when it is continuously heated in static air at 1500℃.

[0053] Table 2 Performance test results of the coatings prepared in Examples 1-5 and comparative examples The test results show that Example 3 exhibits more balanced and superior overall performance. This may be related to the highest fiber content and balanced aggregate ratio in Example 3, resulting in optimal coating adhesion and aging resistance.

[0054] The coatings of Examples 1 and 2 are suitable for brush application and exhibit balanced and reliable performance. The coating of Example 4, due to its highest high-frequency ceramic content, demonstrates the best insulation performance and is suitable for applications with extreme insulation requirements. Example 5, with the addition of a higher amount of silicon carbide, provides good abrasion resistance, but its anti-aging properties are slightly reduced.

[0055] However, all examples exhibited superior performance far exceeding that of conventional coatings (comparative examples: adhesion <5MPa, aging time <100h). All examples with added NiCrAlY and molybdenum disulfide significantly outperformed the comparative examples in adhesion, hardness, insulation resistance, aging time, and thermal shock resistance, demonstrating the synergistic effect of the two new materials.

[0056] Overall, the coating of the present invention can achieve the following effects: 1) Significantly improved thermal shock resistance: Multiple toughening mechanisms work synergistically to enable the coating to withstand more than 25 cycles of rapid cooling and heating from room temperature to 1500°C.

[0057] 2) High-temperature self-healing ability: It can self-repair coating damage through in-situ oxidation reaction, thus extending service life.

[0058] 3) Enhanced high-temperature stability and corrosion resistance: The formation of the composite protective layer significantly improves the chemical stability of the coating at high temperatures.

[0059] 4) Improved adhesion durability: Maintains high adhesion after long-term high-temperature service by reducing interfacial stress and strengthening the interfacial interface.

[0060] 5) Maintain excellent workability: It does not affect the rheological properties of the original coating, enabling flexible application by brushing and spraying to meet the needs of different working conditions.

[0061] 6) High reliability under extreme environments: After heat treatment at 1500℃, the coating has an adhesion of ≥12 MPa and an insulation resistance of >10^8 Ω (800℃), and can withstand more than 20 thermal shock cycles from room temperature to 1500℃.

[0062] 7) Excellent storage and application stability: The paste-like base material can be stored under sealed conditions for 15 days without hard sedimentation, and it atomizes well during spraying.

[0063] The above are preferred embodiments of the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A high-temperature resistant insulating coating, characterized in that, Made from the following raw materials in parts by weight: 58-72 parts of high-temperature resistant aggregate, 3-8 parts of aluminum silicate whisker fiber, 3-8 parts of nickel-chromium-aluminum Y alloy, 0.5-2 parts of molybdenum disulfide, 20-30 parts of silica sol and 0.5-2 parts of rheology modifier; The high-temperature resistant aggregate comprises 15-25 parts by weight of silicon carbide, 10-15 parts by weight of zirconium dioxide, 5-10 parts by weight of high-frequency ceramic material, 10-15 parts by weight of alumina and 8-12 parts by weight of silicon dioxide.

2. The high-temperature resistant insulating coating as described in claim 1, characterized in that, The nickel-chromium-aluminum (NiCr) aluminum Y alloy powder comprises the following components by weight percentage: Cr 15-25wt%, Al 5-15wt%, and Y 0.1-1.0wt%; the NiCr aluminum Y alloy is a powder with a particle size D50 = 5-15μm.

3. The high-temperature resistant insulating coating as described in claim 1, characterized in that, The purity of the molybdenum disulfide is ≥99%, and the molybdenum disulfide is in powder form with a particle size D50 = 1-5 μm.

4. The high-temperature resistant insulating coating as described in claim 1, characterized in that, The rheology modifier is a modified cellulose or fumed silica; the amount of the rheology modifier is 0.5-2% of the total weight of the raw materials.

5. The high-temperature resistant insulating coating as described in claim 1, characterized in that, The raw materials of the high-temperature resistant insulating coating also include solvents; the viscosity of the high-temperature resistant insulating coating is 60,000-100,000 cP.

6. A method for preparing a high-temperature resistant insulating coating as described in any one of claims 1 to 5, characterized in that, Includes the following steps: 1) Mix the high-temperature resistant aggregate with molybdenum disulfide evenly; then add aluminum silicate whisker fibers and nickel-chromium-aluminum Y alloy, mix evenly; then add silica sol and rheology modifier, mix evenly to obtain the base material; 2) Mix the base material obtained in step 1) with the solvent evenly and adjust the viscosity to obtain the final product.

7. The method for preparing the high-temperature resistant insulating coating as described in claim 6, characterized in that, The high-temperature resistant aggregate, molybdenum disulfide, aluminum silicate whisker fiber, and nickel-chromium-aluminum Y alloy are all dried at 110-130℃ for 3-5 hours before use.

8. The method for preparing the high-temperature resistant insulating coating as described in claim 6, characterized in that, In step 1), the high-temperature resistant aggregate and molybdenum disulfide are mixed evenly in a dry mixing process. A planetary mixer is used for dry mixing at a speed of 280-350 rpm for 15-30 min.

9. The high-temperature resistant insulating coating as described in claim 6, characterized in that, In step 1), the aluminum silicate whisker fibers and nickel-chromium-aluminum Y alloy are added and mixed evenly at a speed of 400-600 rpm for 10-20 minutes.

10. The high-temperature resistant insulating coating as described in claim 6, characterized in that, In step 1), after adding silica sol and rheology modifier, the stirring speed after mixing is 280-350 rpm and the stirring time is 15-30 min.

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