A method for improving the surface bonding strength of ultra-high temperature ceramic coatings by additive roughening

Abstract

The present invention discloses a method for enhancing the surface bonding strength of ultra-high temperature ceramic coatings through additive roughening, belonging to the technical field of ceramic coating preparation. A bonding layer slurry is disposed on the surface of the ultra-high temperature ceramic coating to obtain a bonding layer, and then a rough layer slurry is disposed on the surface of the bonding layer for roughening to obtain a rough layer. The range of the maximum surface height difference Ry in the rough layer is controlled to be 0.15 - 0.5 mm. Finally, sintering treatment is carried out to obtain a rough ceramic coating, thus achieving the goal. The method of the present invention can not only significantly enhance the bonding firmness between the surface coating of ceramic materials and other materials, but also effectively avoid the possible negative impact of subtractive roughening process on the mechanical properties of materials. At the same time, it does not depend on specific equipment and material growth characteristics, and therefore has a broader application prospect.

Description

Technical Field

[0001] The present invention belongs to the field of surface roughening of high-temperature ceramics, and relates to a method for improving the surface bonding strength of ultra-high temperature ceramic coatings through additive roughening. Background Art

[0002] At present, with the rapid development of technology, a single type of material has been difficult to meet the increasingly diverse needs of various fields. Therefore, the method of compounding multiple materials has emerged. It can skillfully combine the excellent properties of different materials to meet the requirements of various complex application scenarios. However, between different types of materials, such as metal and ceramic, ceramic and polymer material, metal and polymer material, or between different types of ceramics, due to the differences in physical and chemical properties, the bonding force between them is relatively weak, making it difficult to effectively combine and use them together.

[0003] To solve this problem, it has been found that a rough surface is beneficial to improving the mechanical bonding force between materials with different physical and chemical properties. Therefore, surface roughening technology has become a key means to enhance the bonding force between materials. Among many surface roughening treatment methods, methods such as grinding with emery burs, sandblasting, laser etching, and acid etching are widely used. These roughening methods are not only simple to operate but also extremely efficient, so they are widely used in industry.

[0004] However, these methods also have certain limitations. They adopt a subtractive method to achieve the roughening of the material surface. Such a treatment method often causes great damage to the material, easily leading to stress concentration and defect generation on the material surface. These defects will not only reduce the mechanical properties of the material but also affect the service life and reliability of the material. Moreover, for ceramic materials, especially ultra-high temperature ceramics such as tantalum carbide, hafnium carbide, and zirconium carbide, due to their high melting point, high hardness, and high brittleness, it is very difficult to achieve the roughening of the surface of these ultra-high temperature ceramic coatings through subtractive methods.

[0005] In addition to increasing surface roughness by subtractive methods, there are also some methods to roughen the surface by in-situ growth. For example, preparing rough hafnium nitride films by magnetron sputtering (Growth and Surface Roughening Mechanism of Smooth and Rough Hafnium Nitride Films), or roughening the surface of steel by electrolytic deposition (Fabrication of Roughened Electrodeposited Copper Coating on Steel for Dissimilar Joining of Steel and Thermoplastic Resin), etc. Although these methods can effectively improve the surface roughness of materials and thus enhance the bonding force between materials, they have relatively high requirements for the performance of equipment or the materials themselves. Therefore, it is difficult to promote them on a large scale on the surface of ceramic materials in practical applications. Summary of the Invention

[0006] Aiming at the problems in the prior art, such as the difficulty in roughening the surface of ultra-high temperature ceramic materials with high strength, high hardness, high melting point and significant brittleness, the purpose of the present invention is to provide a method for improving the surface bonding strength of ultra-high temperature ceramic coatings by additive roughening. The method of the present invention can not only significantly improve the bonding firmness between the surface coating of ceramic materials and other materials, but also effectively avoid the possible negative impact of subtractive roughening process on the mechanical properties of materials. At the same time, it does not depend on the specific equipment and material growth characteristics, so it has a broader application prospect.

[0007] In order to achieve the above technical purpose, the present invention adopts the following technical solutions:

[0008] A method for improving the surface bonding strength of ultra-high temperature ceramic coatings by additive roughening. The bonding layer slurry is set on the surface of the ultra-high temperature ceramic coating to obtain a bonding layer, and then the rough layer slurry is set on the surface of the bonding layer for roughening to obtain a rough layer. The range of the maximum surface height difference Ry in the rough layer is controlled to be 0.15 - 0.5 mm, and finally, sintering treatment is carried out to obtain a rough ceramic coating;

[0009] The bonding layer slurry contains metal powder and ultra-high temperature ceramic powder A; the mass fraction of the metal powder in the bonding layer slurry is 30 - 60 wt%, and the mass fraction of the ultra-high temperature ceramic powder A in the bonding layer slurry is 10 - 20 wt%;

[0010] The rough layer slurry contains ultra-high temperature ceramic powder B, and the mass fraction of the ultra-high temperature ceramic powder B in the rough layer slurry is 48 - 80 wt%;

[0011] The ultra-high temperature ceramic powder A in the adhesive layer slurry and the ultra-high temperature ceramic powder B in the rough layer slurry are of the same type of ultra-high temperature ceramic, and are each selected from at least one of carbides, oxides or borides of titanium, zirconium, niobium, vanadium, and tantalum.

[0012] In the present invention, the maximum surface height difference in the rough layer refers to the difference between the vertex of the convex part and the lowest point of the concave part of the rough layer within a certain area range (the measuring instrument is a 0918 roughness meter).

[0013] In the preparation method of the present invention, an adhesive layer is first provided on the surface of a substrate with an ultra-high temperature ceramic coating. During the sintering process, the metal powder in the adhesive layer slowly melts, enabling the ceramic particles in the rough layer and the ultra-high temperature ceramic coating to diffuse and sinter with each other through the metal liquid phase. The adhesive layer contains the same ultra-high temperature ceramic powder as that in the rough layer slurry, which can prevent the metal from flowing in the high-temperature liquid phase state and causing a large displacement of the rough layer morphology. Finally, after sintering, a rough ceramic coating with a rough morphology is obtained. Using this rough ceramic coating as a transition layer and continuing to introduce other heterogeneous materials on the basis of this transition layer, a layered composite coating with high bonding strength can be prepared, broadening the application field of the ceramic coating.

[0014] In the present invention, first, the amount of the metal powder in the bonding layer needs to be controlled within the scope of the present invention. If the addition amount is too large, there will be more residual metal impurities, affecting the coating purity and corrosion resistance at high temperatures. If the addition amount is too small, the liquid phase generated during the sintering process will be insufficient, resulting in insufficient densification of the ceramic sintering. The metal powder controlled within the scope of the present invention can promote ceramic sintering during the sintering process, volatilize in the high-temperature and low-pressure environment in the later stage of the sintering process, and finally be evacuated by a vacuum pump, thus not weakening the high-temperature mechanical properties of the ceramic coating during use. Second, the rough layer slurry is provided on the surface of the adhesive layer. The range of the maximum surface height difference Ry in the dried rough layer is 0.15 - 0.5 mm. If Ry < 0.15 mm, it is easy to cause peeling during the preparation process of the sintered transition layer and the further introduction of heterogeneous materials. If Ry > 0.5 mm, it will affect the subsequent coating surface morphology and component accuracy.

[0015] In a preferred embodiment, the ultra-high temperature ceramic coating is provided on the surface of the substrate, and the substrate is selected from one of graphite, carbon-carbon composite materials, and silicon carbide fiber-reinforced ceramic matrix composite materials.

[0016] During the actual operation process, before using the adhesive layer slurry on the surface of the ultra-high temperature ceramic coating, it is necessary to clean the surface of the ultra-high temperature ceramic coating with acetone and ethanol in sequence.

[0017] In a preferred embodiment, the bonding layer slurry is composed of the following components by mass percentage: 30-60 wt % of metal powder, 10-20 wt % of ultra-high temperature ceramic powder A, 0.5-2 wt % of binder, 0.5-2% wt % of dispersant, and 25-50 wt % of solvent.

[0018] In the present invention, the bonding layer is fixed to the smooth ceramic coating surface by a polymer binder. By controlling the formulation of the bonding layer slurry within the scope of the present invention, the resulting rough transition layer has the best bonding performance with the heterogeneous material.

[0019] Further preferably, in the bonding layer slurry, the metal in the metal powder is selected from at least one of nickel, chromium, cobalt, iron and copper.

[0020] Further preferably, in the adhesive layer slurry, the binder is selected from at least one of polyvinyl butyral and ethyl cellulose.

[0021] Further preferably, in the adhesive layer slurry, the dispersant is selected from at least one of polyethylene glycol, polyethyleneimine, and ammonium polyacrylate.

[0022] Further preferably, in the adhesive layer slurry, the solvent is selected from at least one of anhydrous ethanol, xylene, toluene, acetone, and n-hexane.

[0023] In actual operation, metal powder, ultra-high temperature ceramic powder, binder, dispersant and solvent are mixed and prepared by ball milling according to the designed proportion of the bonding layer slurry.

[0024] In a preferred embodiment, the bonding layer slurry is applied on the surface of the ultra-high temperature ceramic coating by brushing or spraying, and then dried to obtain the bonding layer.

[0025] In a preferred embodiment, the thickness of the adhesive layer is ≤5 μm, preferably 2 μm. The thickness of the adhesive layer needs to be controlled within 5 μm. A too thick adhesive layer will result in excessive metal residues, which will reduce the performance of the coating at high temperatures.

[0026] In a preferred embodiment, the ultrahigh temperature ceramic powder A in the bonding layer is composed of ultrahigh temperature ceramic powder A1 with a particle size of 100-500 nm and ultrahigh temperature ceramic powder A2 with a particle size of 5-10 μm, and the mass ratio of ultrahigh temperature ceramic powder A1:ultrahigh temperature ceramic powder A2 is 0.2-0.5.

[0027] In this preferred embodiment, the slurry of the bonding layer is made of the above-mentioned two ultra-high temperature ceramic powders with different particle sizes. On the one hand, it can increase the packing density of the powder and improve the density and strength of the rough particles or coating in the rough layer during the sintering process. At the same time, different gradings can make large particles swallow small particles during the sintering process, thereby increasing the roughness of the coating.

[0028] In a preferred embodiment, the method of roughening the surface of the bonding layer by applying the roughening layer slurry is selected from one of brushing, plasma spraying, and 3D printing, and brushing is preferably used.

[0029] Further preferably, when the method of roughening the surface of the bonding layer by applying the roughening layer slurry is brushing, the roughening layer slurry used, by mass percentage, has the following composition: ultra-high temperature ceramic powder B 48-80 wt%, organic binder 0.1-5 wt%, dispersant 0.1-5 wt%, metal binder 0.1-5 wt%, solvent 15-50 wt%; the organic binder is selected from at least one of polyvinyl butyral and ethyl cellulose, the dispersant is selected from at least one of polyethyleneimine, polyethylene glycol, and ammonium polyacrylate, the metal binder is selected from at least one of iron, cobalt, and nickel, and the solvent is selected from at least one of ethanol, ethylene glycol, xylene, toluene, n-hexane, and benzene; wherein, the ultra-high temperature ceramic powder B is composed of ultra-high temperature ceramic powder B1 with a particle size of 1-5 μm and ultra-high temperature ceramic powder B2 with a particle size of 15-20 μm, and the mass ratio of ultra-high temperature ceramic powder B1 to ultra-high temperature ceramic powder B2 is 60-80:20-40.

[0030] In the roughening layer slurry, a grading of coarse and fine particle sizes is also adopted. The coarse ceramic particles can form ceramic rough points in the rough ceramic coating. During the sintering process, through the Ostwald ripening mechanism, the smaller ceramic particles nearby are swallowed up. The energy of the large particles is lower than that of the small particles. The energy of the small particles is high, and their solubility is higher than that of the large particles. The small particles dissolved at high temperature will redeposit on the large particles to form larger ceramic particles, increasing the roughness of the coating.

[0031] During the actual operation process, after weighing each component according to the designed ratio, ball milling and ultrasonic dispersion are carried out to obtain the roughening layer slurry used.

[0032] Further preferably, the process of brushing is as follows: First, use a sponge brush to apply the roughening layer slurry on the surface of the ultra-high temperature ceramic coating, and control the brushing thickness within 0.2 mm or less. Then, use a texture can to dip the roughening layer slurry and roll it back and forth on the surface 3-6 times. Finally, use the tip of a hard brush to dip the roughening layer slurry and evenly dot-press dense protrusions on the surface, and the dot-press density is 100-400 per cm 3 。

[0033] Even more preferably, the height difference between the protrusions and depressions on the surface of the texture can is less than 0.3 mm.

[0034] Even more preferably, the amount of roughening layer slurry dipped by the tip of the hard brush each time is no more than 2 g, and the slurry is redipped after dot-pressing 5-10 times.

[0035] In the present invention, first, a random rough texture is formed on the coating through the porous structure or uneven surface of the sponge brush and the texture roller. Subsequently, the tip of the hard bristle brush head is used to dip into the rough layer slurry and perform dot pressing on the surface repeatedly until a uniform and densely dotted convexity is formed on the entire surface. Through the above process, Ry can be controlled between 0.15 - 0.5 mm.

[0036] Further preferably, during the brushing process, the temperature is controlled at 80 - 120°C. During the actual operation, the substrate is placed on a workbench surface with a temperature of 80 - 120°C.

[0037] Further preferably, during the plasma spraying, the rough layer slurry used, by mass percentage, is composed as follows: ultra-high temperature ceramic powder B 54 - 80 wt%, dispersant 0.1 - 1 wt%, binder 0.1 - 1 wt%, volatile substance 5 - 10 wt%, solvent 14 - 40 wt%. The dispersant is selected from at least one of polyvinylpyrrolidone and polycarboxylic acid. The binder is selected from at least one of carboxymethyl cellulose and polyvinyl alcohol. The volatile substance is selected from at least one of PMMA microspheres, ammonium bicarbonate, and paraffin. The solvent is selected from at least one of deionized water, ethanol, and ethylene glycol. Among them, ultra-high temperature ceramic powder B is composed of ultra-high temperature ceramic powder B3 with a particle size of 500 nm - 3 μm and ultra-high temperature ceramic powder B4 with a particle size of 10 - 30 μm. By mass ratio, the mass ratio of ultra-high temperature ceramic powder B3 to ultra-high temperature ceramic powder B4 is 70 - 90:10 - 30. The ultra-high temperature ceramic powder B4 is spherical particles obtained by granulation.

[0038] In the present invention, the rough layer slurry suspension is prepared according to the above formula. In the rough layer slurry formula, a grading of two kinds of particles is adopted, and the coarse particles are spherical powders obtained by granulation. The spherical powders have high fluidity and can uniformly flow into the plasma jet flame during the plasma spraying process. During the spraying process, the finer powders will absorb the energy of the plasma flame and melt, while the larger particle powders are driven by the high-speed flame and have limited energy absorption and are difficult to melt. Therefore, crystal nuclei of rough points are formed, and the subsequent melted small particles can adhere to the crystal nuclei and grow slowly to form rougher sites.

[0039] Further preferably, during the plasma spraying, the physical and chemical droplet size is controlled at 20 - 50 μm, the plasma power is 30 - 100 KW, the spraying distance is 20 - 150 mm, the nozzle moving rate is 30 - 80 cm / s, the spraying times are 5 - 10 times, the temperature of the substrate is 20 - 200°C, and the carrier gas is a mixed gas of Ar and H2. By volume ratio, Ar:H2 = 5 - 25.

[0040] By controlling the parameters of the plasma spraying within the scope of the present invention and cooperating with the ultra-high temperature ceramic powder in the slurry, a rough layer with a Ry range of 0.15 - 0.5 mm can be obtained.

[0041] Further preferably, when performing 3D printing, the rough layer slurry used is composed as follows by mass percentage: 50 - 60% of ultra-high temperature ceramic powder B, 40 - 50% of additives; the additives are composed as follows by mass percentage: 60 - 80% of main binder, 10 - 30% of backbone binder, 0.5 - 2% of sintering aid, 1 - 10% of surfactant; wherein the main binder is selected from at least one of polyoxymethylene and thermoplastic elastomer (TPE), the backbone binder is selected from at least one of polystyrene and high-density polyethylene, the sintering aid is selected from at least one of nickel, cobalt, chromium, copper, and iron, and the surfactant is selected from stearic acid.

[0042] Further preferably, before 3D printing, first, a rough layer model is set on the surface of the substrate model according to the shape of the substrate model by computer-aided (CAD). The rough layer model is an array of wave grooves and columnar protrusions interspersed between the wave grooves. The wavelength of the wave grooves is 1 - 5 mm, the amplitude is 0.1 - 0.5 mm, the diameter of the columnar protrusions is 0.3 - 0.8 mm, the height is 0.1 - 0.5 m, and the density of the columnar protrusions is 50 - 200 per cm 3 . The height of the columnar protrusion is the height of its own printing.

[0043] In the actual operation process, after setting the rough layer model on the surface of the substrate model according to the shape of the substrate model by computer-aided (CAD), the sliced file of the established model is imported into the 3D printer. Then, the rough layer slurry is mixed and kneaded in a mixer, granulated to obtain pellets, and the pellets are placed in the 3D printer for printing.

[0044] Preferably, the process of the sintering treatment is as follows: under vacuum conditions, first, the temperature is raised at a heating rate of 1 - 10 °C / min to 1800 - 1900 °C, then a protective atmosphere is introduced, and the temperature is raised at a heating rate of 3 - 5 °C / min to 2000 - 2500 °C, and heat preservation is carried out for 2 - 4 h under slightly positive pressure.

[0045] In the sintering process of the present invention, heating is first carried out under vacuum conditions, which is beneficial to the decomposition and removal of the polymer additives of the binder, and the subsequent volatilization of metal powders in a high-temperature and low-pressure environment, and finally they are evacuated by a vacuum pump. Finally, under a slightly positive pressure and within the holding time of the present invention, the ultra-high-temperature ceramic is sintered densely to obtain a rough transition layer. During the entire sintering process, the heating rate needs to be controlled in the present invention because the polymer additives decompose in the low-temperature stage, and the sintering rate needs to be reduced, otherwise defects such as bulging and cracking are likely to occur. In the medium-temperature stage, the ceramic sintering additives liquefy, and too fast heating is likely to cause the liquid sintering additives to not have enough time to spread, resulting in uneven sintering and internal stress in the prepared coating, which is not conducive to subsequent use. And in the final high-temperature stage (2000 - 2500 °C), which is the stage of grain growth and pore healing, it is even more necessary to control the heating rate well. If the heating rate is too fast, it is likely to cause the grain growth rate to exceed the pore exclusion rate, ultimately resulting in a large number of closed pores remaining in the coating. In addition, in addition to controlling the heating rate, it is also necessary to ensure the final sintering holding time, otherwise the coating roughness may decrease.

[0046] However, since different methods are used to prepare the rough layer in the present invention, the slurries of the rough layer are different, and the types of ceramics are different. Therefore, in the sintering process under vacuum conditions, by setting a gradient heating program, the polymer additives, metal powders, etc. can be better removed, and the sintering uniformity is better.

[0047] In a preferred embodiment, the thickness of the rough ceramic coating is 300 - 800 μm.

[0048] Compared with the prior art, the present invention has the following advantages:

[0049] 1. The present invention avoids the disadvantage of the decline in the mechanical properties of the coating material caused by subtractive roughening, and can prepare a rough ceramic coating on the surface of large components.

[0050] 2. The present invention can enhance the bonding force between the ceramic coating and other heterogeneous materials, can prepare a layered composite coating with high bonding force, and broaden the application field of the ceramic coating.

[0051] 3. The present invention can design the composition of the rough ceramic coating according to the use requirements, as long as the material can be sintered densely at high temperature, without other special properties of the material itself. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 It is a schematic cross-sectional view of a rough coating prepared by the method of the present invention, from bottom to top are: substrate (100), smooth ceramic coating (200), bonding layer (300), rough ceramic coating (400).

[0053] Figure 2 It is a macroscopic view of the rough tantalum carbide coating prepared in Example 1.

[0054] Figure 3 Scanning electron microscope image of the surface of the rough tantalum carbide coating prepared in Example 1.

[0055] Figure 4 Scanning electron microscope image of the cross-section of the rough tantalum carbide coating prepared in Example 1.

[0056] Figure 5 Macroscopic image of the combination of the rough tantalum carbide coating prepared in Example 1 and the second-phase coating.

[0057] Figure 6 Macroscopic image of the coating peeling off after the coating prepared in Comparative Example 1 is combined with the second-phase coating. Detailed implementation manners

[0058] Example 1

[0059] This example provides a method for improving the surface bonding strength of ultra-high temperature ceramic coatings through additive roughening. In this example, a brush coating process was specifically used to prepare a rough tantalum carbide coating on the surface of the tantalum carbide coating, including the following steps:

[0060] 1) The graphite substrate with a tantalum carbide coating was successively cleaned with acetone and alcohol on the coating surface. The size of the graphite substrate was 20×20×10 mm, and the thickness of the tantalum carbide coating was 100 μm.

[0061] 2) Mix metal nickel, chromium, and cobalt in a ratio of 2:3:5 to form a metal mixed powder. Mix tantalum carbide fine powder with a particle size range of 100 - 500 nm and tantalum carbide coarse powder with a particle size range of 5 - 10 μm in a mass ratio of 1:3 to obtain a tantalum carbide mixed powder. Mix the tantalum carbide mixed powder with the metal mixed powder to obtain a cermet powder. Then, using ethanol and xylene as solvents, polyvinyl butyral as a binder, polyethylene glycol, and polyethyleneimine as dispersants, ball mill them together to obtain an adhesive layer slurry. In the adhesive layer slurry, by mass percentage, the composition is as follows: metal mixed powder 50%, tantalum carbide powder 10%, ethanol 20%, xylene 16%, polyvinyl butyral 2%, polyethylene glycol 1%, and polyethyleneimine 1%;

[0062] 3) Use a fine brush to evenly brush a thin layer of the adhesive layer slurry on the surface of the tantalum carbide coating, and place it in an oven at 80°C for 30 minutes to dry, obtaining an adhesive layer with a thickness of 3 μm.

[0063] 4) Configure the slurry containing tantalum carbide powder as the rough layer slurry, where the tantalum carbide powder is composed of tantalum carbide fine powder with a particle size of 1 - 5 μm and tantalum carbide coarse powder with a particle size of 15 - 20 μm, and the mass ratio of the tantalum carbide fine powder to the tantalum carbide coarse powder is 75:25;

[0064] Weigh tantalum carbide powder, ethylene glycol, toluene, nickel, ethyl cellulose, and polyethylene glycol according to the mass ratio of 80:11:5:1:2:1 respectively, and use a ball milling tank to ball mill and mix them to configure the slurry;

[0065] 5) First, use a sponge brush to brush the rough layer slurry on the surface of the ultra-high temperature ceramic coating, and control the brushing thickness at 0.2 mm. Then, use a texture tank (the average height difference of the surface protrusions and depressions is about 0.25) to dip the rough layer slurry and roll it back and forth on the surface 4 times. Finally, use the pointed tip of a hard brush to dip the rough layer slurry and evenly dot-press dense protrusions on the surface. The amount of rough layer slurry dipped by the pointed tip of the hard brush each time is no more than 2 g. After dot-pressing 5 - 10 times, re-dip the slurry and repeat dot-pressing on the surface until uniform dot-pressed dense protrusions (the average height of the protrusions is about 0.3 mm) are formed on the entire surface, and the density of the protrusions is 200 per cm 3 ;

[0066] 6) Finally, put the sample into an oven for drying. The drying process is to keep it at 70 °C for 1 h, raise the temperature to 120 °C, keep it at this temperature for 30 min, raise the temperature to 160 °C and keep it at this temperature for 1 h, and finally keep it at 190 °C for 1 h. The heating rate is 5 °C / min. After drying, a rough layer is obtained. Use a 0981 roughness meter to measure the rough layer (the average value measured from 15 groups of data at different positions on the coating surface), and the average maximum height difference Ry of its surface is 0.3 mm;

[0067] 7) Put the dried sample into a high-temperature furnace, raise the temperature to 300 °C at a heating rate of 10 °C / min, continuously evacuate, then raise the temperature to 800 °C at a heating rate of 2 °C / min, the negative pressure state pressure is 20,000 Pa, then raise the temperature to 1800 °C at a heating rate of 8 °C / min, the negative pressure state pressure is 50,000 Pa, then raise the temperature to 2300 °C at a heating rate of 3 °C / min, and gradually increase the air pressure to normal pressure. The air pressure at 2300 °C is slightly positive pressure, and the pressure is controlled by the argon flow rate. Keep it at this temperature for 2 h to obtain a rough tantalum carbide ceramic coating.

[0068] The macroscopic view of the surface of the obtained rough tantalum carbide ceramic coating sample is as Figure 2 shown. There are many convex points on the coating surface, and the thickness of the rough tantalum carbide ceramic coating is 500 μm.

[0069] Figure 3The figure shows the secondary electron morphology of the surface of a rough tantalum carbide ceramic coating sample. The coating surface is pitted, with many holes and protrusions, which can provide a barb structure to fix the second-phase coating.

[0070] Figure 4 The figure shows the secondary electron morphology of the cross-section of a rough tantalum carbide ceramic coating sample. The barb structure of the coating can be clearly observed in the cross-sectional view.

[0071] Example 2

[0072] This example provides a method for improving the surface bonding strength of ultra-high temperature ceramic coatings by additive roughening. In this example, a suspension plasma spraying process was specifically used to prepare a rough ZrHfTiTaNbC high-entropy ceramic coating on the surface of the tantalum carbide coating, including the following steps:

[0073] 1) The graphite substrate with a tantalum carbide coating was successively cleaned with acetone and alcohol on the coating surface. The size of the graphite substrate was 20×20×10 mm, and the thickness of the tantalum carbide coating was 100 μm.

[0074] 2) Mix nickel, chromium, and cobalt evenly in a ratio of 2:3:5. Mix fine ZrHfTiTaNbC high-entropy ceramic powder with a particle size range of 100 - 500 nm and coarse ZrHfTiTaNbC high-entropy ceramic powder with a particle size range of 5 - 10 μm in a mass ratio of 1:4 to obtain a ZrHfTiTaNbC high-entropy ceramic mixed powder. Mix the ZrHfTiTaNbC high-entropy ceramic mixed powder with the metal mixed powder to obtain a cermet powder. Then, using ethanol and toluene as solvents, polyvinyl butyral as a binder, polyethylene glycol, and polyethyleneimine as dispersants, ball mill them together to obtain an adhesive layer slurry. In the adhesive layer slurry, by mass percentage, the composition is as follows: metal mixed powder 50%, ZrHfTiTaNbC high-entropy ceramic powder 10%, ethanol 20%, xylene 16%, polyvinyl butyral 2%, polyethylene glycol 1%, and polyethyleneimine 1%;

[0075] 3) Use a fine brush to evenly brush a thin layer of the ball-milled and mixed adhesive layer slurry on the surface of the tantalum carbide coating, and place it in an oven at 80°C for 30 minutes to dry, obtaining an adhesive layer with a thickness of 3 μm.

[0076] 4) Configure the slurry containing ZrHfTiTaNbC high-entropy ceramic powder as the rough layer slurry. The ZrHfTiTaNbC high-entropy ceramic powder is obtained by mixing fine powder with an average particle size of 0.8 μm and spherical powder of 20 μm in a mass ratio of 80:20. The spherical powder is obtained by granulating and spheroidizing the fine powder. Weigh ZrHfTiTaNbC high-entropy ceramic powder, water, ethanol, carboxymethyl cellulose, polycarboxylic acid, and PMMA microspheres according to the mass ratio of 65:18:8:1:1:7 respectively, and use a ball mill jar to ball mill and mix them to configure the slurry.

[0077] 5) Pour the configured slurry into the feeding cavity. Use a plasma power of 55 kW, a spraying distance of 70 mm, keep the substrate temperature at 150 °C, the carrier gas flow rate: 3 slpm (Ar / H2 = 50 / 5). Control the physical and chemical droplet size to be 20 - 50 μm during plasma spraying, the nozzle moving rate is 35 cm / s, and the spraying times are 6 times.

[0078] 6) Finally, put the sample into an oven for drying. The drying process is to keep it at 50 °C for 1 h, heat up to 100 °C and keep it for 2 h, slowly heat up to 140 °C at a rate of 1 °C / min and keep it for 2 h, and finally keep it at 180 °C for 1 h. The other heating rate is 5 °C / min. After drying, a rough layer is obtained. Use a 0981 roughness meter to measure the rough layer (the average value measured from 15 groups of data at different positions on the coating surface), and the average maximum height difference Ry on its surface is 0.3 mm.

[0079] 7) Put the dried sample into a high-temperature furnace. Heat it up to 180 °C at a heating rate of 5 °C / min, continuously evacuate the air. Heat it up to 300 °C at a heating rate of 10 °C / min, continuously evacuate the air. Heat it up to 900 °C at a heating rate of 2 °C / min, the negative pressure state pressure is 20,000 Pa. Heat it up to 1600 °C at a heating rate of 8 °C / min, the negative pressure state pressure is 30,000 Pa. Heat it up to 1900 °C at a heating rate of 5 °C / min, the negative pressure state pressure is 50,000 Pa. Heat it up to 2500 °C at a heating rate of 3 °C / min, and gradually increase the air pressure to normal pressure. The air pressure at 2500 °C is slightly positive pressure, and the pressure is controlled by the argon gas flow rate. Keep it warm for 2 h to obtain a rough tantalum carbide ceramic coating.

[0080] Example 3

[0081] This example provides a method for improving the surface bonding strength of ultra-high temperature ceramic coatings through additive coarsening. In this example, a 3D printing process is specifically used to prepare a rough zirconium boride ceramic coating on the surface of the zirconium boride coating, including the following steps:

[0082] 1) Clean the surface of the graphite matrix with zirconium boride coating successively using acetone and alcohol. The size of the graphite matrix is 20×20×10 mm, and the thickness of the zirconium boride coating is 100 μm.

[0083] 2) Mix metal nickel, chromium, and cobalt in a ratio of 2:3:5 to form a metal mixed powder. Mix fine zirconium boride powder with a particle size range of 100 - 500 nm and coarse zirconium boride powder with a particle size range of 5 - 10 μm in a mass ratio of 1:5 to obtain a zirconium boride mixed powder. Mix the zirconium boride mixed powder with the metal mixed powder to obtain a cermet powder. Then, using ethanol and xylene as solvents, polyvinyl butyral as a binder, polyethylene glycol, and polyethyleneimine as dispersants, ball-mill them together to obtain an adhesive layer slurry. In the adhesive layer slurry, by mass percentage, the composition is as follows: metal mixed powder 50%, zirconium boride powder 10%, ethanol 20%, xylene 16%, polyvinyl butyral 2%, polyethylene glycol 1%, and polyethyleneimine 1%.

[0084] 3) Use a fine brush to evenly brush a thin layer of the adhesive layer slurry on the surface of the zirconium boride coating for the ball-milled and evenly mixed adhesive layer slurry, and place it in an oven at 80°C for drying for 30 minutes to obtain an adhesive layer with a thickness of 3 μm.

[0085] 4) Configure the 3D printing zirconium boride particle feed. Weigh zirconium boride particles and additives according to the designed ratio. The mass ratio of zirconium boride particles to additives is 60:40. Among the additives, by mass percentage, nickel is 1%, polystyrene is 25%, stearic acid is 5%, and polyoxymethylene is 69%. First, dry-ball mill the powders of zirconium boride and nickel for 12 h with a ball-to-material ratio of 6:1, then perform high-temperature calcination at 1000°C, ball-mill crushing, and screening through a 300-mesh sieve to obtain a mixed powder. Add the mixed powder to a mixer at 110°C, keep the rotation speed at 5 r / min, and mix for 1 h. Then add polystyrene and stearic acid to the mixer for mixing. At this time, adjust the temperature of the mixer to 190°C and mix at a rotation speed of 15 r / min for 2 h. Finally, add polyoxymethylene to the mixer and mix at a rotation speed of 50 r / min for 30 min. Put the well-mixed dough-like material into a granulator to obtain 2-mm particle feed.

[0086] 5) Use computer-aided (CAD) to add transverse wave grooves (wavelength 3 mm, amplitude 0.4 mm) and randomly interspersed columnar protrusions (diameter 0.6 mm, height 0.3 m) on the surface of the matrix model, and control the density of the columnar protrusions to be 100 per cm 3 , to obtain a three-dimensional geometric model with special regular protrusions and depressions.

[0087] 6) Add the prepared feedstock into the hopper of the 3D printer. The feedstock is fed through a screw into a heating barrel and heated to a molten state. Subsequently, it is deposited on the surface of the sample on the hot bed under the constraint of a nozzle according to the three-dimensional geometric model. The temperature of the heating barrel is 195°C, the temperature of the hot bed is 150°C, and the extrusion rate is 2 g / cm 3 , the printing rate is 50 mm / s, and the layer thickness is 0.1 mm.

[0088] 6) Put the printed sample into an atmosphere furnace for drying. The drying process is to keep it at 120°C for 2 h, and it is protected by nitrogen throughout the process. After drying, a rough layer is obtained. Use a roughness meter 0981 to measure the rough layer (the average value measured from 15 groups of data at different positions on the coating surface), and the average maximum height difference Ry on its surface is 0.25 mm.

[0089] 7) Put the dried sample into a high-temperature furnace. Heat it up to 900°C at a heating rate of 5°C / min, continuously evacuate, heat it up to 1200°C at a heating rate of 2°C / min, continuously evacuate, heat it up to 1500°C at a heating rate of 5°C / min, the pressure in the negative pressure state is 50,000 Pa, heat it up to 1800°C at a heating rate of 8°C / min, the pressure in the negative pressure state is 80,000 Pa, heat it up to 2000°C at a heating rate of 5°C / min, and gradually increase the air pressure to normal pressure. The air pressure at 2000°C is slightly positive pressure, and the pressure is controlled by the nitrogen flow rate, and keep it at this temperature for 2 h to obtain a rough zirconium boride ceramic coating.

[0090] Comparative Example 1

[0091] Compared with Example 1, the difference is that in the process of step 5, a roller brush, sponge patting, and brush dotting are not used, and a brush coating is directly used to further prepare a uniform and smooth tantalum carbide coating on the surface of the transition layer.

[0092] Using the products obtained in the example and Comparative Example 1 as the substrate, use the thermal spraying technology to prepare a YSZ thermal barrier coating with a thickness of 1 mm on its surface, and test the bonding strength between the YSZ coating and the rough coating in the example or the smooth ceramic coating generated in Comparative Example 1. The obtained bonding strength is shown in Table 1.

[0093] Figure 5 As shown, it is a YSZ thermal barrier coating prepared on the surface of the rough tantalum carbide coating prepared in Example 1 as the substrate using the thermal spraying technology. It can be seen from the macroscopic view that the surface of the YSZ coating is smooth and defect-free.

[0094] Figure 6The YSZ thermal barrier coating prepared by thermal spraying on the surface of the smooth tantalum carbide coating in Comparative Example 1. From the macroscopic view, it can be clearly seen that the YSZ coating cannot adhere to the surface of the smooth tantalum carbide coating, and partial peeling occurs in some areas. This is due to the difference in thermal expansion coefficient and chemical properties between the two coatings, resulting in poor bonding between the coatings, and causing partial peeling of the YSZ coating on the surface of the tantalum carbide coating.

[0095]

[0096] Among them, the tensile strength of the graphite matrix is between 6 - 8 MPa.

[0097] Comparative Example 2

[0098] Compared with Example 1, the difference is that steps 2 and 3 are not carried out, that is, a thin bonding layer is not prepared on the surface of the smooth coating. As a result, the rough particles on the surface of the rough tantalum carbide ceramic after high-temperature sintering are prone to peeling. After spraying the YSZ coating on its surface by thermal spraying, the coating does not crack or peel off, but the bonding strength between the coatings is less than 3 MPa.

[0099] As described above, only the preferred embodiments of the present invention are provided, and there is no limitation in any form and essence to the present invention. It should be noted that for those of ordinary skill in the art in this technical field, without departing from the method of the present invention, several improvements and supplements can still be made, and these improvements and supplements should also be regarded as the protection scope of the present invention. For those skilled in the art, without departing from the spirit and scope of the present invention, any equivalent changes made by using the technical content disclosed above, such as slight modifications, decorations, and evolutions, are all equivalent embodiments of the present invention; at the same time, any equivalent changes, modifications, and evolutions made to the above embodiments based on the substantial technology of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A method for enhancing the surface bonding strength of ultra-high temperature ceramic coatings through additive coarsening, characterized by: The adhesive layer slurry is set on the surface of the ultra-high temperature ceramic coating to obtain an adhesive layer, and then the roughening layer slurry is set on the surface of the adhesive layer for roughening to obtain a roughening layer. The range of the maximum surface height difference Ry in the roughening layer is controlled to be 0.15-0.5 mm. Finally, sintering treatment is carried out to obtain the roughened ceramic coating, and that's it. The adhesive layer slurry contains metal powder and ultra-high temperature ceramic powder A. The mass fraction of the metal powder in the adhesive layer slurry is 30-60 wt%, and the mass fraction of the ultra-high temperature ceramic powder A in the adhesive layer slurry is 10-20 wt%. The roughening layer slurry contains ultra-high temperature ceramic powder B, and the mass fraction of the ultra-high temperature ceramic powder B in the roughening layer slurry is 48-80 wt%. The ultra-high temperature ceramic types in the ultra-high temperature ceramic powder A in the adhesive layer slurry and the ultra-high temperature ceramic powder B in the roughening layer slurry are the same, and are all selected from at least one of carbides, oxides or borides of titanium, zirconium, vanadium, niobium, tantalum.

2. The method for improving the surface bonding strength of an ultra-high temperature ceramic coating by additive roughening according to claim 1, wherein: The ultra-high temperature ceramic coating is set on the surface of the substrate, and the substrate is selected from one of graphite, carbon-carbon composite material, and silicon carbide fiber reinforced ceramic matrix composite material.

3. A method for enhancing the surface bonding strength of ultra-high temperature ceramic coatings through additive roughening according to claim 1, characterized in that: The adhesive layer slurry, by mass percentage, is composed as follows: metal powder 30-60 wt%, ultra-high temperature ceramic powder A 10-20 wt%, binder 0.5-2 wt%, dispersant 0.5-2 wt%, solvent 25-50 wt%. In the adhesive layer slurry, the metal in the metal powder is selected from at least one of nickel, chromium, cobalt, iron, and copper. In the adhesive layer slurry, the binder is selected from at least one of polyvinyl butyral and ethyl cellulose. In the adhesive layer slurry, the dispersant is selected from at least one of polyethylene glycol, polyethyleneimine, and ammonium polyacrylate. In the adhesive layer slurry, the solvent is selected from at least one of absolute ethanol, xylene, toluene, acetone, and n-hexane.

4. According to the method for improving the surface bonding strength of an ultra-high temperature ceramic coating by additive roughening according to claim 1 or 3, it is characterized in that: The adhesive layer slurry is set on the surface of the ultra-high temperature ceramic coating by brushing or spraying, and dried to obtain an adhesive layer. The thickness of the adhesive layer ≤ 5 μm. The ultra-high temperature ceramic powder A in the adhesive layer is composed of ultra-high temperature ceramic powder A1 with a particle size of 100-500 nm and ultra-high temperature ceramic powder A2 with a particle size of 5-10 μm. By mass ratio, ultra-high temperature ceramic powder A1: ultra-high temperature ceramic powder A2 = 0.2-0.

5.

5. The method for improving the surface bonding strength of ultra-high temperature ceramic coatings by additive coarsening according to claim 1, wherein: The method of setting the roughening layer slurry on the surface of the adhesive layer for roughening is selected from one of brushing, plasma spraying, and 3D printing.

6. According to the method for improving the surface bonding strength of an ultra-high temperature ceramic coating by additive roughening according to claim 5, it is characterized in that: When the method of applying the rough layer slurry on the surface of the bonding layer for roughening is brush coating, the rough layer slurry used, by mass percentage, is composed as follows: ultra-high temperature ceramic powder B 48 - 80wt%, organic binder 0.1 - 5wt%, dispersant 0.1 - 5wt%, metal binder 0.1 - 5wt%, solvent 15 - 50wt%; the organic binder is selected from at least one of polyvinyl butyral and ethyl cellulose, the dispersant is selected from at least one of polyethyleneimine, polyethylene glycol, and ammonium polyacrylate, the metal binder is selected from at least one of iron, cobalt, and nickel, and the solvent is selected from at least one of ethanol, ethylene glycol, xylene, toluene, n-hexane, and benzene; wherein, the ultra-high temperature ceramic powder B is composed of ultra-high temperature ceramic powder B1 with a particle size of 1 - 5μm and ultra-high temperature ceramic powder B2 with a particle size of 15 - 20μm, and the mass ratio of ultra-high temperature ceramic powder B1 to ultra-high temperature ceramic powder B2 is 60 - 80:20 - 40; The process of the brush coating is as follows: First, use a sponge brush to brush the rough layer slurry on the surface of the bonding layer, and control the brush coating thickness to be 0.2mm or less. Then, use a texture can to dip in the rough layer slurry and roll it back and forth on the surface 3 - 6 times. Finally, use the tip of a hard brush head to dip in the rough layer slurry and evenly dot-press dense protrusions on the surface; The height difference between the protrusions and depressions on the surface of the texture can is less than 0.3mm; The amount of rough layer slurry dipped by the tip of the hard brush head each time is no more than 2g, and the slurry is re-dipped after dot-pressing 5 - 10 times; When performing the brush coating, control the temperature to be 80 - 120°C.

7. According to the method for improving the surface bonding strength of an ultra-high temperature ceramic coating by additive roughening as described in claim 5, wherein: When performing the plasma spraying, the rough layer slurry used, by mass percentage, is composed as follows: ultra-high temperature ceramic powder B 54 - 80wt%, dispersant 0.1 - 1wt%, binder 0.1 - 1wt%, volatile substance 5 - 10wt%, solvent 14 - 40wt%, the dispersant is selected from at least one of polyvinylpyrrolidone and polycarboxylic acid, the binder is selected from at least one of carboxymethyl cellulose and polyvinyl alcohol, the volatile substance is selected from at least one of PMMA microspheres, ammonium bicarbonate, and paraffin, and the solvent is selected from at least one of deionized water, ethanol, and ethylene glycol. Among them, the ultra-high temperature ceramic powder B is composed of ultra-high temperature ceramic powder B3 with a particle size of 500nm - 3μm and ultra-high temperature ceramic powder B4 with a particle size of 10 - 30μm, and the mass ratio of ultra-high temperature ceramic powder B3 to ultra-high temperature ceramic powder B4 is 70 - 90:10 - 30; the ultra-high temperature ceramic powder B4 is spherical particles obtained by granulation; When performing the plasma spraying, the physical and chemical liquid droplets are controlled to have a size of 20 - 50 μm, the plasma power is 30 - 100 KW, the spraying distance is 20 - 150 mm, the nozzle moving rate is 30 - 80 cm / s, the number of spraying times is 5 - 10 times, the temperature of the substrate is 20 - 200 °C, and the carrier gas is a mixed gas of Ar and H2. By volume ratio, Ar:H2 = 5 - 25.

8. A method for improving the surface bonding strength of an ultra-high temperature ceramic coating by additive roughening according to claim 5, characterized in that: When performing the 3D printing, the rough layer slurry used, by mass percentage, is composed as follows: 50 - 60% of ultra-high temperature ceramic powder B, and 40 - 50% of additives; the additives, by mass percentage, are composed as follows: 60 - 80% of main binder, 10 - 30% of backbone binder, 0.5 - 2% of sintering aid, and 1 - 10% of surfactant; wherein the main binder is selected from at least one of polyoxymethylene and thermoplastic elastomer, the backbone binder is selected from at least one of polystyrene and high-density polyethylene, the sintering aid is selected from at least one of nickel, cobalt, chromium, copper, and iron, and the surfactant is selected from stearic acid; Before the 3D printing, a rough layer model is set on the surface of the substrate model by computer-aided design according to the shape of the substrate model. The rough layer model is an array of wave-shaped grooves and columnar protrusions interspersed between the wave-shaped grooves. The wavelength of the wave-shaped grooves is 1-5 mm, the amplitude is 0.1-0.5 mm, the diameter of the columnar protrusions is 0.3-0.8 mm, the height is 0.1-0.5 m, and the density of the columnar protrusions is 50-200 per cm 3 .

9. A method for improving the surface bonding strength of an ultra-high temperature ceramic coating by additive roughening according to claim 1, characterized in that: The process of the sintering treatment is as follows: Under vacuum conditions, first heat up to 1800 - 1900 °C at a heating rate of 1 - 10 °C / min, then introduce a protective atmosphere, and heat up to 2000 - 2500 °C at a heating rate of 3 - 5 °C / min, and keep the temperature for 2 - 4 h under slightly positive pressure.

10. A method for improving the surface bonding strength of a ultra-high temperature ceramic coating by additive roughening according to claim 1, characterized in that: The thickness of the rough ceramic coating is 300 - 800 μm.

Images