A preparation process of diamond composite sheet

Abstract

The invention relates to the technical field of superhard composite materials and discloses a preparation process of a diamond composite sheet. Diamond micropowder is cleaned, preheated and then subjected to plasma etching treatment to obtain treated diamond micropowder, which is then mixed evenly with carbon nanotubes and a binder to obtain a mixed powder, which is spread on the surface of a pretreated cemented carbide substrate, pressed into blocks, subjected to vacuum heat treatment, sintered and subjected to vacuum aging annealing to obtain a diamond composite sheet precursor, which is then cleaned, surface-plated with Ti and polished to obtain a diamond composite sheet. The mixed powder in the diamond composite sheet has good bonding performance with the pretreated cemented carbide substrate, and the obtained composite material has excellent compactness and uniformity. After cleaning, surface-plated with Ti and polished, the surface finish and flatness of the substrate are improved, and the diamond composite sheet has excellent impact resistance, hardness and wear resistance.

Description

Technical Field

[0001] The invention relates to the technical field of superhard composite materials, in particular to a preparation process of a diamond composite sheet. Background Art

[0002] Diamond is the hardest substance known in nature, with a high melting point, excellent thermal conductivity, stable chemical properties, and low expansion coefficient and friction coefficient. Diamond composite sheets are generally made of diamond layers and cemented carbide substrates sintered under ultra-high temperature and high pressure. They are a composite material with excellent performance. They have both the physical and chemical properties of diamond and the high impact resistance and good processability of cemented carbide. They are widely used in geological exploration, oil extraction, mechanical processing and other fields.

[0003] The spherical diamond composite sheet in the diamond composite sheet can be applied to a variety of formation conditions due to its unique shape, especially medium-hard to hard formations. The special shape can better adapt to the complexity and heterogeneity of the rock formation, reduce the resistance and wear during the drilling process, more effectively break the rock formation during the drilling process, cut the rock formation at high speed, improve the drilling speed and drilling efficiency, and have significant advantages in spherical cutting and complex terrain drilling. However, its preparation process is relatively complicated, and the problem of uneven mixing of diamond particles and matrix materials is prone to occur during the preparation process, and the problem of impact fracture will occur during use, which limits the application of spherical diamond composite sheets. Therefore, it is of great research value to develop a diamond composite sheet in which diamond particles and matrix materials are evenly mixed and have excellent impact resistance, hardness and wear resistance. Summary of the invention

[0004] 1. Technical issues to be resolved

[0005] In view of the deficiencies in the prior art, the present invention provides a high water-retention bonding mortar and a preparation method and application thereof, which solve the problems of poor impact strength and uneven dispersion of diamond composite sheets.

[0006] (II) Technical solution

[0007] In order to achieve the above object, the present invention discloses a process for preparing a diamond composite sheet, comprising the following steps:

[0008] Step (1), cleaning and drying the diamond micropowder to obtain pre-treated diamond micropowder;

[0009] Step (2), preheating the pretreated diamond micropowder, and then performing plasma etching treatment to obtain treated diamond micropowder;

[0010] Step (3), mixing the treated diamond powder, carbon nanotubes and binder uniformly to obtain a mixed powder, spreading it on the surface of the pretreated cemented carbide substrate, pressing it into blocks, performing vacuum heat treatment, sintering and vacuum aging annealing to obtain a diamond composite sheet precursor;

[0011] Step (4), cleaning the diamond composite sheet precursor, coating the surface with Ti, and polishing the surface to obtain a diamond composite sheet.

[0012] Preferably, the specific steps in step (1) are as follows: ultrasonically clean the diamond micropowder using 1 mol / L hydrochloric acid solution, 2 mol / L sodium hydroxide solution and anhydrous ethanol respectively, with the cleaning time being 15-30 min respectively, then wash with deionized water, and dry at 60° C. for 6 h to obtain pretreated diamond micropowder.

[0013] Preferably, the diamond micropowder in step (1) is composed of a first diamond micropowder with a particle size of 5-10 μm and a second diamond micropowder with a particle size of 15-25 μm, wherein the mass ratio of the first diamond micropowder to the second diamond micropowder is 1:10.

[0014] Preferably, the specific steps in step (2) are as follows: preheating the pretreated diamond powder at a temperature of 750-900°C, placing it on a deposition table in a microwave plasma chemical vapor deposition device under vacuum conditions, setting the microwave power to 1800-4500W, controlling the cavity pressure to 8-18kPa, applying a negative bias voltage of -150V to -300V, using a mixed gas of Ar, H2 and O2 as a carrier gas, wherein the carrier gas composition is 12-20% by volume H2 and 2-4% by volume O2, and the remainder is Ar, performing plasma etching treatment, and the plasma etching treatment time is 30-40min to obtain treated diamond powder.

[0015] Preferably, in step (3), the binder is composed of cobalt powder and vanadium powder in a mass ratio of 4:1.

[0016] Preferably, the specific steps in step (3) are as follows: the treated diamond powder, carbon nanotubes and binder are mixed evenly in a mass ratio of 100:1-3:10-20 to obtain a mixed powder, which is spread on the surface of the pretreated cemented carbide substrate, pressed into blocks, and subjected to vacuum heat treatment, with an absolute vacuum degree of 28-30 kPa, a temperature of 650-700°C, and a vacuum heat treatment time of 1-2 h. After the vacuum heat treatment is completed, a six-sided press is used to sinter at 1350-1450°C for 4-6 min, and then vacuum aging annealing is performed to obtain a diamond composite sheet precursor.

[0017] Preferably, the specific pretreatment steps of pretreating the cemented carbide substrate in step (3) are as follows: ultrasonically cleaning the cemented carbide substrate using 1 mol / L nitric acid solution, 2 mol / L sodium hydroxide solution and acetone, respectively, for 10-15 min, then washing with deionized water, and then ultrasonically washing with a cleaning agent for 30 min, wherein the cleaning agent is composed of polyoxyethylene alkylphenol ether, sodium dodecylbenzene sulfonate and deionized water in a mass ratio of 100:135:1500, and drying with nitrogen blowing to obtain a pretreated cemented carbide substrate.

[0018] Preferably, the cemented carbide substrate is WC-13%Co cemented carbide.

[0019] Preferably, the specific steps in step (4) are as follows: washing the diamond composite sheet precursor with acetone, soaking the diamond composite sheet precursor in acetone for 30-60 minutes, ultrasonically washing with deionized water for 15 minutes, ultrasonically washing with 2 mol / L sodium hydroxide solution for 30 minutes, and then washing with deionized water until neutral, drying, to obtain a clean diamond composite sheet precursor, coating the surface of the clean diamond composite sheet precursor with Ti by vacuum magnetron sputtering, placing the clean diamond composite sheet precursor in a magnetron sputtering coating machine, introducing Ar, and using pure metallic titanium with a purity higher than 99.99% as a target material, vacuum magnetron sputtering coating is performed on the surface of the clean diamond composite sheet precursor, wherein the vacuum degree of the reaction chamber is 10 -4 Pa, Ar partial pressure is 10 -1 Pa, the ion deposition rate is 20nm / min, and the coating thickness is controlled at 0.5-0.8μm. After the plating is completed, a coated diamond composite sheet is obtained, and then polishing is performed. First, the coated diamond composite sheet is ultrasonically cleaned with anhydrous ethanol. After ultrasonic treatment for 15 minutes, abrasive paste and nickel powder are used as abrasives for polishing in a polishing disk. The rotation speed of the polishing disk is 3000r / min. After polishing for 8 minutes, a diamond composite sheet is obtained.

[0020] 3. Beneficial technical effects

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] (1) In the present invention, the diamond powder is first treated and ultrasonically cleaned. Acid washing, alkali washing, alcohol washing and water washing are used respectively to effectively remove the attachments, oil stains and tiny particles on the surface of the diamond powder, improve the surface cleanliness, and at the same time improve the dispersibility and wettability of the diamond powder, enhance the surface activity of the diamond powder, and enable more uniform dispersion. The preheating treatment increases the temperature of the diamond powder, removes a small amount of gas and moisture adsorbed on the surface, and reduces pores and defects during the deposition process. A mixed gas of Ar, H2 and O2 is used as a carrier gas for plasma etching treatment, wherein Ar is used as an inert gas and a main gas source to adjust the plasma discharge and density, and H2 is used as a CC bond reaction etching gas to etch the protrusions and non-diamond phases on the surface of the diamond powder; O2 is used as a strong oxidant to etch and remove the non-diamond phase and organic impurities remaining in the preparation of diamond powder. The mixed gas can further clean the surface of the diamond powder, remove fine pollutants and residues, and further improve its bonding strength and interface quality with the matrix material.

[0023] (2) In the present invention, by using two kinds of diamond micropowders with a large difference in particle size, the gap between the powders with a smaller particle size can be filled with the powder with a larger particle size, so that the filling effect is more compact. In the process of powder sintering, the volume fraction of the diamond phase in the sintered diamond and the wear resistance of the diamond are guaranteed. More DD bonds are formed under ultra-high pressure, and larger grains are formed after sintering, thereby improving the fracture toughness of the material due to the increase in grain size, improving the impact resistance of the diamond composite sheet, and having excellent hardness and wear resistance, significantly improving the overall performance of the composite sheet. The cemented carbide substrate is cleaned with acid solution, alkaline solution, and acetone ultrasonically, which can effectively remove metal oxides, oil stains and other impurities on the surface of the substrate. The use of a detergent for washing can further remove stubborn stains and microscopic defects. It has excellent cleaning ability and permeability, can penetrate into the tiny pores on the surface of the substrate, and thoroughly remove dirt, thereby improving the bonding strength between the mixed powder and the cemented carbide substrate, thereby improving the performance and service life of the entire diamond composite sheet. The addition of carbon nanotubes can enhance the toughness and strength of the composite sheet, while improving its conductivity and thermal stability. The synergistic effect of carbon nanotubes and diamond powder helps to form a more uniform and dense microstructure. The use of cobalt powder as a binder has good formability and sintering properties, and can effectively bond diamond powder and carbon nanotubes together to form a solid composite. Furthermore, cobalt powder also has wear resistance, which helps to improve the cutting performance of the composite sheet. The addition of vanadium powder can further improve the strength and hardness of the binder, while increasing its high temperature resistance and corrosion resistance. The synergistic effect of the two not only ensures good bonding performance, but also improves the strength and hardness of the composite sheet. The resulting composite material has excellent density and uniformity.

[0024] (3) The diamond composite sheet precursor is washed in the present invention, which can effectively remove organic pollutants such as grease and dirt on the surface of the diamond composite sheet precursor, and provide a clean substrate for subsequent plating and polishing. A Ti coating is formed on the substrate, and a good metallurgical bond can be formed between the Ti coating and the diamond composite sheet precursor. The TiC layer generated by the reaction with diamond is chemically bonded to the diamond, and has a strong bonding force, which is conducive to heat conduction, and has good thermal stability. It can maintain stable performance at high temperatures and has extremely high hardness. It can effectively prevent the diamond composite sheet from being worn and scratched during use, improve the adhesion and stability of the coating, and thus extend its service life. Polishing can improve the surface finish, remove minor flaws and scratches on the surface of the coated diamond composite sheet, improve the surface finish and flatness, and further improve the surface roughness and friction coefficient of the diamond composite sheet. The resulting diamond composite sheet has excellent impact resistance, hardness and wear resistance. DETAILED DESCRIPTION

[0025] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than 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 work are within the scope of protection of the present invention.

[0026] Embodiment 1, a process for preparing a diamond composite sheet, comprising the following steps:

[0027] (1) using 1 mol / L hydrochloric acid solution, 2 mol / L sodium hydroxide solution and anhydrous ethanol to ultrasonically clean the diamond micropowder for 15 min respectively, wherein the diamond micropowder is composed of a first diamond micropowder with a particle size of 5-10 μm and a second diamond micropowder with a particle size of 15-25 μm, wherein the mass ratio of the first diamond micropowder to the second diamond micropowder is 1:10, then washing with deionized water, and drying at 60° C. for 6 h to obtain pretreated diamond micropowder;

[0028] (2) Preheating the pretreated diamond powder at a temperature of 750°C. After the preheating, the powder was placed on a deposition table in a microwave plasma chemical vapor deposition device under vacuum conditions. The microwave power was set to 1800W, the cavity pressure was controlled at 8kPa, a negative bias voltage was applied, and the bias voltage was -150V. A mixed gas of Ar, H2 and O2 was used as a carrier gas. The carrier gas composition was 12% by volume H2 and 2% by volume O2, and the remainder was Ar. Plasma etching was performed for 30 minutes to obtain treated diamond powder.

[0029] (3) The cemented carbide substrate was ultrasonically cleaned with 1 mol / L nitric acid solution, 2 mol / L sodium hydroxide solution and acetone, respectively. The cemented carbide substrate was WC-13%Co cemented carbide. The cleaning time was 10 min, and then it was washed with deionized water. Then, it was ultrasonically cleaned with a cleaning agent for 30 min. The cleaning agent was composed of polyoxyethylene alkylphenol ether, sodium dodecylbenzene sulfonate and deionized water in a mass ratio of 100:135:1500. It was dried with nitrogen gas to obtain a pretreated cemented carbide substrate.

[0030] (4) The treated diamond powder, carbon nanotubes and binder in a mass ratio of 100:1:10 are mixed evenly to obtain a mixed powder, wherein the binder is composed of cobalt powder and vanadium powder in a mass ratio of 4:1, spread on the surface of the pretreated cemented carbide substrate, pressed into blocks, and subjected to vacuum heat treatment. The absolute vacuum degree is 28 kPa, the temperature is 650°C, and the vacuum heat treatment time is 1 hour. After the vacuum heat treatment is completed, a six-sided press is used to sinter at 1350°C for 6 minutes, and then vacuum aging annealing is performed to obtain a diamond composite sheet precursor;

[0031] (5) Wash the diamond composite sheet precursor with acetone, soak the diamond composite sheet precursor in acetone for 30 minutes, then use deionized water for ultrasonic washing for 15 minutes, 2 mol / L sodium hydroxide solution for ultrasonic washing for 30 minutes, and then use deionized water to wash until neutral, dry, and obtain a clean diamond composite sheet precursor. Use vacuum magnetron sputtering to plate Ti on the surface of the clean diamond composite sheet precursor. Place the clean diamond composite sheet precursor in a magnetron sputtering coating machine, introduce Ar, and use pure metal titanium with a purity higher than 99.99% as a target material to vacuum magnetron sputter the surface of the clean diamond composite sheet precursor. The vacuum degree of the reaction chamber is 10 -4 Pa, Ar partial pressure is 10 -1 Pa, the ion deposition rate is 20nm / min, and the coating thickness is controlled at 0.5μm. After the plating is completed, a coated diamond composite sheet is obtained, and then polishing is performed. First, the coated diamond composite sheet is ultrasonically cleaned with anhydrous ethanol. After ultrasonic treatment for 15 minutes, abrasive paste and nickel powder are used as abrasives for polishing in a polishing disk. The rotation speed of the polishing disk is 3000r / min. After polishing for 8 minutes, a diamond composite sheet is obtained.

[0032] Embodiment 2, a process for preparing a diamond composite sheet, comprising the following steps:

[0033] (1) using 1 mol / L hydrochloric acid solution, 2 mol / L sodium hydroxide solution and anhydrous ethanol to ultrasonically clean the diamond micropowder for 25 min respectively, wherein the diamond micropowder is composed of a first diamond micropowder with a particle size of 5-10 μm and a second diamond micropowder with a particle size of 15-25 μm, wherein the mass ratio of the first diamond micropowder to the second diamond micropowder is 1:10, then washing with deionized water, and drying at 60° C. for 6 h to obtain pretreated diamond micropowder;

[0034] (2) The pretreated diamond powder was preheated at 850°C. After the preheating, it was placed on a deposition table in a microwave plasma chemical vapor deposition device under vacuum conditions. The microwave power was set to 4000W, the cavity pressure was controlled at 16kPa, a negative bias voltage was applied, and the bias voltage was -250V. A mixed gas of Ar, H2 and O2 was used as a carrier gas. The carrier gas composition was 18% by volume H2 and 3% by volume O2, and the remainder was Ar. Plasma etching was performed for 35 minutes to obtain treated diamond powder.

[0035] (3) The cemented carbide substrate was ultrasonically cleaned with 1 mol / L nitric acid solution, 2 mol / L sodium hydroxide solution and acetone, respectively. The cemented carbide substrate was WC-13%Co cemented carbide. The cleaning time was 14 min, and then it was washed with deionized water. Then, it was ultrasonically cleaned with a cleaning agent for 30 min. The cleaning agent was composed of polyoxyethylene alkylphenol ether, sodium dodecylbenzene sulfonate and deionized water in a mass ratio of 100:135:1500. It was dried with nitrogen gas to obtain a pretreated cemented carbide substrate.

[0036] (4) The treated diamond powder, carbon nanotubes and binder in a mass ratio of 100:2:18 are mixed evenly to obtain a mixed powder, wherein the binder is composed of cobalt powder and vanadium powder in a mass ratio of 4:1, spread on the surface of the pretreated cemented carbide substrate, pressed into blocks, and subjected to vacuum heat treatment. The absolute vacuum degree is 29 kPa, the temperature is 680°C, and the vacuum heat treatment time is 1.5 h. After the vacuum heat treatment is completed, a six-sided press is used to sinter at 1400°C for 5 min, and then vacuum aging annealing is performed to obtain a diamond composite sheet precursor;

[0037] (5) Wash the diamond composite sheet precursor with acetone, soak the diamond composite sheet precursor in acetone for 50 minutes, then use deionized water for ultrasonic washing for 15 minutes, 2 mol / L sodium hydroxide solution for ultrasonic washing for 30 minutes, and then use deionized water to wash until neutral, dry, and obtain a clean diamond composite sheet precursor. Use vacuum magnetron sputtering to plate Ti on the surface of the clean diamond composite sheet precursor. Place the clean diamond composite sheet precursor in a magnetron sputtering coating machine, introduce Ar, and use pure metal titanium with a purity higher than 99.99% as a target material to vacuum magnetron sputter the surface of the clean diamond composite sheet precursor. The vacuum degree of the reaction chamber is 10 -4 Pa, Ar partial pressure is 10 -1 Pa, the ion deposition rate is 20nm / min, and the coating thickness is controlled at 0.7μm. After the plating is completed, a coated diamond composite sheet is obtained, and then polishing is performed. First, the coated diamond composite sheet is ultrasonically cleaned with anhydrous ethanol. After ultrasonic treatment for 15 minutes, abrasive paste and nickel powder are used as abrasives for polishing in a polishing disk. The rotation speed of the polishing disk is 3000r / min. After polishing for 8 minutes, a diamond composite sheet is obtained.

[0038] Embodiment 3, a process for preparing a diamond composite sheet, comprising the following steps:

[0039] (1) using 1 mol / L hydrochloric acid solution, 2 mol / L sodium hydroxide solution and anhydrous ethanol to ultrasonically clean the diamond micropowder for 30 min respectively, wherein the diamond micropowder is composed of a first diamond micropowder with a particle size of 5-10 μm and a second diamond micropowder with a particle size of 15-25 μm, wherein the mass ratio of the first diamond micropowder to the second diamond micropowder is 1:10, then washing with deionized water, and drying at 60° C. for 6 h to obtain pretreated diamond micropowder;

[0040] (2) Preheating the pretreated diamond powder at a temperature of 900°C. After the preheating, the powder was placed on a deposition table in a microwave plasma chemical vapor deposition device under vacuum conditions. The microwave power was set to 4500W, the cavity pressure was controlled at 18kPa, a negative bias voltage was applied, and the bias voltage was -300V. A mixed gas of Ar, H2 and O2 was used as a carrier gas. The carrier gas composition was 20% by volume H2 and 4% by volume O2, and the remainder was Ar. Plasma etching was performed for 40 minutes to obtain treated diamond powder.

[0041] (3) The cemented carbide substrate was ultrasonically cleaned with 1 mol / L nitric acid solution, 2 mol / L sodium hydroxide solution and acetone, respectively. The cemented carbide substrate was WC-13%Co cemented carbide. The cleaning time was 15 min, and then it was washed with deionized water. Then, it was ultrasonically cleaned with a cleaning agent for 30 min. The cleaning agent was composed of polyoxyethylene alkylphenol ether, sodium dodecylbenzene sulfonate and deionized water in a mass ratio of 100:135:1500. It was dried with nitrogen gas to obtain a pretreated cemented carbide substrate.

[0042] (4) The treated diamond powder, carbon nanotubes and binder in a mass ratio of 100:3:20 are mixed evenly to obtain a mixed powder, wherein the binder is composed of cobalt powder and vanadium powder in a mass ratio of 4:1, spread on the surface of the pretreated cemented carbide substrate, pressed into blocks, and subjected to vacuum heat treatment. The absolute vacuum degree is 30 kPa, the temperature is 700 ° C, and the vacuum heat treatment time is 2 h. After the vacuum heat treatment is completed, a six-sided top press is used to sinter at 1450 ° C for 4 min, and then vacuum aging annealing is performed to obtain a diamond composite sheet precursor;

[0043] (5) Wash the diamond composite sheet precursor with acetone, soak the diamond composite sheet precursor in acetone for 60 minutes, then use deionized water for ultrasonic washing for 15 minutes, 2 mol / L sodium hydroxide solution for ultrasonic washing for 30 minutes, and then use deionized water to wash until neutral, dry, and obtain a clean diamond composite sheet precursor. Use vacuum magnetron sputtering to plate Ti on the surface of the clean diamond composite sheet precursor. Place the clean diamond composite sheet precursor in a magnetron sputtering coating machine, introduce Ar, and use pure metal titanium with a purity higher than 99.99% as a target material to perform vacuum magnetron sputtering coating on the surface of the clean diamond composite sheet precursor, wherein the vacuum degree of the reaction chamber is 10 -4 Pa, Ar partial pressure is 10 -1 Pa, the ion deposition rate is 20nm / min, and the coating thickness is controlled at 0.8μm. After the plating is completed, a coated diamond composite sheet is obtained, and then polishing is performed. First, the coated diamond composite sheet is ultrasonically cleaned with anhydrous ethanol. After ultrasonic treatment for 15 minutes, abrasive paste and nickel powder are used as abrasives for polishing in a polishing disk. The rotation speed of the polishing disk is 3000r / min. After polishing for 8 minutes, a diamond composite sheet is obtained.

[0044] Comparative Example 1, a process for preparing a diamond composite sheet, comprising the following steps:

[0045] (1) using 1 mol / L hydrochloric acid solution, 2 mol / L sodium hydroxide solution and anhydrous ethanol to ultrasonically clean the diamond micropowder for 25 min respectively, wherein the diamond micropowder is composed of a first diamond micropowder with a particle size of 5-10 μm and a second diamond micropowder with a particle size of 15-25 μm, wherein the mass ratio of the first diamond micropowder to the second diamond micropowder is 1:10, then washing with deionized water, and drying at 60° C. for 6 h to obtain pretreated diamond micropowder;

[0046] (2) The cemented carbide substrate was ultrasonically cleaned with 1 mol / L nitric acid solution, 2 mol / L sodium hydroxide solution and acetone, respectively. The cemented carbide substrate was WC-13%Co cemented carbide. The cleaning time was 14 min, and then it was washed with deionized water. Then, it was ultrasonically cleaned with a cleaning agent for 30 min. The cleaning agent was composed of polyoxyethylene alkylphenol ether, sodium dodecylbenzene sulfonate and deionized water in a mass ratio of 100:135:1500. It was dried with nitrogen gas to obtain a pretreated cemented carbide substrate.

[0047] (3) Pretreated diamond powder, carbon nanotubes and a binder in a mass ratio of 100:2:18 are mixed evenly to obtain a mixed powder, wherein the binder is composed of cobalt powder and vanadium powder in a mass ratio of 4:1, spread on the surface of the pretreated cemented carbide substrate, pressed into blocks, and subjected to vacuum heat treatment. The absolute vacuum degree is 29 kPa, the temperature is 680°C, and the vacuum heat treatment time is 1.5 h. After the vacuum heat treatment is completed, a six-sided press is used to sinter at 1400°C for 5 min, and then vacuum aging annealing is performed to obtain a diamond composite sheet precursor;

[0048] (4) Wash the diamond composite sheet precursor with acetone, soak the diamond composite sheet precursor in acetone for 50 minutes, then use deionized water for ultrasonic washing for 15 minutes, 2 mol / L sodium hydroxide solution for ultrasonic washing for 30 minutes, and then use deionized water to wash until neutral, dry, and obtain a clean diamond composite sheet precursor. Use vacuum magnetron sputtering to plate Ti on the surface of the clean diamond composite sheet precursor. Place the clean diamond composite sheet precursor in a magnetron sputtering coating machine, introduce Ar, and use pure metallic titanium with a purity higher than 99.99% as a target material to perform vacuum magnetron sputtering coating on the surface of the clean diamond composite sheet precursor, wherein the vacuum degree of the reaction chamber is 10 -4 Pa, Ar partial pressure is 10 -1Pa, the ion deposition rate is 20nm / min, and the coating thickness is controlled at 0.7μm. After the plating is completed, a coated diamond composite sheet is obtained, and then polishing is performed. First, the coated diamond composite sheet is ultrasonically cleaned with anhydrous ethanol. After ultrasonic treatment for 15 minutes, abrasive paste and nickel powder are used as abrasives for polishing in a polishing disk. The rotation speed of the polishing disk is 3000r / min. After polishing for 8 minutes, a diamond composite sheet is obtained.

[0049] Comparative Example 2, a process for preparing a diamond composite sheet, comprising the following steps:

[0050] (1) using 1 mol / L hydrochloric acid solution, 2 mol / L sodium hydroxide solution and anhydrous ethanol to ultrasonically clean the diamond micropowder for 25 min respectively, wherein the diamond micropowder is composed of a first diamond micropowder with a particle size of 5-10 μm and a second diamond micropowder with a particle size of 15-25 μm, wherein the mass ratio of the first diamond micropowder to the second diamond micropowder is 1:10, then washing with deionized water, and drying at 60° C. for 6 h to obtain pretreated diamond micropowder;

[0051] (2) The pretreated diamond powder was preheated at 850°C. After the preheating, it was placed on a deposition table in a microwave plasma chemical vapor deposition device under vacuum conditions. The microwave power was set to 4000W, the cavity pressure was controlled at 16kPa, a negative bias voltage was applied, and the bias voltage was -250V. A mixed gas of Ar, H2 and O2 was used as a carrier gas. The carrier gas composition was 18% by volume H2 and 3% by volume O2, and the remainder was Ar. Plasma etching was performed for 35 minutes to obtain treated diamond powder.

[0052] (3) The cemented carbide substrate was ultrasonically cleaned with 1 mol / L nitric acid solution, 2 mol / L sodium hydroxide solution and acetone, respectively. The cemented carbide substrate was WC-13%Co cemented carbide. The cleaning time was 14 min, and then it was washed with deionized water. Then, it was ultrasonically cleaned with a cleaning agent for 30 min. The cleaning agent was composed of polyoxyethylene alkylphenol ether, sodium dodecylbenzene sulfonate and deionized water in a mass ratio of 100:135:1500. It was dried with nitrogen gas to obtain a pretreated cemented carbide substrate.

[0053] (4) The treated diamond micropowder, carbon nanotubes and binder in a mass ratio of 100:2:18 are mixed evenly to obtain a mixed powder, wherein the binder is composed of cobalt powder and vanadium powder in a mass ratio of 4:1, spread on the surface of the pretreated cemented carbide substrate, pressed into blocks, and subjected to vacuum heat treatment. The absolute vacuum degree is 29 kPa, the temperature is 680°C, and the vacuum heat treatment time is 1.5 h. After the vacuum heat treatment is completed, a six-sided top press is used to sinter at 1400°C for 5 min, and then vacuum aging annealing is performed to obtain a diamond composite sheet.

[0054] Comparative Example 3, a process for preparing a diamond composite sheet, comprising the following steps:

[0055] (1) using 1 mol / L hydrochloric acid solution, 2 mol / L sodium hydroxide solution and anhydrous ethanol to ultrasonically clean the diamond micropowder for 25 min respectively, wherein the diamond micropowder is composed of a first diamond micropowder with a particle size of 5-10 μm and a second diamond micropowder with a particle size of 15-25 μm, wherein the mass ratio of the first diamond micropowder to the second diamond micropowder is 1:10, then washing with deionized water, and drying at 60° C. for 6 h to obtain pretreated diamond micropowder;

[0056] (2) The cemented carbide substrate was ultrasonically cleaned with 1 mol / L nitric acid solution, 2 mol / L sodium hydroxide solution and acetone, respectively. The cemented carbide substrate was WC-13%Co cemented carbide. The cleaning time was 14 min, and then it was washed with deionized water. Then, it was ultrasonically cleaned with a cleaning agent for 30 min. The cleaning agent was composed of polyoxyethylene alkylphenol ether, sodium dodecylbenzene sulfonate and deionized water in a mass ratio of 100:135:1500. It was dried with nitrogen gas to obtain a pretreated cemented carbide substrate.

[0057] (3) The treated diamond micropowder, carbon nanotubes and binder in a mass ratio of 100:2:18 were mixed evenly to obtain a mixed powder, wherein the binder consisted of cobalt powder and vanadium powder in a mass ratio of 4:1. The mixed powder was spread on the surface of the pretreated cemented carbide substrate, pressed into blocks, and subjected to vacuum heat treatment. The absolute vacuum degree was 29 kPa, the temperature was 680°C, and the vacuum heat treatment time was 1.5 h. After the vacuum heat treatment was completed, a six-sided press was used to sinter at 1400°C for 5 min, and then vacuum aging annealing was performed to obtain a diamond composite sheet.

[0058] The carbon nanotubes used in the examples and comparative examples of the present invention were purchased from Chengdu Organic Chemistry Co., Ltd., Chinese Academy of Sciences. They are multi-walled carbon nanotubes, model TNIM8, with a diameter of about 80 nm, a purity greater than 90%, and a length range of 20-30 μm.

[0059] The performance tests were performed on the diamond composite sheets prepared in Examples 1-3 and Comparative Examples 1-3:

[0060] (1) Impact resistance test: The gradient method is used. The specific test method is as follows: First, 10 samples are pre-tested to estimate the impact energy at 50% damage. On this basis, an energy close to the impact damage of the sample is selected, and the first sample is impacted to observe whether the sample is damaged. If it is damaged, the energy value △E is reduced and the second sample is impacted. If the second sample is not damaged, △E is increased again. This is repeated and at least 20 samples are impacted. The energy increment △E can be increased by 5%-15% according to the pre-test damage energy. E=H×g×M, M=M0+△M (A / N±0.5), A=Σn i z i , where M0 is the minimum drop weight of the experiment, △M is the increase in the drop weight mass, H is the drop height of the drop weight, g is the free acceleration, and N is the total number of samples that are destroyed or not destroyed n i In M i The number of damaged or undamaged specimens at the time of i is the number of times the mass increases starting from M0;

[0061] (2) Hardness test: Use the indentation method and Vickers hardness tester to test the Vickers hardness. The calculation formula is as follows: Hv=1854.4P / d 2 , where Hv is the Vickers hardness, P is the load, and d is the diagonal length of the indentation (μm), and the Vickers hardness is recorded;

[0062] (3) Wear resistance test: The test adopts the diamond wear ratio determination standard, and selects 80# grit ceramic bond silicon carbide flat grinding wheel (standard SiC grinding wheel C80#100mm×16mm×20mm), the grinding wheel speed is 25m / s, the worktable swing frequency is 0.58-0.67Hz, the grinding wheel wear is not less than 25mg, and the sample wear is not less than 0.2mg, where E=m s / m j , m s is the wear amount of the grinding wheel, m j is the wear amount of the specimen, E is the wear ratio;

[0063] The above test results are shown in Table 1:

[0064] Table 1

[0065]

[0066] According to the test results in Table 1, it can be seen that compared with Comparative Examples 1 to 3, Examples 1 to 3 have excellent impact resistance, high hardness, and good wear resistance. In Comparative Example 1, the diamond powder after pretreatment was not subjected to plasma etching, and the obtained diamond composite sheet was not cleaned, surface plated with Ti, or polished in Comparative Example 2. In Comparative Example 3, the diamond powder after pretreatment was not subjected to plasma etching, and the obtained diamond composite sheet was not cleaned, surface plated with Ti, or polished, and the performance was reduced.

[0067] Although the embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that all equivalent changes and improvements made within the scope of the present invention should still fall within the scope of the patent coverage of the present invention.

Claims

1. A process for preparing a diamond composite sheet, characterized in that: The steps include: Step (1), cleaning and drying the diamond micropowder to obtain pre-treated diamond micropowder; Step (2), preheating the pretreated diamond micropowder, and then performing plasma etching treatment to obtain treated diamond micropowder; Step (3), mixing the treated diamond powder, carbon nanotubes and binder uniformly to obtain a mixed powder, spreading it on the surface of the pretreated cemented carbide substrate, pressing it into blocks, performing vacuum heat treatment, sintering and vacuum aging annealing to obtain a diamond composite sheet precursor; Step (4), cleaning the diamond composite sheet precursor, coating the surface with Ti, and polishing the surface to obtain a diamond composite sheet; In step (1), the diamond powder is composed of a first diamond powder with a particle size of 5-10 μm and a second diamond powder with a particle size of 15-25 μm, wherein the mass ratio of the first diamond powder to the second diamond powder is 1:10; The specific steps in step (2) are as follows: preheating the pretreated diamond micropowder at a temperature of 750-900°C, placing it on a deposition table in a microwave plasma chemical vapor deposition device under vacuum conditions, setting the microwave power to 1800-4500W, controlling the cavity pressure to 8-18kPa, applying a negative bias voltage of -150V to -300V, using a mixed gas of Ar, H2 and O2 as a carrier gas, wherein the carrier gas composition is 12-20% by volume H2 and 2-4% by volume O2, and the remainder is Ar, performing plasma etching treatment, and the plasma etching treatment time is 30-40min to obtain treated diamond micropowder; The specific steps in step (3) are as follows: mixing the treated diamond powder, carbon nanotubes and binder in a mass ratio of 100:1-3:10-20 to obtain a mixed powder, spreading it on the surface of the pretreated cemented carbide substrate, pressing it into blocks, and performing vacuum heat treatment at an absolute vacuum degree of 28-30 kPa, a temperature of 650-700° C., and a vacuum heat treatment time of 1-2 h. After the vacuum heat treatment is completed, sintering is performed at 1350-1450° C. for 4-6 min using a six-sided top press, and then vacuum aging annealing is performed to obtain a diamond composite sheet precursor; In step (3), the binder is composed of cobalt powder and vanadium powder in a mass ratio of 4:1; The specific pretreatment steps of pretreating the cemented carbide substrate in step (3) are as follows: ultrasonically cleaning the cemented carbide substrate with 1 mol / L nitric acid solution, 2 mol / L sodium hydroxide solution and acetone, respectively, for 10-15 min, then washing with deionized water, and then ultrasonically washing with a cleaning agent for 30 min, wherein the cleaning agent is composed of polyoxyethylene alkylphenol ether, sodium dodecylbenzene sulfonate and deionized water in a mass ratio of 100:135:1500, and drying with nitrogen gas to obtain a pretreated cemented carbide substrate; The specific steps in step (4) are as follows: washing the diamond composite sheet precursor with acetone, soaking the diamond composite sheet precursor in acetone for 30-60 minutes, ultrasonically washing with deionized water for 15 minutes, ultrasonically washing with 2 mol / L sodium hydroxide solution for 30 minutes, and then washing with deionized water until neutral, drying, to obtain a clean diamond composite sheet precursor, coating the surface of the clean diamond composite sheet precursor with Ti by vacuum magnetron sputtering, placing the clean diamond composite sheet precursor in a magnetron sputtering coating machine, introducing Ar, and using pure metal titanium with a purity higher than 99.99% as a target material to vacuum magnetron sputter coating the surface of the clean diamond composite sheet precursor, wherein the vacuum degree of the reaction chamber is 10 - 4 Pa, Ar partial pressure is 10 -1 Pa, the ion deposition rate is 20nm / min, and the coating thickness is controlled at 0.5-0.8μm. After the plating is completed, a coated diamond composite sheet is obtained, and then polishing is performed. First, the coated diamond composite sheet is ultrasonically cleaned with anhydrous ethanol. After ultrasonic treatment for 15 minutes, abrasive paste and nickel powder are used as abrasives for polishing in a polishing disk. The rotation speed of the polishing disk is 3000r / min. After polishing for 8 minutes, a diamond composite sheet is obtained.

2. The process for preparing a diamond composite sheet according to claim 1, characterized in that: The specific steps in step (1) are as follows: using 1 mol / L hydrochloric acid solution, 2 mol / L sodium hydroxide solution and anhydrous ethanol to ultrasonically clean the diamond micropowder, respectively, the cleaning time is 15-30 minutes, and then washing with deionized water, and drying at 60° C. for 6 hours to obtain pretreated diamond micropowder.

3. The process for preparing a diamond composite sheet according to claim 1, characterized in that: The cemented carbide substrate is WC-13%Co cemented carbide.

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