A method for preparing oxidation-resistant, dense, complex tungsten carbide-based rare metal ceramics

Abstract

This invention discloses a method for preparing an oxidation-resistant, dense, complex tungsten carbide-based rare metal ceramic, relating to the field of metal ceramics. First, silicon carbide is introduced via polycarbosilane, and zirconium metal fills the ceramic pores through a metal infiltration reaction, improving density while enhancing the oxidation resistance of the ceramic matrix. Then, a combination of ion implantation and spraying is used to form a tungsten carbide-rich layer on the ceramic surface. During spraying, the high-temperature, high-speed tungsten carbide and metal binder combine with the previously implanted tungsten carbide-rich layer to form a unified whole. Next, a high proportion of rare metal nano-rhenium is used to achieve surface densification of the tungsten carbide-based metal ceramic complex coating under high-temperature conditions. Finally, hydrogen reduction treatment further reduces the oxygen content of the powder, producing a highly active, low-oxygen complex carbide rare metal ceramic with a nanocrystalline structure. The ceramic prepared by this invention exhibits oxidation resistance and density.

Description

Technical Field

[0001] This invention relates to the field of ceramic technology, specifically to a method for preparing an oxidation-resistant, dense, complex tungsten carbide-based rare metal ceramic. Background Technology

[0002] Tungsten carbide plays a crucial role in modern industry. Its high hardness and heat resistance make it a common material for cutting tools in the machinery industry, high-hardness armor in the military industry, and armor-piercing projectile cores. Tungsten carbide also possesses high wear resistance and corrosion resistance, thus it is used to manufacture wear-resistant heat-protective coatings for easily worn tools in the aerospace and precision industries. The research direction of this invention is to combine tungsten carbide with cermets to prepare highly oxidation-resistant composite carbide cermets. This is achieved through the introduction of rare metals into sintering and process modification to address the aforementioned problems. Summary of the Invention

[0003] The purpose of this invention is to provide a method for preparing antioxidant dense complex tungsten carbide-based rare metal ceramics, so as to solve the problems existing in the prior art.

[0004] To solve the above-mentioned technical problems, the present invention provides the following technical solution: an anti-oxidation dense complex tungsten carbide-based rare metal ceramic, wherein the ceramic is prepared by infiltrating metallic zirconium as a matrix with tungsten carbide-silicon carbide complex porous ceramic as the matrix, and then spraying a coating containing metallic rhenium and tungsten carbide onto its surface.

[0005] Furthermore, the matrix is ​​polycarbosilane in which silicon carbide is introduced, which is then pyrolyzed to generate tungsten carbide-silicon carbide composite porous ceramic. Zirconium metal is introduced through a metal infiltration reaction, and nanoscale zirconium metal fills the pores of the ceramic during the infiltration process.

[0006] Furthermore, the coating is formed by a combination of ion implantation and spraying. Tungsten carbide is implanted into the ceramic surface using ion implantation, and then a mixture of tungsten carbide powder and rhenium powder is sprayed on.

[0007] Furthermore, the preparation steps include the following:

[0008] (1) Using tungsten carbide as raw material and polycarbosilane precursor as binder, the volume ratio of tungsten carbide and polycarbosilane precursor is 2-52:3. The prepared raw material powder is placed in a ball mill jar. The grinding balls are cemented carbide balls with a ball-to-material ratio of 10:1. Anhydrous ethanol is used as the grinding medium, and the amount of anhydrous ethanol added is half the volume of the ball mill jar. The ball mill jar used is a cemented carbide ball mill jar. The ball mill speed is 200-300 rpm. The total running time of the equipment is 72 hours. The ball mill is stopped for 1 minute after every 5 minutes of operation. n, while changing the rotation direction from clockwise to counterclockwise, continue running for 5 minutes, then stop for 1 minute and change the running direction back to counterclockwise. The ball milling time is 60 hours. After ball milling and mixing, tungsten carbide blanks containing polycarbosilane precursors are prepared by molding. The obtained tungsten carbide blanks containing polycarbosilane precursors are placed in a high-temperature pyrolysis furnace, and under inert gas protection, the temperature is slowly raised to 800-1600℃, held for 0.5-2 hours, and then slowly cooled to prepare tungsten carbide-silicon carbide porous ceramics.

[0009] (2) Using the obtained tungsten carbide-silicon carbide porous ceramic as the substrate and nano-zirconium metal as the infiltrator, the two are placed in a crucible and then placed in a high-temperature heat treatment device. Under the protection of inert gas, the temperature is slowly raised to 1000-2000℃, held for 1-10h and then cooled down at a rate of 10℃ / min. The obtained semi-finished product and crucible are inverted and placed in the high-temperature heat treatment device again. Under the protection of inert gas, the temperature is raised to 1600-2000℃, held for 1-2h and then cooled down at a rate of 10℃ / min to obtain dense metal ceramic.

[0010] (3) Dense metal ceramics are placed in a sealed can-shaped container with inert gas as the medium. Tungsten strips are fixed on the inner wall of the can as the anode and cathode. A high voltage current is passed between the anode and cathode to generate glow discharge. The discharge voltage is 50-1500V. As the discharge current increases, the temperature inside the container increases to 900-1100℃. The tungsten metal at the anode is ionized and injected into the ceramic at high speed under the action of the electric field. It further diffuses into the interior of the workpiece and combines with the carbon element in the ceramic material to generate tungsten carbide. Tungsten carbide is then sprayed onto it. The spraying method is supersonic flame spraying. The raw material for spraying is a mixture of tungsten carbide powder and rhenium powder. The spraying thickness is 0.8-1.2mm. A composite ceramic is obtained.

[0011] (4) Place the composite ceramic in a high-temperature vacuum tube furnace. First, evacuate the vacuum tube furnace to a vacuum, and then introduce high-purity argon gas to equalize the atmospheric pressure. Repeat this step twice. Then, start the heating process and introduce high-purity hydrogen gas with a purity of ≥99.95%. During the reduction process, the temperature should be raised to 600℃ and held for 3 hours. Then, the temperature should be raised to 900℃ and held for 1 hour. The heating rate during the heating process is 10℃ / min, and the hydrogen gas flow rate is 0.5L / min. After the holding period, stop heating. The cooling process is to cool with the furnace to obtain the oxidation-resistant dense composite carbide-based rare metal ceramic.

[0012] Furthermore, the inert gas used in the preparation process is helium.

[0013] Furthermore, the heating rate in step (1) is 10℃ / min.

[0014] Furthermore, in step (2), tungsten carbide-silicon carbide porous ceramic and nano-zirconium metal are mixed at a volume ratio of 4.5-6.5:5.

[0015] Furthermore, in step (3), the volume ratio of tungsten carbide powder to rhenium powder is 1:9-9.5.

[0016] Furthermore, the spraying process parameters in step (3) are as follows: kerosene flow rate is 28-33 L / h, kerosene pressure is 1.6-1.8 MPa, oxygen flow rate is 850-920 L / min, oxygen pressure is 2.0-2.2 MPa, powder feeding rate is 60-80 g / min, nitrogen flow rate is 12-14 L / min, nitrogen pressure is 1.0-1.4 MPa, and spraying distance is 380 mm-410 mm.

[0017] Furthermore, the vacuum degree in step (4) is -0.1 MPa.

[0018] This invention uses tungsten carbide-silicon carbide composite porous ceramic as a matrix, and then sprays a surface containing rhenium and tungsten carbide to prepare composite tungsten carbide-based rare metal ceramics after infiltrating with metallic zirconium, so as to achieve the effects of anti-oxidation and density.

[0019] First, during the preparation process, silicon carbide is introduced into the material system through a polycarbosilane precursor. The polycarbosilane precursor acts as a crosslinking agent and pore-forming agent, which allows the ceramic matrix to decompose at a lower temperature to generate a tungsten carbide-silicon carbide composite porous ceramic with sufficient strength. On this basis, zirconium metal is used as a diffusion agent to introduce zirconium metal through a metal melting reaction. The nano-sized zirconium metal fills the ceramic pores during the melting process, improving the density and strengthening the oxidation resistance of the ceramic matrix. Then, a combination of ion implantation and spraying is used. Tungsten carbide is first implanted into the ceramic surface by ion implantation to form a tungsten carbide enriched layer on the ceramic surface. During spraying, the high-temperature and high-speed tungsten carbide and metal binder combine with the originally implanted tungsten carbide enriched layer to form a whole, forming a transition surface. This greatly improves the bonding strength between the tungsten carbide sprayed layer and the ceramic matrix, thereby achieving the effect of improving density and oxidation resistance.

[0020] Secondly, by employing a high proportion of rare metal rhenium nanoparticles, the surface densification of tungsten carbide-based metal ceramic composite coatings under high-temperature conditions was achieved. The particle size and amount of rhenium added have a significant impact on the high-temperature performance of the composite coating: the operating temperature of the rhenium-containing tungsten carbide rare metal ceramic composite coating is higher than that of ordinary tungsten carbide-based metal ceramic coatings, which greatly improves the high-temperature resistance of the tungsten carbide-based metal ceramic coating, thereby making the prepared grains more stable and dense, thus achieving an anti-oxidation effect; finally, the oxygen content of the powder is further reduced by hydrogen reduction treatment, producing highly active low-oxygen composite carbide rare metal ceramics with nanocrystalline structure. Detailed Implementation

[0021] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0022] To more clearly illustrate the method provided by the present invention, the following embodiments are provided in detail. The testing methods for various indicators of an antioxidant dense composite tungsten carbide-based rare metal ceramic prepared in the following embodiments are as follows:

[0023] Antioxidant properties: The tungsten carbide-based rare metal ceramic samples of the examples and comparative examples were tested using ferric chloride solution with a concentration of 8.5±0.5 g / L. The ferric chloride solution was dropped onto the ceramic substrate, and no color change was observed after 15 minutes, indicating that the antioxidant effect met the standard.

[0024] Density: The density of the tungsten carbide-based rare metal ceramic samples from the examples and comparative examples was tested in accordance with GB / T 25995-2010.

[0025] Example 1

[0026] (1) Using tungsten carbide as raw material and polycarbosilane precursor as binder, the volume ratio of tungsten carbide and polycarbosilane precursor is 2:3. The prepared raw material powder is placed in a ball mill jar. The grinding balls are cemented carbide balls with a ball-to-material ratio of 10:1. Anhydrous ethanol is used as the grinding media, and the amount of anhydrous ethanol added is half the volume of the ball mill jar. The ball mill jar used is a cemented carbide ball mill jar. The ball mill speed is 200 rpm. The total running time of the equipment is 72 hours. The ball mill stops for 1 minute every 5 minutes of operation, and the rotation speed is changed at the same time. The rotation direction was changed from clockwise to counterclockwise, and the rotation continued for 5 minutes. Then, it was stopped for 1 minute and the rotation direction was changed back to counterclockwise. The ball milling time was 60 hours. After ball milling and mixing, tungsten carbide preforms containing polycarbosilane precursors were prepared by molding. The obtained tungsten carbide preforms containing polycarbosilane precursors were placed in a high-temperature pyrolysis furnace and slowly heated to 800°C under the protection of inert helium gas at a heating rate of 10°C / min. After holding at this temperature for 0.5 hours, the temperature was slowly lowered to prepare tungsten carbide-silicon carbide porous ceramics.

[0027] (2) Using the obtained tungsten carbide-silicon carbide porous ceramic as the substrate and nano-zirconium metal as the infiltrator, the tungsten carbide-silicon carbide porous ceramic and nano-zirconium metal are mixed in a volume ratio of 4.5:5 and placed in a crucible, and then placed in a high-temperature heat treatment device; under the protection of inert gas helium, the temperature is slowly raised to 1000℃, held for 1h and then cooled down at a cooling rate of 10℃ / min; the obtained semi-finished product and crucible are inverted and placed in the high-temperature heat treatment device again, under the protection of inert gas helium, the temperature is raised to 1600℃, held for 1h and then cooled down at a cooling rate of 10℃ / min, and dense metal ceramic can be obtained.

[0028] (3) Dense metal ceramics are placed in a sealed canister-shaped container with helium as the inert gas medium. Tungsten strips are fixed on the inner wall of the canister as the anode and cathode. A high-voltage current is passed between the anode and cathode to generate glow discharge. The discharge voltage is 50V. As the discharge current increases, the temperature inside the container increases to 900℃. The tungsten metal at the anode is ionized and injected into the ceramic at high speed under the action of the electric field. It further diffuses into the interior of the workpiece and combines with the carbon element in the ceramic material to form tungsten carbide. Then, carbonization is sprayed onto it. Tungsten was coated using a supersonic flame spraying method. The raw materials for the coating were a mixture of tungsten carbide powder and rhenium powder in a volume ratio of 1:9. The coating thickness was 0.8 mm, resulting in composite ceramics. The coating process parameters were as follows: kerosene flow rate of 28 L / h, kerosene pressure of 1.6 MPa, oxygen flow rate of 850 L / min, oxygen pressure of 2.0 MPa, powder feeding rate of 60 g / min, nitrogen flow rate of 12 L / min, nitrogen pressure of 1.0 MPa, and coating distance of 380 mm.

[0029] (4) Place the composite ceramic in a high-temperature vacuum tube furnace. First, evacuate the vacuum tube furnace to a vacuum of -0.1 MPa, and then introduce high-purity argon gas to equalize the atmospheric pressure. Repeat this step twice. Then, start the heating process and introduce high-purity hydrogen gas with a purity of ≥99.95%. During the reduction process, first raise the temperature to 600℃ and hold for 3 hours, then raise the temperature to 900℃ and hold for 1 hour. The heating rate during the heating process is 10℃ / min, and the hydrogen gas flow rate is 0.5 L / min. After the holding period, stop heating. The cooling process is to cool with the furnace to obtain the oxidation-resistant dense composite carbide-based rare metal ceramic.

[0030] Example 2

[0031] (1) Using tungsten carbide as raw material and polycarbosilane precursor as binder, the volume ratio of tungsten carbide and polycarbosilane precursor is 27:3. The prepared raw material powder is placed in a ball mill jar. The grinding balls are cemented carbide balls with a ball-to-material ratio of 10:1. Anhydrous ethanol is used as the grinding media, and the amount of anhydrous ethanol added is half the volume of the ball mill jar. The ball mill jar used is a cemented carbide ball mill jar. The ball mill speed is 250 rpm. The total running time of the equipment is 72 hours. The ball mill stops for 1 minute every 5 minutes of operation, and the rotation speed is changed at the same time. The direction of rotation was changed from clockwise to counterclockwise, and the rotation continued for 5 minutes. Then, it was stopped for 1 minute and the direction of rotation was changed back to counterclockwise. The ball milling time was 60 hours. After ball milling and mixing, tungsten carbide preforms containing polycarbosilane precursors were prepared by molding. The obtained tungsten carbide preforms containing polycarbosilane precursors were placed in a high-temperature pyrolysis furnace and slowly heated to 1200℃ under the protection of inert helium gas at a heating rate of 10℃ / min. After holding at this temperature for 1.25 hours, the temperature was slowly lowered to prepare tungsten carbide-silicon carbide porous ceramics.

[0032] (2) Using the obtained tungsten carbide-silicon carbide porous ceramic as the substrate and nano-zirconium metal as the infiltrator, the tungsten carbide-silicon carbide porous ceramic and nano-zirconium metal are mixed in a volume ratio of 5.5:5 and placed in a crucible, and then placed in a high-temperature heat treatment device; under the protection of inert gas helium, the temperature is slowly raised to 1500℃, held for 5h and then cooled down at a cooling rate of 10℃ / min; the obtained semi-finished product and crucible are inverted and placed in the high-temperature heat treatment device again, under the protection of inert gas helium, the temperature is raised to 1800℃, held for 1.5h and then cooled down at a cooling rate of 10℃ / min, and dense metal ceramic can be obtained;

[0033] (3) Dense metal ceramics are placed in a sealed canister-shaped container with helium as the inert gas medium. Tungsten strips are fixed on the inner wall of the canister as the anode and cathode. A high-voltage current is passed between the anode and cathode to generate glow discharge. The discharge voltage is 725V. As the discharge current increases, the temperature inside the container increases to 1000℃. The tungsten metal at the anode is ionized and injected into the ceramic at high speed under the action of the electric field. It further diffuses into the interior of the workpiece and combines with the carbon element in the ceramic material to form tungsten carbide. Then, carbon is sprayed onto it. Tungsten carbide was sprayed using a supersonic flame spraying method. The raw materials for spraying were a mixture of tungsten carbide powder and rhenium powder, with a volume ratio of 1:9.25. The spraying thickness was 1 mm, resulting in composite ceramics. The spraying process parameters were: kerosene flow rate of 31 L / h, kerosene pressure of 1.7 MPa, oxygen flow rate of 885 L / min, oxygen pressure of 2.1 MPa, powder feeding rate of 70 g / min, nitrogen flow rate of 13 L / min, nitrogen pressure of 1.2 MPa, and spraying distance of 395 mm.

[0034] (4) Place the composite ceramic in a high-temperature vacuum tube furnace. First, evacuate the vacuum tube furnace to a vacuum of -0.1 MPa, and then introduce high-purity argon gas to equalize the atmospheric pressure. Repeat this step twice. Then, start the heating process and introduce high-purity hydrogen gas with a purity of ≥99.95%. During the reduction process, first raise the temperature to 600℃ and hold for 3 hours, then raise the temperature to 900℃ and hold for 1 hour. The heating rate during the heating process is 10℃ / min, and the hydrogen gas flow rate is 0.5 L / min. After the holding period, stop heating. The cooling process is to cool with the furnace to obtain the oxidation-resistant dense composite carbide-based rare metal ceramic.

[0035] Example 3

[0036] (1) Using tungsten carbide as raw material and polycarbosilane precursor as binder, the volume ratio of tungsten carbide and polycarbosilane precursor is 52:3. The prepared raw material powder is placed in a ball mill jar. The grinding balls are cemented carbide balls with a ball-to-material ratio of 10:1. Anhydrous ethanol is used as the grinding media, and the amount of anhydrous ethanol added is half the volume of the ball mill jar. The ball mill jar used is a cemented carbide ball mill jar. The ball mill speed is 300 rpm. The total running time of the equipment is 72 hours. The ball mill stops for 1 minute every 5 minutes of operation, and the speed is changed at the same time. The rotation direction was changed from clockwise to counterclockwise, and the operation continued for 5 minutes. Then, the rotation was stopped for 1 minute, and the running direction was changed back to counterclockwise. The ball milling time was 60 hours. After ball milling and mixing, tungsten carbide preforms containing polycarbosilane precursors were prepared by molding. The obtained tungsten carbide preforms containing polycarbosilane precursors were placed in a high-temperature pyrolysis furnace and slowly heated to 1600℃ under the protection of inert helium gas at a heating rate of 10℃ / min. After holding at this temperature for 2 hours, the temperature was slowly lowered to prepare tungsten carbide-silicon carbide porous ceramics.

[0037] (2) Using the obtained tungsten carbide-silicon carbide porous ceramic as the substrate and nano-zirconium metal as the infiltrator, the tungsten carbide-silicon carbide porous ceramic and nano-zirconium metal are mixed in a volume ratio of 6.5:5 and placed in a crucible, and then placed in a high-temperature heat treatment device; under the protection of inert gas helium, the temperature is slowly raised to 2000℃, held for 10h and then cooled down at a cooling rate of 10℃ / min; the obtained semi-finished product and crucible are inverted and placed in the high-temperature heat treatment device again, under the protection of inert gas helium, the temperature is raised to 2000℃, held for 2h and then cooled down at a cooling rate of 10℃ / min, and dense metal ceramic can be obtained.

[0038] (3) The dense metal ceramic is placed in a sealed canister-shaped container with helium as the inert gas medium. A tungsten strip is fixed on the inner wall of the canister as the anode. A high-voltage current is passed between the anode and cathode to generate glow discharge. The discharge voltage is 1500V. As the discharge current increases, the temperature inside the container increases to 1100℃. The tungsten metal at the anode is ionized and injected into the ceramic at high speed under the action of the electric field. It further diffuses into the interior of the workpiece and combines with the carbon element in the ceramic material to form tungsten carbide. Then, carbon is sprayed onto it. Tungsten carbide was sprayed using a supersonic flame spraying method. The raw materials for spraying were a mixture of tungsten carbide powder and rhenium powder in a volume ratio of 1:9.5. The spraying thickness was 1.2 mm, resulting in composite ceramics. The spraying process parameters were: kerosene flow rate of 33 L / h, kerosene pressure of 1.8 MPa, oxygen flow rate of 920 L / min, oxygen pressure of 2.2 MPa, powder feeding rate of 80 g / min, nitrogen flow rate of 14 L / min, nitrogen pressure of 1.4 MPa, and spraying distance of 410 mm.

[0039] (4) Place the composite ceramic in a high-temperature vacuum tube furnace. First, evacuate the vacuum tube furnace to a vacuum of -0.1 MPa, and then introduce high-purity argon gas to equalize the atmospheric pressure. Repeat this step twice. Then, start the heating process and introduce high-purity hydrogen gas with a purity of ≥99.95%. During the reduction process, first raise the temperature to 600℃ and hold for 3 hours, then raise the temperature to 900℃ and hold for 1 hour. The heating rate during the heating process is 10℃ / min, and the hydrogen gas flow rate is 0.5 L / min. After the holding period, stop heating. The cooling process is to cool with the furnace to obtain the oxidation-resistant dense composite carbide-based rare metal ceramic.

[0040] Comparative Example 1

[0041] The difference between Comparative Example 1 and Example 2 lies in step (1). Step (1) is changed to: using tungsten carbide as raw material and polycarbosilane precursor as binder, the volume ratio of tungsten carbide and polycarbosilane precursor is 27:3, and tungsten carbide blank containing polycarbosilane precursor is prepared by molding; the obtained tungsten carbide blank containing polycarbosilane precursor is placed in a high-temperature pyrolysis furnace, and under the protection of inert gas helium, it is slowly heated to 1200°C at a heating rate of 10°C / min, held at 1.25h and then slowly cooled to prepare tungsten carbide-silicon carbide porous ceramic; the remaining steps are the same as in Example 2.

[0042] Comparative Example 2

[0043] The difference between Comparative Example 2 and Example 2 is that step (2) is omitted, and step (3) is changed to: placing tungsten carbide-silicon carbide porous ceramic into a sealed can-shaped container with helium as the inert gas medium, and fixing tungsten strips on the inner wall of the can as the anode and cathode. A high voltage current is passed between the anode and cathode to generate glow discharge, and the discharge voltage is 1500V; as the discharge current increases, the temperature inside the container increases to 1100℃, the tungsten metal at the anode is ionized, and under the action of the electric field, it is injected into the ceramic at high speed, and further diffuses into the interior of the workpiece and combines with the carbon element in the ceramic material to form a chemical reaction. Tungsten carbide was formed; then tungsten carbide was sprayed onto it using a supersonic flame spraying method: the raw material for spraying was a mixture of tungsten carbide powder and rhenium powder, with a volume ratio of 1:9.5, and the spraying thickness was 1.2 mm, thus obtaining a composite ceramic; the spraying process parameters were: kerosene flow rate of 33 L / h, kerosene pressure of 1.8 MPa, oxygen flow rate of 920 L / min, oxygen pressure of 2.2 MPa, powder feeding rate of 80 g / min, nitrogen flow rate of 14 L / min, nitrogen pressure of 1.4 MPa, and spraying distance of 410 mm; the remaining steps were the same as in Example 2.

[0044] Comparative Example 3

[0045] The difference between Comparative Example 3 and Example 2 lies in step (2). Step (3) is changed to: spraying dense metal ceramic with tungsten carbide using supersonic flame spraying method: the raw material for spraying is a mixture of tungsten carbide powder and rhenium powder, with a volume ratio of 1:9.25, and the spraying thickness is 1 mm, thus obtaining a composite ceramic; the spraying process parameters are: kerosene flow rate of 31 L / h, kerosene pressure of 1.7 MPa, oxygen flow rate of 885 L / min, oxygen pressure of 2.1 MPa, powder feeding rate of 70 g / min, nitrogen flow rate of 13 L / min, nitrogen pressure of 1.2 MPa, and spraying distance of 395 mm; the remaining steps are the same as in Example 2.

[0046] Comparative Example 4

[0047] The difference between Comparative Example 4 and Example 2 lies in step (3). Step (3) is changed to: placing the dense metal ceramic into a sealed can-shaped container with inert helium as the medium. A tungsten strip is fixed on the inner wall of the can as the anode. A high-voltage current is passed between the anode and cathode to generate glow discharge, with a discharge voltage of 725V. As the discharge current increases, the temperature inside the container increases to 1000℃. The tungsten metal at the anode is ionized and injected into the ceramic at high speed under the action of the electric field, and further diffuses into the interior of the workpiece and interacts with the ceramic. The carbon element in the material combines to form tungsten carbide; then tungsten carbide is sprayed onto it using a supersonic flame spraying method: the raw material for spraying is tungsten carbide powder, the spraying thickness is 1 mm, and a composite ceramic is obtained; the spraying process parameters are: kerosene flow rate is 31 L / h, kerosene pressure is 1.7 MPa, oxygen flow rate is 885 L / min, oxygen pressure is 2.1 MPa, powder feeding rate is 70 g / min, nitrogen flow rate is 13 L / min, nitrogen pressure is 1.2 MPa, and spraying distance is 395 mm; the remaining steps are the same as in Example 2.

[0048] Comparative Example 5

[0049] The difference between Comparative Example 5 and Example 2 lies in step (4). Step (3) is changed to: placing the dense metal ceramic into a sealed can-shaped container with inert helium as the medium, and fixing tungsten strips on the inner wall of the can as the anode and cathode. A high voltage current is passed between the anode and cathode to generate glow discharge, with a discharge voltage of 725V. As the discharge current increases, the temperature inside the container increases to 1000℃. The tungsten metal at the anode is ionized and injected into the ceramic at high speed under the action of the electric field, and further diffuses into the interior of the workpiece and combines with the carbon element in the ceramic material to generate tungsten carbide. Then it is sprayed with... Tungsten carbide was coated using a supersonic flame spraying method. The raw materials for spraying were a mixture of tungsten carbide powder and rhenium powder in a volume ratio of 1:9.25. The coating thickness was 1 mm, resulting in an oxidation-resistant, dense, complex carbide-based rare metal ceramic. The spraying process parameters were as follows: kerosene flow rate of 31 L / h, kerosene pressure of 1.7 MPa, oxygen flow rate of 885 L / min, oxygen pressure of 2.1 MPa, powder feeding rate of 70 g / min, nitrogen flow rate of 13 L / min, nitrogen pressure of 1.2 MPa, and spraying distance of 395 mm. The remaining steps were the same as in Example 2.

[0050] Example of effect

[0051] Table 1 below presents the performance analysis results of an antioxidant dense complex tungsten carbide-based rare metal ceramic using Examples 1 to 3 and Comparative Examples 1 to 5 of the present invention.

[0052] Table 1

[0053]

[0054] A comparison of the experimental data on density of the examples and comparative examples reveals that, during the preparation process, the present invention introduces silicon carbide into the material system through a polycarbosilane precursor. The polycarbosilane precursor acts as a crosslinking agent and pore-forming agent, which allows the ceramic matrix to decompose at a lower temperature to generate a tungsten carbide-silicon carbide composite porous ceramic with sufficient strength. Based on this, zirconium metal is used as a diffusion agent, and it is introduced through a metal melting reaction. The nano-sized zirconium metal fills the ceramic pores during the melting process, improving density while enhancing the oxidation resistance of the ceramic matrix. Then, a combination of ion implantation and spraying is used. Tungsten carbide is first implanted into the ceramic surface using ion implantation, forming a tungsten carbide-rich layer. During spraying, the high-temperature, high-speed tungsten carbide and metal binder combine with the previously implanted tungsten carbide-rich layer to form a transition surface. This greatly improves the bonding strength between the tungsten carbide sprayed layer and the ceramic matrix, thereby achieving the effects of improving density and oxidation resistance. A comparison of the experimental data on the antioxidant properties of the examples and comparative examples reveals that the present invention utilizes a high proportion of rare metal nanorhenium to achieve surface densification of the tungsten carbide-based metal ceramic composite coating under high-temperature conditions. The particle size and amount of rhenium added have a significant impact on the high-temperature performance of the composite coating: the operating temperature of the rhenium-containing tungsten carbide rare metal ceramic composite coating is higher than that of the ordinary tungsten carbide-based metal ceramic coating, which greatly improves the high-temperature resistance of the tungsten carbide-based metal ceramic coating, thereby making the prepared grains more stable and dense, thus achieving the antioxidant effect; finally, the oxygen content of the powder is further reduced by hydrogen reduction treatment to produce a highly active, low-oxygen composite carbide rare metal ceramic with a nanocrystalline structure.

[0055] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No markings in the claims should be construed as limiting the scope of the claims.

Claims

1. A method for preparing an oxidation-resistant, dense, composite tungsten carbide-based rare metal ceramic, characterized in that: It includes the following steps: (1) Using tungsten carbide as raw material and polycarbosilane precursor as binder, the volume ratio of tungsten carbide and polycarbosilane precursor is 27:

3. The prepared raw material powder is placed in a ball mill jar. The grinding balls are cemented carbide balls with a ball-to-material ratio of 10:

1. Anhydrous ethanol is used as the grinding media, and the amount of anhydrous ethanol added is half the volume of the ball mill jar. The ball mill jar used is a cemented carbide ball mill jar. The ball mill speed is 250 rpm. The total running time of the equipment is 72 hours. The ball mill stops for 1 minute every 5 minutes of operation, and the rotation speed is changed at the same time. The direction of rotation was changed from clockwise to counterclockwise, and the rotation continued for 5 minutes. Then, it was stopped for 1 minute and the direction of rotation was changed back to counterclockwise. The ball milling time was 60 hours. After ball milling and mixing, tungsten carbide blanks containing polycarbosilane precursors were prepared by molding. The obtained tungsten carbide blanks containing polycarbosilane precursors were placed in a high-temperature pyrolysis furnace and slowly heated to 1200℃ under the protection of inert helium gas at a heating rate of 10℃ / min. After holding at this temperature for 1.25 hours, the temperature was slowly lowered to prepare tungsten carbide-silicon carbide porous ceramics. (2) Using the obtained tungsten carbide-silicon carbide porous ceramic as the substrate and nano-zirconium metal as the infiltrator, the tungsten carbide-silicon carbide porous ceramic and nano-zirconium metal are mixed in a volume ratio of 5.5:5 and placed in a crucible, and then placed in a high-temperature heat treatment device; under the protection of inert gas helium, the temperature is slowly raised to 1500℃, held for 5h and then cooled down at a cooling rate of 10℃ / min; the obtained semi-finished product and crucible are inverted and placed in the high-temperature heat treatment device again, under the protection of inert gas helium, the temperature is raised to 1800℃, held for 1.5h and then cooled down at a cooling rate of 10℃ / min, and dense metal ceramic can be obtained; (3) Dense metal ceramics are placed in a sealed canister-shaped container with helium as the inert gas medium. Tungsten strips are fixed on the inner wall of the canister as the anode and cathode. A high-voltage current is passed between the anode and cathode to generate glow discharge. The discharge voltage is 725V. As the discharge current increases, the temperature inside the container increases to 1000℃. The tungsten metal at the anode is ionized and injected into the ceramic at high speed under the action of the electric field. It further diffuses into the interior of the workpiece and combines with the carbon element in the ceramic material to form tungsten carbide. Then, carbon is sprayed onto it. Tungsten carbide was coated using a supersonic flame spraying method. The raw materials for spraying were a mixture of tungsten carbide powder and rhenium powder in a volume ratio of 1:9.

25. The coating thickness was 1 mm, resulting in composite ceramics. The spraying process parameters were: kerosene flow rate of 31 L / h, kerosene pressure of 1.7 MPa, oxygen flow rate of 885 L / min, oxygen pressure of 2.1 MPa, powder feeding rate of 70 g / min, nitrogen flow rate of 13 L / min, nitrogen pressure of 1.2 MPa, and spraying distance of 395 mm. (4) Place the composite ceramic in a high-temperature vacuum tube furnace. First, evacuate the vacuum tube furnace to a vacuum of -0.1 MPa, and then introduce high-purity argon gas to equalize the atmospheric pressure. Repeat this step twice. Then, start the heating process and introduce high-purity hydrogen gas with a purity of ≥99.95%. During the reduction process, first raise the temperature to 600℃ and hold for 3 hours, then raise the temperature to 900℃ and hold for 1 hour. The heating rate during the heating process is 10℃ / min, and the hydrogen gas flow rate is 0.5 L / min. After the holding period, stop heating. The cooling process is furnace cooling, which yields an oxidation-resistant, dense composite carbide-based rare metal ceramic.

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