CN111116202A - Method for sintering boron carbide-titanium boride material through discharge plasma reaction - Google Patents

Abstract

The invention belongs to the field of material preparation, and particularly relates to a method for sintering a boron carbide-titanium boride material by discharge plasma reaction. Amorphous boron powder, titanium powder and graphite powder are used as raw materials, and the boron carbide-titanium boride material is obtained through spark plasma sintering. According to the preparation method, amorphous boron powder, titanium powder and graphite powder are reacted in the sintering process to synthesize the required phase, so that the sintering densification temperature can be effectively reduced, the raw material cost can be reduced while the microstructure of the material is more uniform, and the integration of the phase synthesis and the densification process is realized. The ceramic material prepared by the invention has ultrahigh hardness and good fracture toughness on the basis of ensuring the basic complete compactness, the compactness is 98.46 +/-0.03 percent, the Vickers hardness is 25.69 +/-1.49 GPa, and the fracture toughness is 7.39 +/-0.88 MPa.m^1/2。

Description

Method for sintering boron carbide-titanium boride material through discharge plasma reaction

Technical Field

The invention belongs to the field of material preparation, and particularly relates to a method for sintering a boron carbide-titanium boride material by discharge plasma reaction.

Background

Boron carbide (B)₄C) Ceramics have a high hardness (25-40GPa), a hardness which is only lower than that of diamond and cubic boron nitride in materials found in nature, and boron carbide hasHigh modulus of elasticity (448GPa), high melting point (2450 ℃), good wear resistance and chemical inertness, which makes B₄The C ceramic is especially suitable for manufacturing superhard cutters, high-temperature resistant coatings, spray nozzles and the like. But because the crystal structure of the single-phase boron carbide is formed by combining complex B-B bonds and B-C bonds, the content of covalent bonds is as high as 93.4 percent, which is far higher than that of other ceramic materials. Thereby causing poor plasticity of boron carbide, large resistance of grain boundary movement, small surface tension in solid state, low mass transfer capacity in sintering and high required sintering temperature (more than 2000 ℃); the pores generated in the sintering process are difficult to eliminate, the densification degree is low, and the fracture toughness of the sintered sample is poor, thereby limiting the application and development of the boron carbide ceramic. Thus, B is reduced₄The sintering temperature of the C ceramic is B, which improves the obdurability on the basis of ensuring the high hardness of the C ceramic₄The problem to be solved in the application process of the C ceramic is urgent.

The addition of a second phase to a ceramic matrix to form a ceramic matrix composite has become an effective means for solving the problems of sintering and performance of ceramic materials. The addition of the second phase particles can be used as a sintering aid and can also be used for toughening and reinforcing a matrix, and the method is widely applied to sintering of boron carbide ceramic materials. Many attempts have been made by researchers to find titanium boride (TiB) for boron carbide ceramics₂) The boron carbide ceramic is the second-phase reinforcing material with the most potential, and the added titanium boride can obviously improve the fracture toughness and the bending strength of the boron carbide ceramic. Generally for B₄C-TiB₂Preparation of composite ceramic Material, mainly using commercially available B₄C powder and TiB₂And directly mixing the powder, and sintering the composite material by the conventional modes such as pressureless sintering (PLS), Hot Pressing Sintering (HPS), hot isostatic pressing sintering (HIP) and the like. However, the traditional sintering method has more problems, and the biscuit does not have external pressure action and only depends on self-sintering driving force to shrink when pressureless sintering is adopted, so that the sintering temperature is high (about 2200 ℃), the heat preservation time is more than 3 hours, and the densification is difficult; when hot-pressing sintering is adopted, the density of the material can be improved at high temperature and high pressure, but the hot-pressing sintering strictly limits the size of the sintered material, so that large-scale industrial production is restricted, and the sintering cost is high;in order to maintain balanced pressure during hot isostatic pressing sintering, the requirements on the sheath material and the technology are high during sintering, and the sintering cost is high.

Disclosure of Invention

The invention aims to provide a method for sintering a boron carbide-titanium boride material by discharge plasma reaction.

The technical solution for realizing the purpose of the invention is as follows: a method for sintering a boron carbide-titanium boride material through discharge plasma reaction is characterized in that amorphous boron powder, titanium powder and graphite powder are used as raw materials, and the boron carbide-titanium boride material is obtained through discharge plasma sintering.

Furthermore, the particle sizes of the amorphous boron powder, the amorphous titanium powder and the amorphous graphite powder are all 400-600 nm.

Further, the boron powder, the titanium powder and the graphite powder are as follows by mass percent: 52.58-60.62 wt.% of boron powder, 9.90-13.60 wt.% of graphite powder and 37.52-25.78 wt.% of titanium powder.

Further, the method specifically comprises the following steps:

step (1): weighing amorphous boron powder, titanium powder and graphite powder as raw materials in proportion;

step (2): mixing the raw materials in the step (1), taking industrial absolute ethyl alcohol as a mixing medium, and carrying out ultrasonic oscillation and stirring on the mixed raw material powder for 1-5 hours;

and (3): carrying out vacuum drying on the uniformly dispersed powder in the step (2);

and (4): sieving and granulating the powder dried in the step (3);

and (5): pre-pressing and forming the powder sieved in the step (4);

and (6): performing discharge plasma sintering on the pre-pressed powder, wherein boron and carbon react to generate boron carbide and boron and titanium react to generate titanium boride in the sintering process to obtain a boron carbide-titanium boride composite material;

and (7): and demolding to obtain the boron carbide-titanium boride composite material.

Further, in the step (2), the mixed raw material powder is subjected to ultrasonic oscillation and stirring for 2 hours.

Further, the temperature of vacuum drying in the step (3) is 100-200 ℃, and preferably 120 ℃.

Further, the sieving and granulating in the step (4) specifically comprises the following steps: the dried powder passes through a sieve tray with 100 meshes and 400 meshes for sieving and granulating.

Further, the pre-pressing molding in the step (5) specifically comprises: and filling graphite carbon paper in the periphery of the interior of the graphite mold, filling the sieved powder into the mold, applying pressure of 5-10MPa to the graphite mold, maintaining the pressure for 2-5 minutes, and performing pre-pressing molding.

Further, the spark plasma sintering in the step (5) is specifically as follows:

wrapping the carbon felt by the graphite mould pre-pressed in the step (5), putting the graphite mould into a discharge plasma sintering furnace, and vacuumizing to 5-10 Pa; applying sintering pressure, wherein the sintering pressure is 20-30 MPa; controlling the heating rate to be 50-150 ℃/min, the sintering temperature to be 1800 plus-heat 1950 ℃, the reaction time to be 0-9min, the corresponding temperatures for starting timing of the two reaction times to be 850 ℃ and 1250 ℃, the heat preservation time to be 0-15min, and naturally cooling along with the furnace.

Further, the dried powder in the step (4) passes through a sieve tray with 100 meshes for sieving and granulating; step (5), pre-pressing and forming, applying pressure of 5MPa to the graphite mould, and keeping the pressure for 2 minutes;

in the step (6), the sintering pressure is 30MPa, and the heating rate is 100 ℃/min.

Compared with the prior art, the invention has the remarkable advantages that:

(1) according to the preparation method, amorphous boron powder, titanium powder and graphite powder are reacted in the sintering process to synthesize a required phase, so that the sintering densification temperature can be effectively reduced, the raw material cost can be reduced while the microstructure of the material is more uniform, and the integration of the phase synthesis and the densification process is realized;

(2) according to the invention, the variety and microscopic form of the product phase can be regulated and controlled by the proportion of the raw material powder, so that the required material with the optimal performance can be obtained.

Drawings

FIG. 1 is an X-ray diffraction pattern of the boron carbide-titanium boride composite ceramic obtained in example 2.

FIG. 2 is a surface SEM photograph of the boron carbide-titanium boride composite ceramic obtained in example 5.

FIG. 3 is an SEM photograph of a fracture surface of the boron carbide-titanium boride composite ceramic obtained in example 5.

FIG. 4 is a graph showing the temperature and head displacement with time of the sintered boron carbide-titanium boride composite ceramic of example 6.

Detailed Description

The invention provides a boron carbide-titanium boride composite ceramic material sintered by discharge plasma reaction and a preparation process thereof. The invention is further described with reference to the following figures and examples.

A boron carbide-titanium boride composite ceramic material comprises, by volume, 60-75 vol.% of boron carbide and 40-25 vol.% of titanium boride, wherein the corresponding required raw materials comprise, by mass, 52.58-60.62 wt.% of boron powder, 9.90-13.60 wt.% of graphite powder and 37.52-25.78 wt.% of titanium powder.

In order to further explain a method for sintering a boron carbide-titanium boride material by discharge plasma reaction, the invention provides a sintering preparation process flow to realize the rapid and effective preparation of a high-performance boron carbide-titanium boride composite ceramic material, which comprises the following steps:

step 1: weighing amorphous boron powder, titanium powder and graphite powder as raw materials in proportion;

step 2: mixing the raw material powder obtained in the step 1, taking industrial absolute ethyl alcohol as a mixing medium, and carrying out ultrasonic oscillation and stirring on the mixed raw material powder for 1-5 hours, wherein the time is preferably 2 hours in order to fully disperse the powder and simultaneously avoid the oxidation of the raw material in the air;

and step 3: drying the powder uniformly dispersed in the step 2 in vacuum at the drying temperature of 100-200 ℃, preferably at 120 ℃;

and 4, step 4: sieving the dried powder by a sieve tray of 100 meshes and 400 meshes, preferably a sieve tray of 100 meshes, and granulating;

and 5: filling graphite carbon paper in the periphery of the interior of a graphite mold, filling the sieved powder into the mold, applying pressure of 5-10MPa, preferably 5MPa, to the graphite mold, maintaining the pressure for 2-5 minutes, preferably 2 minutes, and performing prepressing molding;

step 6: wrapping the pre-pressed graphite mold with a carbon felt, putting the carbon felt into a discharge plasma sintering furnace, and vacuumizing to 5-10 Pa; applying sintering pressure to the graphite pressure head through an electrode head of a hydraulic system, wherein the sintering pressure is 20-30MPa, and the larger sintering pressure is selected in the bearable range of the graphite mold to facilitate densification, so 30MPa is preferred; the heating rate is controlled to be 50-150 ℃/min by adjusting the current, the slower heating rate is not beneficial to the high-efficiency production of products, the faster heating rate is not beneficial to the full reaction of raw materials and the discharge of air holes in the sintering process, so the moderate heating rate is selected to be 100 ℃/min; the sintering temperature is 1800-;

and 7: demoulding to obtain the boron carbide-titanium boride composite ceramic material.

The principle of the invention is realized as follows: a boron carbide-titanium boride composite ceramic material uses amorphous powder raw materials, and atoms obtain enough energy to cross an atom potential barrier along with the rise of temperature, so that the atoms are diffused and react. The diffusion speed of titanium atoms is maximum at the same temperature, and the titanium atoms and boron atoms react to generate titanium diboride (TiB)₂) The Gibbs free energy is far lower than that of titanium boride (TiB) and titanium carbide (TiC) generated by reaction, so that in the sintering process, along with the rise of temperature, titanium atoms and boron atoms preferentially react at 800 ℃ and only generate titanium diboride, and 850 ℃ is selected as the heat preservation temperature of the reaction between 800 ℃ and 900 ℃, so that the reaction can be maintained to be rapidly carried out, the reaction is more sufficient, and meanwhile, enough time is reserved for the discharge of air holes in the reaction process. As the temperature is increased, the titanium atoms completely react with the boron atoms, and only the titanium diboride, unreacted graphite and residual boron in the reaction are contained in the material. The temperature is further increased, and at 1250 ℃, the temperature meets the requirement of boron andreaction of carbon to form boron carbide (B)₄C) The thermodynamic condition of the material is that new-phase boron carbide is formed, so that the second-stage reaction heat preservation process is started at 1250 ℃, and the generated new-phase boron carbide (B)₄C) Does not react with titanium diboride (TiB)₂) The reaction is carried out, and the titanium diboride is uniformly distributed among the boron carbide matrixes. As the temperature increases further, the material begins to densify, achieving further densification. On one hand, the improvement of the compactness is beneficial to the improvement of the mechanical property, the bending strength and the fracture toughness of the inherent property of the titanium diboride generated by the reaction are higher than those of the boron carbide matrix, and the addition of a proper amount of titanium diboride is beneficial to the improvement of the performance of the composite material; on the other hand, because the thermal expansion coefficients of boron carbide and titanium boride are different in the sintering process, residual stress is generated in the furnace cooling process, titanium boride grains are in a uniform tensile state, radial tensile stress and tangential compressive stress exist in a boron carbide matrix, crack expansion is changed due to the existence of the residual stress, and deflection, branching and bridging of cracks are caused, so that the energy of crack expansion is effectively consumed, and the fracture toughness is improved. Because the titanium boride crystal grains exist at the boundary of the boron carbide matrix crystal grains, the crystal grains of the matrix have pinning effect, the growth of the crystal grains is limited, and the refined crystal grains are beneficial to improving the mechanical property.

Example 1

A boron carbide-titanium boride composite ceramic material and a spark plasma sintering process thereof are disclosed, which specifically comprise the following steps: the method comprises the following components, by volume percentage, of a phase generated by a reaction of a material sintering final product, 60 vol.% of boron carbide and 40 vol.% of titanium boride, correspondingly proportioning according to mass fraction, 52.58 wt.% of boron powder, 9.90 wt.% of graphite powder and 37.52 wt.% of titanium powder, mixing the prepared raw material powder, taking industrial absolute ethyl alcohol as a mixed medium, subjecting the mixed raw material powder to ultrasonic oscillation and stirring for 2 hours, performing vacuum drying after the ultrasonic oscillation is finished, wherein the drying temperature is 120 ℃, subjecting the dried powder to powder sieving and granulation through a sieve tray of 100 meshes, filling graphite carbon paper into the periphery inside a graphite mold, filling the sieved powder into the mold, applying 5MPa pressure to the graphite mold, maintaining the pressure for 2 minutes, pre-pressing and molding, and packaging the graphite carbon paper into the graphite moldWrapping the carbon felt on the outer layer of the graphite mold with the powder, placing the graphite mold in a plasma sintering furnace, vacuumizing the furnace chamber to a vacuum state, setting the uniaxial sintering pressure to be 30MPa when a vacuum gauge shows that the pressure is below 10Pa, starting a plasma power supply to heat, heating a sample to 1800 ℃ at the heating rate of 100 ℃/min, preserving heat for 0min, and then cooling along with the furnace. Tests show that the compactness of the boron carbide-titanium boride composite ceramic material is 77.36 +/-1.85%, the Vickers hardness is 6.10 +/-0.52 GPa, and the fracture toughness is 5.53 +/-0.18 MPa.m^1/2。

Example 2

A boron carbide-titanium boride composite ceramic material and a spark plasma sintering process thereof are disclosed, which specifically comprise the following steps: preparing materials according to the volume percentage of phases generated by the reaction of final products of material sintering, wherein the phases comprise 65 vol.% of boron carbide and 35 vol.% of titanium boride, correspondingly preparing the materials according to the mass fraction, 55.09 wt.% of boron powder, 11.06 wt.% of graphite powder and 33.85 wt.% of titanium powder, mixing the prepared raw material powder, taking industrial absolute ethyl alcohol as a mixed medium, carrying out ultrasonic oscillation and stirring on the mixed raw material powder for 2 hours, carrying out vacuum drying after the ultrasonic oscillation is finished, wherein the drying temperature is 120 ℃, carrying out powder screening and granulation on the dried powder by a sieve tray of 100 meshes, filling graphite carbon paper in the periphery of the interior of a graphite mold, filling the sieved powder into the mold, applying 5MPa pressure to the graphite mold, maintaining the pressure for 2 minutes, carrying out pre-pressing molding, wrapping a carbon felt on the outer layer of the graphite mold filled with the powder, placing the carbon felt in a plasma sintering furnace, vacuumizing the furnace chamber, and displaying the vacuum state below 10Pa, setting the uniaxial sintering pressure to be 30MPa, starting a plasma power supply to heat, firstly heating the sample to 850 ℃ at the heating rate of 100 ℃/min, preserving heat for 9min, then heating the sample to 1250 ℃ at the heating rate of 100 ℃/min, preserving heat for 9min, continuously heating the sample to 1850 ℃ at the heating rate of 100 ℃/min, preserving heat for 0min, and then cooling along with the furnace. Tests show that the compactness of the boron carbide-titanium boride composite ceramic material is 79.53 +/-0.43%, the Vickers hardness is 5.83 +/-0.06 GPa, and the fracture toughness is 6.55 +/-0.29 MPa.m^1/2。

Example 3

Boron carbide-titanium boride composite ceramic material and discharge plasma thereofThe sub-sintering process specifically comprises the following steps: preparing materials according to the mass fraction of 70 vol% of boron carbide and 30 vol% of titanium boride in a material sintering final product reaction mode, correspondingly preparing materials according to the mass fraction of 57.77 wt% of boron powder, 12.29 wt% of graphite powder and 29.94 wt% of titanium powder, mixing the prepared raw material powder, taking industrial absolute ethyl alcohol as a mixed medium, carrying out ultrasonic oscillation and stirring on the mixed raw material powder for 2 hours, carrying out vacuum drying after the ultrasonic oscillation is finished, carrying out powder sieving granulation on the dried powder at the drying temperature of 120 ℃, loading graphite carbon paper around the inner periphery of a graphite mold, filling the sieved powder into the mold, applying 5MPa pressure to the graphite mold, maintaining the pressure for 2 minutes, carrying out pre-pressing molding, wrapping a carbon felt on the outer layer of the graphite mold filled with the powder, placing the graphite mold in a plasma sintering furnace, pumping the furnace cavity into a vacuum state, and displaying the vacuum state below 10Pa, setting the uniaxial sintering pressure to be 30MPa, starting a plasma power supply to heat, firstly heating the sample to 850 ℃ at the heating rate of 100 ℃/min, preserving heat for 0min, then heating the sample to 1250 ℃ at the heating rate of 100 ℃/min, preserving heat for 0min, continuously heating the sample to 1950 ℃ at the heating rate of 100 ℃/min, preserving heat for 0min, and then cooling along with the furnace. Tests show that the compactness of the boron carbide-titanium boride composite ceramic material is 99.43 +/-0.01 percent, the Vickers hardness is 19.54 +/-0.35 GPa, and the fracture toughness is 9.53 +/-0.56 MPa.m^1/2。

Example 4

A boron carbide-titanium boride composite ceramic material and a spark plasma sintering process thereof are disclosed, which specifically comprise the following steps: the method comprises the following components of 75 vol.% of boron carbide and 25 vol.% of titanium boride according to the volume percentage of phases generated by the reaction of final sintered product of the material, correspondingly proportioning according to the mass fraction, 60.62 wt.% of boron powder, 13.60 wt.% of graphite powder and 25.78 wt.% of titanium powder, mixing the prepared raw material powder, taking industrial absolute ethyl alcohol as a mixed medium, carrying out ultrasonic oscillation and stirring on the mixed raw material powder for 2 hours, carrying out vacuum drying after the ultrasonic oscillation is finished, wherein the drying temperature is 120 ℃, sieving and granulating the dried powder by using a sieve tray of 100 meshes, filling graphite carbon paper into the periphery inside a graphite mould, and then feeding the sieved powder into a sieveFilling a mold, applying pressure of 5MPa to the graphite mold, maintaining the pressure for 2 minutes, performing pre-pressing molding, wrapping the outer layer of the graphite mold filled with the powder with a carbon felt, placing the carbon felt in a plasma sintering furnace, vacuumizing the furnace cavity to be in a vacuum state, setting the uniaxial sintering pressure to be 30MPa when a vacuum meter shows that the pressure is below 10Pa, starting a plasma power supply to heat, heating the sample to 850 ℃ at the heating rate of 100 ℃/min, preserving the temperature for 5min, heating the sample to 1250 ℃ at the heating rate of 100 ℃/min, preserving the temperature for 5min, continuously heating the sample to 1950 ℃ at the heating rate of 100 ℃/min, preserving the temperature for 0min, and then cooling along with the furnace. Tests show that the density of the boron carbide-titanium boride composite ceramic material is 98.90 +/-0.02%, the Vickers hardness is 22.71 +/-0.18 GPa, and the fracture toughness is 7.54 +/-0.83 MPa.m^1/2。

Example 5

A boron carbide-titanium boride composite ceramic material and a spark plasma sintering process thereof are disclosed, which specifically comprise the following steps: preparing materials according to the volume percentage of phases generated by the reaction of final products of material sintering, wherein the phases comprise 60 vol% of boron carbide and 40 vol% of titanium boride, correspondingly preparing the materials according to the mass fraction, 52.58 wt% of boron powder, 9.90 wt% of graphite powder and 37.52 wt% of titanium powder, mixing the prepared raw material powder, taking industrial absolute ethyl alcohol as a mixed medium, carrying out ultrasonic oscillation and stirring on the mixed raw material powder for 2 hours, carrying out vacuum drying after the ultrasonic oscillation is finished, wherein the drying temperature is 120 ℃, carrying out powder screening and granulation on the dried powder by a sieve tray of 100 meshes, filling graphite carbon paper in the periphery of the interior of a graphite mold, filling the sieved powder into the mold, applying 5MPa pressure to the graphite mold, maintaining the pressure for 2 minutes, carrying out pre-pressing molding, wrapping a carbon felt on the outer layer of the graphite mold filled with the powder, placing the carbon felt in a plasma sintering furnace, vacuumizing the furnace chamber, and displaying the vacuum state below 10Pa, setting the uniaxial sintering pressure to be 30MPa, starting a plasma power supply to heat, firstly heating the sample to 850 ℃ at the heating rate of 100 ℃/min as shown in figure 1, preserving heat for 3min, then heating the sample to 1250 ℃ at the heating rate of 100 ℃/min, preserving heat for 3min, continuously heating the sample to 1850 ℃ at the heating rate of 100 ℃/min, preserving heat for 5min, and then cooling along with the furnace. Tests show that the boron carbide-titanium boride composite ceramicThe density of the material is 98.66 +/-0.79%, the Vickers hardness is 21.68 +/-1.35 GPa, and the fracture toughness is 7.43 +/-0.23 MPa.m^1/2。

The comparison example shows that the sintering temperature has great influence on the density and the mechanical property of the material, the sintering temperature of the boron carbide-titanium boride composite material is increased, the densification driving force of the powder in the sintering process is higher, the density of the material is improved, and the mechanical property is obviously improved along with the densification driving force.

Example 6

A boron carbide-titanium boride composite ceramic material and a spark plasma sintering process thereof are disclosed, which specifically comprise the following steps: preparing materials according to the volume percentage of phases generated by the reaction of final products of material sintering, wherein the phases comprise 65 vol.% of boron carbide and 35 vol.% of titanium boride, correspondingly preparing the materials according to the mass fraction, 55.09 wt.% of boron powder, 11.06 wt.% of graphite powder and 33.85 wt.% of titanium powder, mixing the prepared raw material powder, taking industrial absolute ethyl alcohol as a mixed medium, carrying out ultrasonic oscillation and stirring on the mixed raw material powder for 2 hours, carrying out vacuum drying after the ultrasonic oscillation is finished, wherein the drying temperature is 120 ℃, carrying out powder screening and granulation on the dried powder by a sieve tray of 100 meshes, filling graphite carbon paper in the periphery of the interior of a graphite mold, filling the sieved powder into the mold, applying 5MPa pressure to the graphite mold, maintaining the pressure for 2 minutes, carrying out pre-pressing molding, wrapping a carbon felt on the outer layer of the graphite mold filled with the powder, placing the carbon felt in a plasma sintering furnace, vacuumizing the furnace chamber, and displaying the vacuum state below 10Pa, setting the uniaxial sintering pressure to be 30MPa, starting a plasma power supply to heat, firstly heating the sample to 850 ℃ at the heating rate of 100 ℃/min, preserving heat for 6min, then heating the sample to 1250 ℃ at the heating rate of 100 ℃/min after boron carbide-titanium boride, preserving heat for 6min, continuously heating the sample to 1800 ℃ at the heating rate of 100 ℃/min, preserving heat for 5min, and then cooling along with the furnace. Tests show that the density of the composite ceramic material is 98.20 +/-0.07 percent, the Vickers hardness is 25.36 +/-1.32 GPa, and the fracture toughness is 7.54 +/-0.50 MPa.m^1/2。

The example shows that the heat preservation time has great influence on the density and the mechanical property of the material, and even under the condition of reducing the sintering temperature and the reaction time, the heat preservation time of the boron carbide-titanium boride composite material is prolonged, so that the crystal grains grow in a limited way, the number of air holes in a sintered body is reduced, the density of the material is obviously improved, the bonding strength among the crystal grains is higher, and the mechanical property is obviously improved.

Example 7

A boron carbide-titanium boride composite ceramic material and a spark plasma sintering process thereof are disclosed, which specifically comprise the following steps: preparing materials according to the mass fraction of 70 vol% of boron carbide and 30 vol% of titanium boride in a material sintering final product reaction mode, correspondingly preparing materials according to the mass fraction of 57.77 wt% of boron powder, 12.29 wt% of graphite powder and 29.94 wt% of titanium powder, mixing the prepared raw material powder, taking industrial absolute ethyl alcohol as a mixed medium, carrying out ultrasonic oscillation and stirring on the mixed raw material powder for 2 hours, carrying out vacuum drying after the ultrasonic oscillation is finished, carrying out powder sieving granulation on the dried powder at the drying temperature of 120 ℃, loading graphite carbon paper around the inner periphery of a graphite mold, filling the sieved powder into the mold, applying 5MPa pressure to the graphite mold, maintaining the pressure for 2 minutes, carrying out pre-pressing molding, wrapping a carbon felt on the outer layer of the graphite mold filled with the powder, placing the graphite mold in a plasma sintering furnace, pumping the furnace cavity into a vacuum state, and displaying the vacuum state below 10Pa, setting the uniaxial sintering pressure to be 30MPa, starting a plasma power supply to heat, firstly heating the sample to 850 ℃ at the heating rate of 100 ℃/min, preserving heat for 6min, then heating the sample to 1250 ℃ at the heating rate of 100 ℃/min, preserving heat for 6min, continuously heating the sample to 1850 ℃ at the heating rate of 100 ℃/min, preserving heat for 15min, and then cooling along with the furnace. Tests show that the density of the boron carbide-titanium boride composite ceramic material is 98.83 +/-0.17%, the Vickers hardness is 23.98 +/-0.50 GPa, and the fracture toughness is 7.15 +/-0.29 MPa.m^1/2。

The comparative example shows that the reaction time has little influence on the density and the mechanical property of the material, the reaction time of the boron carbide-titanium boride composite material is moderately improved, sufficient reaction time can be provided for the material, the reaction is completely generated to generate a required phase, the density and the hardness are slightly increased, the fracture toughness is slightly reduced, but excessive reaction time does not contribute much to the densification and the mechanical property, and energy is consumed instead.

Example 8

A boron carbide-titanium boride composite ceramic material and a spark plasma sintering process thereof are disclosed, which specifically comprise the following steps: preparing materials according to the volume percentage of phases generated by the reaction of final products of material sintering, wherein the phases comprise 65 vol.% of boron carbide and 35 vol.% of titanium boride, correspondingly preparing the materials according to the mass fraction, 55.09 wt.% of boron powder, 11.06 wt.% of graphite powder and 33.85 wt.% of titanium powder, mixing the prepared raw material powder, taking industrial absolute ethyl alcohol as a mixed medium, carrying out ultrasonic oscillation and stirring on the mixed raw material powder for 2 hours, carrying out vacuum drying after the ultrasonic oscillation is finished, wherein the drying temperature is 120 ℃, carrying out powder screening and granulation on the dried powder by a sieve tray of 100 meshes, filling graphite carbon paper in the periphery of the interior of a graphite mold, filling the sieved powder into the mold, applying 5MPa pressure to the graphite mold, maintaining the pressure for 2 minutes, carrying out pre-pressing molding, wrapping a carbon felt on the outer layer of the graphite mold filled with the powder, placing the carbon felt in a plasma sintering furnace, vacuumizing the furnace chamber, and displaying the vacuum state below 10Pa, setting the uniaxial sintering pressure to be 30MPa, starting a plasma power supply to heat, firstly heating the sample to 850 ℃ at the heating rate of 100 ℃/min, preserving heat for 3min, then heating the sample to 1250 ℃ at the heating rate of 100 ℃/min, preserving heat for 3min, continuously heating the sample to 1900 ℃ at the heating rate of 100 ℃/min, preserving heat for 10min, and then cooling along with the furnace. Tests show that the density of the boron carbide-titanium boride composite ceramic material is 100 percent, the Vickers hardness is 25.29 +/-2.86 GPa, and the fracture toughness is 9.30 +/-0.70 MPa.m^1/2。

The comparative example shows that the component proportion has smaller influence on the density and the mechanical property of the material, and the content of boron carbide in the component proportion of the boron carbide-titanium boride composite material is increased, so that the hardness of the material is slightly increased, but the density and the fracture toughness are slightly reduced. The ceramic material prepared by the invention has ultrahigh hardness and good fracture toughness on the basis of ensuring the basic complete compactness, the compactness is 98.46 +/-0.03 percent, the Vickers hardness is 25.69 +/-1.49 GPa, and the fracture toughness is 7.39 +/-0.88 MPa.m^1/2。

Claims (10)

1. A method for sintering a boron carbide-titanium boride material through discharge plasma reaction is characterized in that amorphous boron powder, titanium powder and graphite powder are used as raw materials, and the boron carbide-titanium boride material is obtained through discharge plasma sintering.

2. The method as claimed in claim 1, wherein the particle sizes of the amorphous boron powder, titanium powder and graphite powder are 400-600 nm.

3. The method according to claim 2, wherein the boron powder, the titanium powder and the graphite powder are as follows in mass percent: 52.58-60.62 wt.% of boron powder, 9.90-13.60 wt.% of graphite powder and 37.52-25.78 wt.% of titanium powder.

4. The method according to claim 3, characterized in that it comprises in particular the steps of:

step (1): weighing amorphous boron powder, titanium powder and graphite powder as raw materials in proportion;

step (2): mixing the raw materials in the step (1), taking industrial absolute ethyl alcohol as a mixing medium, and carrying out ultrasonic oscillation and stirring on the mixed raw material powder for 1-5 hours;

and (3): carrying out vacuum drying on the uniformly dispersed powder in the step (2);

and (4): sieving and granulating the powder dried in the step (3);

and (5): pre-pressing and forming the powder sieved in the step (4);

and (6): performing discharge plasma sintering on the pre-pressed powder, wherein boron and carbon react to generate boron carbide and boron and titanium react to generate titanium boride in the sintering process to obtain a boron carbide-titanium boride composite material;

and (7): and demolding to obtain the boron carbide-titanium boride composite material.

5. The method according to claim 4, wherein in the step (2), the mixed raw material powder is subjected to ultrasonic oscillation and stirring for 2 hours.

6. The method according to claim 4, wherein the temperature of the vacuum drying in step (3) is 100 ℃ to 200 ℃, preferably 120 ℃.

7. The method according to claim 4, wherein the sieving granulation in the step (4) is specifically: the dried powder passes through a sieve tray with 100 meshes and 400 meshes for sieving and granulating.

8. The method according to claim 7, wherein the pre-press forming of the step (5) is specifically: and filling graphite carbon paper in the periphery of the interior of the graphite mold, filling the sieved powder into the mold, applying pressure of 5-10MPa to the graphite mold, maintaining the pressure for 2-5 minutes, and performing pre-pressing molding.

9. The method according to claim 8, wherein the spark plasma sintering in step (5) is specifically:

wrapping the carbon felt by the graphite mould pre-pressed in the step (5), putting the graphite mould into a discharge plasma sintering furnace, and vacuumizing to 5-10 Pa; applying sintering pressure, wherein the sintering pressure is 20-30 MPa; controlling the heating rate to be 50-150 ℃/min, the sintering temperature to be 1800 plus-heat 1950 ℃, the reaction time to be 0-9min, the corresponding temperatures for starting timing of the two reaction times to be 850 ℃ and 1250 ℃, the heat preservation time to be 0-15min, and naturally cooling along with the furnace.

10. The method as claimed in claim 9, wherein in the step (4), the dried powder passes through a sieve tray with 100 meshes for sieve powder granulation;

step (5), pre-pressing and forming, applying pressure of 5MPa to the graphite mould, and keeping the pressure for 2 minutes;

in the step (6), the sintering pressure is 30MPa, and the heating rate is 100 ℃/min.

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