Method for repairing aluminum-silicon alloy coating on metal surface

Abstract

The invention provides a method for repairing an aluminum-silicon alloy coating on a metal surface, and belongs to the field of coating repairing paints.The method comprises the following steps that S1, repairing coating slurry is prepared, specifically, raw materials of a coating with a silicon-based ceramic precursor and filler as main materials and an auxiliary solvent and an auxiliary curing agent as auxiliary materials are evenly mixed, and the repairing coating slurry is obtained; s2, surface pretreatment of a to-be-repaired part is conducted, specifically, the to-be-repaired position is polished, and an arc-shaped transition slope is formed on the edge of an original plating layer; s3, coating is conducted, specifically, the polishing area is evenly coated with the repairing coating slurry, the repairing coating slurry is additionally coated outwards till the edge of the plating layer expands outwards by 1-3 mm, and meanwhile the coating slurry is coated to be higher than the original plating layer plane; and S4, curing: keeping the coated repairing coating slurry at 20-300 DEG C for 0.3 min to 120 h, and curing the coating slurry to complete repairing. According to the invention, the paint and the coating are designed, so that the obtained patch coating can be subjected to subsequent hot working together with the original plating plate, and the substrate at the repaired position has the same excellent oxidation resistance as the original plating in the hot working process.

Description

Technical Field

[0001] The invention relates to the field of coating repair paint, in particular to a method for repairing an aluminum-silicon alloy coating on a metal surface. Background Art

[0002] Low alloy steel has excellent mechanical properties and economy, and is widely used in various industrial fields. However, due to the low content of alloy components, low carbon steel has poor antioxidant and corrosion resistance. Especially during hot working, the iron oxide scale produced on the surface of low carbon steel will seriously affect product quality and production efficiency. For low alloy steel, coating / plating on the surface of the substrate to avoid its oxidation behavior during hot working is one of the most economical and effective anti-oxidation methods. The coating / plating can also effectively improve the corrosion resistance of processed parts. At present, the aluminum silicon coated plate is the most widely used in industrial production.

[0003] Aluminum-silicon coating is a commonly used coating on steel substrates, which is composed of aluminum, silicon and a small amount of iron, which usually contains metal compounds such as aluminum-iron, aluminum-silicon-iron, etc. Aluminum-silicon coating can prevent surface oxidation and decarburization of steel plates and improve the corrosion resistance of steel plates. However, under some specific processes, aluminum-silicon coating will affect the subsequent processing of the substrate, such as welding. Taking the production process of automobile bodies as an example, when producing automobile door knockers, several coated plates need to be spliced ​​and welded first, and then transferred to hot stamping equipment for hot forming. During welding, the coating at the reserved weld position needs to be removed first to prevent the coating from mixing into the weld molten pool during the welding process, thereby affecting the mechanical properties of the weld. At the same time, the parts after hot forming also need to be spliced ​​by welding to form an integral body. At this time, if part of the protective coating is removed, the corrosion resistance of the substrate at the removal position will be seriously reduced, resulting in product quality defects. Therefore, for workpieces that need to be protected by aluminum-silicon coating, it is very necessary to repair the aluminum-silicon coating in time after it is lost, which is not only conducive to improving product quality, but also to improving the service life of the workpiece.

[0004] Prior art CN116903396A discloses a repair method for high temperature resistant coatings, but this type of coating repair method is mainly for carbon / carbon composite materials; prior art CN113025197A discloses a zinc-aluminum coating repair coating and method, but this repair material and repair method cannot be applied to coating / plating repair of coated / plated workpieces that require thermal processing.

[0005] Therefore, in response to the current technical problems in this field, it is necessary to develop a repair material and repair method that can repair coatings / platings and adapt to thermal processing environments, especially for aluminum silicon coatings. Summary of the invention

[0006] The present invention is made in view of the deficiencies in the prior art, and aims to provide a method for repairing an aluminum-silicon alloy coating on a metal surface.

[0007] In order to achieve the above object, the technical solution of the present invention is as follows:

[0008] The present invention provides a method for repairing an aluminum-silicon alloy coating on a metal surface, comprising the following steps:

[0009] S1. Preparation of repair coating slurry: The raw materials of the coating with a silicon-based ceramic precursor and a filler as the main material and an auxiliary solvent and an auxiliary curing agent as auxiliary materials are mixed evenly without lumps to obtain a repair coating slurry;

[0010] S2. Surface pretreatment of the repaired part: Grind the repaired part to expose the smooth substrate surface, and form an arc-shaped transition slope at the edge of the original coating during grinding; after grinding, use a brush, anhydrous ethanol and acetone to clean the polished surface and the coating surface 3~5mm outside the coating edge;

[0011] Preferably, the roughness of the exposed substrate surface is Ra≤0.3 μm;

[0012] Preferably, the slope angle of the arc-shaped transition slope is ≤60°;

[0013] S3. Coating: Apply the repair coating slurry evenly on the polished area and apply it outward to the edge of the coating 1~3mm to ensure that the coating slurry completely covers the repair position and the coating slurry is higher than the original coating plane;

[0014] Preferably, the distance above which the coating slurry is applied is 0.5 to 2 times the thickness of the coating;

[0015] S4. Curing: In a dry environment, keep the applied repair coating slurry at 20~300℃ for 0.3min~120h, the coating slurry is cured to form a patch coating, and the metal surface coating is repaired.

[0016] Furthermore, in the step S1, the repair coating slurry can be divided into two parts: the main material and the auxiliary material; the main material is the key component of the coating slurry, which is composed of a silicon-based ceramic precursor and a filler. The mass ratio of the ceramic precursor to the filler is 1:1~10:1; the auxiliary material is an auxiliary component of the coating slurry, which is composed of an auxiliary solvent and an auxiliary curing agent, and the auxiliary material can be selectively added or not; based on the mass fraction of the coating slurry as 100%, the main material accounts for 40~100% of the coating slurry, the auxiliary solvent in the auxiliary material accounts for 0~60% of the coating slurry, and the auxiliary curing agent in the auxiliary material accounts for 0~20% of the coating slurry, and the sum of the mass percentages of the above components is 100%; preferably, in the coating slurry, the main material accounts for 40~95% of the coating slurry, the auxiliary solvent in the auxiliary material accounts for 5~60% of the coating slurry, and the auxiliary curing agent in the auxiliary material accounts for 0~20% of the coating slurry, and the sum of the mass percentages of the above components is 100%.

[0017] In the repair coating slurry, the silicon-based ceramic precursor refers to an organic polymer material containing silicon in the main chain and / or side chain, which can be partially or completely converted into an inorganic ceramic phase after high-temperature pyrolysis, and is selected from at least one of polysilazane, polysiloxane, polycarbosilane, and polysilane, or an organic polymer modified with functional groups on the basis of the above organic polymers;

[0018] Preferably, in the silicon-based ceramic precursor, the mass fraction of polysilazane is ≥90%. Since polysilazane usually has excellent antioxidant and corrosion resistance below 1200°C, in order for the coating to obtain excellent protective effects, the content of polysilazane in the silicon-based ceramic precursor must meet the above conditions. However, after sintering at above 300°C, polysiloxane, polycarbosilane, polysilane, etc., usually cannot protect the substrate from oxidation and corrosion, but their products can fill the gaps caused by sintering of polysilazane in the coating and improve the coating performance. Therefore, it is preferred to increase the content of polysilazane in the silicon-based ceramic precursor, and add a small amount of other types of silicon-based ceramic precursors.

[0019] In the repair coating slurry, the filler is aluminum powder; the aluminum powder is pure aluminum or aluminum alloy powder, and the aluminum alloy is preferably an alloy type with an aluminum mass fraction of ≥90%; the microscopic shape of the aluminum powder is preferably lamellar, and the size of the aluminum powder is preferably an equivalent diameter of ≤70μm. Since the coating slurry of the present invention is specifically used to repair aluminum silicon coatings, in order to avoid other metal elements from affecting the consistency of the mechanical properties of the weld and the substrate, the aluminum powder used as the filler of the present invention is further preferably aluminum metal powder with an aluminum mass fraction of ≥95%.

[0020] When the filler is added to the repair coating slurry, the filler can be in the form of powder or filler slurry formed by mixing the filler with an auxiliary solvent. After the filler and the auxiliary solvent are mixed into a slurry, the filler is wrapped by the auxiliary solvent; the auxiliary solvent can form a protective film on the surface of the filler, effectively avoiding the denaturation of the filler powder, and greatly improving the bonding between the filler powders and the wettability with different solutions; preferably, when the filler is added to the coating slurry, the filler is in the form of a slurry. Furthermore, the amount of the auxiliary solvent used in the slurry should be included in the total amount of the auxiliary solvent in the raw material.

[0021] In the repair coating slurry, the auxiliary solvent component is selected from: one or more of hydrocarbons (such as isoalkanes, xylene, petroleum spirits), ethers (such as aromatic ethers, methyl ethers), alcohols (such as ethanol, methanol), esters (such as butyl acetate, ethyl acetate, methyl acetate), and silane coupling agents; when mixing the coating slurry, the auxiliary solvent plays a role in adjusting the viscosity of the solution and improving the wettability of the coating, so that the coating slurry can be more easily adhered to various substrate surfaces and is suitable for a variety of different working conditions.

[0022] In the repair coating slurry, the auxiliary curing agent is selected from one or more of diazabicyclo, aluminum triacetylacetonate, and phosphazene; in the repair coating slurry, the auxiliary curing agent mainly plays the role of adjusting the curing time of the coating slurry, improving the interface bonding between the metal and the coating, and enhancing the adhesion of the coating on the substrate. When the mass content of the auxiliary curing agent is greater than 20%, increasing the content of the auxiliary curing agent has no effect on shortening the curing time of the coating slurry. Therefore, according to the time and adhesion requirements of the curing process, the mass content of the auxiliary curing agent in the slurry ranges from 0 to 20%.

[0023] Furthermore, in the step S2, the position to be repaired is polished in sequence using sandpapers with mesh sizes from low to high to obtain a smooth and flat repair surface. In order to obtain a suitable roughness, the sandpaper with a mesh size of 400#~2000# is finally used to ensure that the roughness of the exposed substrate surface is ≤3μm.

[0024] Furthermore, in the step S3, the coating method is one of roller coating, brush coating, and spray coating, and the specific method is as follows:

[0025] a) Roller coating: Use the coating roller as a carrier to coat the coating slurry on the surface of the metal substrate, and control the thickness of the coating by using the coating roller reasonably to ensure that the coating meets the above process requirements;

[0026] b) Brush coating: Use a brush as a carrier to apply the coating slurry on the surface of the metal substrate, and control the thickness of the coating by using the brush reasonably to ensure that the coating meets the above process requirements;

[0027] c) Spraying: The coating slurry is atomized and then sprayed on the surface of the substrate. Before the coating slurry on at least one surface of the substrate is deposited and layered, the thickness of the coating is controlled by adjusting the process parameters such as the nozzle spraying amount and the moving speed of the workpiece during spraying.

[0028] Furthermore, in the S4 step, the solid patch coating is composed of a preceramic phase and a filler phase formed by a silicon-based ceramic precursor, the preceramic phase is connected into a three-dimensional network structure in the coating, and the filler phase is distributed in the gaps of the preceramic phase, and the coating presents a three-dimensional network-gap structure; wherein the volume fraction of the preceramic phase is ≤80%, and the volume fraction of the filler phase is ≥20%.

[0029] Furthermore, the curing time of S4 should be determined in combination with the coating slurry ratio, curing temperature, and coating thickness factors: when there is no auxiliary curing agent, the coating takes 4 to 120 hours to cure at a temperature range of 20 to 150°C, and takes 30 to 240 minutes to cure at a temperature range of 150 to 300°C; when an auxiliary curing agent is added, the curing time is shortened to 1 to 24 hours when the coating is cured at a temperature range of 20 to 150°C, and takes 0.3 to 50 minutes to cure at a temperature range of 150 to 300°C.

[0030] Furthermore, the patch coating is a three-dimensional network-gap structure, the three-dimensional network structure is a pre-ceramic phase, and fillers exist in its gaps; the patch coating is tightly combined with the original coating without gaps.

[0031] Compared with the prior art, the present invention has the following advantages:

[0032] 1. The patch coating prepared on the surface to be repaired in the present invention can be subjected to subsequent heat processing along with the workpiece to protect the substrate from oxidation.

[0033] 2. The preparation method and use method of the repair coating slurry of the present invention are simple, the composition can be flexibly adjusted, it is conducive to industrial application, and it is suitable for different working conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0035] Figure 1 The figure is a schematic diagram of the metal surface aluminum-silicon alloy coating repair method of the present invention, which explains in detail the position requirements when pre-treating the surface of the repaired part and coating the coating slurry;

[0036] Figure 2 It is a schematic diagram of the structure of the patch coating of the present invention;

[0037] Figure 3 This is a flow chart of a method for repairing an aluminum-silicon alloy coating on a metal surface according to the present invention, wherein S1 to S4 are steps for preparing a coating patch;

[0038] Figure 4 The surface macroscopic morphology of the sample before and after repair in Example 1, wherein (a) is the morphology before repair, and (b) is the morphology after repair;

[0039] Figure 5 This is an enlarged view of the cross-sectional morphology of the entire coating / plating layer after repair in Example 1;

[0040] Figure 6 The cross-sectional morphology of the coating at the repaired position in Example 1;

[0041] Figure 7 This is the surface macroscopic morphology of the sample in Example 1 after oxidation at 920°C;

[0042] Figure 8 This is the cross-sectional morphology of the sample in Example 1 after oxidation at 920°C. DETAILED DESCRIPTION

[0043] In order to make the technical problems, technical solutions and advantages to be solved by the present invention more clear, a detailed description will be given below with reference to the accompanying drawings and specific embodiments.

[0044] The plates used in all the examples and comparative examples are aluminum-silicon coated plates with a base of 22MnB5, wherein the thickness of the coated plate is 2 mm, the thickness of the aluminum-silicon coating is 23 μm, and the composition of the aluminum-silicon coating is 87% Al-10% Si-3% Fe.

[0045] Example 1

[0046] In this embodiment, the present invention relates to a repair process method for an aluminum-silicon alloy coating on a metal surface, which includes the following steps: S1 preparation of a repair coating slurry, S2 surface pretreatment of the part to be repaired, S3 coating, and S4 curing. Each step will be described in detail below.

[0047] S1. Preparation of repair coating slurry: The coating slurry of this embodiment is prepared in a dry room temperature environment. In the coating slurry, the mass ratio of each component is: 80% of the main material, 20% of the auxiliary solvent, 0% of the auxiliary curing agent, and the sum of the mass fractions of the above components is 100%. In the main material, the mass ratio of the silicon-based ceramic precursor to the filler is 4:1. In the silicon-based ceramic precursor, the mass fraction of polysilazane is 100%.

[0048] Before adding fillers, in order to make the fillers have better wettability in the coating slurry, a proper amount of auxiliary solvent is used to mix the fillers to form a slurry, and then the filler slurry is mixed with other components of the coating slurry. The composition and content of the auxiliary solvent used in the coating slurry are: 50% dimethyl methanol, 30% light aromatic hydrocarbons, and 20% silane coupling agent. The sum of the mass fractions of the above components is 100%.

[0049] The above ingredients are weighed according to the above mass percentages and added into the container. The above ingredients are mixed by mechanical stirring for 3 minutes. At this time, the state of the mixed solution is a suspension of solid-liquid phases, and each ingredient is evenly dispersed in the solution without any agglomeration, agglomeration, sedimentation or other uneven mixing phenomenon.

[0050] S2. Surface pretreatment of the part to be repaired: Use 200#, 400#, 800#, and 1200# sandpaper to grind the part to be repaired in turn to obtain a repair surface with a roughness of Ra≤0.3μm, and use tools and reagents such as a brush, anhydrous ethanol, acetone, etc. to clean the repair surface, remove oxides, oil stains, etc. on the surface of the part to be coated, and clean up residual debris and other impurities to avoid affecting the use effect of the repair coating.

[0051] S3. Coating: Use a coating roller to apply the coating to the area to be repaired, with the coating height being about 32μm higher than the original coating plane.

[0052] S4. Curing: Place the sample in a dry environment at 250°C for 1 hour. At the end of this time, the coating is completely cured.

[0053] At this point, the aluminum silicon coating in this embodiment has been repaired.

[0054] Figure 1 The schematic diagram of the metal surface aluminum-silicon alloy coating repair method of the present invention explains in detail the surface pretreatment of the repaired part and the position requirements when coating the coating slurry. It can be seen that the repaired position is polished before coating, and an arc-shaped transition slope is formed at the edge of the original coating, and the slope angle of the arc-shaped transition slope is ≤60°; the repair coating slurry is evenly coated on the polished area and coated outward to 1~3mm outside the edge of the coating, and the coated coating slurry is 0.5~2 times higher than the thickness of the original coating.

[0055] Figure 2 The schematic diagram of the structure of the patch coating of the present invention shows that the patch coating presents a three-dimensional network-gap structure, wherein the pre-ceramic phase is connected into a three-dimensional network structure in the coating, and its volume fraction is in the range of 20-80%, and the filler phase is distributed in the gap of the pre-ceramic phase, and its volume fraction is in the range of 20-80%.

[0056] Figure 3This is a flow chart of a method for repairing an aluminum-silicon alloy coating on a metal surface according to the present invention, wherein S1 to S4 are steps for preparing a coating patch;

[0057] Figure 4 The surface macroscopic morphology of the sample before and after repair in Example 1, where (a) is the morphology before repair and (b) is the morphology after repair. It can be seen from the figure that after the coating repairs the exposed position of the substrate on the aluminum-silicon plate, the patch coating completely covers the exposed substrate, and has a good repair effect.

[0058] Figure 5 This is an enlarged cross-sectional view of the overall coating / plating layer after repair in Example 1. As shown in the figure, the patch coating has a good bonding interface with the substrate and the original plating layer, and forms a uniform protective layer on the substrate.

[0059] Figure 6 The cross-sectional morphology of the coating at the repair position in Example 1. As shown in the figure, the patch coating is well bonded to the substrate, and the patch coating presents a three-dimensional network-gap structure. In the patch coating, the white or silvery white strips are flaky aluminum powder fillers, and the dark area is a pre-ceramic phase. The pre-ceramic phase is connected into a three-dimensional network structure in the coating, and its volume fraction is in the range of 20-80%. The filler phase is distributed in the gaps of the pre-ceramic phase, and its volume fraction is in the range of 20-80%.

[0060] Figure 7 This is the surface macroscopic morphology of the sample of Example 1 after oxidation at 920°C. As can be seen from the figure, the patch coating reacts with the aluminum silicon coating in an environment of 920°C, and the color changes from the original silver white to gray black. After the reaction, the patch coating is still firmly attached to the surface of the substrate to protect the substrate.

[0061] Figure 8 This is the cross-sectional morphology of the sample of Example 1 after oxidation at 920° C. As shown in the figure, the oxidized patch coating has a good bonding interface with the substrate and the original coating, and forms a uniform protective layer on the substrate.

[0062] Example 2

[0063] In this embodiment, the present invention relates to a repair process method for an aluminum-silicon alloy coating on a metal surface, which includes the following steps: S1 preparation of a repair coating slurry, S2 surface pretreatment of the part to be repaired, S3 coating, and S4 curing. Each step will be described in detail below.

[0064] S1. Preparation of repair coating slurry: The coating slurry of this embodiment is prepared in a dry room temperature environment. In the coating slurry, the mass ratio of each component is: 95% of the main material, 5% of the auxiliary solvent, and 0% of the auxiliary curing agent, and the sum of the mass fractions of the above components is 100%. In the main material, the mass ratio of the silicon-based ceramic precursor to the filler is 8:1. In the silicon-based ceramic precursor, the mass fraction of polysilazane is ≥90%, and the rest uses polysiloxane, and the sum of the mass fractions of the above components is 100%.

[0065] Before adding fillers, in order to make the fillers have better wettability in the coating slurry, a proper amount of auxiliary solvent is used to mix the fillers to form a slurry, and then the filler slurry is mixed with other components of the coating slurry. The composition and content of the auxiliary solvent used in the coating slurry are: 10% light aromatics, 70% petroleum spirit, 10% ethanol, 10% silane coupling agent, and the sum of the mass fractions of the above components is 100%.

[0066] The above ingredients are weighed according to the above mass percentages and added into the container. The above ingredients are mixed by mechanical stirring for 3 minutes. At this time, the state of the mixed solution is a suspension of solid-liquid phases, and each ingredient is evenly dispersed in the solution without any agglomeration, agglomeration, sedimentation or other uneven mixing phenomenon.

[0067] S2. Surface pretreatment of the part to be repaired: Use 200#, 400#, 800#, and 1200# sandpaper to grind the part to be repaired in turn to obtain a repair surface with a roughness of Ra≤0.3μm, and use tools and reagents such as a brush, anhydrous ethanol, acetone, etc. to clean the repair surface, remove oxides, oil stains, etc. on the surface of the part to be coated, and clean up residual debris and other impurities to avoid affecting the use effect of the repair coating.

[0068] S3. Coating: Apply the paint to the area to be repaired, with the paint height being about 20μm higher than the original coating plane.

[0069] S4. Curing: Place the sample in a dry environment at 200°C for 1.5 hours. At the end of this time, the coating is completely cured.

[0070] At this point, the aluminum silicon coating in this embodiment has been repaired.

[0071] Example 3

[0072] In this embodiment, the present invention relates to a repair process method for an aluminum-silicon alloy coating on a metal surface, which includes the following steps: S1 preparation of a repair coating slurry, S2 surface pretreatment of the part to be repaired, S3 coating, and S4 curing. Each step will be described in detail below.

[0073] S1. Preparation of repair coating slurry: The coating slurry of this embodiment is prepared in a dry room temperature environment. In the coating slurry, the mass ratio of each component is: 40% of the main material, 60% of the auxiliary solvent, and 0% of the auxiliary curing agent, and the sum of the mass fractions of the above components is 100%. In the main material, the mass ratio of the silicon-based ceramic precursor to the filler is 7:1. In the silicon-based ceramic precursor, the mass fraction of polysilazane is ≥90%, and the rest uses polysiloxane, and the sum of the mass fractions of the above components is 100%.

[0074] Before adding fillers, in order to make the fillers have better wettability in the coating slurry, a proper amount of auxiliary solvent is used to mix the fillers to form a slurry, and then the filler slurry is mixed with other components of the coating slurry. The composition and content of the auxiliary solvent used in the coating slurry are: 60% butyl acetate, 25% ethanol, 15% silane coupling agent, and the sum of the mass fractions of the above components is 100%.

[0075] The above ingredients are weighed according to the above mass percentages and added into the container. The above ingredients are mixed by mechanical stirring for 3 minutes. At this time, the state of the mixed solution is a suspension of solid-liquid phases, and each ingredient is evenly dispersed in the solution without any agglomeration, agglomeration, sedimentation or other uneven mixing phenomenon.

[0076] S2. Surface pretreatment of the part to be repaired: Use 200#, 400#, 800#, and 1200# sandpaper to grind the part to be repaired in turn to obtain a repair surface with a roughness of Ra≤0.3μm, and use tools and reagents such as a brush, anhydrous ethanol, acetone, etc. to clean the repair surface, remove oxides, oil stains, etc. on the surface of the part to be coated, and clean up residual debris and other impurities to avoid affecting the use effect of the repair coating.

[0077] S3. Coating: Spray the paint on the area to be repaired, with the paint height being about 40μm higher than the original coating plane.

[0078] S4. Curing: Place the sample in a dry environment at 280°C for 0.7h. At the end of this time, the coating is completely cured.

[0079] At this point, the aluminum silicon coating in this embodiment has been repaired.

[0080] Example 4

[0081] In this embodiment, the present invention relates to a repair process method for an aluminum-silicon alloy coating on a metal surface, which includes the following steps: S1 preparation of a repair coating slurry, S2 surface pretreatment of the part to be repaired, S3 coating, and S4 curing. Each step will be described in detail below.

[0082] S1. Preparation of repair coating slurry: The coating slurry of this embodiment is prepared in a dry room temperature environment. In the coating slurry, the mass ratio of each component is: 80% of the main material, 20% of the auxiliary solvent, 0% of the auxiliary curing agent, and the sum of the mass fractions of the above components is 100%. In the main material, the mass ratio of the silicon-based ceramic precursor to the filler is 1:1. In the silicon-based ceramic precursor, the mass fraction of polysilazane is ≥90%, and the rest uses polysiloxane, and the sum of the mass fractions of the above components is 100%.

[0083] Before adding fillers, in order to make the fillers have better wettability in the coating slurry, a proper amount of auxiliary solvent is used to mix the fillers to form a slurry, and then the filler slurry is mixed with other components of the coating slurry. The composition and content of the auxiliary solvent used in the coating slurry are: 85% petroleum spirit, 10% ethanol, 5% dimethyl carbinol, and the sum of the mass fractions of the above components is 100%.

[0084] The above ingredients are weighed according to the above mass percentages and added into the container. The above ingredients are mixed by mechanical stirring for 3 minutes. At this time, the state of the mixed solution is a suspension of solid-liquid phases, and each ingredient is evenly dispersed in the solution without any agglomeration, agglomeration, sedimentation or other uneven mixing phenomenon.

[0085] S2. Surface pretreatment of the part to be repaired: Use 200#, 400#, 800#, and 1200# sandpaper to grind the part to be repaired in turn to obtain a repair surface with a roughness of Ra≤0.3μm, and use tools and reagents such as a brush, anhydrous ethanol, acetone, etc. to clean the repair surface, remove oxides, oil stains, etc. on the surface of the part to be coated, and clean up residual debris and other impurities to avoid affecting the use effect of the repair coating.

[0086] S3. Coating: Apply the paint to the area to be repaired with a brush, with the paint height being about 25μm higher than the original coating plane.

[0087] S4. Curing: Place the sample in a dry environment at 180°C for 2.5 hours. At the end of this time, the coating is completely cured.

[0088] At this point, the aluminum silicon coating in this embodiment has been repaired.

[0089] Example 5

[0090] In this embodiment, the present invention relates to a repair process method for an aluminum-silicon alloy coating on a metal surface, which includes the following steps: S1 preparation of a repair coating slurry, S2 surface pretreatment of the part to be repaired, S3 coating, and S4 curing. Each step will be described in detail below.

[0091] S1. Preparation of repair coating slurry: The coating slurry of this embodiment is prepared in a dry room temperature environment. In the coating slurry, the mass ratio of each component is: main material is 70%, auxiliary solvent is 15%, auxiliary curing agent is 15%, and the sum of the mass fractions of the above components is 100%. In the main material, the mass ratio of silicon-based ceramic precursor to filler is 6:1. In the silicon-based ceramic precursor, the mass fraction of polysilazane is ≥90%, and the rest uses polysiloxane, and the sum of the mass fractions of the above components is 100%.

[0092] Before adding fillers, in order to make the fillers have better wettability in the coating slurry, a proper amount of auxiliary solvent is used to mix the fillers to form a slurry, and then the filler slurry is mixed with other components of the coating slurry. The composition and content of the auxiliary solvent used in the coating slurry are: 20% dimethyl methanol, 70% light aromatic hydrocarbons, 10% silane coupling agent, and the sum of the mass fractions of the above components is 100%. The auxiliary curing agent is diazabicyclic.

[0093] The above ingredients are weighed according to the above mass percentages and added into the container. The above ingredients are mixed by mechanical stirring for 3 minutes. At this time, the state of the mixed solution is a suspension of solid-liquid phases, and each ingredient is evenly dispersed in the solution without any agglomeration, agglomeration, sedimentation or other uneven mixing phenomenon.

[0094] S2. Surface pretreatment of the part to be repaired: Use 200#, 400#, 800#, and 1200# sandpaper to grind the part to be repaired in turn to obtain a repair surface with a roughness of Ra≤0.3μm, and use tools and reagents such as a brush, anhydrous ethanol, acetone, etc. to clean the repair surface, remove oxides, oil stains, etc. on the surface of the part to be coated, and clean up residual debris and other impurities to avoid affecting the use effect of the repair coating.

[0095] S3. Coating: Apply the paint to the area to be repaired with a height of about 32 μm higher than the original coating plane.

[0096] S4. Curing: Place the sample in a dry environment at 120°C for 5 hours. At the end of the time, the coating is completely cured.

[0097] At this point, the aluminum silicon coating in this embodiment has been repaired.

[0098] In order to more fully demonstrate the repair coating and repair process method of the aluminum silicon coating involved in the present invention, comparative examples 1 to 4 are set.

[0099] Comparative Example 1

[0100] In this comparative example, the present invention relates to a repair process method for aluminum-silicon alloy coating on a metal surface, which comprises the following steps: S1 preparation of repair coating slurry, S2 surface pretreatment of the part to be repaired, S3 coating, and S4 curing. Each step will be described in detail below.

[0101] S1. Preparation of repair coating slurry: The coating slurry of this embodiment is prepared in a dry room temperature environment. In the coating slurry, the mass ratio of each component is: the main material is 100%, the auxiliary solvent is 0%, the auxiliary curing agent is 0, and the sum of the mass fractions of the above components is 100%. In the main material, the mass ratio of the silicon-based ceramic precursor to the filler is 100:1. In the silicon-based ceramic precursor, the mass fraction of polysilazane is 100%.

[0102] Before adding fillers, in order to make the fillers have better wettability in the coating slurry, a proper amount of auxiliary solvent is used to mix the fillers to form a slurry, and then the filler slurry is mixed with other components of the coating slurry. The composition and content of the auxiliary solvent used in the coating slurry are: 40% dimethyl methanol, 50% light aromatic hydrocarbons, and 10% silane coupling agent, and the sum of the mass fractions of the above components is 100%.

[0103] The above ingredients are weighed according to the above mass percentages and added into the container. The above ingredients are mixed by mechanical stirring for 3 minutes. At this time, the state of the mixed solution is a suspension of solid-liquid phases, and each ingredient is evenly dispersed in the solution without any agglomeration, agglomeration, sedimentation or other uneven mixing phenomenon.

[0104] S2. Surface pretreatment of the part to be repaired: Use 200#, 400#, 800#, and 1200# sandpaper to grind the part to be repaired in turn to obtain a repair surface with a roughness of Ra≤0.3μm, and use tools and reagents such as a brush, anhydrous ethanol, acetone, etc. to clean the repair surface, remove oxides, oil stains, etc. on the surface of the part to be coated, and clean up residual debris and other impurities to avoid affecting the use effect of the repair coating.

[0105] S3. Coating: Apply the paint to the area to be repaired with a brush, with the paint height being about 25μm higher than the original coating plane.

[0106] S4. Curing: Place the sample in a dry environment at 250°C for 1 hour. At the end of this time, the coating is completely cured.

[0107] At this point, the aluminum silicon coating in this embodiment has been repaired.

[0108] Comparative Example 2

[0109] In this comparative example, the present invention relates to a repair process method for aluminum-silicon alloy coating on a metal surface, which comprises the following steps: S1 preparation of repair coating slurry, S2 surface pretreatment of the part to be repaired, S3 coating, and S4 curing. Each step will be described in detail below.

[0110] S1. Preparation of repair coating slurry: The coating slurry of this embodiment is prepared in a dry room temperature environment. In the coating slurry, the mass ratio of each component is: 95% of the main material, 5% of the auxiliary solvent, and 0% of the auxiliary curing agent, and the sum of the mass fractions of the above components is 100%. In the main material, the mass ratio of the silicon-based ceramic precursor to the filler is 13:1. In the silicon-based ceramic precursor, the mass fraction of polysilazane is 100%.

[0111] Before adding fillers, in order to make the fillers have better wettability in the coating slurry, a proper amount of auxiliary solvent is used to mix the fillers to form a slurry, and then the filler slurry is mixed with other components of the coating slurry. The composition and content of the auxiliary solvent used in the coating slurry are: 90% butyl acetate, 10% silane coupling agent, and the sum of the mass fractions of the above components is 100%.

[0112] The above ingredients are weighed according to the above mass percentages and added into the container. The above ingredients are mixed by mechanical stirring for 3 minutes. At this time, the state of the mixed solution is a suspension of solid-liquid phases, and each ingredient is evenly dispersed in the solution without any agglomeration, agglomeration, sedimentation or other uneven mixing phenomenon.

[0113] S2. Surface pretreatment of the part to be repaired: Use 200#, 400#, 800#, and 1200# sandpaper to grind the part to be repaired in turn to obtain a repair surface with a roughness of Ra≤0.3μm, and use tools and reagents such as a brush, anhydrous ethanol, acetone, etc. to clean the repair surface to remove oxides, oil stains, etc. on the surface of the part to be repaired, and clean up residual debris and other impurities to avoid affecting the use effect of the repair coating.

[0114] S3. Coating: Apply the paint to the area to be repaired with a brush, with the paint height being about 25μm higher than the original coating plane.

[0115] S4. Curing: Place the sample in a dry environment at 250°C for 1 hour. At the end of this time, the coating is completely cured.

[0116] At this point, the aluminum silicon coating in this embodiment has been repaired.

[0117] Comparative Example 3

[0118] In this comparative example, the present invention relates to a repair process method for aluminum-silicon alloy coating on a metal surface, which comprises the following steps: S1 preparation of repair coating slurry, S2 surface pretreatment of the part to be repaired, S3 coating, and S4 curing. Each step will be described in detail below.

[0119] S1. Preparation of repair coating slurry: The coating slurry of this embodiment is prepared in a dry room temperature environment. In the coating slurry, the mass ratio of each component is: main material is 75%, auxiliary solvent is 15%, auxiliary curing agent is 10%, and the sum of the mass fractions of the above components is 100%. In the main material, the mass ratio of silicon-based ceramic precursor to filler is 1:2. In the silicon-based ceramic precursor, the mass fraction of polysilazane is ≥90%, and the rest uses polysilane and polycarbosilane, and the sum of the mass fractions of the above components is 100%.

[0120] Before adding fillers, in order to make the fillers have better wettability in the coating slurry, a proper amount of auxiliary solvent is used to mix the fillers to form a slurry, and then the filler slurry is mixed with other components of the coating slurry. The composition and content of the auxiliary solvent used in the coating slurry are: 90% butyl acetate, 10% silane coupling agent, and the sum of the mass fractions of the above components is 100%. The auxiliary curing agent is diazabicyclic.

[0121] The above ingredients are weighed according to the above mass percentages and added into the container. The above ingredients are mixed by mechanical stirring for 3 minutes. At this time, the state of the mixed solution is a suspension of solid-liquid phases, and each ingredient is evenly dispersed in the solution without any agglomeration, agglomeration, sedimentation or other uneven mixing phenomenon.

[0122] S2. Surface pretreatment of the part to be repaired: Use 200#, 400#, 800#, and 1200# sandpaper to grind the part to be repaired in turn to obtain a repair surface with a roughness of Ra≤0.3μm, and use tools and reagents such as a brush, anhydrous ethanol, acetone, etc. to clean the repair surface to remove oxides, oil stains, etc. on the surface of the part to be repaired, and clean up residual debris and other impurities to avoid affecting the use effect of the repair coating.

[0123] S3. Coating: Apply the paint to the area to be repaired with a brush, with the paint height being about 25μm higher than the original coating plane.

[0124] S4. Curing: Place the sample in a dry environment at 250°C for 1 hour. At the end of this time, the coating is completely cured.

[0125] At this point, the aluminum silicon coating in this embodiment has been repaired.

[0126] Comparative Example 4

[0127] Comparative Example 4 is an aluminum-silicon coated plate that has not undergone any treatment.

[0128] Table 1 lists the parameters of Examples 1 to 5 and Comparative Examples 1 to 4 to facilitate comparison of the differences between the parameters of different Examples and Comparative Examples.

[0129] Table 1

[0130]

[0131] Appearance evaluation and adhesion evaluation were performed on Examples 1 to 5 and Comparative Examples 1 to 3, and thickness measurement and phase ratio statistics were performed on Examples 1 to 5 and some comparative examples.

[0132] The coating samples were prepared for metallographic observation, and the coating cross section was photographed and observed using a scanning electron microscope; Image-Pro Plus 6.0 software was used to calculate the proportion of the filler phase in the coating cross section.

[0133] The coating appearance is evaluated by visual inspection. In a clean environment with sufficient light, the surface quality of the coating is observed with the naked eye, especially whether the coating is flat, whether the thickness is uniform, whether the coating is damaged or cracked, and whether there are defects such as pits and peeling.

[0134] For the embodiments and comparative examples without obvious defects in appearance, the coating adhesion was evaluated. The grid method in standard GB / T9286-2021 was used as the evaluation method to visually inspect the coating shedding. The adhesion of 0 to 5 levels decreased in this order, with 0 being the best and 5 being the worst.

[0135] Table 2 lists the coating structure characteristics, coating thickness, proportion of filler phase, coating appearance evaluation results and coating adhesion evaluation results of each embodiment and comparative example.

[0136] Table 2

[0137]

[0138] In industry, after the aluminum-silicon plate is welded, it is generally kept in a heating furnace at 900~930℃ for 5~8min, and then transferred to the hot stamping die for hot stamping process. In order to verify the oxidation resistance of the repair coating and its compatibility with the original coating in the hot forming thermal history, the sample after coating repair was placed in an air atmosphere at 920℃ for 6min, and then cooled to room temperature, and then the sample was characterized and analyzed.

[0139] The Fe oxide content on the surface of the sample was tested by X-ray diffractometer (XRD), and the Fe oxide content obtained by XRD analysis was used as the standard to evaluate the oxidation degree of the coating. Among them, Fe oxide content ≥ 50% is severe oxidation; 50%>Fe oxide content ≥ 20% is relatively severe oxidation; 20%>Fe oxide content ≥ 5% is slight oxidation; 5%>Fe oxide content is no oxidation.

[0140] Coating evaluations were performed on example coatings where no oxidation was determined.

[0141] The appearance of the coating is determined by visual inspection. In a clean environment with sufficient light, the surface quality of the coating is observed with the naked eye, especially whether the coating is flat, whether the thickness is uniform, whether the coating is damaged or cracked, and whether there are defects such as pits and peeling.

[0142] After high temperature heat experience, the adhesion of the oxidized coating is evaluated according to the standard GB / T9286-2021. The coating shedding is visually inspected by the grid method. The adhesion decreases from level 0 to level 5, with level 0 being the best and level 5 being the worst.

[0143] After high temperature thermal history, the XRD test results, coating appearance rating and adhesion rating results of the coating are shown in Table 3.

[0144] Table 3

[0145]

[0146] The above-mentioned Examples 1 to 5 and Comparative Examples 1 to 4 illustrate that good repairing effect can be obtained after repairing the aluminum-silicon alloy coating on the metal surface according to the repairing method of the present invention. The repaired patch coating can be heat-treated together with the original coating on the coating plate, and the substrate at the repair position is protected during the entire heat treatment process. When the repair coating slurry is not prepared according to the ratio described in the repairing method, the patch coating cannot achieve a good repairing effect.

[0147] In Comparative Example 1, since no filler was added, the pre-ceramic phase shrank after being kept in an air atmosphere at 920°C, resulting in cracks at the patch coating and exposing part of the substrate, and the anti-oxidation effect was poor. In Comparative Example 2, since the filler addition ratio was too small, the filler could not fully coordinate the deformation of the patch coating and fill the gaps caused by the shrinkage of the pre-ceramic phase, resulting in cracks at the patch coating and exposing part of the substrate, and the anti-oxidation effect was poor. In Comparative Example 3, since the content of ceramic precursor in the coating slurry was too low, the ceramic precursor could not fully bond with the filler and the substrate, resulting in poor effect after coating, and no protective coating could be formed.

[0148] It should be noted that in all the above embodiments and comparative examples, when pre-treating the surface of the repaired part, the requirements of "the roughness of the exposed substrate surface is Ra≤0.3μm, the slope angle is ≤60°, and the coating surface 3~5mm outside the edge of the clean coating" are followed. When applying the coating slurry, "the coating is applied outward to 1~3mm outside the edge of the coating, and the coating slurry is 0.5~2 times the coating thickness of the original coating plane". The above parameters are all empirically optimal parameter ranges obtained during actual operation, so no comparative examples are specifically added to illustrate their necessity. When the actual surface pretreatment and coating process do not comply with the requirements of the above S2 and S3 steps, the patch coating may be prepared, but the surface of the patch coating cannot be relatively flat with the coating, and there is a certain probability that the patch coating will fall off from the coating plate during subsequent processing.

[0149] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art who is familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for repairing an aluminum-silicon alloy coating on a metal surface, characterized in that: The following steps are involved: S1. Preparation of repair coating slurry: The raw materials of the coating with a silicon-based ceramic precursor and a filler as the main material and an auxiliary solvent and an auxiliary curing agent as auxiliary materials are mixed evenly without lumps to obtain a repair coating slurry; S2. Surface pretreatment of the repaired part: Grind the repaired part to expose the smooth substrate surface, and form an arc-shaped transition slope at the edge of the original coating during grinding; The roughness of the exposed substrate surface is Ra≤0.3μm; The slope angle of the arc transition slope is ≤60°; S3. Coating: Apply the repair coating slurry evenly on the polished area and apply it outward to 1~3mm outside the edge of the coating; The distance that the coating slurry is higher than is 0.5 to 2 times the thickness of the coating; S4. Curing: In a dry environment, keep the applied repair coating slurry at 20~300℃ for 0.3min~120h, the coating slurry is cured to form a patch coating, and the metal surface coating is repaired.

2. The method for repairing aluminum-silicon alloy coating on metal surface according to claim 1, characterized in that: In the step S1, the repair coating slurry is divided into two parts: a main material and an auxiliary material; The main material is composed of a silicon-based ceramic precursor and a filler, wherein the mass ratio of the ceramic precursor to the filler is 1:1 to 10:1; Auxiliary materials are auxiliary components of coating slurry, which are composed of auxiliary solvents and auxiliary curing agents. Auxiliary materials can be added selectively or not; Taking the mass percentage of the coating slurry as 100%, the main material accounts for 40-100% of the coating slurry, the auxiliary solvent in the auxiliary material accounts for 0-60% of the coating slurry, and the auxiliary curing agent in the auxiliary material accounts for 0-20% of the coating slurry. The sum of the mass percentages of the above components is 100%.

3. The method for repairing aluminum-silicon alloy coating on metal surface according to claim 2, characterized in that: In the repair coating slurry, the silicon-based ceramic precursor is selected from at least one of polysilazane, polysiloxane, polycarbosilane, and polysilane; In the silicon-based ceramic precursor, the mass fraction of polysilazane is ≥90%.

4. The method for repairing aluminum-silicon alloy coating on metal surface according to claim 2, characterized in that: In the repair coating slurry, the filler is aluminum metal powder with an aluminum mass fraction of ≥95%.

5. The method for repairing aluminum-silicon alloy coating on metal surface according to claim 2, characterized in that: In the repair coating slurry, the auxiliary solvent component is selected from: one or more of hydrocarbons, ethers, alcohols, esters, and silane coupling agents.

6. The method for repairing aluminum-silicon alloy coating on metal surface according to claim 2, characterized in that: In the repair coating slurry, the auxiliary curing agent is selected from one or more of diazabicyclo, aluminum triacetylacetonate, and phosphazene.

7. The method for repairing aluminum-silicon alloy coating on metal surface according to claim 1, characterized in that: In the step S2, the position to be repaired is polished with sandpapers of low to high mesh numbers in sequence to obtain a smooth and flat repair surface, and finally the sandpaper with a mesh number ranging from 400# to 2000# is used.

8. The method for repairing aluminum-silicon alloy coating on metal surface according to claim 1, characterized in that: In the step S3, the coating method is one of roller coating, brush coating and spray coating.

9. The method for repairing aluminum-silicon alloy coating on metal surface according to claim 1, characterized in that: In the step S4, when there is no auxiliary curing agent, the curing time of the coating is 4 to 120 hours when it is cured in the temperature range of 20 to 150°C, and the curing time is 30 to 240 minutes when it is cured in the temperature range of 150 to 300°C; when an auxiliary curing agent is added, the curing time of the coating is 1 to 24 hours when it is cured in the temperature range of 20 to 150°C, and the curing time is 0.3 to 50 minutes when it is cured in the temperature range of 150 to 300°C.

10. The patch coating obtained by the method according to any one of claims 1 to 9.

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