A composite layer structure of carbide transition layer-diamond layer and a method for preparing the same

Abstract

The present application relates to the technical field of diamond coating, and proposes a carbide transition layer-diamond layer composite layer structure and a preparation method thereof.The carbide transition layer-diamond layer composite layer structure comprises a tantalum base, a carbide gradient layer deposited on the surface of the tantalum base, wherein the content of C atoms in the carbide gradient layer gradually decreases towards the tantalum base, and a diamond layer deposited on the surface of the carbide gradient layer.The present application prepares a carbide layer with gradient distribution of composition and smooth transition of structure on the surface of the tantalum base through plasma carbonization treatment, the surface layer of the carbide layer provides C-C bonds capable of closely combining with the diamond layer at the atomic level, thereby realizing high bonding strength between the base material and the diamond layer.Meanwhile, the thermal expansion coefficient of the carbide layer is between the thermal expansion coefficients of the film and the base, and shows gradient change, which can reduce the internal stress of the film and the base.

Description

Technical Field

[0001] The present invention relates to the technical field of diamond coatings, and in particular to a carbide transition layer-diamond layer composite layer structure and a preparation method thereof. Background Art

[0002] Many key components in the aerospace and defense industries must operate in extremely complex environments, subject to the interaction of multiple thermal, mechanical, and chemical processes. This places increasingly stringent demands on the comprehensive performance of key component materials. With the advancement of technologies such as next-generation fighter aircraft and aerospace engines, materials with high wear resistance, abrasion resistance, and thermal shock resistance in high or rapidly heated environments are urgently needed in this cutting-edge field.

[0003] Tantalum and its alloys are renowned for their heat-resistant, high-strength strategic materials. They are currently widely used in components such as rocket engines, turbine blades, and turbine disks, and hold enormous potential for application and development. However, due to their relatively low hardness, tantalum and its alloys can rapidly fail when subjected to severe friction and wear. This leads to a loss of protection and a dramatic reduction in the service life of critical components, limiting their application in aerospace and military applications.

[0004] In the prior art, surface strengthening of tantalum and its alloys can improve their wear resistance. For example, surface heat treatments such as carburizing and nitriding can be performed on the surface of tantalum and its alloys to improve their surface hardness and wear resistance. However, the performance improvement achieved by this process technology is single and cannot meet the requirements of long-term stable use in extremely complex environments. Diamond film has extremely high hardness, excellent tribological properties and high thermal conductivity. Introducing it into the surface protection of tantalum and its alloys can comprehensively improve the service performance under high temperature or rapid temperature increase. However, due to the inherent physical and chemical property differences between tantalum and its alloys and diamond, this will reduce the bonding strength of the film-substrate, the quality of diamond growth, the overall thermal shock resistance and reliability. At the same time, current research often uses physical and chemical methods to pre-treat the substrate, using mechanical grinding and acid-base corrosion to form scratches and pits on the substrate surface to improve the adhesion of the diamond film during deposition. However, there are problems with the unevenness and contamination of the prepared diamond film, and there is an urgent need to improve the existing technology process. Summary of the Invention

[0005] In view of this, the present invention proposes a composite layer structure of a carbide transition layer-diamond layer and a preparation method thereof, which utilizes the film-substrate transition layer structure to reduce the physicochemical differences between the metal matrix and the diamond, alleviate material stress, and achieve a smooth gradual change in properties and performance; at the same time, the film-substrate transition layer is pre-treated by precision machining technology femtosecond laser to construct a highly ordered micro-nano structure, which can effectively solve the defects of the film-substrate microlayered structure, overcome the problem of low diamond nucleation growth at the deposition interface, alleviate film-substrate thermal shock, and achieve high surface hardness, high wear resistance and excellent overall thermal shock resistance of tantalum and its alloys.

[0006] The technical solution of the present invention is implemented as follows: On the one hand, the present invention provides a composite layer structure of a carbide transition layer-diamond layer, comprising: a tantalum substrate; a carbide gradient layer deposited on the surface of the tantalum substrate, wherein the C atom content in the carbide gradient layer gradually decreases toward the tantalum substrate; and a diamond layer deposited on the surface of the carbide gradient layer.

[0007] To further improve the film-substrate bonding strength, existing process methods use both physical and chemical methods. Physical methods mostly use mechanical grinding to produce a large number of irregular scratches on the substrate surface to increase the adhesion of diamond during the deposition process. However, the surface roughness of the diamond film deposited in this way is relatively large. Chemical methods use an acid-base two-step method to corrode the substrate surface, thereby increasing the adhesion of diamond. However, the residual chemical agents will contaminate the deposited diamond film, resulting in the problem of impure film.

[0008] Specifically, the present invention uses a pre-process to carburize the tantalum substrate before depositing the diamond film, and tantalum carbide is generated on the surface of the tantalum substrate as a transition layer, forming a smooth transition layer in structure and composition, thereby solving the defect of a large difference in physical and chemical properties between tantalum and diamond. The transition layer presents a gradient in composition, which can reduce the stress between the film and the substrate.

[0009] At the same time, based on the above technical solution, preferably, the components of the carbide gradient layer are TaC and Ta2C.

[0010] Based on the above technical solution, preferably, a plurality of grooves are etched on the surface of the carbide gradient layer.

[0011] Specifically, after the carburizing process and before depositing the diamond film, the present invention uses a precise surface processing technology, femtosecond laser, to treat the surface of the carburized sample, and efficiently prepares grooves with micro-nano structures on its surface. These structures have been proven to significantly enhance the bonding ability, erosion resistance, and thermal shock resistance of the tantalum base and diamond.

[0012] On the basis of the above technical solution, preferably, the tantalum substrate is a pure tantalum sheet or a tantalum alloy.

[0013] On the other hand, the present invention also provides a method for preparing a carbide transition layer-diamond layer composite layer structure, comprising the following steps:

[0014] S1, tantalum substrate surface polishing treatment;

[0015] S2, tantalum substrate carbonization treatment: placing the tantalum substrate in a reaction chamber of a microwave plasma chemical vapor deposition device, bombarding the substrate with hydrogen plasma to etch and remove surface impurities, and then introducing a carbon source gas to deposit a carbide gradient layer;

[0016] S3, placing the carburized tantalum substrate in a femtosecond laser device to etch a plurality of transverse and longitudinal intersecting grooves on the surface of the carbide gradient layer;

[0017] S4, placing the tantalum substrate after etching in step S3 into a reaction chamber of a microwave plasma chemical vapor deposition device, introducing a carbon source gas to deposit a diamond layer, and obtaining a composite layer of a carbide transition layer-diamond layer on the tantalum substrate.

[0018] On the basis of the above technical solution, preferably, in step S2, the reaction chamber is evacuated to below 1 Pa, 300 sccm of hydrogen is introduced, the microwave power is adjusted to 4250-5000 W, the cavity pressure is 18-22 KPa, and the temperature is 600-750°C. The substrate is bombarded with hydrogen plasma for 15-25 minutes to etch and remove impurities.

[0019] Based on the above technical solution, preferably, during the carbonization treatment in step S2, the microwave power is 4250-5000W, the deposition time is 3-6h, the carbonization deposition temperature is 850-1050°C, and the atomic percentage of carbon atoms in the reaction chamber is 0.5%-2%.

[0020] On the basis of the above technical solution, preferably, in step S3, the laser power is 10-15 W, the scanning period is 20-30 μm, the scanning speed is 5-8 mm / s, and the number of scans is 4-6 times.

[0021] Based on the above technical solution, preferably, in step S3, the groove depth is 4-6 μm.

[0022] Based on the above technical solution, preferably, in step S4, when the diamond layer is deposited, the atomic percentage of carbon atoms in the reaction chamber is 2.5%-5%, the cavity pressure is 8-10KPa, the microwave power is 4250-5000W, the deposition time is 4-8h, and the deposition temperature is 750-850℃.

[0023] The carbide transition layer-diamond layer composite layer structure and preparation method thereof of the present invention have the following beneficial effects compared with the prior art:

[0024] (1) First, the present invention utilizes the activation, diffusion, and sputtering effects of microwave plasma to perform efficient plasma carbonization on the substrate, producing a carbide layer with a gradient composition distribution and a smooth structural transition on the substrate surface. The surface of the carbide layer provides C—C bonds that can tightly bond with the diamond layer at the atomic level, thereby achieving a high bonding strength between the substrate material and the diamond layer. At the same time, since the thermal expansion coefficient of the carbide layer is between that of the film base, it exhibits a gradient change, which can reduce the internal stress of the film base.

[0025] (2) Secondly, the present invention uses femtosecond laser technology to form a highly ordered micro-nano structure in the carburized transition layer. On the one hand, it improves the deposition and adhesion of carbon atoms, avoiding the density difference and pollution problems caused by the traditional physical and chemical methods of increasing diamond deposition and adhesion, and greatly improves the nucleation density of the diamond film and the film-base bonding strength. On the other hand, it realizes the micro-interlocking of the carbide layer and the diamond, and the carbide and diamond at the interface are staggered and the dislocation increases, thereby achieving interface strengthening, which can effectively buffer the long-term severe friction and impact experienced by the surface during the use of the force effect, and prevent cracks from extending to the substrate; under the thermal effect environment, the temperature of the component will rise sharply, of which about one-fifth of the heat is absorbed by the workpiece material, and the thermal action time is 10 microseconds. The heat on the workpiece surface has no time to transfer outward. Due to the large difference in thermal expansion coefficient between the film and the substrate, there is a large temperature gradient, and the resulting thermal stress will cause the diamond film to fall off. The micro-nanostructure of the carburized transition layer prepared by the present invention can increase the heat transfer area between the film and the substrate, improve the heat dissipation efficiency, alleviate the thermal conductivity difference between metal and diamond, reduce the resulting thermal stress, and thus improve the overall thermal shock resistance.

[0026] (3) Finally, the present invention utilizes microwave plasma chemical vapor deposition, which uses waveguides to transmit plasma generated by microwave excitation, and there is no impurity source in the synthesis process. By regulating the process parameters for depositing diamond films, the diamond films efficiently prepared have the advantages of high quality purity and no pollution. At the same time, the microwave deposition temperature is relatively low, so the thermal mismatch between the epitaxial layer and the substrate and the resulting stress are small. Combined with the multilayer structure of nano-scale grains prepared by the present invention, it is beneficial to reduce the internal stress of the film layer and improve the hardness of the film layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0028] Figure 1 This is a schematic diagram of the preparation process of the composite layer of carbide transition layer-diamond layer of the present invention, Figure (a) is the tantalum substrate, Figure (b) is the carburizing treatment, Figure (c) is the femtosecond laser etching, and Figure (d) is the deposited diamond layer. DETAILED DESCRIPTION

[0029] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0030] The carbide transition layer / diamond layer composite structure of the present invention includes a tantalum substrate, a carbide gradient layer deposited on the surface of the tantalum substrate by microwave plasma chemical deposition, grooves subsequently etched into the surface of the deposited carbide gradient layer by femtosecond laser equipment, and then a diamond layer deposited on the surface of the carbide gradient layer by microwave plasma chemical deposition to obtain a carbide transition layer-diamond layer composite layer. The specific preparation method is described in detail in the following examples.

[0031] Example 1

[0032] The carbide transition layer / diamond layer composite layer structure and its preparation method in this embodiment include the following steps:

[0033] S1. Tantalum substrate and surface grinding and polishing. The tantalum substrate used in the present invention has a size of 13.5 mm × 13.5 mm × 2.7 mm (length, width, and thickness), but is not limited to tantalum substrates of other specific sizes. The purity level of the tantalum substrate is 3N5 or above, with a purity of 99.95% or above, and the total metal impurity content does not exceed 500 ppm. The material of the tantalum substrate is not limited to pure tantalum, and includes a series of tantalum alloys, such as Ta-2.5W, Ta-10W, and Ta-40Nb. In this embodiment, pure tantalum sheets are used. The sample surface is polished with sandpaper of 240, 400, 800, 1000, 1500, 2000, 3000, 5000, and 7000 mesh, and then polished with polishing cloth of 9, 3, 1, and 0.05 μm, respectively, to obtain a tantalum substrate with a mirror surface. The grinding and polishing standards for the samples are shown in GB / T 13298-2015.

[0034] S2, carbonization treatment of the tantalum substrate: the tantalum substrate treated in step S1 is placed in the reaction chamber of a microwave plasma chemical vapor deposition device, and the reaction chamber is wiped with anhydrous ethanol and dried with helium before use. Then, the reaction chamber is vacuumed to below 1 Pa, 300 sccm of hydrogen is introduced, the microwave power is adjusted to 5000 W, the cavity pressure is maintained at 22 KPa, the temperature is controlled at 750°C, and the substrate is bombarded by hydrogen plasma for 20 min to etch and further remove impurities on the surface. Then, a carbon source gas is introduced, and the gas flow is adjusted to deposit a carbide gradient layer. The microwave power is 5000 W, the deposition time is 6 h, the carbonization deposition temperature is 1050°C, and the atomic percentage of carbon in the mixed gas in the reaction chamber is 2%. A carbide gradient layer is obtained on the surface of the tantalum, and the content of C atoms in the carbide layer gradually decreases in the direction close to the tantalum surface. The carbide gradient layer is TaC and Ta2C.

[0035] S3, femtosecond laser surface pretreatment of the carburized sample: the carburized sample treated in step S2 is placed in a femtosecond laser device to prepare a well-shaped papillary periodic micro-nano structure array with a depth of 6 μm and an aspect ratio of 2-2.5 using laser parameters of 15 W laser power, 30 μm scanning period, 8 mm / s scanning speed, and 6 scanning times.

[0036] S4, deposition of diamond layer on the carbonized layer of tantalum: the tantalum substrate sample with the generated carbide layer after step S2 treatment is not removed, the flow rate of the carbon source gas is adjusted so that the atomic percentage of carbon in the mixed gas in the reaction chamber is 5%, and the deposition of the diamond layer is carried out. The cavity pressure is maintained at 10 KPa, the microwave power is 5000 W, the deposition time is 8 h, and the carbonization deposition temperature is 850°C. A carbide transition layer / diamond layer composite layer is obtained on the tantalum substrate. The carbon source gas and microwave power are turned off, hydrogen is continuously introduced to cool the reaction system to room temperature at a rate of 15°C / min, and finally the hydrogen is turned off. After adjusting the gas pressure in the reaction chamber to atmospheric pressure, the sample is removed.

[0037] Example 2

[0038] The carbide transition layer / diamond layer composite layer structure and its preparation method of this embodiment include the following steps:

[0039] S1, polishing and polishing treatment of the tantalum substrate and its surface same as in the example.

[0040] S2, carbonization treatment of the tantalum substrate: The tantalum substrate treated in step S1 is placed in a reaction chamber of a microwave plasma chemical vapor deposition device. Prior to this, the reaction chamber needs to be wiped with anhydrous ethanol and blown dry with helium. Then, the reaction chamber is evacuated to below 1 Pa, 300 sccm of hydrogen is introduced, the microwave power is adjusted to 4500 W, the chamber pressure is maintained at 20 kPa, and the temperature is controlled at 700°C. The substrate is bombarded with hydrogen plasma for 20 minutes to etch and further remove surface impurities. Subsequently, a carbon source gas is introduced and the gas flow rate is adjusted to deposit a carbide gradient layer. The microwave power is 4500 W, the deposition time is 4 hours, the carbonization deposition temperature is 950°C, and the atomic percentage of carbon atoms in the mixed gas in the reaction chamber is 1%. A carbide gradient layer is obtained on the tantalum surface, wherein the carbon atom content of the carbide layer gradually decreases as it approaches the tantalum surface, and the carbide gradient layer is composed of TaC and Ta2C.

[0041] S3, femtosecond laser surface pretreatment of the carburized sample: the carburized sample treated in step S2 is placed in a femtosecond laser device, and a papillary periodic micro-nanostructure array with a depth of 5 μm and an aspect ratio of 2.25 is prepared with laser parameters of 12 W laser power, 25 μm scanning period, 6 mm / s scanning speed, and 5 scanning times.

[0042] S4, deposition of a diamond layer on the carbide layer of tantalum: The tantalum substrate sample with a carbide layer generated on the surface after treatment in step S2 does not need to be removed. The flow rate of the carbon source gas is adjusted so that the atomic percentage of carbon atoms in the mixed gas in the reaction chamber is 3%, and the diamond layer is deposited. The cavity pressure is maintained at 9 kPa, the microwave power is 4500 W, the deposition time is 6 hours, and the carbonization deposition temperature is 800 ° C. A composite layer of a carbide transition layer / diamond layer is obtained on the tantalum substrate. The carbon source gas and microwave power are turned off, and hydrogen is continued to be introduced to cool the reaction system to room temperature at a rate of 15 ° C / min. Finally, the hydrogen is turned off, the pressure in the reaction chamber is adjusted to atmospheric pressure, and the sample is removed.

[0043] Example 3

[0044] The carbide transition layer / diamond layer composite layer structure and its preparation method in this embodiment include the following steps:

[0045] S1, the tantalum substrate and its surface grinding and polishing treatment are the same as in the embodiment.

[0046] S2, carbonization treatment of the tantalum substrate: the tantalum substrate treated in step S1 is placed in the reaction chamber of a microwave plasma chemical vapor deposition device, and the reaction chamber is wiped with anhydrous ethanol and dried with helium before use. Then, the reaction chamber is vacuumed to below 1 Pa, 300 sccm of hydrogen is introduced, the microwave power is adjusted to 4250 W, the cavity pressure is maintained at 18 KPa, and the temperature is controlled at 600°C. The substrate is bombarded by hydrogen plasma for 20 min to etch and further remove impurities on the surface. Then, a carbon source gas is introduced, and the gas flow is adjusted to deposit a carbide gradient layer. The microwave power is 425 W, the deposition time is 3 h, the carbonization deposition temperature is 850°C, and the atomic percentage of carbon in the mixed gas in the reaction chamber is 0.5%. A carbide gradient layer is obtained on the surface of the tantalum, and the content of C atoms in the carbide layer gradually decreases in the direction close to the tantalum surface. The carbide gradient layer is TaC and Ta2C.

[0047] S3, femtosecond laser surface pretreatment of the carburized sample: the carburized sample treated in step S2 is placed in a femtosecond laser device to prepare a papillary periodic micro-nano structure array with a depth of 4 μm and an aspect ratio of 2 using laser parameters of a laser power of 10 W, a scanning period of 20 μm, a scanning speed of 5 mm / s, and a scanning number of 4 times.

[0048] S4, deposition of a diamond layer on the carbonized layer of tantalum: the tantalum substrate sample with a carbide layer generated on the surface after step S2 is not removed, the flow of the carbon source gas is adjusted so that the atomic percentage of carbon in the mixed gas in the reaction chamber is 2.5%, and the deposition of a diamond layer is performed. The cavity pressure is maintained at 8 KPa, the microwave power is 4250 W, the deposition time is 4 h, and the carbonization deposition temperature is 750°C. A carbide transition layer / diamond layer composite layer is obtained on the tantalum substrate. The carbon source gas and the microwave power are turned off, hydrogen is continuously introduced to cool the reaction system to room temperature at a rate of 15°C / min, and finally the hydrogen is turned off. After adjusting the gas pressure in the reaction chamber to atmospheric pressure, the sample is removed.

[0049] Example 4

[0050] Example 4 differs from Example 1 in that the tantalum substrate is Ta-2.5W tantalum alloy.

[0051] Example 5

[0052] Example 5 differs from Example 2 in that the tantalum substrate is Ta-2.5W tantalum alloy.

[0053] Example 6

[0054] Example 6 differs from Example 3 in that the tantalum substrate is Ta-2.5W tantalum alloy.

[0055] Comparative Example 1

[0056] The difference between Comparative Example 1 and Example 1 is that S2 and S3 steps are absent, and the diamond layer is directly deposited on the surface of the pure tantalum sheet.

[0057] Comparative Example 2

[0058] The difference between Comparative Example 2 and Example 1 is that S3 step is absent, and the diamond layer is directly deposited on the carbide gradient layer.

[0059] Comparative Example 3

[0060] The difference between Comparative Example 3 and Example 1 is that S3 and S4 steps are absent, and only the carbide gradient layer is deposited on the surface of the pure tantalum sheet.

[0061] Comparative Example 4

[0062] The difference between Comparative Example 4 and Example 6 is that S2 and S3 steps are absent, and only the diamond layer is deposited on the surface of the Ta-2.5W tantalum alloy.

[0063] Comparative Example 5

[0064] The difference between Comparative Example 5 and Example 6 is that S3 step is absent, and the diamond layer is directly deposited on the carbide gradient layer.

[0065] Comparative Example 6

[0066] The difference between Comparative Example 6 and Example 6 is that S3 and S4 steps are absent, and only the carbide gradient layer is deposited on the surface of the Ta-2.5W tantalum alloy.

[0067] The materials prepared in the above examples and comparative examples were subjected to nanoindentation hardness testing, solid particle erosion testing of coating adhesion, friction coefficient testing, and thermal shock resistance testing, and the test results are shown in Table 1, and the test methods are as follows:

[0068] Microhardness testing: A Bruker TI980 TriboIndenter nanoindenter was used, with a tip radius of about 50 nm, a load and displacement resolution of 1 μN and 0.03 nm, respectively, and a 10-second holding time between loading and unloading cycles. To avoid errors, each sample was measured 5 times and the average value was taken.

[0069] Solid particle erosion testing of coating adhesion: The anti-erosion performance of the diamond coating was determined by repeatedly impacting solid particles on the surface of the workpiece, thereby gradually removing the coating material from the surface of the substrate. The erosion time was 150 s, and the anti-erosion performance of the diamond coating was determined by microscopic observation and measurement of the erosion width size of the diamond coating. The smaller the erosion width, the greater the adhesion.

[0070] Friction coefficient test: the linear reciprocating friction and wear test of the substrate and the sample after nitriding treatment was performed by using Rtec MFT-5000 type friction and wear tester, the friction and wear test used GCr15 steel ball with a diameter of 6 mm, set the normal load to 5 N, the friction rate to 0.032 m / s, the amplitude to 5 mm, and the friction time to 1800 s.

[0071] Thermal shock resistance test: the thermal shock cycle test of the coating sample from room temperature to 1273 K was performed by using vertical tube furnace, before the test, the coating sample to be tested was dried for 4 h by using a drying oven, and after cooling, the weight was measured by using an electronic analytical balance with a precision of 0.0001 g, after the temperature of the tube furnace was raised to 1273 K and kept for 30 min to ensure uniform temperature, the sample was quickly put into the furnace for 5 min and then taken out immediately, and placed in the air environment for cooling for 5 min, which was 1 thermal shock cycle. After 5 times of continuous thermal shock cycle, the sample was cooled and weighed, and the cycle was repeated, so that the weight loss curve of the sample after a certain number of thermal shock cycles was obtained, and the thermal shock resistance of the coating sample was judged by the weight loss of the coating sample.

[0072] Table 1: Coating performance test results

[0073]

[0074] As shown in Table 1, compared with Comparative Example 1, the hardness of the carbide transition layer / diamond layer composite layer sample of Examples 1-7 was increased by 259%-331%, the coating adhesion was increased by 290%-342%, the friction coefficient was reduced to one sixth, and the thermal shock weight loss was reduced to one half, indicating that the preparation method of the present application can significantly improve the hardness, coating adhesion and anti-erosion of the material, while the friction coefficient is also significantly reduced, and the thermal shock resistance is obviously improved.

[0075] The surface carburizing treatment of tantalum and its alloy is helpful for the next step of diamond deposition, and it is easier to form diamond film with high quality and large thickness, and the transition of carbon element is beneficial to the stability of the overall material, improves the mechanical properties, reduces the friction coefficient, and improves the thermal shock resistance. In Comparative Example 1, there is no carburizing transition layer structure, the bonding between diamond and tantalum substrate mainly depends on the weak surface contact, and the atomic level bonding is not achieved, the bonding strength is insufficient, and the interface may fall off or delaminate, resulting in a significant decrease in the coating adhesion. In addition, the diamond-tantalum surface contact forms a micro-layered structure, and there is a large difference in physical and chemical properties between the diamond layer and the tantalum substrate, which will cause stress when subjected to thermal and mechanical effects in the test environment, resulting in insufficient overall coating adhesion. At the same time, the adhesion rate of diamond deposition is very low, and it is difficult to nucleate and grow, resulting in poor quality of diamond film, thereby reducing the density and hardness of the material.

[0076] In Comparative Example 2, the carburized layer was not laser processed, resulting in no micro-nanostructure formation within the carburized layer. Consequently, the interlocking microstructure with the diamond layer was lost. The insufficient overall material density and the absence of a stress buffer zone resulted in micropores and defects in the coating's microstructure, which failed to mitigate thermal shock and shock. This reduced hardness and coating adhesion in the test environment, leading to decreased thermal shock resistance. Furthermore, insufficient density increases the likelihood of wear and surface unevenness during friction, increasing the coefficient of friction.

[0077] The present invention couples the advantages of femtosecond laser precision processing technology and microwave plasma chemical vapor deposition technology, proposes a structural design for a film-based transition layer, and the prepared carbide transition layer / diamond layer composite layer structure has a structure with a gradual composition gradient; by introducing a micro-nanoscale pretreatment process, the highly ordered surface micro-nanostructure greatly enhances the film-based bonding strength, alleviates the impact of thermal effects during the use of the material, realizes the transition of the film-based physicochemical properties, reduces internal stress, enhances bonding strength, and has excellent thermal shock resistance, thereby preparing a dense and smooth surface and ultra-high hardness diamond film.

[0078] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a composite layer structure of a carbide transition layer and a diamond layer, characterized in that: The following steps are involved: S1, tantalum substrate surface polishing treatment; S2, carbonization treatment of the tantalum substrate: placing the tantalum substrate in a reaction chamber of a microwave plasma chemical vapor deposition device, bombarding the substrate with hydrogen plasma to etch and remove surface impurities, and then introducing a carbon source gas to deposit a carbide gradient layer to obtain a carbide gradient layer; the carbon atom content in the carbide gradient layer gradually decreases toward the tantalum substrate; S3, placing the carburized tantalum substrate in a femtosecond laser device to etch a plurality of transverse and longitudinal intersecting grooves on the surface of the carbide gradient layer; S4, placing the tantalum substrate after etching in step S3 into a reaction chamber of a microwave plasma chemical vapor deposition device, introducing a carbon source gas to deposit a diamond layer, and obtaining a composite layer of a carbide transition layer-diamond layer on the tantalum substrate.

2. The method for preparing a composite layer structure of a carbide transition layer and a diamond layer according to claim 1, characterized in that: The carbide gradient layer comprises TaC and Ta2C.

3. The method for preparing a composite layer structure of a carbide transition layer and a diamond layer according to claim 1, wherein: The tantalum substrate is a pure tantalum sheet or a tantalum alloy.

4. The method for preparing a composite layer structure of a carbide transition layer and a diamond layer according to claim 1, wherein: In step S2, when bombarding the substrate with hydrogen plasma to etch and remove surface impurities, the reaction chamber is evacuated to below 1 Pa, 300 sccm of hydrogen is introduced, the microwave power is adjusted to 4250-5000 W, the cavity pressure is 18-22 kPa, and the temperature is 600-750°C. The substrate is bombarded with hydrogen plasma for 15-25 minutes to etch and remove impurities.

5. The method for preparing a composite layer structure of a carbide transition layer and a diamond layer according to claim 1, wherein: In step S2, when the carbon source gas is introduced to deposit the carbide gradient layer, the microwave power is 4250-5000 W, the deposition time is 3-6 h, the deposition temperature is 850-1050 °C, and the atomic percentage of carbon atoms in the reaction chamber is 0.5%-2%.

6. The method for preparing a composite layer structure of a carbide transition layer and a diamond layer according to claim 1, characterized in that: In step S3, the laser power is 10-15 W, the scanning period is 20-30 μm, the scanning speed is 5-8 mm / s, and the number of scans is 4-6 times.

7. The method for preparing a composite layer structure of a carbide transition layer and a diamond layer according to claim 1, characterized in that: In step S3, the groove depth is 4-6 μm.

8. The method for preparing a composite layer structure of a carbide transition layer and a diamond layer according to claim 1, characterized in that: In step S4, when the diamond layer is deposited, the atomic percentage of carbon atoms in the reaction chamber is 2.5%-5%, the chamber pressure is 8-10 kPa, the microwave power is 4250-5000 W, the deposition time is 4-8 h, and the deposition temperature is 750-850 °C.

9. A composite layer structure of a carbide transition layer and a diamond layer, characterized in that: Prepared by the preparation method according to any one of claims 1 to 8.

Images