An oxidation-resistant dense complex tungsten carbide-based rare metal cermet and a method for preparing the same

Abstract

The application discloses an antioxidative dense complex tungsten carbide-based rare metal ceramic and a preparation method thereof, and relates to the field of metal ceramics. The application introduces silicon carbide by polycarbosilane, and metal zirconium fills the ceramic pores through metal infiltration reaction, so that the antioxidativity of the ceramic matrix is strengthened while the denseness is improved; then, the ion injection and spraying are combined 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 injected tungsten carbide enrichment layer to form an integrated whole. Secondly, high-proportion rare metal nano-rhenium is adopted to realize the densification of the material surface of the tungsten carbide-based metal ceramic complex coating in a high-temperature environment; finally, hydrogen reduction treatment is carried out to further reduce the oxygen content of the powder, and the high-activity low-oxygen complex carbide rare metal ceramic with a nano-crystal structure is produced. The ceramic prepared by the application has the effects of antioxidation and denseness.

Description

TECHNICAL FIELD

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

[0002] Metal ceramic is a composite material composed of ceramic hard phase and metal binder phase. It has good mechanical properties and use performance, and is an ideal structural material for manufacturing cutters, molds, wear-resistant parts, etc. It is well known that high-performance metal ceramic materials are important topics for industrialized countries to research and develop, are the teeth of modern industry, and are an important basis for measuring the industrial level of a country. Hard and super-hard materials are new materials supported by the state, and as processing materials for hard and super-hard materials and difficult-to-machine metal materials, their importance is self-evident. China's high-performance metal ceramic materials are basically dependent on imports, which not only has a high price, but also is limited in many aspects, which has a great impact on the process of China's industrial modernization.

[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, so it is also used to manufacture wear-resistant thermal protection coatings for tools that are easily worn in the aerospace and precision industries. How to combine tungsten carbide with metal ceramic to prepare a high-oxidation-resistant composite carbide metal ceramic is the research direction of the present application. Rare metals are introduced into sintering and process modification to solve the above problems. SUMMARY

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

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

[0006] Further, the matrix is prepared by introducing silicon carbide into polycarbosilane, cracking to form a tungsten carbide-silicon carbide composite porous ceramic, and introducing metal zirconium through a metal infiltration reaction to fill the ceramic pores in the infiltration process.

[0007] Further, the coating is prepared by a combination of ion implantation and spraying, wherein 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 following preparation steps are included:

[0009] (1) Using tungsten carbide as raw material, polycarbosilane precursor as binder, the volume ratio of tungsten carbide and polycarbosilane precursor is 2-52:3, the mixed raw material powder is placed in a ball mill jar, the ball milling beads are hard alloy beads, the ball-to-material ratio is 10:1; the ball milling medium is anhydrous ethanol, 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, the ball mill rotation speed is 200-300 rpm, the total running time of the equipment is 72 h, the ball mill is operated for 5 min, then it is stopped for 1 min, at the same time the rotation direction is changed from clockwise to counterclockwise, and the operation is continued for 5 min, then it is stopped for 1 min again, and 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, slowly heated to 800-1600℃ under inert gas protection, and slowly cooled after 0.5-2h of heat preservation, to prepare tungsten carbide-silicon carbide porous ceramic.

[0010] (2) The obtained tungsten carbide-silicon carbide porous ceramic is used as a substrate, and nano-metallic zirconium is used as a penetrant, both of which are placed in a crucible and then placed in a high-temperature heat treatment device; slowly heated to 1000-2000℃ under inert gas protection, heat preserved for 1-10h, and then cooled at a rate of 10℃ / min; the obtained semi-finished product and the crucible are inverted and placed again in a high-temperature heat treatment device, heated to 1600-2000℃ under inert gas protection, heat preserved for 1-2h, and then cooled at a rate of 10℃ / min, to obtain a dense metal ceramic;

[0011] (3) The dense metal ceramic is placed in a sealed tank-shaped container with inert gas as the medium, a tungsten strip is fixed on the inner wall of the heat insulation layer of the tank body as the anode and the cathode to generate glow discharge by passing high-voltage current between the anode and the cathode, and the discharge voltage is 50-1500V; 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 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 elements in the ceramic material to form 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 spraying thickness is 0.8-1.2mm, and a composite ceramic is prepared;

[0012] (4) placing the composite ceramic into a high-temperature vacuum tube furnace, first vacuumizing the vacuum tube furnace, then introducing high-purity argon to balance the atmospheric pressure, repeating the step twice, then starting the temperature rising process and introducing high-purity hydrogen, the purity of the hydrogen being greater than or equal to 99.95%, the reduction process needing to first raise the temperature to 600 DEG C, keeping the temperature for 3 hours, then raising the temperature to 900 DEG C, keeping the temperature for 1 hour, the temperature rising rate being 10 DEG C / min, the hydrogen flow rate being 0.5 L / min, after the keeping temperature process is over, stopping heating, and the cooling process being furnace cooling, thus obtaining the oxidation-resistant dense composite carbide-based rare metal ceramic.

[0013] Further, the inert gas in the preparation process is helium.

[0014] Further, the temperature rising rate in the step (1) is 10 DEG C / min.

[0015] Further, in the step (2), the tungsten carbide-silicon carbide porous ceramic and the nano metal zirconium are mixed in a volume ratio of 4.5-6.5:5.

[0016] Further, in the step (3), the volume ratio of the tungsten carbide powder and the rhenium powder is 1:9-9.5.

[0017] Further, in the step (3), the spraying process parameters are as follows: kerosene flow rate 28-33 L / h, kerosene pressure 1.6-1.8 MPa, oxygen flow rate 850-920 L / min, oxygen pressure 2.0-2.2 MPa, powder feeding rate 60-80 g / min, nitrogen flow rate 12-14 L / min, nitrogen pressure 1.0-1.4 MPa, and spraying distance 380-410 mm.

[0018] Further, in the step (4), the vacuum degree is -0.1 MPa.

[0019] The present application uses tungsten carbide-silicon carbide composite porous ceramic as the substrate, sprays the surface with metal rhenium and tungsten carbide after infiltrating metal zirconium, thus preparing the composite tungsten carbide-based rare metal ceramic, so as to realize the oxidation-resistant and dense effects.

[0020] 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 is introduced by metal infiltration reaction, the nanoscale 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, tungsten carbide is 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, which greatly improves the bonding strength of the tungsten carbide spraying layer and the ceramic matrix, thereby improving the density and oxidation resistance.

[0021] Secondly, a 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 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

[0022] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the embodiments of the present application. Obviously, the described embodiments are only a 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.

[0023] In order to more clearly illustrate the method provided by the present application, the following embodiments are described in detail. In the following embodiments, the test methods of various indexes of the oxidation-resistant and dense composite tungsten carbide-based rare metal ceramic are as follows:

[0024] 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 used for detection, the ferric chloride solution is dropped on the ceramic substrate, and no discoloration is observed after 15min, and the oxidation resistance effect meets the standard.

[0025] Density: The composite tungsten carbide-based rare metal ceramic samples of the examples and the comparative examples were detected, and the density test was performed according to GB / T 25995-2010.

[0026] Example 1

[0027] (1) Taking tungsten carbide as a raw material and polycarbosilane precursor as a binder, the volume ratio of tungsten carbide and polycarbosilane precursor was 2:3, the prepared raw material powder was placed in a ball mill jar, the ball milling beads were cemented carbide beads, the ball-to-material ratio was 10:1; the ball milling medium was anhydrous ethanol, and the anhydrous ethanol addition amount was half of the volume of the ball mill jar; the ball mill jar used was a cemented carbide ball mill jar, the ball mill rotation speed was 200 rpm, the total operation time of the equipment was 72 h, and every 5 min of operation, the rotation was stopped for 1 min, and the rotation direction was changed from clockwise to counterclockwise, and then the operation was continued for 5 min, and then the rotation was stopped for 1 min, and the rotation direction was changed to counterclockwise, and the ball milling time was 60 h; after ball milling and mixing, the tungsten carbide green body containing polycarbosilane precursor was prepared by molding; the obtained tungsten carbide green body containing polycarbosilane precursor was placed in a high-temperature pyrolysis furnace, and slowly heated to 800℃ under the protection of inert gas helium, the heating rate was 10℃ / min, and after 0.5 h of heat preservation, the temperature was slowly decreased, and the tungsten carbide-silicon carbide porous ceramic was prepared.

[0028] (2) The obtained tungsten carbide-silicon carbide porous ceramic was used as a substrate, and nano-metallic zirconium was used as a penetrant, the tungsten carbide-silicon carbide porous ceramic and the nano-metallic zirconium were mixed in a volume ratio of 4.5:5, and then placed in a crucible and then placed in a high-temperature heat treatment device; under the protection of inert gas helium, slowly heated to 1000℃, heat preservation for 1 h, and then cooled at a rate of 10℃ / min; the obtained semi-finished product and the crucible were inverted and then placed in a high-temperature heat treatment device, and under the protection of inert gas helium, heated to 1600℃, heat preservation for 1 h, and then cooled at a rate of 10℃ / min, and a dense metal ceramic was obtained;

[0029] (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 50V; as the discharge current continuously increases, the temperature in the container continuously 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 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, the spraying thickness is 0.8mm, and the composite ceramic is prepared; the spraying process parameters are: kerosene flow is 28L / h, kerosene pressure is 1.6MPa, oxygen flow is 850L / min, oxygen pressure is 2.0MPa, powder feeding rate is 60g / min, nitrogen flow is 12L / min, nitrogen pressure is 1.0MPa, and spraying distance is 380mm;

[0030] (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 period is over, stop heating, and cool down in the furnace to obtain the oxidation-resistant dense composite carbide-based rare metal ceramic.

[0031] Example 2

[0032] (1) Use tungsten carbide as raw material, polycarbosilane precursor as binder, and mix tungsten carbide and polycarbosilane precursor in a volume ratio of 27:3, 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 250rpm, the total operation time of the equipment is 72h, the ball mill is operated for 5min, then it is stopped for 1min, at the same time, the rotation direction is changed from clockwise to counterclockwise, and the operation is continued for 5min, then it is stopped for 1min again, 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 1200℃ at a heating rate of 10℃ / min, and slowly cooled after holding for 1.25h to prepare tungsten carbide-silicon carbide porous ceramic.

[0033] (2) The obtained porous tungsten carbide-silicon carbide ceramic is used as a base material, and nano-metallic zirconium is used as a penetrant. The porous tungsten carbide-silicon carbide ceramic and the nano-metallic zirconium are mixed at a volume ratio of 5.5:5, 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 1500°C, and after 5h 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 1800°C, and after 1.5h of heat preservation, the temperature is decreased at a rate of 10°C / min. A dense metal ceramic is obtained.

[0034] (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 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 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 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 1:9.25. The spraying thickness is 1mm. A composite ceramic is prepared. The spraying process parameters are as follows: kerosene flow rate is 31L / h, kerosene pressure is 1.7MPa, oxygen flow rate is 885L / min, oxygen pressure is 2.1MPa, powder feeding rate is 70g / min, nitrogen flow rate is 13L / min, nitrogen pressure is 1.2MPa, and spraying distance is 395mm.

[0035] (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 3h. Then, the temperature is increased to 900°C, and then heat preserved for 1h. 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 the furnace. An oxidation-resistant dense composite carbide-based rare metal ceramic is obtained.

[0036] Example 3

[0037] (1) taking tungsten carbide as raw material, polycarbosilane precursor as binder, mixing tungsten carbide and polycarbosilane precursor in a volume ratio of 52:3, placing the prepared raw material powder in a ball mill jar, using hard alloy beads as ball milling beads, the ball-to-material ratio being 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, the ball milling rotation speed is 300 rpm, the total running time of the equipment is 72 h, and every 5 min of operation of the ball mill is followed by 1 min of stop, while the rotation direction is changed from clockwise to counterclockwise, and then the operation is continued for 5 min, followed by 1 min of stop and change of the running direction to counterclockwise, the ball milling time being 60 h; after ball milling and mixing, the tungsten carbide green body containing polycarbosilane precursor is prepared by mold pressing; the obtained tungsten carbide green body containing polycarbosilane precursor is placed in a high-temperature pyrolysis furnace, slowly heated to 1600℃ under the protection of inert gas helium, and slowly cooled after 2 h of heat preservation, to prepare tungsten carbide-silicon carbide porous ceramic.

[0038] (2) taking the obtained tungsten carbide-silicon carbide porous ceramic as base material, mixing nano metal zirconium as infiltrant, mixing the two in a volume ratio of 6.5:5, and then placing them in a crucible and then into a high-temperature heat treatment device; slowly heating to 2000℃ under the protection of inert gas helium, and cooling after 10 h of heat preservation at a cooling rate of 10℃ / min; inverting the obtained semi-finished product and the crucible, and then placing them into the high-temperature heat treatment device again, heating to 2000℃ under the protection of inert gas helium, and cooling after 2 h of heat preservation at a cooling rate of 10℃ / min, to obtain dense metal ceramic;

[0039] (3) placing the dense metal ceramic into a sealed tank-shaped container with inert gas helium as medium, fixing a tungsten strip on the inner lining of the heat insulation layer of the inner wall of the tank body as anode and cathode to generate glow discharge by passing high-voltage current, and setting the discharge voltage to 1500V; as the discharge current continuously increases, the temperature in the container continuously increases to 1100℃, 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 elements in the ceramic material to generate tungsten carbide; then spraying tungsten carbide on it, and using the supersonic flame spraying method as the spraying method: the raw material for spraying is a mixture of tungsten carbide powder and rhenium powder, and the volume ratio of the two is 1:9.5, the spraying thickness is 1.2 mm, and the composite ceramic is prepared; the spraying process parameters are as follows: kerosene flow rate is 33 L / h, kerosene pressure is 1.8 MPa, oxygen flow rate is 920 L / min, oxygen pressure is 2.2 MPa, powder feeding rate is 80 g / min, nitrogen flow rate is 14 L / min, nitrogen pressure is 1.4 MPa, and spraying distance is 410 mm;

[0040] (4) Put the duplex ceramic into a high temperature vacuum tube furnace, first, vacuumize the tube furnace to -0.1 MPa, then, introduce high purity argon to balance the atmospheric pressure, 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°C, keep the temperature for 3 hours, then increase the temperature to 900°C, keep the temperature for 1 hour, the heating rate is 10°C / min, the hydrogen flow rate is 0.5 L / min; after the temperature keeping process, stop heating, cool down with the furnace, then the oxidation resistant dense duplex carbide based cermet is obtained.

[0041] Comparative Example 1

[0042] The difference between Comparative Example 1 and Example 2 is that step (1) is changed, the step (1) is changed to: use tungsten carbide as raw material, polycarbosilane precursor as binder, mix tungsten carbide and polycarbosilane precursor with a volume ratio of 27:3, prepare tungsten carbide green body containing polycarbosilane precursor by molding; put the obtained tungsten carbide green body containing polycarbosilane precursor into a high temperature pyrolysis furnace, slowly heat to 1200°C under the protection of inert gas helium, the heating rate is 10°C / min, keep the temperature for 1.25 hours, then slowly cool down, prepare tungsten carbide-silicon carbide porous ceramic; the rest of the steps are the same as Example 2.

[0043] Comparative Example 2

[0044] The difference between Comparative Example 2 and Example 2 is that there is no step (2), step (3) is changed to: put the tungsten carbide-silicon carbide porous ceramic 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 anode and cathode to generate glow discharge by passing high voltage current, 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, 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 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 1:9.5, the spraying thickness is 1.2mm, the duplex ceramic is prepared; the spraying process parameters are: kerosene flow is 33 L / h, kerosene pressure is 1.8 MPa, oxygen flow is 920 L / min, oxygen pressure is 2.2 MPa, powder feeding rate is 80 g / min, nitrogen flow is 14 L / min, nitrogen pressure is 1.4 MPa, spraying distance is 410 mm; the rest of the steps are the same as Example 2.

[0045] Comparative Example 3

[0046] The difference between Comparative Example 3 and Example 2 is that step (2) is different, and step (3) is changed to: spray the dense cermet with tungsten carbide by supersonic flame spraying method, the sprayed raw material is a mixture of tungsten carbide powder and rhenium powder, the volume ratio of the two is 1:9.25, the spraying thickness is 1 mm, and the composite ceramic is prepared; the spraying process parameters are: kerosene flow is 31 L / h, kerosene pressure is 1.7 MPa, oxygen flow is 885 L / min, oxygen pressure is 2.1 MPa, powder feeding rate is 70 g / min, nitrogen flow is 13 L / min, nitrogen pressure is 1.2 MPa, and spraying distance is 395 mm; the remaining steps are the same as those in Example 2.

[0047] Comparative Example 4

[0048] The difference between Comparative Example 4 and Example 2 is that step (3) is different, and step (3) is changed to: place the dense cermet into a sealed tank-shaped container with inert gas helium as the medium, the inner wall of the heat insulation layer of the tank is lined with a tungsten strip fixed as an anode and a cathode, and a high-voltage current is passed to generate glow discharge between the anode and the cathode, the discharge voltage is 725 V; 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 is 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 elements in the ceramic material to form tungsten carbide; then spray the tungsten carbide, the spraying method is supersonic flame spraying method: the sprayed raw material is tungsten carbide powder, the spraying thickness is 1 mm, and the composite ceramic is prepared; the spraying process parameters are: kerosene flow is 31 L / h, kerosene pressure is 1.7 MPa, oxygen flow is 885 L / min, oxygen pressure is 2.1 MPa, powder feeding rate is 70 g / min, nitrogen flow is 13 L / min, nitrogen pressure is 1.2 MPa, and spraying distance is 395 mm; the remaining steps are the same as those in Example 2.

[0049] Comparative Example 5

[0050] Comparative Example 5 differs from Example 2 in that step (4) is different, step (3) is changed as follows: the dense cermet is placed in a closed pot-shaped container with inert gas helium as medium, a tungsten rod is fixed on the inner wall of the heat insulation layer of the pot body as anode and cathode to generate glow discharge by passing high voltage current, the discharge voltage is 725 V; 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 form 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 1 mm, and the obtained dense composite carbide-based rare metal cermet is obtained; spraying process parameters: kerosene flow is 31 L / h, kerosene pressure is 1.7 MPa, oxygen flow is 885 L / min, oxygen pressure is 2.1 MPa, powder feeding rate is 70 g / min, nitrogen flow is 13 L / min, nitrogen pressure is 1.2 MPa, spraying distance is 395 mm; the rest of the steps are the same as Example 2.

[0051] Effect Example

[0052] The performance analysis results of one kind of dense composite tungsten carbide-based rare metal cermet with oxidation resistance using Examples 1 to 3 and Comparative Examples 1 to 5 of the present application are given in Table 1 below.

[0053] Table 1

[0054] Antioxidancy (discoloration) Density (percent) Example 1 No discoloration 98.25 Example 2 No discoloration 98.41 Example 3 No discoloration 98.28 Comparative Example 1 Slight discoloration 97.52 Comparative Example 2 Slight discoloration 92.36 Comparative Example 3 Slight discoloration 90.21 Comparative Example 4 Slight discoloration 92.68 Comparative Example 5 Slight discoloration 98.10

[0055] 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.

[0056] It will be apparent to those skilled in the art that the application is not limited to the details of the above-exemplified embodiments and can be implemented in other concrete forms without departing from the spirit or essential characteristics of the application. Therefore, the embodiments should be considered in all respects as illustrative and not restrictive, the scope of the application being defined by the appended claims rather than by the above description, and it is intended that all changes which come within the meaning and range of equivalency of the claims are embraced therein. Any reference signs in the claims should not be construed as limiting the claims.

Claims

1. A method for preparing an antioxidant, dense, complex tungsten carbide-based rare metal ceramic, characterized in that, The preparation steps include the following: (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. (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. (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. (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, and then 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. The inert gas used in the preparation process is helium; the heating rate in step (1) is 10℃ / min; 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; in step (3), the volume ratio of tungsten carbide powder and rhenium powder is 1:9-9.5; the spraying process parameters in step (3) are: kerosene flow rate of 28-33L / h, kerosene pressure of 1.6-1.8MPa, oxygen flow rate of 850-920L / min, oxygen pressure of 2.0-2.2MPa, powder feeding rate of 60-80g / min, nitrogen flow rate of 12-14L / min, nitrogen pressure of 1.0-1.4MPa, and spraying distance of 380mm-410mm; the vacuum degree in step (4) is -0.1MPa.