High-performance composite ceramic based on large-particle-size SiC powder and rapid preparation method

Abstract

The application discloses a high-performance composite ceramic based on large-diameter SiC powder and a rapid preparation method, and belongs to the technical field of ceramic matrix composite material preparation. The composite ceramic material is formed by pressure sintering with (Ti, Cr)B2 and ZrB2 formed in situ as a reinforcing and toughening phase and SiC as a matrix. The raw materials are composed of the following materials: TiH2 powder 8-10%, ZrH2 powder 15-19%, Cr powder 7-11%, TiSi2 powder 5-7%, ZrSi2 powder 8-10%, CrSi2 powder 6-8%, B4C powder 18-23%, and the rest is SiC powder; the mixed powder is prepared by a mechanical powder mixing method, the mixed powder is sintered into a blank body by a spark plasma sintering method, and the SiC-(Ti, Cr)B2-ZrB2 composite ceramic is obtained. The application solves the problems of sintering difficulty and poor product performance in the sintering preparation of SiC and its composite materials by using large-diameter SiC powder, and realizes the low-temperature densification sintering of the SiC-(Ti, Cr)B2-ZrB2 composite ceramic.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of ceramic matrix composite material preparation, and particularly relates to a high-performance composite ceramic based on large-particle-size SiC powder and a rapid preparation method thereof. BACKGROUND

[0002] SiC ceramics have been widely used in the fields of machinery, chemical industry, energy and military industry due to their high high-temperature strength, good wear and corrosion resistance, strong high-temperature oxidation resistance, high thermal conductivity and good chemical stability. However, SiC ceramics have problems such as high sintering temperature, low fracture toughness and difficult mechanical processing (non-conductive SiC ceramics prepared by pressureless sintering). The particle size and purity of SiC powder have a significant influence on the sintering density and mechanical properties of SiC ceramics. Studies have shown that SiC ceramics prepared by using submicron (0.1-1 μm) or nanoscale SiC powder under the same sintering conditions have more excellent performance than those prepared by using micron-sized powder. For example, the bending strength of SiC ceramics prepared by using SiC powder with an average particle size of 0.8 μm and 2.0 μm is 428 MPa and 315 MPa, respectively (Research on the process of sintering densification of SiC ceramics under normal pressure, Journal of the Chinese Ceramic Society, 2017, 1 (38) 20-25). However, the use of high-purity and ultra-fine SiC powder greatly increases the production cost, which is not conducive to the popularization and application of products. Therefore, it is of great practical significance to study the formula and process for preparing high-performance ceramics by using large-particle-size (average particle size > 10 μm) SiC powder based on the requirements of industrial application and production practice.

[0003] On the other hand, studies have shown that increasing the sintering temperature can increase the density of SiC ceramics, thereby improving their bending strength and fracture toughness. However, high sintering temperature requires high sintering equipment, thereby increasing the production cost. Therefore, it is of great significance to reduce the sintering temperature of SiC ceramics while improving their comprehensive mechanical properties and mechanical processing performance for their application.

[0004] Transition metal borides have excellent mechanical properties such as high melting point, high hardness and high wear resistance, as well as good electrical conductivity and chemical stability. Studies have shown that the introduction of an appropriate amount of TiB2 or ZrB2 and other borides into SiC powder can improve the sintering performance of SiC (reduce the sintering temperature) and improve the comprehensive performance (mechanical properties and mechanical processing performance) of SiC ceramics. However, if TiB2 or ZrB2 and other borides are directly mixed into SiC powder in the form of ordinary powder, a high sintering temperature or a long sintering time is still required to obtain a dense bulk, thereby limiting the improvement of the overall performance of SiC ceramic composites and increasing the production cost. In addition, the improvement of the comprehensive performance of SiC ceramics by introducing only one kind of boride is limited. At present, there is no report on the sintering technology for preparing large-particle-size SiC ceramics by using borides as sintering additives.

[0005] Therefore, in view of the problems of sintering difficulty and poor performance of SiC ceramic products for large particle size SiC powder, it is an urgent problem for those skilled in the art to provide a method for using large particle size (average particle size > 20 μm) SiC powder as raw material, which can quickly sinter and densify SiC ceramic at a lower temperature, and improve the comprehensive mechanical properties and machining performance. SUMMARY

[0006] Therefore, the present application provides a preparation method of high-performance composite ceramic. Specifically, it relates to how to design a formula and a preparation method of composite material which can quickly sinter and densify SiC ceramic at a lower temperature and improve the comprehensive mechanical properties and machining performance of the composite material under the premise of using large particle size SiC powder as raw material. The present application uses large particle size SiC powder (average particle size 20-30 μm) as raw material, generates (Ti, Cr)B2 and ZrB2 two borides at a lower sintering temperature to improve the comprehensive performance of the composite material, and realizes the low-temperature and short-time densification sintering of high-performance composite ceramic material which can be processed by wire electrical discharge machining.

[0007] In order to achieve the above-mentioned purpose, the present application adopts the following technical scheme:

[0008] A rapid preparation method of high-performance composite ceramic based on large particle size SiC powder, comprising the following steps:

[0009] 1) configuring a mixed powder

[0010] Take transition metal hydride powder, transition metal powder, transition metal silicide powder, B4C powder and SiC powder, and prepare a mixed powder by mechanical mixing;

[0011] 2) preparing a composite ceramic

[0012] Place the obtained mixed powder in a graphite mold, and perform pressure sintering under vacuum conditions to obtain a composite ceramic.

[0013] The transition metal hydride powder in step 1) is a mixture of TiH2 and ZrH2; the transition metal powder is Cr; and the transition metal silicide powder is a mixture of TiSi2, ZrSi2 and CrSi2.

[0014] The mixed powder is composed of raw materials with the following mass percentages: TiH2 powder 8-10%, ZrH2 powder 15-19%, Cr powder 7-11%, TiSi2 powder 5-7%, ZrSi2 powder 8-10%, CrSi2 powder 6-8%, B4C powder 18-23%, and the balance is SiC powder.

[0015] The beneficial effect is that TiH2 powder and ZrH2 powder are used instead of Ti powder and Zr powder, the main purpose is that Ti and Zr are easy to oxidize, and TiH2 and ZrH2 powder will decompose into pure metal and hydrogen during heating, thereby avoiding the oxidation of Ti and Zr.

[0016] By in-situ reaction, Ti, Zr and Cr and transition metal silicide MSi2 (M = Ti, Cr, Zr) and B4C react to form metal boride and SiC during heating, reduce the sintering temperature, and form uniformly distributed boride and SiC.

[0017] TiH2 and ZrH2 powder decompose into Ti and Zr and hydrogen when heated to about 700℃. At a sintering temperature of about 1000℃, MSi2 begins to decompose and release Si, and Ti, Zr and Cr transition metal elements and metal element M in transition metal silicide MSi2 (M = Ti, Cr, Zr) begin to react with B element in B4C to form MB2. At about 1300℃, MSi2 is completely decomposed, Si exists in a free state in the powder, and continues to react to form MB2. At about 1410℃, Si begins to melt and reacts with C element in B4C to form SiC. During sintering, because the atomic radii of Ti and Cr are relatively close, the positions of some Ti atoms or Cr atoms in the TiB2 or CrB2 lattice can be replaced by each other, thus forming a (Ti, Cr)B2 phase. The final sintered product is SiC, (Ti, Cr)B2 and ZrB2. During sintering, the following reactions mainly occur:

[0018] 3ZrH2(s) + ZrSi2(s) + 2B4C(s) = 4ZrB2(s) + 2SiC(s) + 3H2(g)

[0019] 3TiH2(s) + 3Cr(s) + TiSi2(s) + CrSi2(s) + 4B4C(s) = 8(Ti,Cr)B2(s) + 4SiC(s) + 3H2(g)

[0020] In step 1), the average particle size of the transition metal hydride powder, the transition metal powder, the transition metal silicide powder and the B4C powder is 1-10 μm, and the purity is not less than 98%; the average particle size of the SiC powder is 20-30 μm, and the purity is not less than 98%.

[0021] In step 1), the mechanical mixing of the powder is wet ball milling, and the mixed raw materials are put into a ball mill, and wet milling is carried out for 4 h with anhydrous ethanol as the medium to obtain a wet mixed powder;

[0022] The ball milling speed is 300 r / min, and the ball-to-material ratio is 4:1.

[0023] The obtained wet mixed powder is taken out and dried and sieved;

[0024] The drying temperature is 50 DEG C, and the drying time is 10 h; and the mesh number of the sieve is 200 meshes.

[0025] The pressure sintering is discharge plasma sintering, the sintering vacuum degree is less than 20 Pa, and the gradient heating and stepwise pressurizing mode is adopted.

[0026] The gradient heating and stepwise pressurizing mode is as follows:

[0027] The graphite mold is pre-pressed at a pressure of 1-3 MPa, heated to 650-800 DEG C at a heating rate of 80-120 DEG C / min, and then pressurized to 10-15 MPa, and heated to 1300-1350 DEG C at a heating rate of 80-120 DEG C / min, and pressurized to 45-55 MPa, and kept for 5-10 min; the heating rate is kept unchanged, and the temperature is continuously increased to 1500-1600 DEG C, and kept for 5-15 min; after the keeping, the pressure is decreased to 0 MPa at a rate of 30-50 MPa / min, and the sample is cooled in the furnace.

[0028] Preferably, the graphite mold is pre-pressed at a pressure of 3 MPa, heated to 700 DEG C at a heating rate of 100 DEG C / min, and kept for 10 min, so that the TiH2 and ZrH2 powders are decomposed into Ti and Zr and hydrogen; then pressurized to 15 MPa, and heated to 1350 DEG C at a heating rate of 100 DEG C / min, and pressurized to 50 MPa, and kept for 10 min; the heating rate is kept unchanged, and the temperature is continuously increased to 1500-1600 DEG C, and kept for 10 min; after the keeping, the pressure is decreased to 0 MPa at a rate of 30 MPa / min, and the sample is cooled in the furnace.

[0029] The gradient heating is mainly to make the hydrogen gas generated in the heating process of the hydride powder be discharged, and to control the formation of chemical reaction products (boride and free silicon formed in the process). The stepwise pressurizing is mainly to cooperate with the gradient heating, and is beneficial to the discharge of the hydrogen gas generated in the heating process of the hydride powder, and is beneficial to the improvement of the density of the sintered body.

[0030] The application also protects the high-performance composite ceramic prepared by the above method, wherein the composite ceramic material is prepared by pressure sintering, and (Ti, Cr)B2 and ZrB2 formed in situ by reaction are used as a reinforcing and toughening phase, and SiC is used as a matrix.

[0031] Compared with the prior art, the application has the following beneficial effects:

[0032] (1) The present application uses TiH2, ZrH2, Cr, TiSi2, ZrSi2, CrSi2, B4C and SiC powder as raw materials, and through pressure sintering, a SiC composite ceramic material with high density, good mechanical properties and excellent sintering performance is prepared, realizing low-temperature (1500-1600℃) and short-time (5-15min) densification sintering of SiC composite ceramic, solving the problems of high sintering temperature and long holding time of SiC ceramic.

[0033] (2) Since the present application uses large-particle-size SiC powder (average particle size 20-30μm) as raw material, compared with the products prepared by sintering with high-purity and ultra-fine SiC powder as raw material, it has the advantage of low cost, and is suitable for industrial application requirements and actual production.

[0034] (3) After TiH2, ZrH2, Cr, TiSi2, ZrSi2, CrSi2, B4C and SiC powder are mixed in a specific ratio, (Ti,Cr)B2 and ZrB2 phases are generated in-situ during the process of spark plasma sintering, promoting sintering densification, and making the combination strength between the matrix and the toughening phase high. Since the thermal expansion coefficients of (Ti,Cr)B2 and ZrB2 are different from that of SiC, the presence of these phases can improve the fracture toughness of SiC ceramic, thereby improving the comprehensive mechanical properties of the composite ceramic.

[0035] (4) Compared with the method of directly adding TiB2 powder, CrB2 powder and ZrB2 powder to SiC, the present application introduces multiple second phases through in-situ reaction and makes them uniformly distributed in the composite ceramic, solving the problem of uniform dispersion of TiB2, CrB2 and ZrB2 in the composite ceramic, and improving the comprehensive performance of the ceramic.

[0036] (5) Through in-situ reaction, (Ti,Cr)B2 and ZrB2 with good electrical conductivity are generated at the same time, making the composite ceramic capable of being processed using electric spark cutting, and solving the problem of difficult mechanical processing of SiC ceramic. BRIEF DESCRIPTION OF DRAWINGS

[0037] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are only embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor on the basis of the provided drawings.

[0038] Figure 1 XRD pattern of the composite ceramic material prepared according to embodiment 2 of the present application.

[0039] Figure 2SEM image of the composite ceramic material prepared according to the embodiment 2 of the present application.

[0040] Figure 3 SEM image of the composite ceramic material prepared according to the embodiment 3 of the present application.

[0041] Figure 4 SEM high-magnification image of the composite ceramic material prepared according to the embodiment 3 of the present application.

[0042] Figure 5 SEM image of the composite ceramic material prepared according to the embodiment 4 of the present application. DETAILED DESCRIPTION

[0043] The technical solutions in the embodiments of the present application will be apparently and completely described in combination with the drawings of 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 the other embodiments obtained by a person of ordinary skill in the art without any creative work fall within the protection scope of the present application.

[0044] Embodiment 1

[0045] A rapid preparation method of high-performance composite ceramic based on large-particle-size SiC powder is prepared according to the following steps:

[0046] Preparation of mixed powder

[0047] According to the mass percentage, 9.67% TiH2 powder (purity 99%, average particle size 5 μm), 18.08% ZrH2 powder (purity 99%, average particle size 5 μm), 10.47% Cr powder (purity 99%, average particle size 5 μm), 6.73% TiSi2 powder (purity 99%, average particle size 10 μm), 9.53% ZrSi2 powder (purity 99%, average particle size 10 μm), 7% CrSi2 powder (purity 99%, average particle size 10 μm), 22.32% B4C powder (purity 97%, average particle size 3 μm), and 16.2% SiC powder (purity 98%, average particle size 23 μm) are weighed. The weighed powder is poured into a ball milling tank, anhydrous ethanol is used as a ball milling medium, the ball-to-material ratio is 4:1, the ball milling tank is placed in a planetary ball mill, the rotation speed of the ball mill is 300 r / min, ball milling is performed for 4 h until complete mixing and uniformity, and then the ball milling tank is placed in a vacuum drying box for drying at 50°C for 10 h, and then the mixed powder is obtained by passing through a 200-mesh sieve;

[0048] Discharge plasma sintering

[0049] The mixed powder was assembled into a graphite mold with an inner diameter of 20 mm, and was placed into a spark plasma sintering furnace. The graphite mold was pre-pressed at a pressure of 3 MPa, and the sintering furnace was vacuumized to 15 Pa at room temperature. The temperature was raised to 700 ℃ at a rate of 100 ℃ / min, and the pressure was increased to 15 MPa. Then, the temperature was continuously raised to 1350 ℃, and the pressure was increased to 50 MPa. The temperature was maintained for 10 min, and then the temperature was continuously raised to 1600 ℃ at the same rate. The pressure was decreased to 0 MPa at a rate of 30 MPa / min after the temperature maintenance was completed, and the sample was cooled in the furnace.

[0050] Example 2

[0051] A high-performance composite ceramic based on large-particle-size SiC powder and a rapid preparation method thereof are prepared according to the following steps:

[0052] Preparation of mixed powder

[0053] According to the mass percentage, 8.53% TiH2 powder (purity 99%, average particle size 5 μm), 15.94% ZrH2 powder (purity 99%, average particle size 5 μm), 8.89% Cr powder (purity 99%, average particle size 5 μm), 5.87% TiSi2 powder (purity 99%, average particle size 10 μm), 8.32% ZrSi2 powder (purity 99%, average particle size 10 μm), 6.11% CrSi2 powder (purity 99%, average particle size 10 μm), 18.9% B4C powder (purity 97%, average particle size 3 μm), and 27.44% SiC powder (purity 98%, average particle size 23 μm) were weighed. The weighed powder was poured into a ball mill tank, anhydrous ethanol was used as the ball milling medium, and the ball-to-material ratio was 4:1. The ball mill tank was placed in a planetary ball mill, the rotation speed of the ball mill was 360 r / min, and the ball milling was performed for 10 h until the powder was completely mixed and uniform. Then, the ball mill tank was placed in a vacuum drying box and dried at 50 ℃ for 10 h. The mixed powder was sieved through a 200-mesh sieve.

[0054] Spark plasma sintering

[0055] The mixed powder was assembled into a graphite mold with an inner diameter of 20 mm, and was placed into a spark plasma sintering furnace. The graphite mold was pre-pressed at a pressure of 3 MPa, and the sintering furnace was vacuumized to 15 Pa at room temperature. The temperature was raised to 700 ℃ at a rate of 100 ℃ / min, and the pressure was increased to 15 MPa. Then, the temperature was continuously raised to 1350 ℃, and the pressure was increased to 50 MPa. The temperature was maintained for 10 min, and then the temperature was continuously raised to 1500 ℃ at the same rate. The pressure was decreased to 0 MPa at a rate of 30 MPa / min after the temperature maintenance was completed, and the sample was cooled in the furnace.

[0056] Example 3

[0057] A high-performance composite ceramic based on large-particle-size SiC powder and a rapid preparation method thereof, the mixed powder is prepared in the same manner as in Example 2, and the spark plasma sintering step is as follows:

[0058] The mixed powder is assembled into a graphite mold with an inner diameter of 20 mm, placed into a spark plasma sintering furnace, and the graphite mold is pre-pressed at a pressure of 3 MPa. The sintering furnace is vacuumed to 15 Pa at room temperature, heated to 700°C at a rate of 100°C / min, and held for 10 min. The pressure is increased to 15 MPa, and then the temperature is continuously increased to 1350°C, the pressure is increased to 50 MPa, and held for 10 min. The temperature is continuously increased to 1500°C at the same rate, and held for 15 min. After the holding is completed, the pressure is decreased to 0 MPa at a rate of 30 MPa / min, and the sample is cooled in the furnace.

[0059] Example 4

[0060] A high-performance composite ceramic based on large-particle-size SiC powder and a rapid preparation method thereof, the mixed powder is prepared in the same manner as in Example 2, and the spark plasma sintering step is as follows:

[0061] The mixed powder is assembled into a graphite mold with an inner diameter of 20 mm, placed into a spark plasma sintering furnace, and the graphite mold is pre-pressed at a pressure of 3 MPa. The sintering furnace is vacuumed to 15 Pa at room temperature, heated to 700°C at a rate of 100°C / min, and held for 10 min. The pressure is increased to 15 MPa, and then the temperature is continuously increased to 1350°C, the pressure is increased to 50 MPa, and held for 10 min. The temperature is continuously increased to 1600°C at the same rate, and held for 10 min. After the holding is completed, the pressure is decreased to 0 MPa at a rate of 30 MPa / min, and the sample is cooled in the furnace.

[0062] Comparative Example 1

[0063] This comparative example is prepared by a process of spark plasma sintering technology for pure SiC ceramic as follows:

[0064] SiC powder (purity 98%, average particle size 23 μm) is assembled into a graphite mold with an inner diameter of 20 mm, placed into a spark plasma sintering furnace, and the graphite mold is pre-pressed at a pressure of 3 MPa. The sintering furnace is vacuumed to 15 Pa at room temperature, heated to 700°C at a rate of 100°C / min, and held for 10 min. The pressure is increased to 15 MPa, and then the temperature is continuously increased to 1350°C, the pressure is increased to 50 MPa, and held for 10 min. The temperature is continuously increased to 1500°C at the same rate, and held for 10 min. After the holding is completed, the pressure is decreased to 0 MPa at a rate of 30 MPa / min, and the sample is cooled in the furnace.

[0065] Comparative Example 2

[0066] The comparative example 1 is prepared by the following process of SiC ceramic by the technique of spark plasma sintering:

[0067] The SiC powder (purity 98%, average particle size 23 μm) powder is assembled into a graphite mold with an inner diameter of 20 mm, and is put into a spark plasma sintering furnace. The graphite mold is pre-pressed at a pressure of 3 MPa, and the sintering furnace is vacuumed at room temperature to 15 Pa. The temperature is raised to 700 °C at a rate of 100 °C / min, and the pressure is increased to 15 MPa. Then the temperature is continuously raised to 1350 °C, and the pressure is increased to 50 MPa. The temperature is maintained for 10 min, and the temperature is continuously raised to 1600 °C at the same rate. The pressure is reduced to 0 MPa at a rate of 30 MPa / min after the temperature maintaining is finished, and the sample is cooled with the furnace.

[0068] Comparative example 3

[0069] The comparative example 1 is prepared by the following process of SiC ceramic by the technique of spark plasma sintering:

[0070] (1) Preparation of mixed powder

[0071] According to the mass percentage, 41.34% of SiC powder (purity 98%, average particle size 23 μm), 15.93% of TiB2 powder (purity 98.5%, average particle size 5 μm), 16.87% of CrB2 powder (purity 98.5%, average particle size 5 μm) and 25.86% of ZrB2 powder (purity 98.5%, average particle size 5 μm) are weighed, and the powders are poured into a ball mill tank with anhydrous ethanol as the ball milling medium. The ball-to-material ratio is 4:1, and the ball mill tank is placed in a planetary ball mill with a rotation speed of 300 r / min. The ball milling is carried out for 4 h until the powders are completely mixed and uniform. Then the ball mill tank is placed in a vacuum drying box at 50 °C for 10 h, and the mixed powder is obtained by sieving through a 200 mesh sieve.

[0072] (2) Spark plasma sintering

[0073] The mixed powder is assembled into a graphite mold with an inner diameter of 20 mm, and is put into a spark plasma sintering furnace. The graphite mold is pre-pressed at a pressure of 3 MPa, and the sintering furnace is vacuumed at room temperature to 15 Pa. The temperature is raised to 700 °C at a rate of 100 °C / min, and the pressure is increased to 15 MPa. Then the temperature is continuously raised to 1350 °C, and the pressure is increased to 50 MPa. The temperature is maintained for 10 min, and the temperature is continuously raised to 1500 °C at the same rate. The pressure is reduced to 0 MPa at a rate of 30 MPa / min after the temperature maintaining is finished, and the sample is cooled with the furnace.

[0074] Characterization analysis:

[0075] The composite ceramic material prepared in Example 2 was characterized by XRD. Figure 1 The results show that the composite ceramic material prepared in this application is based on SiC as the matrix and (Ti, Cr) B2 and ZrB2 formed by in-situ reaction as the reinforcing and toughening phases.

[0076] Performance Testing

[0077] The various properties of the embodiments of the present invention were tested according to the following methods: (1) relative density was measured using the Archimedes drainage method; (2) Vickers hardness was measured using an HV5 Vickers hardness tester; (3) fracture toughness was tested using the single-edge notched beam method using an electronic universal material testing machine; (4) flexural strength was tested using the three-point bending method using an electronic universal material testing machine. Three samples were selected for each group, and the data are the average of the three samples. The ceramic material data obtained from Examples 1-4 and Comparative Examples 1-3 are shown in Table 1 below:

[0078] Table 1 Properties of SiC-(Ti,Cr)B2-ZrB2 composite ceramic materials

[0079]

[0080] The data in the table above demonstrate that, under identical sintering conditions, the composite material obtained using the present invention exhibits significantly superior performance to the ceramic material obtained using the comparative example. Furthermore, compared to direct powder mixing, the composite ceramic prepared using the in-situ reaction to form SiC, (Ti,Cr)B2, and ZrB2 exhibits significantly improved performance.

[0081] Figures 2-5 The SEM images of the products prepared in Examples 2-4 are shown in FIG. Figures 2-5 It can be seen that during the spark plasma sintering process, in addition to large-grained SiC, evenly distributed SiC, (Ti,Cr)B2 and ZrB2 phases were generated by in-situ reaction.

[0082] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. Reference can be made to the common and similar parts between the various embodiments. For the devices disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple, and the relevant parts can be referred to the method description.

[0083] The foregoing description of the disclosed embodiments enables a person skilled in the art to make or use the application. Modifications of these embodiments will occur to persons of skill in the art, and that the appended claims are intended to cover all such modifications that do not depart from the true spirit and scope of the application. Therefore, the application is not limited to the embodiments shown but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for rapidly preparing high-performance composite ceramics based on large-particle SiC powder, characterized in that: The steps include: 1) Prepare mixed powder Taking transition metal hydride powder, transition metal powder, transition metal silicide powder, B4C powder and SiC powder, and preparing mixed powder by mechanical mixing; The transition metal hydride powder, transition metal powder, transition metal silicide powder and B4C powder all have an average particle size of 1 to 10 μm and a purity of not less than 98%; The average particle size of the SiC powder is 20-30 μm, and the purity is not less than 98%; The transition metal hydride powder is a mixture of TiH2 and ZrH2; The transition metal powder is Cr; The transition metal silicide powder is a mixture of TiSi2, ZrSi2 and CrSi2; The mixed powder is composed of the following raw materials in percentage by mass: TiH2 powder 8-10%, ZrH2 powder 15-19%, Cr powder 7-11%, TiSi2 powder 5-7%, ZrSi2 powder 8-10%, CrSi2 powder 6-8%, B4C powder 18-23%, and the balance is SiC powder; 2) Preparation of composite ceramics The obtained mixed powder is placed in a graphite mold and pressure sintered under vacuum conditions to obtain a composite ceramic; The pressure sintering is spark plasma sintering, the sintering vacuum is less than 20Pa, and it is carried out by gradient heating and gradual pressure increase; The specific operation of the gradient heating and gradual pressurization is as follows: The graphite mold was pre-pressed at a pressure of 1~3MPa, and the temperature was increased to 650~800℃ at a heating rate of 80~120℃ / min, and kept warm for 5~10min. Then, the pressure was increased to 10~15MPa, and the temperature was increased to 1300~1350℃ at a heating rate of 80~120℃ / min, and the pressure was increased to 45~55MPa, and kept warm for 5~10min. The heating rate was maintained unchanged, and the temperature was continued to be increased to 1500~1600℃, and kept warm for 5~15min. After the insulation was completed, the pressure was reduced to 0MPa at a rate of 30~50MPa / min, and the sample was cooled with the furnace.

2. The method for rapidly preparing high-performance composite ceramics based on large-particle SiC powder according to claim 1, characterized in that: The mechanical powder mixing in step 1) is wet ball milling, wherein the mixed raw materials are placed in a ball mill and wet-milled for 4 hours using anhydrous ethanol as a medium to obtain a wet mixed powder; Among them, the ball mill speed is 300r / min, and the ball-to-material ratio is 4:1; The obtained wet mixed powder is taken out and then dried and sieved; The drying temperature is 50° C., the drying time is 10 h, and the mesh size of the sieving process is 200 meshes.

3. The method for rapidly preparing high-performance composite ceramics based on large-particle SiC powder according to claim 1, characterized in that: The specific operation of the gradient heating and gradual pressurization is as follows: The graphite mold was pre-pressed at a pressure of 3 MPa, and the temperature was increased to 700 ° C at a heating rate of 100 ° C / min, kept warm for 10 minutes, and then the pressure was increased to 15 MPa, and the temperature was continued to be increased to 1350 ° C at a heating rate of 100 ° C / min, and the pressure was increased to 50 MPa, and kept warm for 10 minutes; the heating rate was maintained unchanged, and the temperature was continued to be increased to 1500~1600 ° C, and kept warm for 10 minutes; after the insulation was completed, the pressure was reduced to 0 MPa at a rate of 30 MPa / min, and the sample was cooled with the furnace.

4. A high-performance composite ceramic prepared by the method according to any one of claims 1 to 3, characterized in that: The high-performance composite ceramic is formed by using (Ti, Cr) B2 and ZrB2 formed by in-situ reaction as reinforcing and toughening phases and SiC as a matrix, and is formed through pressure sintering.

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