Preparation method for preparing ceramic glaze composite coating on alloy surface

Abstract

The invention belongs to the technical field of alloy material surface treatment, and particularly relates to a preparation method for preparing a ceramic glaze composite coating on an alloy surface, which comprises the following steps: S1, carrying out multi-stage polishing on an alloy until the roughness of the alloy surface reaches a micron level; s2, carrying out chemical activation treatment on the surface of the polished alloy; s3, the activated alloy is placed in an electrolyte, and a micro-arc oxidation layer is generated through a bipolar pulse power supply; s4, carrying out oxidation modification on the micro-arc oxidation layer by adopting a plasma method; s5, the alloy subjected to oxidation modification is coated with low-temperature glaze containing phosphate active ingredients; and S6, performing multi-stage gradient sintering on the alloy coated with the low-temperature glaze, wherein the temperature t of the multi-stage gradient sintering is more than or equal to 200 DEG C and less than or equal to 750 DEG C. Through oxidation modification, plasma treatment, multi-stage gradient sintering and other treatments on the alloy, the compactness, bonding strength and stability of the glaze layer are improved.

Description

Technical Field

[0001] The invention belongs to the technical field of alloy material surface treatment, and particularly relates to a method for preparing a ceramic glaze composite coating on an alloy surface. Background Art

[0002] Lightweight alloy materials such as magnesium alloys, aluminum alloys and titanium alloys are widely used in aerospace, automobile manufacturing, consumer electronics and other fields due to their excellent specific strength, thermal conductivity and processing properties. However, the surface of such metal materials is easily oxidized, has poor corrosion resistance, and has limited surface decorativeness and thermal stability, which restricts their application in harsh service environments. In order to improve the corrosion resistance, mechanical strength and aesthetic properties of the alloy surface, researchers have proposed a variety of surface modification methods. Among them, micro-arc oxidation (MAO) technology, as a way to generate ceramic coatings in situ on the alloy surface, has attracted widespread attention due to its advantages such as strong adhesion and good wear resistance.

[0003] However, the traditional micro-arc oxidation process has the following shortcomings: the ceramic layer it produces has a single color and poor decorative properties; the coating has a generally high porosity and is prone to penetration failure under long-term service or corrosive media; at the same time, when the service temperature exceeds 400°C, the internal phase structure of the micro-arc oxidation layer changes and causes cracks, leading to high-temperature failure. In addition, in order to improve the decorativeness and functionality of the coating, ceramic glaze or coloring layer is often used for compounding, but traditional glazes need to be sintered at a high temperature of 1200~1400°C, which is much higher than the melting point of magnesium and aluminum alloys, and is prone to causing alloy matrix melting or deformation. Summary of the invention

[0004] In view of the above problems, the present invention proposes a method for preparing a ceramic glaze composite coating on an alloy surface, by subjecting the alloy to oxidation modification, plasma treatment and multi-stage gradient sintering and other treatments to improve the density, bonding strength and stability of the glaze layer.

[0005] To achieve the above purpose, the technical solution adopted is: The present invention provides a method for preparing a ceramic glaze composite coating on an alloy surface, comprising the following steps: S1. Perform multi-stage polishing on the alloy until the roughness of the alloy surface reaches the micron level; S2. chemically activating the surface of the polished alloy; S3. placing the activated alloy in an electrolyte and generating a micro-arc oxidation layer through a bipolar pulse power supply; S4. Oxidative modification of the micro-arc oxidation layer by plasma method; S5. coating a low-temperature glaze containing a phosphate active ingredient on the oxidation-modified alloy; S6. Performing gradient sintering on the alloy coated with the low-temperature glaze, the temperature t of the multi-stage gradient sintering satisfies: 200°C≤t≤750°C.

[0006] Furthermore, in step S1, the multi-stage polishing is mechanical polishing, and the surface roughness Ra of the alloy after polishing satisfies 0.08 μm≤Ra≤0.18 μm.

[0007] Furthermore, in step S2, the chemical activation treatment is alkali washing, water washing, acid washing and water washing; the time of the alkali washing is 3 to 10 minutes, and the time of the acid washing is 10 to 60 seconds.

[0008] Furthermore, in step S2, the material for alkaline washing includes one or more of NaOH solution, KOH solution and Na3PO4 solution; the material for acid washing includes one or more of HNO3 solution, H2SO4 solution and H3PO4 solution.

[0009] Furthermore, in step S4, the micro-arc oxidation layer on the surface of the alloy is oxidized and modified by a plasma method to form hydroxyl groups on the surface of the micro-arc oxidation layer.

[0010] Furthermore, in step S4, the material used in the plasma method is Ar / O2 mixed plasma, the gas flow ratio of Ar to O2 is 3:1~5:1, and the radio frequency power density is 1.5~3.0W / cm 2 , processing time 5~15min, vacuum pressure 3~8Pa.

[0011] Furthermore, in step S5, a low-temperature glaze containing a phosphate active ingredient is coated on the oxidatively modified alloy by inkjet printing and glazing immersion process; the inkjet printing adopts a piezoelectric nozzle for electrostatic spraying, the ink droplet volume is 4-8pL, and the resolution is ≥300dpi; the voltage range of electrostatic spraying is 40~60kV, and the atomization pressure is 0.2~0.5MPa; the glaze slurry viscosity range of the glaze immersion process is 25~50mPa·s (25℃), and the pulling speed range is 1~3mm / s.

[0012] Further, in step S5, the low-temperature glaze includes: one or more of micron SiO2, B2O3, nano ZnO, NaH2PO4, nano ZrO2 and transition metal oxide colorants.

[0013] Further, in step S5, in the low-temperature glaze, the mass proportion of the micron SiO2 is 45~55wt%, and the particle size Dv50 of the micron SiO2 is 2.5μm; the mass proportion of the B2O3 is 15~25wt%; the mass proportion of the nano ZnO is 10~20wt%, and the particle size Dv50 of the nano ZnO is 50nm; the mass proportion of the NaH2PO4 is 5~8wt%; the mass proportion of the nano ZrO2 is 1~2wt%, and the particle size Dv50 of the nano ZrO2 is 100nm; the mass proportion of the transition metal oxide colorant is 1~5wt%, and the color difference ΔE≤2.0 of the transition metal oxide colorant.

[0014] Further, in step S6, the multi-stage gradient sintering is a three-stage gradient sintering, the first stage sintering process is: heating from room temperature to 200°C, a heating rate of 3~5°C / min, and constant temperature treatment for 20~40min; the second stage sintering process is: heating from 200°C to 600°C, a heating rate of 2~3°C / min, and constant temperature treatment for 15~30min; the third stage sintering process is: heating from 600°C to 750°C, a heating rate of 1~2°C / min, and constant temperature treatment for 10~20min.

[0015] The above technical solution has at least the following beneficial effects: ① In the present invention, the surface roughness of the alloy is controlled within the micrometer range of 0.08~0.18μm by mechanically polishing the surface, which helps to improve the structural stability and functional performance of the entire coating system. The micrometer-level surface can not only promote the uniform distribution of discharge during micro-arc oxidation, generate a denser and more uniform oxide layer, significantly reduce the porosity, and improve corrosion resistance; at the same time, it provides an ideal active interface for subsequent plasma surface modification, which is conducive to the uniform introduction of hydroxyl groups and enhances the wettability and bonding strength of ceramic glazes. In addition, the smooth micrometer-level surface also improves the spreadability of the glaze during inkjet printing, glaze dipping or electrostatic spraying, avoids the occurrence of defects such as uneven coating thickness, sagging or shedding, and further improves the decorativeness and surface aesthetics; ② In the present invention, a plasma method is used to oxidatively modify the micro-arc oxidation layer on the surface of the alloy, so that the surface of the micro-arc oxidation layer is enriched with hydroxyl (-OH) groups. This process significantly improves the chemical activity and wetting properties of the surface of the micro-arc oxidation layer. As a highly polar functional group, hydroxyl can enhance the spreadability and adhesion of the glaze on the surface of the micro-arc oxidation layer, forming a more uniform and dense coating layer, and avoiding defects such as bubbles and cracks caused by uneven coating. At the same time, hydroxyl can also chemically bond with the phosphate components in the glaze to construct a strong interface bonding structure, which has stronger peeling strength and thermal stability than physical adhesion, thereby effectively improving the bonding between the ceramic glaze layer and the micro-arc oxidation layer. In addition, the oxidation modification treatment adopts a low-temperature and low-pressure plasma process, which is suitable for heat-sensitive substrates such as magnesium-aluminum alloys, does not cause thermal deformation of the substrate, and ensures the thermal stability and adaptability of the overall process; ③ In the present invention, the present invention uses a low-temperature glaze containing phosphate active ingredients to coat the surface of the oxidized modified alloy, which not only effectively solves the problem of alloy deformation caused by excessively high firing temperatures of traditional high-temperature glazes, but also significantly improves the chemical bonding and comprehensive performance of the coating. Phosphate components (such as NaH2PO4) can undergo condensation reactions with the hydroxyl groups on the surface of the micro-arc oxidation layer during low-temperature sintering to form a strong chemical bonding interface, greatly enhancing the adhesion between the glaze layer and the bottom layer, and preventing the coating from peeling off due to thermal cycles or mechanical stress; ④ In the present invention, the alloy coated with low-temperature glaze is subjected to multi-stage gradient sintering in the range of 200~750℃, which can effectively coordinate the thermal stress difference between the glaze and the base material during the sintering process, and avoid cracking, shedding of the coating or deformation of the alloy base due to drastic temperature difference or too fast heating. Gradient sintering promotes the gradual softening, melting and rearrangement of the components in the glaze by slowly heating up in stages and properly keeping warm, so that the glass phase fully wets and fills the surface micropores, forming a dense, continuous and highly adhesive ceramic coating. DETAILED DESCRIPTION

[0016] The technical solution of the present invention will be described clearly and completely below in conjunction with the specific embodiments of the present invention. Unless otherwise defined, the technical terms or scientific terms used in the present invention should have the common meanings understood by people with ordinary skills in the relevant field.

[0017] The present invention provides a method for preparing a ceramic glaze composite coating on an alloy surface, comprising the following steps: S1. Perform multi-stage polishing on the alloy until the roughness of the alloy surface reaches the micron level; S2. chemically activating the surface of the polished alloy; S3. placing the activated alloy in an electrolyte and generating a micro-arc oxidation layer through a bipolar pulse power supply; S4. Oxidative modification of the micro-arc oxidation layer by plasma method; S5. coating a low-temperature glaze containing a phosphate active ingredient on the oxidation-modified alloy; S6. Performing gradient sintering on the alloy coated with the low-temperature glaze, the temperature t of the multi-stage gradient sintering satisfies: 200°C≤t≤750°C.

[0018] In the present invention, the surface roughness of the alloy is controlled within the micrometer range of 0.08 to 0.18 μm by mechanically polishing the surface of the alloy, which helps to improve the structural stability and functional performance of the entire coating system. The micrometer-level surface can not only promote the uniform distribution of discharge during micro-arc oxidation, generate a denser and more uniform oxide layer, significantly reduce porosity, and improve corrosion resistance; at the same time, it provides an ideal active interface for subsequent plasma surface modification, which is conducive to the uniform introduction of hydroxyl groups and enhances the wettability and bonding force of ceramic glazes. In addition, the flat micrometer-level surface also improves the spreadability of the glaze during inkjet printing, glaze dipping or electrostatic spraying, avoids the generation of defects such as uneven coating thickness, sagging or shedding, and further improves the decorativeness and surface aesthetics.

[0019] In the present invention, the micro-arc oxidation layer on the surface of the alloy is oxidatively modified by a plasma method, so that the surface of the micro-arc oxidation layer is enriched with hydroxyl (-OH) groups. This process significantly improves the chemical activity and wetting properties of the surface of the micro-arc oxidation layer. As a highly polar functional group, the hydroxyl group can enhance the spreadability and adhesion of the glaze on the surface of the micro-arc oxidation layer, forming a more uniform and dense coating layer, and avoiding defects such as bubbles and cracks caused by uneven coating. At the same time, the hydroxyl group can also chemically bond with the phosphate component in the glaze to construct a strong interface bonding structure, which has more peeling strength and thermal stability than physical adhesion, thereby effectively improving the bonding force between the ceramic glaze layer and the micro-arc oxidation layer, and ensuring the thermal stability and adaptability of the overall process.

[0020] In the present invention, the present invention uses a low-temperature glaze containing a phosphate active ingredient to coat the surface of the oxidized modified alloy, which not only effectively solves the problem of alloy deformation caused by the high firing temperature of the traditional high-temperature glaze, but also significantly improves the chemical bonding and comprehensive performance of the coating. Phosphate components (such as NaH2PO4) can undergo a condensation reaction with the hydroxyl groups on the surface of the micro-arc oxidation layer during the low-temperature sintering process to form a strong chemical bonding interface, greatly enhancing the adhesion between the glaze layer and the bottom layer, and avoiding the peeling of the coating caused by thermal cycling or mechanical stress.

[0021] In the present invention, the alloy coated with low-temperature glaze is subjected to multi-stage gradient sintering in the range of 200-750°C, which can effectively coordinate the thermal stress difference between the glaze and the base material during the sintering process, and avoid cracking, shedding of the coating or deformation of the alloy base due to drastic temperature difference or too fast heating. Gradient sintering promotes the gradual softening, melting and rearrangement of the components in the glaze by slowly heating up in stages and properly keeping warm, so that the glass phase fully wets and fills the surface micropores, forming a dense, continuous and highly adhesive ceramic coating.

[0022] It should be noted that, in the present invention, the alloy is a magnesium alloy, a titanium alloy, an aluminum alloy or other common alloys.

[0023] In some embodiments, in step S1, the multi-stage polishing is mechanical polishing, and the surface roughness Ra of the alloy after polishing satisfies 0.08 μm≤Ra≤0.18 μm.

[0024] Controlling the alloy surface roughness Ra between 0.08μm and 0.18μm can effectively balance the interface bonding force and process adaptability, and improve the quality of subsequent coatings. It not only has appropriate mechanical bite, but also is conducive to the uniformity of micro-arc oxidation discharge and the uniform introduction of hydroxyl groups in plasma modification, enhancing the wettability and adhesion of the glaze, and forming a dense and smooth composite coating. When the roughness Ra is greater than 0.18μm, it is easy to cause uneven discharge and increased pores during micro-arc oxidation, reducing the density and stability of the coating; if it is less than 0.08μm, the alloy surface is too smooth, the adhesion is reduced, and the modification reaction efficiency is affected.

[0025] In some embodiments, in step S2, the chemical activation treatment is alkali washing, water washing, acid washing and water washing; the alkali washing time is 3 to 10 minutes, and the acid washing time is 10 to 60 seconds. Specifically, the water washing uses deionized water.

[0026] In some embodiments, in step S2, the material for alkaline washing includes one or more of NaOH solution, KOH solution and Na3PO4 solution; the material for acid washing includes one or more of HNO3 solution, H2SO4 solution and H3PO4 solution.

[0027] The multi-step chemical activation treatment process of "alkali washing, water washing, pickling and re-washing" can remove oil, oxides and processing residues on the alloy surface, while improving the surface reaction activity, laying a good foundation for the subsequent formation of the coating. Among them, alkali washing uses alkaline solutions such as sodium hydroxide, potassium hydroxide or sodium phosphate to effectively remove organic pollution and weak bonding layers within 3~10min, so that the surface is initially cleaned and has a certain roughening effect, which is conducive to enhancing adhesion. After that, it is fully washed with deionized water to avoid the interference of alkaline ion residues in the subsequent pickling reaction. The pickling step is treated with diluted nitric acid, phosphoric acid or sulfuric acid for a short time (10~60s) to further remove the dense oxide layer, activate the metal surface, and increase its hydrophilicity and reactivity. Finally, rinse with deionized water again to thoroughly remove residual acid and prevent corrosion and impurities. This staged treatment method can not only effectively improve the surface cleanliness and flatness, but also enhance the surface energy and interface bonding activity, providing a clean and active substrate for micro-arc oxidation and glaze sintering.

[0028] In some embodiments, in step S4, the micro-arc oxidation layer on the surface of the alloy is oxidatively modified by a plasma method to form hydroxyl groups on the surface of the micro-arc oxidation layer.

[0029] The plasma method is used to oxidatively modify the micro-arc oxide layer on the alloy surface, so that the surface of the micro-arc oxide layer is enriched with hydroxyl (-OH) groups. This process significantly improves the chemical activity and wetting properties of the surface of the micro-arc oxide layer. The hydroxyl group enhances the spreadability and adhesion of the glaze on the surface of the micro-arc oxide layer, forming a more uniform and dense coating layer, avoiding defects such as bubbles and cracks caused by uneven coating. At the same time, the hydroxyl group can also chemically bond with the phosphate components in the glaze to build a strong interface bonding structure, which has stronger peeling strength and thermal stability than physical adhesion, thereby effectively improving the bonding between the ceramic glaze layer and the micro-arc oxide layer, and ensuring the thermal stability and adaptability of the overall process.

[0030] In some embodiments, in step S4, the material used in the plasma method is Ar / O2 mixed plasma, the gas flow ratio of Ar to O2 is 3:1~5:1, and the RF power density is 1.5~3.0W / cm 2 , the processing time is 5~15min, and the vacuum pressure is 3~8Pa.

[0031] Ar / O2 mixed plasma combines the high-energy physical bombardment capability of argon with the chemical activity of oxygen, and can achieve both physical cleaning and chemical modification when treating the alloy surface: Ar gas, as an inert gas, can improve discharge stability and remove impurities through momentum transfer; O2 gas can provide active oxygen species, promote the formation of surface hydroxyl groups, and enhance the polarity and hydrophilicity of the oxide layer; the mixed use of Ar and O2 can achieve a surface modification effect with high uniformity, low damage and strong activity.

[0032] By controlling the gas flow ratio of Ar to O2 in the range of 3:1~5:1, a balance between discharge stability and oxidation reaction activity can be achieved. An appropriate amount of oxygen ensures sufficient hydroxyl formation, while using argon as the main gas can avoid violent discharge or local overoxidation and protect the surface structure. When there is too little oxygen, insufficient hydroxyl formation on the alloy surface occurs, the oxidation modification effect is weak, the surface activity is low, and the subsequent glaze adhesion decreases. When there is too much oxygen, the solution causes unstable discharge, which is prone to local overheating or oxygen corrosion, resulting in ablation of the micro-arc oxide layer, increased roughness, and even microcracks.

[0033] Control the RF power density between 1.5 and 3.0 W / cm 2 The power density range is moderate, which can form a uniform hydroxyl layer without destroying the structure of the micro-arc oxide layer. When the RF power density is too high, it is easy to cause excessive bombardment on the surface, resulting in microstructural damage, thermal stress concentration, and reduced coating adhesion. When the RF power density is too low, the RF energy is insufficient, the plasma is unstable or the reaction is insufficient, the amount of hydroxyl introduced is low, and the surface modification effect is poor.

[0034] Controlling the treatment time within the range of 5 to 15 minutes can ensure that the surface reaction is sufficient and uniform, and avoid thermal damage caused by long-term exposure of the material to plasma. When the treatment time is too long, it is easy to cause excessive surface oxidation, coarsening of the structure, and formation of a non-uniform layer, affecting the subsequent bonding performance. When the treatment time is too short, the surface hydroxyl group is not generated sufficiently, the activity is uneven, and the adhesion and density of the coating are reduced.

[0035] In some embodiments, in step S5, a low-temperature glaze containing a phosphate active ingredient is coated on the oxidation-modified alloy through inkjet printing and glazing immersion process; the inkjet printing adopts a piezoelectric nozzle for electrostatic spraying, the ink droplet volume is 4~8pL, and the resolution is ≥300dpi; the voltage range of electrostatic spraying is 40~60kV, and the atomization pressure is 0.2~0.5MPa; the glaze slurry viscosity range of the glaze immersion process is 25~50mPa·s (25℃), and the pulling speed range is 1~3mm / s.

[0036] Step S5 uses a combination of inkjet printing and glazing process to evenly apply the low-temperature glaze containing phosphate active ingredients to the surface of the oxidatively modified alloy, which has significant advantages in process flexibility and coating uniformity. Inkjet printing uses a piezoelectric nozzle, and the ink droplet volume is controlled at 4~8pL. With a high-resolution design of ≥300dpi, it can achieve precise patterned distribution and micro-control of the glaze, which is suitable for complex geometric surfaces and personalized decoration needs. The glazing process controls the glaze slurry viscosity (25~50mPa·s) and the pulling speed (1~3mm / s) to ensure that the glaze forms a uniform and continuous coating on the substrate surface, avoiding defects such as sagging, accumulation or bubbles, and improving the density and aesthetics of the coating. In addition, electrostatic spraying can further enhance the adsorption efficiency of glaze particles on the substrate surface by controlling the voltage (40~60kV) and atomization pressure (0.2~0.5MPa), thereby improving the process coverage and adhesion strength. The combined application of multiple coating methods not only improves the process adaptability and controllability, but also significantly enhances the uniformity, functionality and decorativeness of the ceramic glaze composite coating, providing a reliable guarantee for large-scale, high-consistency preparation.

[0037] In some embodiments, in step S5, the low-temperature glaze includes: one or more of micron SiO2, B2O3, nano ZnO, NaH2PO4, nano ZrO2 and transition metal oxide colorants. Specifically, the transition metal oxide colorants include colorants of multiple color systems such as red, blue and green. The red colorant is a mixture of Fe2O3, Cr2O3 and CeO2; the blue colorant is a mixture of CoAl2O4 spinel and CoO-micron SiO2 solid solution; the green colorant is a mixture of Cr2O3-CuO complex and V2O5.

[0038] In some embodiments, in step S5, in the low-temperature glaze, the mass proportion of the micron SiO2 is 45~55wt%, and further, the particle size Dv50 of the micron SiO2 is 2.5μm; the mass proportion of the B2O3 is 15~25wt%; the mass proportion of the nano ZnO is 10~20wt%, and the particle size Dv50 of the nano ZnO is 50nm; the mass proportion of the NaH2PO4 is 5~8wt%; the mass proportion of the nano ZrO2 is 1~2wt%, and the particle size Dv50 of the nano ZrO2 is 100nm; the mass proportion of the transition metal oxide colorant is 1~5wt%, and the color difference ΔE≤2.0 (D65 light source) of the transition metal oxide colorant.

[0039] In the low-temperature glaze formula used in step S5, each component is optimized and designed according to a specific mass range, has good functional complementarity and system synergy, and can achieve a dense, high-performance ceramic glaze composite coating at a lower temperature. Specifically, SiO2 (45~55wt%) is used as the main glass phase precursor to construct the network skeleton of the coating, provide structural strength and stability, and its Dv50 particle size is 2.5μm, which helps to achieve the flatness and uniformity of the glaze layer. B2O3 (15~25wt%) is used as a flux to significantly reduce the melting temperature of the glaze, enhance its fluidity under low-temperature sintering conditions, and avoid thermal deformation of the substrate. ZnO (10~20wt%) is used to regulate the thermal expansion coefficient, so that the glaze layer and the micro-arc oxide layer have better thermal matching and reduce the risk of cracking caused by thermal stress. NaH2PO4 (5~8wt%) is used as an interfacial reaction accelerator, which can chemically react with the hydroxyl groups on the surface of the micro-arc oxide layer to generate stable phosphate bonds, significantly improving the chemical bonding between the glaze and the oxide layer. The colorant (1~5wt%) is composed of transition metal oxides, which can achieve stable and vivid color expression and enhance the decorative effect under the condition of ensuring ΔE≤2.0 (D65 light source). Nano ZrO2 (1~2wt%) exists in the form of tetragonal phase, which can significantly enhance the mechanical strength and crack resistance of the coating. The overall formula achieves a good balance between performance, process and decorativeness, and is suitable for preparing ceramic glaze composite coatings with high adhesion, high density and high aesthetics under medium and low temperature sintering conditions.

[0040] In some embodiments, in step S6, the multi-stage gradient sintering is a three-stage gradient sintering, and the first stage sintering process is: heating from room temperature to 200°C, with a heating rate of 3~5°C / min, and constant temperature treatment for 20~40min; the second stage sintering process is: heating from 200°C to 600°C, with a heating rate of 2~3°C / min, and constant temperature treatment for 15~30min; the third stage sintering process is: heating from 600°C to 750°C, with a heating rate of 1~2°C / min, and constant temperature treatment for 10~20min.

[0041] Multi-stage gradient sintering of alloys coated with low-temperature glazes in the range of 200~750℃ can effectively coordinate the thermal stress difference between the glaze and the base material during the sintering process, avoiding cracking, shedding of the coating or deformation of the alloy base due to drastic temperature difference or too fast heating. Gradient sintering promotes the gradual softening, melting and rearrangement of the components in the glaze by slowly heating up in stages and properly keeping warm, so that the glass phase fully wets and fills the surface micropores, forming a dense, continuous and highly adhesive ceramic coating. Specifically, the first stage of the sintering process is to slowly heat up from room temperature to 200℃ (heating rate 3~5℃ / min) and keep it warm for 20~40min, which can remove residual solvents and adsorbed water in the glaze and prevent bubbles or bulging in subsequent sintering; the second stage continues to heat up to 600℃ (heating rate 2~3℃ / min) at a medium rate and keep it at a constant temperature for 15~30min, so that the glaze softens and begins to melt and flow, fills the pores of the micro-arc oxidation layer, and enhances the physical bonding with the substrate; the third stage is heated to 750℃ at a lower rate (heating rate 1~2℃ / min) and kept warm for 10~20min, so that the components in the glaze fully react, rearrange and form a dense and continuous glass phase, while controlling the release of thermal stress to avoid cracking or peeling of the coating due to sudden temperature changes. This multi-stage gradient sintering path takes into account the density, adhesion and thermal matching of the coating, which is an important guarantee for the construction of high-performance ceramic glaze composite coatings.

[0042] The present invention is further described below by way of examples.

[0043] Example 1. Surface coating of AZ31 magnesium alloy (Φ40 mm × 2 mm) S1. The AZ31 magnesium alloy is polished with diamond until the surface roughness Ra of the AZ31 magnesium alloy reaches 0.1 μm; S2. Soak the polished AZ31 magnesium alloy in a 50g / L NaOH solution for 5 min at a soaking temperature of 60°C; remove the AZ31 magnesium alloy from the NaOH solution and completely rinse off the residual NaOH solution on the surface of the AZ31 magnesium alloy with deionized water; soak the AZ31 magnesium alloy in a 10% HNO3 solution for activation for 30 s at a soaking temperature of 60°C; remove the AZ31 magnesium alloy from the HNO3 solution and completely rinse off the residual HNO3 solution on the surface of the AZ31 magnesium alloy with deionized water; S3. The activated AZ31 magnesium alloy was placed in an electrolyte for micro-arc oxidation. The electrolyte composition included Na2SiO3·9H2O (30 g / L), Na2B4O7 (15 g / L) and KF (10 g / L). The parameters of the bipolar pulse power supply were: positive voltage 400 V, negative voltage 50 V, frequency 500 Hz, duty cycle 20%, and micro-arc oxidation time 15 min. AZ31 magnesium alloy generates a micro-arc oxidation layer with a film thickness of 22μm, a porosity of 12%, and a surface hardness HV of 940kgf / mm 2 , the water contact angle is 112°‌; S4. The micro-arc oxidation layer on the surface of AZ31 magnesium alloy was oxidized and modified by plasma method, wherein the gas flow ratio of Ar to O2 was 4:1, the RF power density was 2.0 W / cm², the treatment time was 7 min, and the vacuum pressure was 4 Pa; The oxygen content of the micro-arc oxidation layer on the surface of AZ31 magnesium alloy after oxidation modification is 28at.%, the porosity is 4%, and the water contact angle is 35°; S5. The low-temperature glaze is applied to the oxidation-modified alloy by inkjet printing and glazing process; the nano ZnO inkjet printing uses a piezoelectric nozzle, the ink drop volume is 6pL, and the resolution is 350dpi; The glaze viscosity range of the nano ZnO glazing process is 30mPa·s (25℃), and the pulling speed range is 2mm / s; the voltage range of the electrostatic spraying is 45kV, and the atomization pressure is 0.25MPa; Low-temperature glazes, including: micron SiO2 (52% by mass), nano B2O3 (20% by mass), nano ZnO (15% by mass) and NaH2PO4 (8% by mass), transition metal oxide colorant CoAl2O4 (3% by mass, ΔE=1.0) and CoO-micron SiO2 (2% by mass); S6. The AZ31 magnesium alloy coated with low-temperature glaze was subjected to multi-stage gradient sintering. The first sintering process was: heating from room temperature to 200°C, with a heating rate of 3°C / min, and constant temperature treatment for 25 minutes; the second sintering process was: heating from 200°C to 600°C, with a heating rate of 2.5°C / min, and constant temperature treatment for 20 minutes; the third sintering process was: heating from 600°C to 750°C, with a heating rate of 1°C / min, and constant temperature treatment for 10 minutes.

[0044] At this point, the blue ceramic glaze composite coating was prepared on the surface of AZ31 magnesium alloy (Φ40mm×2mm).

[0045] Example 2. TC4 titanium alloy (Φ10mm×50mm) surface coating S1. The TC4 titanium alloy was sandblasted and polished with Al2O3 particles having a particle size of less than 0.125 mm until the surface roughness Ra of the TC4 titanium alloy reached 0.15 μm; S2. Soak the polished TC4 titanium alloy in a 45g / L NaOH solution for 8 minutes at a soaking temperature of 50°C; remove the TC4 titanium alloy from the NaOH solution and completely rinse off the residual NaOH solution on the surface of the TC4 titanium alloy with deionized water; soak the TC4 titanium alloy in a 12% HNO3 solution for activation for 50 minutes at a soaking temperature of 50°C; remove the TC4 titanium alloy from the HNO3 solution and completely rinse off the residual HNO3 solution on the surface of the TC4 titanium alloy with deionized water; S3. The activated TC4 titanium alloy was placed in an electrolyte for micro-arc oxidation. The electrolyte composition included Na3PO4·12H2O (25 g / L), NaOH (10 g / L), and Na2MoO4 (4 g / L). The parameters of the bipolar pulse power supply were: positive voltage 400 V, negative voltage 50 V, frequency 500 Hz, duty cycle 20%, and micro-arc oxidation time 20 min. TC4 titanium alloy generates a micro-arc oxidation layer with a film thickness of 15μm, a porosity of 13%, and a surface hardness HV of 850kgf / mm 2 , the water contact angle is 115°‌; S4. The micro-arc oxidation layer on the surface of TC4 titanium alloy was oxidized and modified by plasma method, wherein the gas flow ratio of Ar to O2 was 3:1, the RF power density was 2.5W / cm², the treatment time was 10min, and the vacuum pressure was 6Pa; The oxygen content of the micro-arc oxidation layer on the surface of TC4 titanium alloy after oxidation modification is 31at.%, the porosity is 6%, and the water contact angle is 32°; S5. The low-temperature glaze is applied to the oxidized modified alloy by inkjet printing and glazing process; the nano ZnO inkjet printing uses a piezoelectric nozzle, the ink drop volume is 7pL, and the resolution is 380dpi; The glaze viscosity range of the nano ZnO glazing process is 45mPa·s (25℃), and the pulling speed range is 2.7mm / s; the voltage range of the electrostatic spraying is 56kV, and the atomization pressure is 0.46MPa; Low-temperature glazes, including: micron SiO2 (50% by mass), nano B2O3 (21% by mass), nano ZnO (17% by mass) and NaH2PO4 (7% by mass), transition metal oxide colorant Fe2O3 (5% by mass, ΔE=1.3); S6. The TC4 titanium alloy coated with low-temperature glaze was subjected to multi-stage gradient sintering. The first sintering process was: heating from room temperature to 200°C, with a heating rate of 4.5°C / min, and constant temperature treatment for 35 minutes; the second sintering process was: heating from 200°C to 600°C, with a heating rate of 2.3°C / min, and constant temperature treatment for 25 minutes; the third sintering process was: heating from 600°C to 750°C, with a heating rate of 1.8°C / min, and constant temperature treatment for 12 minutes.

[0046] At this point, the red ceramic glaze composite coating was prepared on the surface of AZ31TC4 titanium alloy (Φ40mm×2mm).

[0047] Example 3. Surface coating of 6061 aluminum alloy (150 mm × 70 mm × 0.8 mm) S1. Mechanically polishing the 6061 aluminum alloy until the surface roughness Ra of the 6061 aluminum alloy reaches 0.15 μm; S2. Soak the polished 6061 aluminum alloy in a 40g / L NaOH solution for 8 minutes at a soaking temperature of 45°C; remove the 6061 aluminum alloy from the NaOH solution and completely rinse off the residual NaOH solution on the surface of the 6061 aluminum alloy with deionized water; soak the 6061 aluminum alloy in an 8% HNO3 solution for activation for 40 seconds at a soaking temperature of 60°C; remove the 6061 aluminum alloy from the HNO3 solution and completely rinse off the residual HNO3 solution on the surface of the 6061 aluminum alloy with deionized water; S3. The activated 6061 aluminum alloy was placed in an electrolyte for micro-arc oxidation. The electrolyte composition included Na2SiO3·9H2O (30 g / L), Na2B4O7 (15 g / L) and KF (10 g / L). The parameters of the bipolar pulse power supply were: positive voltage 400 V, negative voltage 50 V, frequency 500 Hz, duty cycle 20%, and micro-arc oxidation time 15 min. 6061 aluminum alloy generates a micro-arc oxidation layer with a film thickness of 15μm, a porosity of 8%, and a surface hardness HV of 1050kgf / mm 2 , the water contact angle is 115°‌; S4. The micro-arc oxidation layer on the surface of 6061 aluminum alloy was oxidized and modified by plasma method, wherein the gas flow ratio of Ar to O2 was 5:1, the RF power density was 3.0 W / cm², the treatment time was 13 min, and the vacuum pressure was 7 Pa; The oxygen content of the micro-arc oxidation layer on the surface of 6061 aluminum alloy after oxidation modification is 30at.%, the porosity is 3%, and the water contact angle is 25°; S5. The low-temperature glaze is applied to the oxidation-modified alloy by inkjet printing and glazing process; the nano ZnO inkjet printing uses a piezoelectric nozzle, the ink drop volume is 6pL, and the resolution is 350dpi; The glaze viscosity range of the nano ZnO glazing process is 30mPa·s (25℃), and the pulling speed range is 2mm / s; the voltage range of the electrostatic spraying is 45kV, and the atomization pressure is 0.25MPa; Low-temperature glazes, including: micron SiO2 (50% by mass), nano B2O3 (22% by mass), nano ZnO (15% by mass) and NaH2PO4 (8% by mass), transition metal oxide colorants Cr2O3-CuO complex (3% by mass, ΔE=1.6) and V2O5 (2% by mass); S6. The 6061 aluminum alloy coated with low-temperature glaze was subjected to multi-stage gradient sintering. The first sintering process was: heating from room temperature to 200°C, with a heating rate of 3°C / min, and constant temperature treatment for 25 minutes; the second sintering process was: heating from 200°C to 600°C, with a heating rate of 2.5°C / min, and constant temperature treatment for 20 minutes; the third sintering process was: heating from 600°C to 750°C, with a heating rate of 1°C / min, and constant temperature treatment for 10 minutes.

[0048] At this point, the ceramic glaze composite coating on the surface of 6061 aluminum alloy (Φ40mm×2mm) is completed.

[0049] It can be seen from Example 1 (AZ31 magnesium alloy), Example 2 (TC4 titanium alloy) and Example 3 (6061 aluminum alloy) that the present invention shows significant advantages in controlling porosity, water contact angle and sintering density of the coating through the combined process of "plasma oxidation modification and multi-stage gradient sintering".

[0050] First, before plasma treatment, the porosity of the coatings formed by micro-arc oxidation on the three alloy substrates was 12%, 13% and 8%, respectively, which is a typical porous ceramic structure. Although it has a certain surface roughness and mechanical strength, the pore structure is easy to become a source of coating failure. After plasma oxidation modification, the porosity of the three materials was reduced to 4%, 6% and 3%, respectively, indicating that the surface structure has been significantly densified and the number of defects has been greatly reduced, providing an ideal interface for the uniform spreading and high bonding strength of the glaze.

[0051] Secondly, from the perspective of the change in water contact angle, the surface after micro-arc oxidation is highly hydrophobic (contact angle 112°~115°), which is not conducive to the wetting and adhesion of subsequent glazes. After plasma treatment with the introduction of hydroxyl groups, the water contact angle dropped significantly to 35° (AZ31 magnesium alloy), 32° (TC4 titanium alloy) and 25° (6061 aluminum alloy), showing excellent hydrophilicity. This improvement in wettability promotes the rapid spreading and adhesion of low-temperature glazes on the surface of the metal oxide layer, which is conducive to the formation of a smooth and continuous glaze layer.

[0052] Finally, the three-stage gradient sintering process is customized according to the characteristics of different materials, controlling the heating rate and constant temperature time, avoiding thermal stress concentration or interface peeling caused by rapid temperature changes. Segmented heating makes the solvent volatilization, glass phase formation and dense sintering process more controllable, ensuring that the glaze is fully transformed and rearranged under mild conditions, thereby improving the density, bonding strength and stability of the glaze layer.

[0053] The preferred embodiments for implementing the present invention have been described in detail above, but it should be understood that the role of these embodiments is only to exemplify, and is not intended to limit the scope, applicability or configuration of the present invention in any way. The protection scope of the present invention is defined by the attached claims and their equivalents. A person of ordinary skill in the art can make many changes to the above embodiments under the guidance of the present invention, and these changes all fall within the protection scope of the present invention.

Claims

1. A method for preparing a ceramic glaze composite coating on an alloy surface, characterized in that: The following steps are involved: S1. Perform multi-stage polishing on the alloy until the roughness of the alloy surface reaches the micron level; S2. chemically activating the surface of the polished alloy; S3. placing the activated alloy in an electrolyte and generating a micro-arc oxidation layer through a bipolar pulse power supply; S4. Oxidative modification of the micro-arc oxidation layer by plasma method; S5. coating a low-temperature glaze containing a phosphate active ingredient on the oxidation-modified alloy; S6. Perform multi-stage gradient sintering on the alloy coated with the low-temperature glaze, wherein the temperature t of the multi-stage gradient sintering satisfies: 200°C≤t≤750°C.

2. The method for preparing a ceramic glaze composite coating on an alloy surface according to claim 1, characterized in that: In step S1, the multi-stage polishing is mechanical polishing, and the surface roughness Ra of the alloy after polishing satisfies 0.08 μm≤Ra≤0.18 μm.

3. The method for preparing a ceramic glaze composite coating on an alloy surface according to claim 1, characterized in that: In step S2, the chemical activation treatment includes alkali washing, water washing, acid washing and water washing; the time of the alkali washing is 3 to 10 minutes, and the time of the acid washing is 10 to 60 seconds.

4. The method for preparing a ceramic glaze composite coating on an alloy surface according to claim 3, characterized in that: In step S2, the material for alkaline washing includes one or more of NaOH solution, KOH solution and Na3PO4 solution; the material for acid washing includes one or more of HNO3 solution, H2SO4 solution and H3PO4 solution.

5. The method for preparing a ceramic glaze composite coating on an alloy surface according to claim 1, characterized in that: In step S4, the micro-arc oxidation layer on the surface of the alloy is oxidized and modified by a plasma method to form hydroxyl groups on the surface of the micro-arc oxidation layer.

6. The method for preparing a ceramic glaze composite coating on an alloy surface according to claim 1 or 5, characterized in that: In step S4, the material used in the plasma method is Ar / O2 mixed plasma, the gas flow ratio of Ar to O2 is 3:1~5:1, the RF power density is 1.5~3.0W / cm², the processing time is 5~15min, and the vacuum pressure is 3~8Pa.

7. The method for preparing a ceramic glaze composite coating on an alloy surface according to claim 1, characterized in that: In step S5, a low-temperature glaze containing a phosphate active ingredient is coated on the oxidation-modified alloy by inkjet printing and glazing process; The inkjet printing adopts a piezoelectric nozzle for electrostatic spraying, the ink drop volume is 4~8pL, and the resolution is ≥300dpi; the voltage range of electrostatic spraying is 40~60kV, and the atomization pressure is 0.2~0.5MPa; The glaze slurry viscosity of the dipping process is in the range of 25-50 mPa·s, and the pulling speed is in the range of 1-3 mm / s.

8. The method for preparing a ceramic glaze composite coating on an alloy surface according to claim 1, characterized in that: In step S5, the low-temperature glaze comprises one or more of micron SiO2, B2O3, nano ZnO, NaH2PO4, nano ZrO2 and transition metal oxide colorants.

9. The method for preparing a ceramic glaze composite coating on an alloy surface according to claim 8, characterized in that: In step S5, in the low temperature glaze, The mass proportion of the micron SiO2 is 45-55wt%, and the particle size Dv50 of the micron SiO2 is 2.5μm; The mass proportion of B2O3 is 15-25wt%; The mass proportion of the nano ZnO is 10-20wt%, and the particle size Dv50 of the nano ZnO is 50nm; The mass proportion of the NaH2PO4 is 5-8wt%; The mass proportion of the nano ZrO2 is 1-2wt%, and the particle size Dv50 of the nano ZrO2 is 100nm; The mass proportion of the transition metal oxide colorant is 1-5wt%, and the color difference ΔE of the transition metal oxide colorant is ≤2.

0.

10. The method for preparing a ceramic glaze composite coating on an alloy surface according to claim 1, characterized in that: In step S6, the multi-stage gradient sintering is a three-stage gradient sintering. The first sintering process is: heating from room temperature to 200℃, heating rate 3~5℃ / min, constant temperature treatment for 20~40min; The second sintering process is: heating from 200℃ to 600℃, heating rate 2~3℃ / min, constant temperature treatment 15~30min; The third sintering process is: heating from 600°C to 750°C, with a heating rate of 1~2°C / min, and constant temperature treatment for 10~20min.