Hole sealing method based on porosity of thermal spraying coating

Abstract

The invention belongs to the technical field of thermal spraying coating hole sealing, and discloses a hole sealing method based on the porosity of a thermal spraying coating, which comprises the following steps: forming a coating on the surface of a base material through a thermal spraying process, applying hole sealing glue on the surface of the coating, and forming a hole by utilizing the structural characteristic that open pores are communicated with one another. Enabling the hole sealing glue to naturally permeate into the coating under the action of gravity, enabling the hole sealing glue to at least permeate into the coating by 500 microns before curing by controlling the surface tension, viscosity and curing conditions of the hole sealing glue, and continuously filling holes; and then the coating is subjected to low-temperature curing treatment, so that the hole sealing glue forms a stable hole sealing structure in the holes. After the method disclosed by the invention is adopted, no less than 95% of open pores in the coating can be effectively sealed under the condition of not applying external pressure or vacuum assistance, so that the voltage resistance of the thermal spraying coating is stabilized at 500V or above, and the resistance value is improved from megohm level to gigaohm level, thereby obviously improving the electrical property and corrosion resistance of the coating.

Description

Technical Field

[0001] This invention belongs to the field of thermal spray coating sealing technology, specifically a sealing method based on the porosity of thermal spray coatings. Background Technology

[0002] Thermal spraying technology is a surface modification process that uses a high-energy heat source to heat the spraying material to a molten or semi-molten state and deposits it on the surface of the substrate to form a coating through high-speed spraying. It is widely used in fields such as wear resistance, corrosion resistance, and electrical insulation.

[0003] However, due to factors such as the semi-molten state of the sprayed powder, gas entrapment during the spraying process, and irregular accumulation and rapid cooling of molten particles after high-speed impact, a certain number of pores are usually formed inside the thermal spray coating. These pores are structural defects that are difficult to avoid in the spraying process.

[0004] Based on whether the pores are interconnected, coating pores can be classified into open pores and closed pores. Open pores are interconnected, easily forming channels for air and moisture flow, which can lead to substrate corrosion and reduce the electrical insulation performance of the coating. To address these issues, existing technologies typically introduce a sealing process after coating formation. However, current sealing processes generally suffer from problems such as insufficient fluidity of the sealing adhesive, limited penetration depth, and long curing times. This results in inadequate sealing within the coating, especially in areas close to the substrate, ultimately making it difficult to consistently meet the requirements for high voltage resistance and high insulation performance. Summary of the Invention

[0005] The purpose of this invention is to provide a pore-sealing method based on the porosity of thermal spray coatings, so as to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a pore-sealing method based on the porosity of a thermal spray coating, comprising the following steps: (1) A coating is formed on the surface of a substrate by a thermal spraying process, wherein the coating contains pores formed by powder semi-melting, gas entrainment or high-speed impact accumulation during the spraying process, and the pores include at least interconnected open pores. (2) After the coating is formed, a sealing adhesive is applied to the surface of the coating. The sealing adhesive is naturally penetrated into the interior of the coating along the pore channels under the action of gravity by utilizing the interconnected structure of the open pores. (3) By controlling the surface tension, viscosity and curing conditions of the sealing adhesive, the sealing adhesive can penetrate into the coating at least 500μm before curing, so as to continuously fill the pores. (4) After the coating has been penetrated, it is cured at low temperature so that the sealing adhesive forms a stable sealing structure inside the pores, thereby improving the coating’s voltage resistance, electrical resistance and corrosion resistance.

[0007] Preferably, the sealing adhesive is a resin-based sealing adhesive with a surface tension lower than the wetting critical value of the pore walls of the thermal spray coating, and has a low viscosity in its uncured state, enabling it to fully penetrate the open pores by gravity alone without the application of external pressure or vacuum assistance. Preferably, the resistivity of the sealing layer formed after the sealing adhesive has cured matches the electrical properties of the thermal spray coating, thereby improving the overall insulation performance and voltage resistance stability of the coating after sealing.

[0008] Preferably, the sealing adhesive mainly penetrates along the pores in the coating and fills to a depth of at least 500 μm from the coating surface before curing, so as to avoid the sealing adhesive only staying on the surface of the coating and causing insufficient sealing of the internal pores. When the porosity of the thermal spray coating reaches 20%, the sealing adhesive can still effectively seal no less than 95% of the pores in the coating.

[0009] Preferably, the curing process of the sealing adhesive is completed at a temperature not exceeding 60°C, and the overall curing time is controlled within three days, so as to improve production efficiency while ensuring the integrity of the sealing. Preferably, the thermal spray coating after the sealing treatment has a stable voltage resistance of over 500V, and the overall resistance value is improved from the megohm level before sealing to the gigaohm level.

[0010] The beneficial effects of this invention are as follows: 1. This invention utilizes the interconnected pore structure of thermal spray coatings and rationally controls the surface tension, viscosity, and curing conditions of the sealing adhesive. This allows the sealing adhesive to fully penetrate the coating under gravity before curing, continuously filling the pores and significantly improving the uniformity and integrity of the sealing process. 2. Through an innovative sealing method, the overall electrical and corrosion resistance of the thermal spray coating is significantly improved. The coating resistance is increased from the megohm level before sealing to the gigaohm level, and the voltage withstand performance is stable at over 500V. Moreover, the sealing structure is stable during long-term use and is not prone to peeling or performance degradation, making it suitable for industrial applications. Attached Figure Description

[0011] Figure 1 This is a flowchart of the sealing method of the present invention; Figure 2 This is a flowchart illustrating the process steps of the present invention. Detailed Implementation

[0012] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the 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.

[0013] like Figures 1 to 2 As shown, this embodiment of the invention provides a pore-sealing method based on the porosity of a thermally sprayed coating. First, a metal substrate is selected as the substrate to be treated, and a thermally sprayed coating is formed on its surface through a thermal spraying process. During the thermal spraying process, the sprayed powder is in a molten or semi-molten state under the action of a high-energy heat source and is deposited on the substrate surface by high-speed impact. Due to factors such as gas entrainment, irregular accumulation of molten particles, and rapid cooling during the spraying process, a porous structure is inevitably generated inside the formed coating. The pores include at least interconnected open pores, and in some areas, independent closed pores may also exist.

[0014] After the thermal spray coating is formed, a sealing adhesive is applied to the coating surface. The sealing adhesive is a resin-based sealing adhesive with a surface tension lower than the wetting critical value of the pore walls of the thermal spray coating and a low viscosity in the uncured state. This allows the sealing adhesive to naturally penetrate into the coating through the interconnected channels of the pores in the coating without the application of external pressure or vacuum assistance, relying solely on gravity.

[0015] During the sealing process, by controlling the surface tension, viscosity, and curing conditions of the sealing adhesive, the sealing adhesive can penetrate at least 500μm into the coating before curing and continuously fill the interior of the coating along the pores, thereby avoiding the problem of insufficient sealing of the interior pores caused by the sealing adhesive only staying on the surface of the coating.

[0016] After penetration, the coating is subjected to low-temperature curing treatment. The curing process is completed at a temperature not exceeding 60°C, and the overall curing time is controlled within three days, so that the sealing adhesive forms a stable sealing structure inside the coating pores.

[0017] After the above sealing treatment, the resistivity of the sealed layer formed by the cured sealing adhesive matches the dielectric properties of the thermal spray coating, thereby improving the overall insulation performance and voltage resistance stability of the coating. Even when the porosity of the thermal spray coating reaches 20%, the sealing adhesive can still effectively seal no less than 95% of the open pores in the coating.

[0018] The thermal spray coating treated with the sealing method in this embodiment has a stable voltage resistance of over 500V, and the overall resistance value is improved from the megohm level before sealing to the gigaohm level. Moreover, the sealing structure is stable, which can effectively improve the coating's corrosion resistance and long-term reliability.

[0019] Working principle: This invention is based on the formation mechanism of pore structure in thermal spray coatings and its influence on coating performance. By specifically utilizing the connectivity characteristics of open pores, it achieves effective sealing of pores inside the coating.

[0020] During thermal spraying, the sprayed material impacts the substrate surface at high speed in a molten or semi-molten state and cools rapidly. Due to insufficient particle spreading, gas entrapment, and irregular accumulation, a porous structure inevitably forms inside the coating. Among these, open pores are interconnected, forming through or semi-through pore channels. These pores not only provide migration paths for water vapor and corrosive media, but also tend to cause electric field concentration in electrical insulation applications, thereby reducing the coating's voltage withstand performance.

[0021] Based on the aforementioned structural characteristics of interconnected pores, a sealing adhesive with low surface tension and low viscosity is applied to the coating surface after the thermal spray coating is formed. Because the sealing adhesive has good wetting ability to the pore walls, it can naturally penetrate into the coating interior along the channels formed by the pores under gravity in its uncured state, without the need for additional pressure or vacuum assistance.

[0022] During the penetration process, by reasonably controlling the surface tension, viscosity and curing conditions of the sealing adhesive, the sealing adhesive can continuously migrate into the interior of the coating before curing and penetrate into the interior of the coating to a depth of at least 500μm, thereby continuously filling the pores and avoiding the problem of insufficient sealing of the internal pores caused by the sealing adhesive only staying on the surface of the coating.

[0023] After the penetration process is complete, the coating is cured at a temperature below 60°C. The sealing adhesive solidifies inside the pores, forming a stable sealing structure that effectively blocks the previously interconnected open pores. This sealing structure not only cuts off the migration path of corrosive media within the coating but also significantly improves the overall electrical resistance and voltage stability of the coating.

[0024] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0025] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A pore-sealing method based on the porosity of a thermally sprayed coating, comprising (1), characterized in that, Includes the following steps: (1) A coating is formed on the surface of a substrate by a thermal spraying process, wherein the coating contains pores formed by powder semi-melting, gas entrainment or high-speed impact accumulation during the spraying process, and the pores include at least interconnected open pores. (2) After the coating is formed, a sealing adhesive is applied to the surface of the coating. The sealing adhesive is naturally penetrated into the interior of the coating along the pore channels under the action of gravity by utilizing the interconnected structure of the open pores. (3) By controlling the surface tension, viscosity and curing conditions of the sealing adhesive, the sealing adhesive can penetrate into the coating at least 500μm before curing, so as to continuously fill the pores. (4) After the coating has been penetrated, it is cured at low temperature so that the sealing adhesive forms a stable sealing structure inside the pores, thereby improving the coating’s voltage resistance, electrical resistance and corrosion resistance.

2. The sealing method based on the porosity of thermal spray coating according to claim 1, characterized in that: The sealing adhesive is a resin-based sealing adhesive with a surface tension lower than the wetting critical value of the pore walls of the thermal spray coating. It also has a low viscosity in the uncured state, which allows it to fully penetrate the pores by gravity alone without the application of external pressure or vacuum assistance.

3. The sealing method based on the porosity of the thermal spray coating according to claim 2, characterized in that: The resistivity of the sealing layer formed after the sealing adhesive cures matches the electrical properties of the thermal spray coating, thereby improving the overall insulation performance and voltage resistance stability of the coating after sealing.

4. The sealing method based on the porosity of the thermal spray coating according to claim 3, characterized in that: The sealing adhesive mainly penetrates along the pores in the coating and fills to a depth of at least 500μm from the coating surface before curing. This is to avoid the sealing adhesive remaining only on the surface of the coating and causing insufficient sealing of the internal pores. Even when the porosity of the thermal spray coating reaches 20%, the sealing adhesive can still effectively seal at least 95% of the pores in the coating.

5. The sealing method based on the porosity of the thermal spray coating according to claim 4, characterized in that: The curing process of the sealing adhesive is completed at a temperature not exceeding 60°C, and the overall curing time is controlled within three days, so as to improve production efficiency while ensuring the integrity of the sealing.

6. The sealing method based on the porosity of thermal spray coating according to claim 5, characterized in that: After the sealing treatment, the thermal spray coating has a stable voltage resistance of over 500V, and the overall resistance value is improved from the megohm level before sealing to the gigaohm level.

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