Preparation method of antioxidant compact compound tungsten carbide-based rare metal ceramic

Abstract

The invention discloses a preparation method of antioxidant compact compound tungsten carbide-based rare metal ceramic, and relates to the field of metal ceramic. Firstly, a silicon carbide substance is introduced through polycarbosilane, ceramic pores are filled with metal zirconium through a metal infiltration reaction, compactness is improved, and meanwhile the oxidation resistance of a ceramic matrix is enhanced; and then, a tungsten carbide enrichment layer is formed on the surface of the ceramic in a mode of combining ion injection infiltration and spraying, and the high-temperature and high-speed tungsten carbide and the metal adhesive are combined with the originally injected tungsten carbide enrichment layer into a whole during spraying. Secondly, high-proportion rare metal nano rhenium is adopted, and material surface densification of the tungsten carbide-based metal ceramic compound coating in a high-temperature environment is achieved; finally, through hydrogen reduction treatment, the oxygen content of the powder is further reduced, and the high-activity low-oxygen compound carbide rare metal ceramic with the nanocrystalline structure is produced. The ceramic prepared by the invention has the effects of oxidation resistance and compactness.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of ceramics, in particular to a preparation method of an oxidation-resistant dense composite tungsten carbide-based rare metal ceramic. BACKGROUND

[0003] Tungsten carbide plays an important role in modern industry. Its high hardness and heat resistance make it often used as a cutting tool material in the mechanical industry, high-hardness armor or armor-piercing bullet cores in the military industry. Tungsten carbide has high wear resistance and corrosion resistance, and is therefore also used to manufacture wear-resistant thermal protective coatings for easily-worn tools in the aerospace and precision industries. The research direction of the present application is how to combine tungsten carbide with metal ceramics to prepare a high-oxidation-resistant composite carbide metal ceramic. Rare metals are introduced into sintering and process modification to solve the above problems. SUMMARY

[0004] The present application aims to provide a preparation method of an oxidation-resistant dense composite tungsten carbide-based rare metal ceramic to solve the problems in the prior art.

[0005] To solve the above technical problems, the present application provides the following technical solution: an oxidation-resistant dense composite tungsten carbide-based rare metal ceramic, which is prepared by using tungsten carbide-silicon carbide composite porous ceramic as a matrix, infiltrating metal zirconium as a matrix, and then spraying a coating containing metal rhenium and tungsten carbide on the surface.

[0006] Further, the matrix is polycarbosilane into which silicon carbide material is introduced, and the cracking generates tungsten carbide-silicon carbide composite porous ceramic. Metal zirconium is introduced by metal infiltration reaction, and nanoscale metal zirconium fills the ceramic pores during the infiltration process to prepare the ceramic.

[0007] Further, the coating is prepared by a combination of ion implantation and spraying. Tungsten carbide is implanted on the surface of the ceramic by ion implantation, and then a mixture of tungsten carbide powder and rhenium powder is sprayed to form the coating.

[0008] Further, the preparation method comprises the following steps: (1) taking tungsten carbide as raw material, polycarbosilane precursor as binder, mixing tungsten carbide and polycarbosilane precursor in a volume ratio of 2-52:3, placing the mixed raw material powder in a ball mill jar, using hard alloy beads as ball milling beads, and the ball-to-material ratio being 10:1; using anhydrous ethanol as the ball milling medium, and the anhydrous ethanol being added in an amount of half of the volume of the ball mill jar; using a hard alloy ball mill jar, and the ball milling rotation speed being 200-300 rpm, the total running time of the equipment being 72 h, and the ball mill being stopped for 1 min every 5 min of running, and the rotation direction being changed from clockwise to counterclockwise, and the ball mill being stopped for 1 min again every 5 min of running, and the running direction being changed to counterclockwise, and the ball milling time being 60 h; after ball milling and mixing, a tungsten carbide green body containing polycarbosilane precursor is prepared by molding; the obtained tungsten carbide green body containing polycarbosilane precursor is placed in a high-temperature pyrolysis furnace, slowly heated to 800-1600 ℃ under inert gas protection, kept at the temperature for 0.5-2 h, and then slowly cooled to prepare a tungsten carbide-silicon carbide porous ceramic.

[0009] (2) taking the obtained tungsten carbide-silicon carbide porous ceramic as a base material, and nano-metallic zirconium as a penetrant, placing the two in a crucible, and then placing the crucible in a high-temperature heat treatment device; slowly heating to 1000-2000 ℃ under inert gas protection, keeping at the temperature for 1-10 h, and then cooling at a rate of 10 ℃ / min; inverting the obtained semi-finished product and the crucible, and then placing them in the high-temperature heat treatment device again, heating to 1600-2000 ℃ under inert gas protection, keeping at the temperature for 1-2 h, and then cooling at a rate of 10 ℃ / min, to obtain a dense metal ceramic; (3) placing the dense metal ceramic in a sealed tank-shaped container with inert gas as the medium, fixing a tungsten strip on the inner wall of the heat insulation layer of the tank body as an anode and a cathode to generate glow discharge by passing high-voltage current between the anode and the cathode, and the discharge voltage being 50-1500 V; as the discharge current continuously increases, the temperature in the container continuously increases to 900-1100 ℃, the tungsten metal of the anode is ionized, and is injected into the ceramic at a high speed under the action of the electric field, and further diffuses into the interior of the workpiece and combines with the carbon elements in the ceramic material to generate tungsten carbide; then, the tungsten carbide is sprayed, and the spraying method is supersonic flame spraying: the raw material for spraying is a mixture of tungsten carbide powder and rhenium powder, and the spraying thickness is 0.8-1.2 mm, to obtain a composite ceramic; (4) placing the duplex ceramic into a high-temperature vacuum tube furnace, first pumping the vacuum tube furnace to vacuum, and then introducing high-purity argon to atmospheric pressure, repeating the step twice; then starting the temperature rising process and introducing high-purity hydrogen, the purity of hydrogen is greater than or equal to 99.95%; the reduction process needs to first increase the temperature to 600 DEG C, and keep for 3 hours, then increase the temperature to 900 DEG C, and keep for 1 hour, the temperature rising rate is 10 DEG C / min, and the hydrogen flow rate is 0.5 L / min; after the keeping process is finished, stop heating, and the cooling process is furnace cooling, thus the oxidation-resistant dense duplex carbide-based rare metal ceramic is obtained.

[0010] Further, the inert gas in the preparation process is helium.

[0011] Further, the temperature rising rate in the step (1) is 10 DEG C / min.

[0012] Further, the volume ratio of the tungsten carbide-silicon carbide porous ceramic and the nano metal zirconium in the step (2) is 4.5-6.5:5.

[0013] Further, the volume ratio of the tungsten carbide powder and the rhenium powder in the step (3) is 1:9-9.5.

[0014] Further, the spraying process parameters in the step (3) are as follows: kerosene flow is 28-33 L / h, kerosene pressure is 1.6-1.8 MPa, oxygen flow is 850-920 L / min, oxygen pressure is 2.0-2.2 MPa, powder feeding rate is 60-80 g / min, nitrogen flow is 12-14 L / min, nitrogen pressure is 1.0-1.4 MPa, and spraying distance is 380 mm-410 mm.

[0015] Further, the vacuum degree in the step (4) is -0.1 MPa.

[0016] The duplex tungsten carbide-based rare metal ceramic is prepared by taking the tungsten carbide-silicon carbide duplex porous ceramic as a matrix, spraying the surface of the tungsten carbide-silicon carbide duplex porous ceramic after infiltrating the metal zirconium, and containing the metal rhenium and the tungsten carbide, so that the oxidation-resistant and dense effects are realized.

[0017] Firstly, the silicon carbide material is introduced into the material system by polycarbosilane precursor in the preparation process, the polycarbosilane precursor acts as a crosslinking agent and a pore-forming agent, which makes the ceramic matrix crack at a lower temperature to generate a tungsten carbide-silicon carbide composite porous ceramic with sufficient strength; on this basis, zirconium metal is introduced by metal infiltration reaction with zirconium metal as the infiltrant, the nanoscale zirconium metal fills the ceramic pores in the infiltration process, improves the density and strengthens the oxidation resistance of the ceramic matrix; then, the ion implantation and spraying are combined, the tungsten carbide is first implanted on the ceramic surface by ion implantation to form a tungsten carbide enrichment layer on the ceramic surface, and the high-temperature and high-speed tungsten carbide and the metal adhesive are combined with the original tungsten carbide enrichment layer to form a transition surface during spraying, which greatly improves the bonding strength of the tungsten carbide spraying layer and the ceramic matrix, thereby improving the density and oxidation resistance.

[0018] Secondly, a high proportion of rare metal nanometer rhenium is used to realize the surface densification of the tungsten carbide-based cermet composite coating in a high-temperature environment, the particle size and the amount of rhenium have a great influence on the high-temperature performance of the composite coating: the use temperature of the tungsten carbide-based cermet composite coating containing rhenium is higher than that of the ordinary tungsten carbide-based cermet coating, which greatly improves the high-temperature performance of the tungsten carbide-based cermet coating, thereby making the prepared grains more stable and dense, and achieving the effect of oxidation resistance; finally, the oxygen content of the powder is further reduced by hydrogen reduction treatment, and a high-activity low-oxygen composite carbide rare metal ceramic with nanocrystalline structure is produced. DETAILED DESCRIPTION

[0019] The technical solutions in the embodiments of the present application will be clearly and completely described below in combination with the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0020] In order to more clearly illustrate the method provided by the present application, the following embodiments are used for detailed description, and the test methods of various indexes of an oxidation-resistant dense composite tungsten carbide-based rare metal ceramic prepared in the following embodiments are as follows: Oxidation resistance: the composite tungsten carbide-based rare metal ceramic samples of the examples and the comparative examples are detected, ferric chloride solution with a concentration of 8.5±0.5g / L is dropped on the ceramic substrate, and no discoloration is observed after 15min, and the oxidation resistance effect meets the standard.

[0021] Density: the composite tungsten carbide-based rare metal ceramic samples of the examples and the comparative examples are detected, and the density test is carried out according to GB / T 25995-2010.

[0022] Example 1 (1) The tungsten carbide is used as raw material, and the polycarbosilane precursor is used as binder. The volume ratio of tungsten carbide and polycarbosilane precursor is 2:3. The mixed raw material powder is placed in a ball mill jar. The ball milling beads are cemented carbide beads, and the ball-to-material ratio is 10:1. The ball milling medium is anhydrous ethanol, and the amount of anhydrous ethanol added is half of the volume of the ball mill jar. The ball mill jar used is a cemented carbide ball mill jar, the ball milling speed is 200 rpm, the total running time of the equipment is 72 h, and the ball mill is operated for 5 min and then stopped for 1 min. At the same time, the rotation direction is changed from clockwise to counterclockwise. The ball mill is operated for another 5 min and then stopped for 1 min. The running direction is changed to counterclockwise. The ball milling time is 60 h. After ball milling and mixing, the tungsten carbide green body containing polycarbosilane precursor is prepared by molding. The obtained tungsten carbide green body containing polycarbosilane precursor is placed in a high-temperature pyrolysis furnace under the protection of inert gas helium. Slow heating to 800℃ at a rate of 10℃ / min, and slow cooling after holding for 0.5 h. The tungsten carbide-silicon carbide porous ceramic is prepared.

[0023] (2) The obtained tungsten carbide-silicon carbide porous ceramic is used as the base material, and nano-metallic zirconium is used as the infiltrant. The volume ratio of tungsten carbide-silicon carbide porous ceramic and nano-metallic zirconium is 4.5:5. After mixing, the mixture is placed in a crucible and then put into a high-temperature heat treatment equipment. Slow heating to 1000℃ under the protection of inert gas helium, holding for 1 h, and then cooling at a rate of 10℃ / min. The obtained semi-finished product and the crucible are inverted and then put into a high-temperature heat treatment equipment again. Slow heating to 1600℃ under the protection of inert gas helium, holding for 1 h, and then cooling at a rate of 10℃ / min. The dense metal ceramic is obtained. (3) The dense metal ceramic is placed in a sealed tank-shaped container with inert gas helium as the medium. The inner wall of the heat insulation layer of the tank body is lined with a tungsten strip as the anode and cathode to generate glow discharge by passing high-voltage current. The discharge voltage is 50 V. As the discharge current increases, the temperature in the container increases to 900℃. The tungsten metal of 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 elements in the ceramic material to form tungsten carbide. Then, the tungsten carbide is sprayed. The spraying method is supersonic flame spraying. The raw material for spraying is a mixture of tungsten carbide powder and rhenium powder with a volume ratio of 1:9. The spraying thickness is 0.8 mm. The prepared composite ceramic is obtained. The spraying process parameters are as follows: kerosene flow rate is 28 L / h, kerosene pressure is 1.6 MPa, oxygen flow rate is 850 L / min, oxygen pressure is 2.0 MPa, powder feeding rate is 60 g / min, nitrogen flow rate is 12 L / min, nitrogen pressure is 1.0 MPa, and spraying distance is 380 mm. (4) The compound ceramic is placed in a high-temperature vacuum tube furnace. The vacuum tube furnace is first evacuated to a vacuum degree of -0.1 MPa, and then high-purity argon is introduced to balance the atmospheric pressure. This step is repeated twice. Then, the temperature rising process is started, and high-purity hydrogen gas with a purity of ≥99.95% is introduced. The reduction process requires the temperature to be raised to 600°C first, and then the temperature is raised to 900°C after 3 hours of heat preservation. The temperature rising rate is 10°C / min, and the hydrogen flow rate is 0.5 L / min. After the heat preservation is completed, the heating is stopped, and the cooling process is carried out by cooling with the furnace to obtain the oxidation-resistant dense compound carbide-based rare metal ceramic.

[0024] Example 2 (1) The tungsten carbide is used as the raw material, and the polycarbosilane precursor is used as the binder. The volume ratio of tungsten carbide to polycarbosilane precursor is 27:3. The mixed raw material powder is placed in a ball mill jar. The ball milling beads are hard alloy beads, and the ball-to-material ratio is 10:1. The ball milling medium is anhydrous ethanol, and the anhydrous ethanol addition amount is half of the volume of the ball mill jar. The ball mill jar used is a hard alloy ball mill jar, and the ball mill rotation speed is 250 rpm. The total running time of the equipment is 72 hours. The ball mill is stopped every 5 minutes of operation for 1 minute, and the rotation direction is changed from clockwise to counterclockwise. The ball mill is then operated for another 5 minutes, and then stopped for 1 minute with the rotation direction changed to counterclockwise. The ball milling time is 60 hours. After ball milling and mixing, the tungsten carbide green body containing polycarbosilane precursor is prepared by molding. The obtained tungsten carbide green body containing polycarbosilane precursor is placed in a high-temperature pyrolysis furnace under the protection of inert gas helium. The temperature is slowly raised to 1200°C at a rate of 10°C / min, and the temperature is maintained for 1.25 hours before slowly cooling down. The tungsten carbide-silicon carbide porous ceramic is prepared.

[0025] (2) The obtained tungsten carbide-silicon carbide porous ceramic is used as the substrate, and nano-metallic zirconium is used as the infiltrant. The tungsten carbide-silicon carbide porous ceramic and nano-metallic zirconium are mixed in a volume ratio of 5.5:5 and then placed in a crucible, which is then placed in a high-temperature heat treatment device. The temperature is slowly raised to 1500°C under the protection of inert gas helium, and the temperature is maintained for 5 hours before cooling down at a rate of 10°C / min. The obtained semi-finished product and the crucible are inverted and placed again in the high-temperature heat treatment device. The temperature is raised to 1800°C under the protection of inert gas helium, and the temperature is maintained for 1.5 hours before cooling down at a rate of 10°C / min. The dense metal ceramic is obtained. (3) Put the dense cermet into a sealed tank container with inert gas helium as medium, the inner wall of the heat insulation layer of the tank is lined with a tungsten strip as an anode and a cathode to generate glow discharge by passing high voltage current between the anode and the cathode, the discharge voltage is 725V; as the discharge current continuously increases, the temperature in the container continuously increases to 1000℃, the tungsten metal of the anode is ionized and injected into the ceramic at high speed under the action of the electric field, and further diffuses into the workpiece and combines with the carbon element in the ceramic material to form tungsten carbide; then spray tungsten carbide on it, the spraying method is supersonic flame spraying method: the raw material for spraying is a mixture of tungsten carbide powder and rhenium powder, the volume ratio of the two is 1:9.25, the spraying thickness is 1mm, and the composite ceramic is prepared; the spraying process parameters are: kerosene flow is 31L / h, kerosene pressure is 1.7MPa, oxygen flow is 885L / min, oxygen pressure is 2.1MPa, powder feeding rate is 70g / min, nitrogen flow is 13L / min, nitrogen pressure is 1.2MPa, and spraying distance is 395mm; (4) Place the composite ceramic in a high-temperature vacuum tube furnace, first evacuate the vacuum tube furnace to a vacuum degree of -0.1MPa, then introduce high-purity argon to balance the atmospheric pressure, and repeat this step twice; then start the heating process and introduce high-purity hydrogen, the purity of hydrogen is ≥99.95%; the reduction process needs to first increase the temperature to 600℃, and keep it for 3h, then increase the temperature to 900℃, and keep it for 1h, the heating rate is 10℃ / min, and the hydrogen flow rate is 0.5L / min; after the holding is completed, stop heating, and cool down with the furnace to obtain the oxidation-resistant dense composite carbide-based rare metal ceramic.

[0026] Example 3 (1) Use tungsten carbide as raw material, polycarbosilane precursor as binder, and mix tungsten carbide and polycarbosilane precursor in a volume ratio of 52:3, place the mixed raw material powder in a ball mill jar, the ball milling beads are cemented carbide beads, the ball-to-material ratio is 10:1; the ball milling medium is anhydrous ethanol, and the anhydrous ethanol addition amount is half of the volume of the ball mill jar; the ball mill jar used is a cemented carbide ball mill jar, the ball mill rotation speed is 300rpm, the total running time of the equipment is 72h, and every 5min of operation is followed by 1min of stop, while the rotation direction is changed from clockwise to counterclockwise, and then every 5min of operation is followed by 1min of stop, and the running direction is changed to counterclockwise, the ball milling time is 60h; after ball milling and mixing, the tungsten carbide containing polycarbosilane precursor green body is prepared by molding; the obtained tungsten carbide containing polycarbosilane precursor green body is placed in a high-temperature pyrolysis furnace under the protection of inert gas helium, slowly heated to 1600℃ at a heating rate of 10℃ / min, and slowly cooled after holding for 2h to prepare tungsten carbide-silicon carbide porous ceramic.

[0027] (2) The obtained tungsten carbide-silicon carbide porous ceramic is used as a base material, and nano-metallic zirconium is used as a penetrant. The tungsten carbide-silicon carbide porous ceramic and the nano-metallic zirconium are mixed at a volume ratio of 6.5:5, and then 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 increased to 2000°C, and after 10 hours of heat preservation, the temperature is decreased at a rate of 10°C / min. The obtained semi-finished product and the crucible are inverted, and then placed in a high-temperature heat treatment device again. Under the protection of inert gas helium, the temperature is increased to 2000°C, and after 2 hours of heat preservation, the temperature is decreased at a rate of 10°C / min. A dense metal ceramic is obtained. (3) The dense metal ceramic is placed in a sealed tank-shaped container with inert gas helium as the medium. A tungsten strip is fixed on the inner wall of the heat insulation layer of the tank body as an anode and a cathode to generate glow discharge by passing high-voltage current between the anode and the cathode. The discharge voltage is 1500V. As the discharge current continuously increases, the temperature in the container continuously increases to 1100°C. The tungsten metal of the anode is ionized and injected into the ceramic at a high speed under the action of the electric field, and further diffuses into the workpiece and combines with the carbon elements in the ceramic material to form tungsten carbide. Then, the tungsten carbide is sprayed on the ceramic. The spraying method is supersonic flame spraying. The raw material for spraying is a mixture of tungsten carbide powder and rhenium powder at a volume ratio of 1:9.5. The spraying thickness is 1.2mm. A composite ceramic is prepared. The spraying process parameters are as follows: kerosene flow rate is 33L / h, kerosene pressure is 1.8MPa, oxygen flow rate is 920L / min, oxygen pressure is 2.2MPa, powder feeding rate is 80g / min, nitrogen flow rate is 14L / min, nitrogen pressure is 1.4MPa, and spraying distance is 410mm. (4) The composite ceramic is placed in a high-temperature vacuum tube furnace. The vacuum tube furnace is first evacuated to a vacuum degree of -0.1MPa, and then high-purity argon is introduced to balance the atmospheric pressure. This step is repeated twice. Then, the temperature is increased and high-purity hydrogen is introduced. The purity of the hydrogen is ≥99.95%. The reduction process requires that the temperature be increased to 600°C first, and then heat preserved for 3 hours. Then, the temperature is increased to 900°C, and then heat preserved for 1 hour. The temperature increasing rate is 10°C / min, and the hydrogen flow rate is 0.5L / min. After the heat preservation is completed, the heating is stopped, and the cooling process is carried out by cooling with the furnace. An oxidation-resistant dense composite carbide-based rare metal ceramic is obtained.

[0028] Comparative Example 1 The difference between Comparative Example 1 and Example 2 is that step (1) is changed, and step (1) is changed to: using tungsten carbide as raw material, polycarbosilane precursor as binder, mixing tungsten carbide and polycarbosilane precursor in a volume ratio of 27:3, and preparing tungsten carbide green body containing polycarbosilane precursor by molding; the obtained tungsten carbide green body containing polycarbosilane precursor is placed in a high-temperature pyrolysis furnace, protected by inert gas helium, slowly heated to 1200°C at a heating rate of 10°C / min, and slowly cooled after holding for 1.25 h to prepare tungsten carbide-silicon carbide porous ceramic; the rest of the steps are the same as those of Example 2.

[0029] Comparative Example 2 The difference between Comparative Example 2 and Example 2 is that there is no step (2), and step (3) is changed to: placing the tungsten carbide-silicon carbide porous ceramic into a sealed tank-shaped container with inert gas helium as the medium, lining the heat insulation layer of the inner wall of the tank with a tungsten strip as the anode and cathode to generate glow discharge by passing high-voltage current, and the discharge voltage is 1500V; as the discharge current continuously increases, the temperature in the container continuously increases to 1100°C, the tungsten metal of 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 generate tungsten carbide; then it is sprayed with tungsten carbide, and the spraying method is supersonic flame spraying: the raw material for spraying is a mixture of tungsten carbide powder and rhenium powder, the volume ratio of the two is 1:9.5, the spraying thickness is 1.2mm, and the composite ceramic is prepared; the spraying process parameters are: kerosene flow is 33L / h, kerosene pressure is 1.8MPa, oxygen flow is 920L / min, oxygen pressure is 2.2MPa, powder feeding rate is 80g / min, nitrogen flow is 14L / min, nitrogen pressure is 1.4MPa, and spraying distance is 410mm; the rest of the steps are the same as those of Example 2.

[0030] Comparative Example 3 The difference between Comparative Example 3 and Example 2 is that step (2) is changed, and step (3) is changed to: spraying the dense metal ceramic with tungsten carbide, and the spraying method is supersonic flame spraying: the raw material for spraying is a mixture of tungsten carbide powder and rhenium powder, the volume ratio of the two is 1:9.25, the spraying thickness is 1mm, and the composite ceramic is prepared; the spraying process parameters are: kerosene flow is 31L / h, kerosene pressure is 1.7MPa, oxygen flow is 885L / min, oxygen pressure is 2.1MPa, powder feeding rate is 70g / min, nitrogen flow is 13L / min, nitrogen pressure is 1.2MPa, and spraying distance is 395mm; the rest of the steps are the same as those of Example 2.

[0031] Comparative Example 4 Comparative Example 4 differs from Example 2 in that step (3) is changed to: the dense cermet is placed in a sealed pot-shaped container with inert gas helium as medium, a tungsten strip is fixed on the inner lining of the heat insulation layer of the inner wall of the pot body as anode and cathode to generate glow discharge by passing high voltage current between the anode and cathode, the discharge voltage is 725V; as the discharge current continuously increases, the temperature in the container continuously increases to 1000°C, the tungsten metal of 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 workpiece and combines with the carbon element in the ceramic material to generate tungsten carbide; then it is sprayed with tungsten carbide, the spraying method is supersonic flame spraying method: the raw material for spraying is tungsten carbide powder, the spraying thickness is 1mm, and the composite ceramic is prepared; the spraying process parameters are: kerosene flow is 31L / h, kerosene pressure is 1.7MPa, oxygen flow is 885L / min, oxygen pressure is 2.1MPa, powder feeding rate is 70g / min, nitrogen flow is 13L / min, nitrogen pressure is 1.2MPa, and spraying distance is 395mm; the remaining steps are the same as those of Example 2.

[0032] Comparative Example 5 Comparative Example 5 differs from Example 2 in that step (4) is changed to: the dense cermet is placed in a sealed pot-shaped container with inert gas helium as medium, a tungsten strip is fixed on the inner lining of the heat insulation layer of the inner wall of the pot body as anode and cathode to generate glow discharge by passing high voltage current between the anode and cathode, the discharge voltage is 725V; as the discharge current continuously increases, the temperature in the container continuously increases to 1000°C, the tungsten metal of 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 workpiece and combines with the carbon element in the ceramic material to generate tungsten carbide; then it is sprayed with tungsten carbide, the spraying method is supersonic flame spraying method: the raw material for spraying is a mixture of tungsten carbide powder and rhenium powder, the volume ratio of the two is 1:9.25, the spraying thickness is 1mm, and the obtained anti-oxidation dense composite tungsten carbide-based rare metal ceramic is prepared; the spraying process parameters are: kerosene flow is 31L / h, kerosene pressure is 1.7MPa, oxygen flow is 885L / min, oxygen pressure is 2.1MPa, powder feeding rate is 70g / min, nitrogen flow is 13L / min, nitrogen pressure is 1.2MPa, and spraying distance is 395mm; the remaining steps are the same as those of Example 2.

[0033] Effect Example The performance analysis results of one kind of anti-oxidation dense composite tungsten carbide-based rare metal ceramic prepared by using Examples 1 to 3 and Comparative Examples 1 to 5 of the present application are given in Table 1 below.

[0034] Table 1 From the experimental data comparison of the density of the examples and the comparative examples, it can be found that in the preparation process, the polycarbosilane precursor is used to introduce the silicon carbide material into the material system, the polycarbosilane precursor acts as a crosslinking agent and a pore-forming agent, which makes the ceramic matrix crack at a lower temperature to generate a tungsten carbide-silicon carbide composite porous ceramic with sufficient strength; on this basis, the metal zirconium is introduced by using the metal infiltration reaction, the nanoscale metal zirconium fills the ceramic pores in the infiltration process, improves the density, and strengthens the oxidation resistance of the ceramic matrix; then the ion implantation and spraying are combined, the tungsten carbide is implanted on the ceramic surface by using the ion implantation method, the tungsten carbide enrichment layer is formed on the surface of the ceramic, and the high-temperature and high-speed tungsten carbide and the metal adhesive are combined with the original tungsten carbide enrichment layer as a whole to form a transition surface, so that the bonding strength of the tungsten carbide spraying layer and the ceramic matrix is greatly improved, and the effects of improving the density and the oxidation resistance are achieved. From the experimental data comparison of the oxidation resistance of the examples and the comparative examples, it can be found that the high proportion of rare metal nanometer rhenium is used to realize the densification of the material surface of the tungsten carbide-based cermet composite coating in a high-temperature environment, the particle size of rhenium and the addition amount have a great influence on the high-temperature performance of the composite coating: the use temperature of the tungsten carbide rare metal ceramic composite coating containing rhenium is higher than that of the ordinary tungsten carbide-based cermet coating, the high-temperature performance of the tungsten carbide-based cermet coating is greatly improved, so that the prepared grains are more stable and dense, and the effect of oxidation resistance is achieved; finally, the hydrogen reduction treatment is used to further reduce the oxygen content of the powder, and the high-activity low-oxygen composite carbide rare metal ceramic with nanocrystalline structure is produced.

[0035] It will be obvious to a person skilled in the art that the application is not limited to the details of the above-described exemplary embodiments, and the application can be implemented in other specific forms without departing from the spirit or essential characteristics of the application. Therefore, the examples should be considered as exemplary and non-limiting, and the scope of the application is defined by the appended claims rather than the above description, and all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the application. Any mark in the claims should not be considered as limiting the involved claims.

Claims

1. A method for preparing an antioxidant, dense, complex 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 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. (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.

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