Novel method for preparing small-hole coating wire-drawing die

Abstract

The invention discloses a novel method for preparing a small-hole coating wire-drawing die, and relates to the technical field of coating wire-drawing die preparation, in particular to a device for preparing the small-hole coating wire-drawing die, which comprises a reaction furnace chamber, an exhaust passage, an air inlet mechanism, a wire-drawing cavity and a high-temperature ceramic tube, and a tungsten steel die core is placed in the high-temperature ceramic tube. The hot wire is arranged in the tungsten steel die core in the horizontal direction, the two ends of the hot wire extend to the outer side of the wire drawing cavity and are connected with the heat-resistant spring, the other side of the heat-resistant spring is connected with the heating electrode, reaction gas is introduced into the reaction furnace cavity, and the wire drawing die is prepared through a hot wire chemical vapor deposition method. A good diamond coating can be effectively grown in the small-hole die, the overall temperature is relatively concentrated, the diamond synthesis speed is increased, the overall performance of the wire drawing die is improved through the directional flowing air inlet effect of airflow, the interior of the high-temperature ceramic tube is annular, tungsten steel die cores can be automatically arranged in order, and the production efficiency is improved. And the positioning effect is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of coating wire drawing die preparation, in particular to a new method for preparing a coating wire drawing die with relatively small pores. Background Art

[0002] A wire drawing die is a tool used during metal pressure processing to compress the metal's cross-sectional area and obtain the desired cross-sectional shape and size. As the aperture of the wire drawing decreases, friction and wear accelerate, necessitating the use of a diamond coating with high hardness, high wear resistance, low friction coefficient, and high surface finish. However, the currently commonly used large-cavity coating growth method for dies with smaller apertures has significant drawbacks during the preparation of wire drawing die coatings. Due to the small aperture of the die and the high temperature of the hot wire, hot gas diffuses outward during the coating growth process, preventing the reactive gas from fully reaching the aperture, making it difficult to meet the optimal conditions for diamond synthesis. Consequently, high-quality coatings cannot be formed in small-aperture dies, limiting the performance and application range of related products.

[0003] Based on this, a new method for preparing a relatively small-pore coated wire drawing die is now provided, which can eliminate the disadvantages of the existing technical solutions. Summary of the Invention

[0004] The object of the present invention is to provide a new method for preparing a relatively small-pore coating drawing die, so as to solve the problem in the background art that it is difficult to form a good diamond coating on the existing small-pore die.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] A new method for preparing a small-pore coated wire drawing die uses a small-pore cemented carbide wire drawing die core with a pore diameter of 0.1 mm to 0.8 mm as a substrate. The die core surface is ultrasonically cleaned with acetone, alkali solution, and deionized water to remove oil, impurities, and oxides. After pretreatment with dilute nitric acid solution to remove cobalt, a small-pore diamond coated wire drawing die is prepared using a hot-wire chemical vapor deposition method.

[0007] The hard alloy wire drawing die core adopts a YG series tungsten steel die core containing less than 6% cobalt;

[0008] The dilute nitric acid solution cobalt removal pretreatment comprises: placing the tungsten steel mold core in a dilute nitric acid solution, etching at room temperature for 5 to 10 minutes to remove the surface cobalt binder phase, and then ultrasonically oscillating in an alcohol suspension containing nano-diamond particles for 30 to 60 minutes, wherein the mixing ratio of nitric acid to water in the dilute nitric acid solution is 1:3 to 1:5, the particle size of the nano-diamond particles is set to 5 to 10 nm, and the mass fraction of the nano-diamond particles is set to 0.1% to 1%;

[0009] The hot wire chemical vapor deposition method is as follows: after the reaction gases are mixed in a specific proportion, they are passed into the interior of the reaction furnace chamber, and the reaction gases are decomposed by the hot wire at high temperature to form a variety of active groups. After complex adsorption and desorption reactions, the active groups nucleate and grow to form a diamond coating on the surface of the tungsten steel mold core.

[0010] Preferably, the acetone ultrasonic cleaning operation is: placing the above-mentioned tungsten steel mold core in an acetone solution and using an ultrasonic cleaning device to clean it for 15 to 30 minutes. The alkali solution ultrasonic cleaning operation is: using a sodium hydroxide solution with a concentration of 5% to 10%, the temperature is set to 50 to 70°C, and cleaning it for 10 to 15 minutes using an ultrasonic cleaning device. The deionized water ultrasonic cleaning operation is: placing the above-mentioned tungsten steel mold core in deionized water and ultrasonically cleaning it for 5 to 10 minutes. The frequency of the ultrasonic cleaning device is set to 40 to 60 kHz, and the power of the ultrasonic cleaning device is set to 100 to 300 W.

[0011] Preferably, the process parameters for preparing the drawing die with a relatively small pore coating are:

[0012] The heating wire is made of tantalum or tungsten material, and the temperature of the heating wire is always maintained at 2000-2300°C. The surface temperature of the tungsten steel mold core is adjusted according to the temperature of the heating wire, and the temperature range is set to 800-900°C.

[0013] The preparation process of the relatively small-pore coating drawing die includes three stages: nucleation, growth, and surface nanocrystallization. The reaction pressure of the nucleation stage is set to 3.0-5.0 KPa, the volume fraction of the carbon source gas is 4%-6%, and the reaction time is set to 30-60 min. The reaction pressure of the growth stage is set to 6.0-8.0 KPa, the volume fraction of the carbon source gas is 2%-4%, and the deposition time is set to 5-7 h. The reaction pressure of the surface nanocrystallization stage is set to 4.0-5.0 KPa, the volume fraction of the carbon source gas is 4%-6%, and the reaction time is set to 30-60 min.

[0014] The reaction gas in the above three stages is a mixture of carbon source gas methane and hydrogen, the volume ratio of methane to hydrogen is set to 1:20-1:50, and the total gas flow rate is set to 300-500 ml / min.

[0015] Preferably, before the reaction gas is introduced into the reaction furnace chamber, a protective gas is first introduced into the reaction furnace chamber, and the protective gas is set to be a mixture of argon and hydrogen.

[0016] Preferably, the device for preparing a smaller-pore coating drawing die includes a reaction furnace chamber, an exhaust channel is provided on one side of the reaction furnace chamber, an air intake mechanism for conveying reaction gas is provided on the other side of the reaction furnace chamber, a plurality of drawing cavities are provided inside the reaction furnace chamber, a plurality of high-temperature ceramic tubes are placed inside the drawing cavities, a plurality of tungsten steel mold cores are placed inside the high-temperature ceramic tubes, the hot wire is arranged horizontally along the inside of the tungsten steel mold core, both ends of the hot wire extend to the outside of the drawing cavity and are connected to a heat-resistant spring, the other side of the heat-resistant spring is connected to a heating electrode, the heating electrode is provided at the inlet and outlet positions of the drawing cavity, and the heating electrode is connected to the positive and negative poles of the power supply through a cable.

[0017] Preferably, the air intake mechanism includes an air intake channel, one end of which is fixedly connected to a plurality of air intake branch channels, the ends of the air intake branch channels correspond to the inlet positions of the high-temperature ceramic tubes, and a gas flow meter is provided on each of the air intake branch channels.

[0018] Preferably, an air pump is provided on one side of the exhaust channel.

[0019] Preferably, the high-temperature ceramic tube includes an upper ceramic tube part and a lower ceramic tube part, and the upper ceramic tube part and the lower ceramic tube part are enclosed to form a cylindrical structure with a hollow interior. The upper ceramic tube part and the lower ceramic tube part are connected together by welding, mechanical connection or gluing, and a circumferential arrangement is used to automatically align several tungsten steel mold cores.

[0020] Preferably, the tungsten steel mold core is cylindrical, and a funnel-shaped through hole with a large opening facing the air intake mechanism is provided inside the core.

[0021] Preferably, the heat-resistant spring is made of a high-temperature alloy spring with good thermal conductivity, and the surface of the heat-resistant spring is provided with an anti-oxidation coating.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] This new method for preparing smaller-pore coated wire drawing dies can effectively grow good diamond coatings inside the small-pore dies, breaking through the bottleneck of traditional methods in preparing small-pore die coatings. It is convenient for batch production of coatings, saving the investment cost required for production, and the overall reaction temperature is relatively concentrated, which effectively accelerates the synthesis speed of diamonds and improves actual production efficiency. The directional flow of air intake improves the uniformity of the coating and enhances the overall performance of the wire drawing die. The interior of the high-temperature ceramic tube is annular, so that the tungsten steel mold core can be automatically arranged neatly, creating good conditions for hot wire positioning and further optimizing the production process. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 2 is a diagram showing the internal structure of the device of the present invention.

[0025] Figure 2 It is a cross-sectional view of the front view of the device of the present invention.

[0026] Figure 3 It is a schematic diagram of the local structure of the present invention.

[0027] Figure 4 Schematic diagram of the structure of the high-temperature ceramic tube of the present invention.

[0028] Notes on the accompanying drawings: reaction furnace chamber 1, exhaust channel 2, air intake mechanism 3, air intake channel 31, air intake branch channel 32, high-temperature ceramic tube 4, ceramic tube upper part 41, ceramic tube lower part 42, tungsten steel mold core 5, hot wire 6, heat-resistant spring 7, heating electrode 8, power supply 9. DETAILED DESCRIPTION

[0029] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments.

[0030] In this embodiment, if Figures 1-4 As shown, a new method for preparing a relatively small-pore coated wire drawing die is described. A relatively small-pore cemented carbide wire drawing die core with a pore size of Φ0.1mm to Φ0.8mm is used as a substrate. The die core surface is ultrasonically cleaned with acetone, alkali solution, and deionized water to remove oil, impurities, and oxides to ensure the effectiveness of subsequent treatment and coating deposition. After pretreatment with dilute nitric acid solution to remove cobalt, a relatively small-pore diamond coated wire drawing die is prepared by hot wire chemical vapor deposition.

[0031] The carbide wire drawing die core adopts the YG series tungsten steel die core 5 with a cobalt content of less than 6%;

[0032] The dilute nitric acid solution cobalt removal pretreatment comprises: placing a tungsten steel mold core 5 in a dilute nitric acid solution, etching at room temperature for 5 to 10 minutes to remove the cobalt binder phase on the surface, and then ultrasonically oscillating in an alcohol suspension containing nano-diamond particles for 30 to 60 minutes to form a microscopic rough structure on the mold core surface by etching, thereby increasing the surface specific surface area, improving the bonding force between the nano-diamond coating and the mold core, and generating tiny pits and protrusions on the surface. The mixing ratio of nitric acid to water in the dilute nitric acid solution is 1:3 to 1:5, the particle size of the nano-diamond particles is set to 5 to 10 nm, and the mass fraction of the nano-diamond particles is set to 0.1% to 1%, thereby promoting the formation of nano-diamond crystal nuclei.

[0033] The hot wire chemical vapor deposition method is as follows: a tungsten steel mold core 5 is placed inside a reaction furnace chamber 1, reaction gases are mixed in a specific ratio and introduced into the reaction furnace chamber 1 through an air inlet mechanism 3, and the reaction gases are decomposed at high temperature by a hot wire 6 to form a variety of active groups. The active groups undergo complex adsorption and desorption reactions, nucleating and growing, forming a diamond coating on the surface of the tungsten steel mold core 5;

[0034] Among them Figures 1-4 As shown, the acetone ultrasonic cleaning operation is as follows: the tungsten steel mold core 5 is placed in an acetone solution and cleaned for 15 to 30 minutes using an ultrasonic cleaning device. Acetone can effectively dissolve oil stains, and the high-frequency vibration of the ultrasonic wave can enhance the cleaning effect and remove tiny particles of impurities. The alkali solution ultrasonic cleaning operation is as follows: a sodium hydroxide solution with a concentration of 5% to 10% is used, the temperature is set to 50 to 70°C, and the ultrasonic cleaning device is used to clean for 10 to 15 minutes to further remove residual organic pollutants and some metal oxides. The deionized water ultrasonic cleaning operation is as follows: the tungsten steel mold core 5 is placed in deionized water and ultrasonically cleaned for 5 to 10 minutes to remove residual acid and alkali solution and ensure that the mold core surface is clean and free of residue. The frequency of the ultrasonic cleaning device is set to 40 to 60kHz, and the power of the ultrasonic cleaning device is set to 100 to 300W.

[0035] Among them Figures 1-4 As shown in Figure 2, the process parameters for preparing a smaller hole coating drawing die are:

[0036] The hot wire 6 is made of tantalum or tungsten. The temperature of the hot wire 6 is always maintained at 2000-2300°C to ensure that the reaction gas is fully decomposed. The surface temperature of the tungsten steel mold core 5 is adjusted according to the temperature of the hot wire 6. The temperature range is set to 800-900°C, which is conducive to the formation and growth of diamond nuclei.

[0037] The preparation process of the relatively small-pore coating drawing die includes three stages: nucleation, growth, and surface nanocrystallization. The reaction pressure in the nucleation stage is set to 3.0-5.0 kPa, the volume fraction of the carbon source gas is 4%-6%, and the reaction time is set to 30-60 minutes. The reaction pressure in the growth stage is set to 6.0-8.0 kPa, the volume fraction of the carbon source gas is 2%-4%, and the deposition time is set to 5-7 hours. The reaction pressure in the surface nanocrystallization stage is set to 4.0-5.0 kPa, the volume fraction of the carbon source gas is 4%-6%, and the reaction time is set to 30-60 minutes.

[0038] The reaction gas in the above three stages is a mixture of carbon source gas methane and hydrogen. Hydrogen inhibits the growth of the graphite phase by providing atomic hydrogen, while promoting the formation of the diamond phase. The volume ratio of methane to hydrogen is set to 1:20 to 1:50, and the total gas flow rate is set to 300 to 500 ml / min, which can be fine-tuned according to the size of the mold and the size of the reaction furnace chamber 1.

[0039] Among them Figure 1 As shown, before the reaction gas is introduced into the reaction furnace chamber 1, a protective gas is first introduced into the reaction furnace chamber 1, and the protective gas is set to be a mixture of argon and hydrogen;

[0040] Among them Figures 1-4 As shown, a device for preparing a relatively small-pore coating drawing die includes a reaction furnace chamber 1, and a temperature detector, a pressure detector and a gas detector (not shown in the figure) are provided inside the reaction furnace chamber 1, so as to closely monitor the changes in temperature, pressure and gas composition in the furnace chamber during the reaction process, and adjust parameters such as the air intake volume and temperature in a timely manner. An exhaust channel 2 is provided on one side of the reaction furnace chamber 1, and an air intake mechanism 3 for conveying the reaction gas is provided on the other side of the reaction furnace chamber 1, so that the gas forms a directional and stable flow in the high-temperature ceramic tube 4, ensuring the uniformity and stability of the gas flow, and promoting the reaction gas to fully react. A plurality of drawing cavities are provided inside the reaction furnace chamber 1, and a plurality of high-temperature ceramic tubes 4 are placed inside the drawing cavities, and a plurality of tungsten steel mold cores 5 are placed inside the high-temperature ceramic tubes 4. The hot wire 6 is arranged horizontally along the inside of the tungsten steel mold core 5, and both ends of the hot wire 6 extend to the outside of the drawing cavity and are connected to the heat-resistant spring 7, and the other side of the heat-resistant spring 7 is connected to the heating electrode 8. , after the hot wire 6 is energized, it generates a high temperature of 2000-2300℃, decomposes the reaction gas, and at the same time, the heat-resistant spring 7 buffers the thermal stress, maintains the temperature stable, and promotes the reaction gas to decompose and react at a suitable temperature, so as to deposit and form a diamond coating on the surface of the tungsten steel mold core 5. The heating electrode 8 is arranged at the inlet and outlet positions of the wire drawing cavity. The heating electrode 8 is connected to the positive and negative poles of the power supply 9 through a cable. The positive pole of the power supply 9 is connected to one heating electrode 8, and the negative pole is connected to another heating electrode 8. The cable must be resistant to high temperature and well insulated. The connection parts must be well insulated and fixed to prevent short circuit and loosening. The power supply 9 can choose a power supply device with voltage stabilization and current stabilization function to ensure that it can continuously provide stable electric energy to the hot wire 6 during the entire working process, maintain the current required for the hot wire 6 to heat up, so that the output voltage and current fluctuation range should be controlled within a small range. The working current intensity can be determined according to the material, diameter, length and other parameters of the hot wire 6 to ensure that the circuit is always in a good conduction state;

[0041] Among them Figure 1 As shown, the air intake mechanism 3 includes an air intake channel 31, one end of which is fixedly connected to a plurality of air intake branch channels 32. The ends of the air intake branch channels 32 correspond to the inlet positions of the high-temperature ceramic tubes 4. The gas flow rate and pressure of the air intake branch channels 32 are adjusted according to the reaction requirements so that the reaction gas can enter each high-temperature ceramic tube 4 evenly and stably. A gas flow meter is provided on each air intake branch channel 32 to facilitate the detection of the gas flow rate. A valve body should also be provided on the air intake branch channel 32 to control the opening and closing state of the reaction gas.

[0042] Among them Figure 1 As shown, an air pump is provided on one side of the exhaust channel 2 to facilitate the transportation of the gas inside the reaction furnace chamber 1 and the drawing chamber to the outside of the reaction furnace chamber 1 to achieve an airflow effect;

[0043] Among them Figure 4 As shown, the high-temperature ceramic tube 4 includes a ceramic tube upper portion 41 and a ceramic tube lower portion 42, which enclose a cylindrical structure with a hollow interior. The ceramic tube upper portion 41 and the ceramic tube lower portion 42 are connected together by welding, mechanical connection or adhesive bonding, and a circumferential arrangement is used to automatically align the plurality of tungsten steel mold cores 5. The high-temperature ceramic tube 4 has good high-temperature resistance and insulation properties, providing a stable reaction environment for the tungsten steel mold core 5, so that it can smoothly interact with the reaction gas during the coating preparation process.

[0044] Among them Figure 1 and Figure 3 As shown, the tungsten steel mold core 5 is set to a cylindrical shape, and a funnel-shaped through hole with a large opening facing the air intake mechanism 3 is set inside it;

[0045] Among them Figure 1 and Figure 3 As shown, the heat-resistant spring 7 adopts a high-temperature alloy spring with good thermal conductivity, such as a spring made of copper alloy, nickel alloy, etc., which has low resistance and can reduce energy loss during current transmission. The spring must have appropriate elasticity. When the hot wire 6 expands and contracts due to temperature changes, it can always maintain close contact with the hot wire 6 and the heating electrode 8, which can buffer the stress caused by thermal expansion and contraction of the hot wire 6 and avoid breakage. The surface of the heat-resistant spring 7 is provided with an anti-oxidation coating. During installation, the hot wire 6 needs to be firmly wound around one end of the heat-resistant spring 7 to increase the contact area. The other end of the heat-resistant spring 7 is tightly connected to the heating electrode 8 and can be fixed by welding, crimping, etc. to ensure a tight connection.

[0046] Example 1

[0047] 1. Preprocessing process:

[0048] A Φ0.2 mm YG6 tungsten steel mold core 5 having a cobalt content of 6% was selected as the substrate. The tungsten steel mold core 5 was placed in an acetone solution and cleaned for 20 minutes using an ultrasonic cleaning device with an ultrasonic frequency of 40 kHz and a power of 200 W. Residual organic matter was detected by FTIR. An 8% sodium hydroxide solution was used at 60° C. and cleaned for 12 minutes using an ultrasonic cleaning device. The oxygen atom content was detected by XPS. Deionized water was used for ultrasonic cleaning for 5 minutes to remove residual alkali solution. The tungsten steel mold core 5 was placed in a dilute nitric acid solution with a mixing ratio of nitric acid to water of 1:4. The mold core was etched at room temperature for 8 minutes to remove the surface cobalt binder phase. The mold core was then ultrasonically oscillated for 45 minutes in an alcohol suspension containing nanodiamond particles, with a particle size of 8 nm and a mass fraction of 0.5%. A microscopic rough structure was formed on the mold core surface by etching. The surface cobalt content was detected by ICP-MS, and the roughness was measured.

[0049] 2. Hot Wire Chemical Vapor Deposition:

[0050] Argon and hydrogen in a ratio of 1:1 are transported to the interior of the reaction furnace chamber 1 at a flow rate of 200 ml / min. After the ventilation time reaches 10 minutes, the tungsten steel mold core 5 is installed, and methane and hydrogen in a ratio of 1:30 are transported to the reaction furnace chamber 1 at a total flow rate of 400 ml / min. The hot wire 6 is made of tungsten wire material, and the power supply 9 is used to make the temperature of the hot wire 6 reach 2200±50°C, so that the surface temperature of the mold core reaches 850±10°C. The reaction pressure in the nucleation stage is set to 4.0 KPa, the volume fraction of the carbon source gas is 4%, and the reaction time is 50 minutes. The reaction pressure in the growth stage is set to 7.0 KPa, the volume fraction of the carbon source gas is 3%, and the deposition time is 6 hours. The reaction pressure in the nano-sizing stage is set to 4.5 KPa, the volume fraction of the carbon source gas is 5%, and the reaction time is 40 minutes.

[0051] Data results: SEM measurement shows that the thickness of the diamond coating is about 12±0.5μm, its bonding force is >50N, the surface roughness is less than 0.1μm using white light interferometry, and its wear resistance value is lower than 2.1×10 -4 mm 3 / N·m, effectively improving actual production efficiency, conducting cyclic wear tests and high-temperature durability tests on the above coatings, effectively increasing coating life and improving production efficiency;

[0052] Example 2

[0053] 1. Preprocessing process:

[0054] A Φ0.5 mm YG4 tungsten steel mold core 5 having a cobalt content of 4% was selected as the substrate. The tungsten steel mold core 5 was placed in an acetone solution and cleaned for 30 minutes using an ultrasonic cleaning device with an ultrasonic frequency of 50 kHz and a power of 200 W. Residual organic matter was detected by FTIR. A 10% sodium hydroxide solution was used at 60° C. and cleaned for 15 minutes using an ultrasonic cleaning device. The oxygen atom content was detected by XPS. The tungsten steel mold core 5 was ultrasonically cleaned for 10 minutes using deionized water to remove residual alkali solution. The tungsten steel mold core 5 was placed in a dilute nitric acid solution having a mixing ratio of nitric acid to water of 1:5. The mold core was etched at room temperature for 10 minutes to remove the surface cobalt binder phase. The mold core was then ultrasonically oscillated for 40 minutes in an alcohol suspension containing nanodiamond particles, wherein the particle size of the nanodiamond particles was set to 8 nm and the mass fraction of the nanodiamond particles was set to 0.5%. A microscopic rough structure was formed on the mold core surface by etching. The surface cobalt content was detected by ICP-MS, and the roughness was measured.

[0055] 2. Hot Wire Chemical Vapor Deposition:

[0056] Argon and hydrogen in a ratio of 1:1 are transported to the interior of the reaction furnace chamber 1 at a flow rate of 200 ml / min. After the ventilation time reaches 10 minutes, the tungsten steel mold core 5 is installed, and methane and hydrogen in a ratio of 1:40 are transported to the reaction furnace chamber 1 at a total flow rate of 450 ml / min. The hot wire 6 is made of tantalum wire material, and the power supply 9 is used to make the temperature of the hot wire 6 reach 2100±50°C. The reaction pressure in the nucleation stage is set to 3.5KPa, the volume fraction of the carbon source gas is 5%, and the reaction time is 40 minutes, so that the surface temperature of the mold core reaches 820±10°C. The reaction pressure in the growth stage is set to 6.5KPa, the volume fraction of the carbon source gas is 2.5%, and the deposition time is 7 hours. The reaction pressure in the nano-sizing stage is set to 5.0KPa, the volume fraction of the carbon source gas is 4%, and the reaction time is 50 minutes;

[0057] Data results: SEM measurement shows that the thickness of the diamond coating is about 15±1μm, its bonding force is >55N, the surface roughness is less than 0.1μm using white light interferometry, and its wear resistance value is lower than 2.1×10 - 4 mm 3 / N·m, effectively improving actual production efficiency, conducting cyclic wear tests and high-temperature durability tests on the above coatings, effectively increasing coating life and improving production efficiency;

[0058] Comparative Example 1

[0059] Using the traditional large-cavity hot-wire chemical vapor deposition method:

[0060] A Φ0.2 mm YG6 tungsten steel mold core 5 was selected as the substrate, and its cobalt content was 6%. The tungsten steel mold core 5 was pretreated according to Example 1. Conventional hot wire chemical vapor deposition was used with a non-directional airflow design. Methane and hydrogen were delivered to the reaction furnace chamber 1 at a ratio of 1:30 and a total flow rate of 400 ml / min. The power supply 9 was used to set the temperature of the hot wire 6 to 2200±50°C, so that the surface temperature of the mold core reached 850±10°C. SEM measurement showed that the coating thickness at the inlet of the diamond coating was approximately 10 μm. The uneven airflow resulted in an incomplete coating thickness at the outlet, and its bonding strength was <30N.

[0061] The conclusion is: the directional airflow design can significantly improve the uniformity of the coating inside the small hole, the cobalt removal pretreatment design can enhance the bonding force, and the nano-diamond suspension treatment can increase the nucleation density and reduce coating defects. It can effectively grow a good diamond coating inside the small hole mold, breaking through the bottleneck of traditional methods in the preparation of small hole mold coatings, facilitating batch production operations of coatings, and saving production investment costs.

[0062] The above description is merely a specific embodiment of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this application should be included in the scope of protection of the present application. Therefore, the scope of protection of the present application should be based on the scope of protection of the claims.

Claims

1. A new method for preparing a relatively small-pore coating drawing die, characterized in that: A relatively small-pore carbide wire drawing die with a pore size of 0.1 mm to 0.8 mm was used as the substrate. The surface of the die was ultrasonically cleaned with acetone, alkali solution, and deionized water to remove oil, impurities, and oxides. After pretreatment with dilute nitric acid solution to remove cobalt, a relatively small-pore diamond-coated wire drawing die was prepared by hot-wire chemical vapor deposition. The hard alloy wire drawing die core adopts a YG series tungsten steel die core (5) containing less than 6% cobalt; The dilute nitric acid solution cobalt removal pretreatment comprises: placing the tungsten steel mold core (5) in a dilute nitric acid solution, etching for 5 to 10 minutes at room temperature to remove the surface cobalt bonding phase, and then ultrasonically oscillating in an alcohol suspension containing nano-diamond particles for 30 to 60 minutes, wherein the mixing ratio of nitric acid to water in the dilute nitric acid solution is 1:3 to 1:5, the particle size of the nano-diamond particles is set to 5 to 10 nm, and the mass fraction of the nano-diamond particles is set to 0.1% to 1%; The hot wire chemical vapor deposition method comprises the following steps: using a device for preparing a relatively small-pore coating drawing die, placing a tungsten steel mold core (5) into a reaction furnace chamber (1), mixing reaction gases in a specific proportion and then introducing them into the reaction furnace chamber (1) using an air intake mechanism (3), and using a hot wire (6) to decompose the reaction gases at high temperature to form a variety of active groups. The active groups undergo complex adsorption and desorption reactions, nucleate and grow, and form a diamond coating on the surface of the tungsten steel mold core (5).

2. A novel method for preparing a relatively small-pore coating drawing die according to claim 1, characterized in that: The acetone ultrasonic cleaning operation is as follows: placing the tungsten steel mold core (5) in an acetone solution and using an ultrasonic cleaning device to clean it for 15 to 30 minutes. The alkali solution ultrasonic cleaning operation is as follows: using a sodium hydroxide solution with a concentration of 5% to 10%, the temperature is set to 50 to 70° C., and using an ultrasonic cleaning device to clean it for 10 to 15 minutes. The deionized water ultrasonic cleaning operation is as follows: placing the tungsten steel mold core (5) in deionized water and ultrasonically cleaning it for 5 to 10 minutes. The frequency of the ultrasonic cleaning device is set to 40 to 60 kHz, and the power of the ultrasonic cleaning device is set to 100 to 300 W.

3. A novel method for preparing a relatively small-pore coating drawing die according to claim 1, characterized in that: The process parameters for preparing the relatively small-pore coating drawing die are: The hot wire (6) is made of tantalum wire or tungsten wire, and the temperature of the hot wire (6) is always maintained at 2000-2300° C. The surface temperature of the tungsten steel mold core (5) is adjusted according to the temperature of the hot wire (6), and the temperature range is set to 800-900° C.; The preparation process of the relatively small-pore coating drawing die includes three stages: nucleation, growth, and surface nanocrystallization. The reaction pressure of the nucleation stage is set to 3.0-5.0 KPa, the volume fraction of the carbon source gas is 4%-6%, and the reaction time is set to 30-60 min. The reaction pressure of the growth stage is set to 6.0-8.0 KPa, the volume fraction of the carbon source gas is 2%-4%, and the deposition time is set to 5-7 h. The reaction pressure of the surface nanocrystallization stage is set to 4.0-5.0 KPa, the volume fraction of the carbon source gas is 4%-6%, and the reaction time is set to 30-60 min. The reaction gas in the above three stages is a mixture of carbon source gas methane and hydrogen, the volume ratio of methane to hydrogen is set to 1:20-1:50, and the total gas flow rate is set to 300-500 ml / min.

4. A novel method for preparing a relatively small-pore coating drawing die according to claim 3, characterized in that: Before the reaction gas is introduced into the reaction furnace chamber (1), a protective gas is first introduced into the interior of the reaction furnace chamber (1), and the protective gas is set to be a mixture of argon and hydrogen.

5. The novel method for preparing a relatively small-pore coating drawing die according to claim 1, characterized in that: The device for preparing a drawing die with a smaller hole coating includes a reaction furnace chamber (1), an exhaust channel (2) is provided on one side of the reaction furnace chamber (1), an air intake mechanism (3) for conveying reaction gas is provided on the other side of the reaction furnace chamber (1), a plurality of drawing cavities are provided inside the reaction furnace chamber (1), a plurality of high-temperature ceramic tubes (4) are placed inside the drawing cavities, a plurality of tungsten steel mold cores (5) are placed inside the high-temperature ceramic tubes (4), the hot wire (6) is arranged horizontally along the inside of the tungsten steel mold core (5), both ends of the hot wire (6) extend to the outside of the drawing cavity and are connected to a heat-resistant spring (7), the other side of the heat-resistant spring (7) is connected to a heating electrode (8), the heating electrode (8) is provided at the inlet and outlet positions of the drawing cavity, and the heating electrode (8) is connected to the positive and negative poles of a power supply (9) through a cable.

6. A novel method for preparing a relatively small-pore coating drawing die according to claim 5, characterized in that: The air intake mechanism (3) comprises an air intake channel (31), one end of the air intake channel (31) is fixedly connected to a plurality of air intake branch channels (32), the ends of the air intake branch channels (32) correspond to the inlet positions of the high-temperature ceramic tubes (4), and a gas flow meter is provided on each of the air intake branch channels (32).

7. A novel method for preparing a relatively small-pore coating drawing die according to claim 5, characterized in that: An air pump is provided on one side of the exhaust channel (2).

8. The novel method for preparing a relatively small-pore coating drawing die according to claim 5, characterized in that: The high-temperature ceramic tube (4) comprises a ceramic tube upper portion (41) and a ceramic tube lower portion (42), wherein the ceramic tube upper portion (41) and the ceramic tube lower portion (42) enclose a cylindrical structure with a hollow interior, and the ceramic tube upper portion (41) and the ceramic tube lower portion (42) are connected together by welding, mechanical connection or adhesive connection, and a plurality of tungsten steel mold cores (5) are automatically aligned in a circumferential arrangement.

9. The novel method for preparing a relatively small-pore coating drawing die according to claim 5, characterized in that: The tungsten steel mold core (5) is cylindrical and has a funnel-shaped through hole with a large opening facing the air intake mechanism (3) arranged inside.

10. The novel method for preparing a relatively small-pore coating drawing die according to claim 5, characterized in that: The heat-resistant spring (7) is made of a high-temperature alloy spring with good thermal conductivity, and the surface of the heat-resistant spring (7) is provided with an anti-oxidation coating.

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