CN113105243A - B with silicon carbide and silicon coating on surface4C/graphite composite material and preparation method thereof - Google Patents

B with silicon carbide and silicon coating on surface4C/graphite composite material and preparation method thereof Download PDF

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CN113105243A
CN113105243A CN202110464571.0A CN202110464571A CN113105243A CN 113105243 A CN113105243 A CN 113105243A CN 202110464571 A CN202110464571 A CN 202110464571A CN 113105243 A CN113105243 A CN 113105243A
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powder
graphite
silicon
composite material
graphite composite
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江涛
韩慢慢
付甲
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Xian Shiyou University
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Abstract

B with silicon carbide and silicon coating on surface4The C/graphite composite material comprises the following components: b is4C material, graphite material; al (Al)2O3Powder; y is2O3Powder; the preparation method comprises the following steps: step 1, mixing boron carbide powder and graphite powder to obtain B4C/graphite composite powder; adding Al2O3Powder and Y2O3Ball milling the powder, adding absolute ethyl alcohol and agate milling balls, mixing, preparing slurry through ball milling, and drying the slurry to obtain B4C/graphite mixed powder; step 2, mixing B4The C/graphite composite powder is filled into a graphite die and prepared by hot-pressing sinteringGo out B4C/graphite composite material wafer, hot pressing sintering under vacuum condition; step 3, the B prepared in the step 24Preparing a strip sample from a C/graphite composite material wafer, putting the strip sample into a graphite crucible, covering coarse silicon powder on the surface of the strip sample, putting the graphite crucible into a high-temperature siliconizing furnace for siliconizing, and obtaining B through siliconizing reaction4The C/graphite composite material siliconizing sample has the advantages of improving the surface hardness, the wear resistance and the high-temperature oxidation resistance.

Description

The surface has silicon carbide and silicon coatingB of (A)4C/graphite composite material and preparation method thereof
Technical Field
The invention belongs to the technical field of composite materials, and particularly relates to a silicon carbide/silicon carbide composite material B with a silicon carbide coating on the surface4A C/graphite composite material and a preparation method thereof.
Background
Boron carbide ceramic materials have high strength, high toughness, high melting point, high hardness, good wear resistance, corrosion resistance and high temperature oxidation resistance, and are widely used in the engineering field. Boron carbide ceramic materials are widely used in the engineering field due to their high strength and hardness, good wear resistance and good high temperature oxidation resistance. However, boron carbide ceramics have high hardness and are difficult to machine, so that the machining cost is high. Therefore, the boron carbide ceramic material has poor machinability and high machinability cost. Therefore, in order to improve and enhance the machinability of the boron carbide ceramic material, a machinable phase needs to be added into the boron carbide ceramic matrix to prepare the machinable boron carbide-based complex phase ceramic. The graphite material has low strength and toughness, good processability, good thermal shock resistance and the like. The graphite material can be used as a machinable phase of the boron carbide ceramic material, and the graphite material can be added into the boron carbide ceramic matrix to form B4C/graphite composite material. Adding graphite material to the boron carbide ceramic matrix to form machinable B4The C/graphite composite material can obviously improve and enhance the processability, thermal shock resistance and the like of the boron carbide ceramic material. It is therefore necessary to add a graphite phase to the boron carbide ceramic matrix to form a machinable B4C/graphite composite material. The graphite material has good compatibility with the boron carbide ceramic material, and can be added into the boron carbide ceramic matrix to form B through compounding4The C/graphite composite material greatly improves and enhances the processability and thermal shock resistance of the boron carbide ceramic material. B is4The C/graphite composite material has high mechanical property, good processability and good thermal shock resistance, and has good performanceSelf-lubricating properties of the composition, etc. But B is caused by adding a large amount of graphite material to the boron carbide ceramic matrix4The surface hardness and wear resistance of the C/graphite composite material are remarkably reduced, and B4The high temperature oxidation resistance of the C/graphite composite material is also poor.
The object of the present invention is to provide4Machining the C/graphite composite material to obtain required parts, and machining the formed B4The C/graphite composite material adopts a high-temperature liquid siliconizing process to carry out a surface modification treatment process. Therefore, to improve and increase B4The surface hardness, wear resistance and high temperature oxidation resistance of the C/graphite composite material are improved by adopting a high temperature liquid siliconizing process to the B4And carrying out surface modification treatment on the C/graphite composite material. B prepared by hot-pressing sintering process4The C/graphite composite material has a relative density of 95% and a porosity of 5%, so that liquid silicon can penetrate into B4The surface of the C/graphite composite material is inside. Can be processed in B by high-temperature liquid siliconizing process4And preparing a layer of compact and hard silicon carbide and silicon coating on the surface of the C/graphite composite material sample. Thereby realizing the machinable B4A siliconizing process surface modification technology of the C/graphite composite material.
In view of the above problems, B prepared by the hot pressing sintering process4The surface hardness and wear resistance of the C/graphite composite material gradually decrease with the increase of the graphite content in the matrix, and B4The high temperature oxidation resistance of the C/graphite composite material is gradually reduced along with the increase of the oxidation temperature and the oxidation time. So B prepared by the hot-pressing sintering process4The surface hardness and wear resistance of the C/graphite composite material are poor, and the high-temperature oxidation resistance is poor. B prepared by hot-pressing sintering process4The C/graphite composite material may be applied to the field of wear-resistant engineering or high-temperature resistant engineering in the future, so that the carbon-graphite composite material is used for the carbon-graphite composite material B4It is important to perform surface modification treatment on the C/graphite composite material. The object of the present invention is to provide4Machining the C/graphite composite material to obtain required parts, and machining the formed B4The C/graphite composite material adoptsThe high-temperature liquid siliconizing process is used for carrying out surface modification treatment process, and can be used for B4And carrying out surface treatment on the C/graphite composite material. The invention adopts the high-temperature liquid siliconizing process to prepare the B prepared by the hot-pressing sintering process4And carrying out surface treatment on the C/graphite composite material. Since liquid silicon can react with B4Both the boron carbide material and the graphite material on the surface of the C/graphite composite material sample can react to generate silicon carbide, and residual silicon exists on the surface of the siliconized sample, so that a silicon carbide coating and a silicon coating are formed on the surface of the siliconized sample. Liquid silicon can react with boron carbide to produce silicon carbide, and liquid silicon can react with graphite to produce silicon carbide. While residual silicon is also present on the sample surface. So that the silicon is penetrated in the step B4And forming a silicon carbide and silicon coating on the surface of the C/graphite composite material. Because the silicon carbide and the silicon coating on the surface of the siliconized sample have higher hardness, the Vickers hardness can reach 20GPa, and the siliconized sample has good wear resistance, good high-temperature oxidation resistance and the like, the B can be greatly improved and enhanced4The surface hardness and the wear resistance of the C/graphite composite material are improved, and the high-temperature oxidation resistance of the C/graphite composite material is improved. So that B is caused to be in a siliconizing process4The surface performance of the C/graphite composite material is obviously improved, thereby realizing the B4And (3) carrying out surface modification treatment on the C/graphite composite material by a siliconizing process.
Disclosure of Invention
To overcome the above-mentioned disadvantages of the prior art, it is an object of the present invention to provide a silicon carbide-coated silicon B4The C/graphite composite material and the preparation method thereof can obviously improve and enhance B4The surface hardness, the wear resistance and the high-temperature oxidation resistance of the C/graphite composite material. Aiming at the defects of the prior art, the invention aims to provide a high-temperature liquid siliconizing method for B4Surface modification treatment is carried out on the C/graphite composite material, and the surface modification treatment is carried out on the C/graphite composite material B through a siliconizing process4And a compact and hard silicon carbide and silicon coating is formed on the surface of the C/graphite composite material. B prepared by hot-pressing sintering process4The C/graphite composite material has a relative density of 95% and a porosity of 5%, so that liquid siliconCan permeate into B4The surface of the C/graphite composite material is inside. In the process of high-temperature liquid siliconizing, a sample is completely immersed into liquid silicon, so that the liquid silicon can completely react with the boron carbide ceramic material and the graphite material on the surface of the sample to generate silicon carbide and a silicon coating, the heat preservation time is long, and the generated silicon carbide and silicon coating has certain thickness. Thereby carrying out the siliconizing process on the B4A layer of compact and hard silicon carbide and silicon coating with a certain thickness is prepared on the surface of a C/graphite composite material sample, and the silicon carbide and silicon coating is combined with a matrix to be compact. Because the silicon carbide and the silicon coating on the surface of the siliconized sample have higher hardness, the Vickers hardness can reach 20GPa, the siliconized sample has higher wear resistance and good high-temperature oxidation resistance, the B can be obviously improved and enhanced4The surface hardness, the wear resistance and the high-temperature oxidation resistance of the C/graphite composite material. The reaction of liquid silicon with boron carbide to produce silicon carbide is shown below: 3B4C+5Si=3SiC+2SiB6Or B4C+2Si=SiC+SiB4The reaction of liquid silicon and graphite to form silicon carbide is as follows: si + C = SiC. The liquid silicon can react with the boron carbide to generate silicon carbide, the liquid silicon reacts with the graphite to generate silicon carbide, and residual silicon exists in the formed coating, so that the silicon carbide and silicon coating is formed on the surface of the siliconized sample, and the silicon carbide and silicon coating has certain thickness which can reach 300-400 mu m. The hardness of the silicon carbide and the silicon coating is higher, the Vickers hardness can reach 20GPa, and the wear resistance of the surface of the siliconized sample can be improved due to the higher Vickers hardness of the surface of the siliconized sample, so that the surface hardness and the wear resistance of the siliconized sample can be improved. Because the silicon carbide and the silicon coating have good high-temperature oxidation resistance, the silicon carbide and the silicon coating react with oxygen at the high temperature of 1000-1300 ℃ to generate a silicon dioxide film, the generated silicon dioxide film prevents further oxidation reaction, so that the effect of preventing the sample from being continuously oxidized can be achieved, and the reaction formula of the silicon carbide and the silicon coating reacting with the oxygen to generate the silicon dioxide is as follows: SiC(s) +2O2(g)=SiO2(s)+CO2(g) Or SiC(s) +3/2O2(g)=SiO2(s)+CO(g)，Si(s)+O2(g)=SiO2(s) SiO generated on the surface of the silicon carbide and silicon coating on the surface of the siliconized sample2The film can prevent further oxidation reaction and has the function of oxidation resistance. Therefore, the siliconized sample has higher hardness, good wear resistance and good high-temperature oxidation resistance.
In order to achieve the purpose, the invention adopts the technical scheme that: b with silicon carbide and silicon coating on surface4The C/graphite composite material is characterized by comprising the following components in parts by weight:
with B4The material C is a matrix phase, and the graphite material is a machinable phase; the graphite material is in B4The mass fraction of the C/graphite composite material is 10-40 parts; b is4The mass fraction of the material C is 90-60 parts; al (Al)2O3The mass fraction of the powder is 4 to 7; y is2O3The mass fraction of the powder is 3 to 6;
b is4The material C adopts micron-sized boron carbide powder as a raw material, and the particle size of the powder is about 3-5 mu m; the graphite material adopts micron-sized graphite powder as a raw material, and the particle size of the powder is 10-15 mu m;
the surface of the silicon carbide coating B4The preparation method of the C/graphite composite material comprises the following steps:
step one, taking 90-60 parts of micron-sized boron carbide powder as a raw material I, wherein the granularity of the boron carbide powder is 3-5 mu m; 10-40 parts of micron-sized graphite powder serving as a second raw material, wherein the granularity of the graphite powder is 10-15 mu m; mixing boron carbide powder and graphite powder in proportion to obtain B4C/graphite composite powder; in B4Adding 4 to 7 parts of Al into the C/graphite composite powder2O3Powder and 3-6 parts of Y2O3The powder is used as a sintering aid; will add Al2O3Powder and Y2O3B of the powder4The C/graphite composite powder is filled into a ball milling tank, 100-300ml of absolute ethyl alcohol and 20 agate milling balls with the diameter of 15mm are added for mixing, and mechanical balls are carried outGrinding and mixing for 24h to obtain slurry, and drying the slurry to obtain B4C/graphite mixed powder;
step two, drying the B obtained in the step one4Filling the C/graphite composite powder into a graphite mold, placing the graphite mold into a hot-pressing sintering furnace to perform a hot-pressing sintering process, wherein the hot-pressing sintering temperature is 1800 ℃, the hot-pressing pressure is 30MPa, the heat preservation time is 1h, and performing hot-pressing sintering under a vacuum condition; preparing B by a hot-pressing sintering process4C/graphite composite material wafer;
step three, the B prepared in the step two4Preparing a C/graphite composite material wafer into a strip sample, carrying out siliconizing treatment on the strip sample, putting the strip sample into a graphite crucible, covering coarse silicon powder on the surface of the strip sample, putting the graphite crucible into a high-temperature siliconizing furnace for high-temperature liquid siliconizing treatment, and obtaining the siliconizing sample after siliconizing treatment; the siliconizing treatment comprises the following steps: the siliconizing temperature is 1550 ℃, the siliconizing time is 2 hours, and the siliconizing time is 1 multiplied by 10-2Carrying out siliconizing reaction under the Pa vacuum condition. Obtaining B by siliconizing4The C/graphite composite material siliconizing sample has the melting point of 1410 deg.c, so that the solid silicon is completely melted at 1550 deg.c to form liquid silicon, which is then mixed with B4The boron carbide and the graphite on the surface of the C/graphite composite material react to generate silicon carbide, and residual silicon also exists in the formed coating, so that the silicon carbide and silicon coating is formed on the surface of the siliconized sample; obtaining B by siliconizing4C/graphite composite material siliconizing sample, and forming a silicon carbide and silicon coating on the surface of the siliconizing sample; the silicon carbide and silicon coating formed on the surface of the siliconized sample has higher hardness and good wear resistance.
In the first step: the particle size of the boron carbide powder is 3-5 μm; the particle size of the graphite powder is 10-15 μm.
In the second step, the vacuum condition is 1 × 10-2Pa。
Mixing in proportion as described in step one, B4C: graphitic material =9:1 or B4C: graphitic material =4:1 or B4C: graphitic material =7:3 or B4C: graphite materialMaterial =3: 2.
The invention has the beneficial effects that:
the invention adopts a high-temperature liquid siliconizing process to carry out the step B4Surface modification treatment is carried out on the C/graphite composite material, and the surface modification treatment is carried out on the C/graphite composite material B through a siliconizing process4And a compact and hard silicon carbide and silicon coating is formed on the surface of the C/graphite composite material. B prepared by hot-pressing sintering process4The C/graphite composite material has a relative density of 95% and a porosity of 5%, so that liquid silicon can penetrate into B4The surface of the C/graphite composite material is inside. In the process of high-temperature liquid siliconizing, a sample is completely immersed into liquid silicon, so that the liquid silicon can completely react with the boron carbide ceramic material and the graphite material on the surface of the sample to generate silicon carbide and a silicon coating, the heat preservation time is long, and the generated silicon carbide and silicon coating has certain thickness. Thereby carrying out the siliconizing process on the B4A layer of compact and hard silicon carbide and silicon coating with a certain thickness is prepared on the surface of a C/graphite composite material sample, and the silicon carbide and silicon coating is combined with a matrix to be compact. Because the silicon carbide and the silicon coating on the surface of the siliconized sample have higher hardness, the Vickers hardness can reach 20GPa, the siliconized sample has higher wear resistance and good high-temperature oxidation resistance, the B can be obviously improved and enhanced4The surface hardness, the wear resistance and the high-temperature oxidation resistance of the C/graphite composite material. The reaction of liquid silicon with boron carbide to produce silicon carbide is shown below: 3B4C+5Si=3SiC+2SiB6Or B4C+2Si=SiC+SiB4The reaction of liquid silicon and graphite to form silicon carbide is as follows: si + C = SiC. The liquid silicon can react with the boron carbide to generate silicon carbide, the liquid silicon reacts with the graphite to generate silicon carbide, and residual silicon exists in the formed coating, so that the silicon carbide and silicon coating is formed on the surface of the siliconized sample, and the silicon carbide and silicon coating has certain thickness which can reach 300-400 mu m. Because the hardness of the silicon carbide and the silicon coating is higher, the Vickers hardness can reach 20GPa, and the surface of the siliconized sample has higher Vickers hardness, so that the wear resistance of the surface of the siliconized sample can be improved, and the surface hardness and the wear resistance of the siliconized sample can be improvedAnd (3) wear resistance. Because the silicon carbide and the silicon coating have good high-temperature oxidation resistance, the silicon carbide and the silicon coating react with oxygen at the high temperature of 1000-1300 ℃ to generate a silicon dioxide film, the generated silicon dioxide film prevents further oxidation reaction, so that the effect of preventing the sample from being continuously oxidized can be achieved, and the reaction formula of the silicon carbide and the silicon coating reacting with the oxygen to generate the silicon dioxide is as follows: SiC(s) +2O2(g)=SiO2(s)+CO2(g) Or SiC(s) +3/2O2(g)=SiO2(s)+CO(g)，Si(s)+O2(g)=SiO2(s) SiO generated on the surface of the silicon carbide and silicon coating on the surface of the siliconized sample2The film can prevent further oxidation reaction and has the function of oxidation resistance. Therefore, the siliconized sample has higher hardness, good wear resistance and good high-temperature oxidation resistance.
Since the melting point of silicon is 1410 ℃, at the temperature of 1550 ℃, the solid silicon powder can be completely melted to form liquid silicon, the liquid silicon reacts with the surface of the sample, and the liquid silicon reacts with B4Reacting boron carbide on the surface of the C/graphite composite material to generate silicon carbide, reacting liquid silicon with graphite to generate silicon carbide, and forming a silicon carbide and silicon coating on the surface of a siliconized sample by using a siliconizing process since residual silicon exists in the formed coating4And preparing a layer of silicon carbide and silicon coating with thicker thickness on the surface of the C/graphite composite material. The invention adopts a high-temperature liquid siliconizing process in the B4And preparing compact and hard silicon carbide and silicon coatings on the surface of the C/graphite composite material.
B prepared by hot-pressing sintering process4The C/graphite composite material sample is machined to be manufactured into a part, and because the surface hardness is low and the abrasion resistance is poor, a surface modification process is required to be adopted for B4Post-treating the C/graphite composite material, so that the siliconizing process is adopted to process the formed B4The C/graphite composite material is subjected to surface modification treatment, and the B content is improved by a siliconizing process4The surface hardness and the wear resistance of the C/graphite composite material are improved, and the high-temperature oxidation resistance of the C/graphite composite material is improved. The invention proposesBy high-temperature liquid siliconizing process to B4Surface modification treatment is carried out on the C/graphite composite material, and the surface modification treatment is carried out on the C/graphite composite material B through a siliconizing process4And a compact and hard silicon carbide and silicon coating is formed on the surface of the C/graphite composite material. In the process of high-temperature liquid siliconizing, a sample is completely immersed into liquid silicon, so that the liquid silicon can completely react with the boron carbide ceramic material and the graphite material on the surface of the sample to generate silicon carbide and a silicon coating, the heat preservation time is long, and the generated silicon carbide and silicon coating has certain thickness. Thereby carrying out the siliconizing process on the B4A layer of compact and hard silicon carbide and silicon coating with a certain thickness is prepared on the surface of a C/graphite composite material sample, and the silicon carbide and silicon coating is combined with a matrix to be compact. And the silicon carbide and silicon coating is combined with the composite material matrix compactly, and the silicon carbide and silicon coating is thick in thickness, compact and hard. B can be obviously improved and enhanced by the siliconizing process4The surface hardness, the wear resistance, the high-temperature oxidation resistance and the like of the C/graphite composite material. B obtained by siliconizing treatment4The C/graphite composite material siliconizing sample has high surface hardness, high wear resistance, high temperature oxidation resistance and other excellent performances, and may be used widely in engineering.
Drawings
FIG. 1 is an X-ray diffraction pattern of silicon carbide and silicon coatings prepared according to the method of the present invention.
FIG. 2 is a scanning electron micrograph of silicon carbide and silicon coatings prepared according to the method of the present invention.
Detailed Description
The present invention will be described in further detail with reference to the following specific embodiments and the accompanying drawings.
Example 1
B with silicon carbide and silicon coating on surface4The C/graphite composite material comprises the following components in parts by weight:
with B4The material C is a matrix phase, and the graphite material is a machinable phase; 10 parts of graphite material; b is490 parts of a material C; al (Al)2O3Powder 7 parts and Y2O33 parts of powder; b is4The material C adopts micron-sized boron carbide powder as a raw material, and the particle size of the powder is 3 mu m; the graphite material adopts micron-sized graphite powder as a raw material, and the particle size of the powder is 10 mu m.
Example 2
B with silicon carbide and silicon coating on surface4The C/graphite composite material comprises the following components in parts by weight:
with B4The material C is a matrix phase, and the graphite material is a machinable phase; 20 parts of graphite material; b is480 parts of material C; al (Al)2O36 parts of powder; y is2O34 parts of powder; b is4The material C adopts micron-sized boron carbide powder as a raw material, and the particle size of the powder is about 4 mu m; the graphite material adopts micron-sized graphite powder as a raw material, and the particle size of the powder is 13 mu m.
Example 3
B with silicon carbide and silicon coating on surface4The C/graphite composite material comprises the following components in parts by weight:
with B4The material C is a matrix phase, and the graphite material is a machinable phase; 30 parts of graphite material; b is470 parts of a material C; al (Al)2O35 parts of powder; y is2O3And 5 parts of powder.
B is4The material C adopts micron-sized boron carbide powder as a raw material, and the particle size of the powder is about 5 mu m; the graphite material adopts micron-sized graphite powder as a raw material, and the particle size of the powder is 15 mu m.
Example 4
B with silicon carbide and silicon coating on surface4The C/graphite composite material comprises the following components in parts by weight:
with B4The material C is a matrix phase, and the graphite material is a machinable phase; the graphite material is in B4The mass fraction of the C/graphite composite material is 40 parts; b is4The mass fraction of the material C is 60 parts; al (Al)2O34 parts of powder; y is2O36 parts of powder;
b is4The material C adopts micron-sized boron carbide powder as a raw material, and the particle size of the powder is about 3 mu m; graphite materialThe material adopts micron-sized graphite powder as a raw material, and the particle size of the powder is 12 mu m.
Example 5
The surface of the silicon carbide coating B4The preparation method of the C/graphite composite material comprises the following steps:
step 1, adopting 90 parts of micron-sized boron carbide ceramic powder with the particle size of 3 microns; mixing 10 parts of micron-sized graphite powder with the particle size of 10 mu m, and adding B4Adding 7 parts of Al in the C/graphite composite powder2O3Powder and 3 parts of Y2O3The powder is used as sintering aid, and boron carbide ceramic powder, graphite powder and Al are added2O3Powder and Y2O3Putting the powder into a ball milling tank, adding 300ml of absolute ethyl alcohol and agate milling balls, mixing, mechanically milling for 24 hours to prepare slurry, and drying the slurry to obtain B4C/graphite mixed powder;
step 2, mixing and drying the mixture B obtained by mechanical ball milling4Filling the C/graphite composite powder into a graphite mold, placing the graphite mold into a hot-pressing sintering furnace for hot-pressing sintering, wherein the hot-pressing sintering temperature is 1800 ℃, the hot-pressing pressure is 30MPa, the heat preservation time is 1h, the hot-pressing sintering process is carried out under the vacuum condition, and the hot-pressing sintering process is used for preparing the B4C/graphite composite material wafer;
step 3, preparing B by the hot-pressing sintering process4Preparing a C/graphite composite material wafer sample into a strip sample, wherein the size of the strip sample is 4mm multiplied by 30mm, and carrying out siliconizing treatment on the strip sample. And putting the strip sample into a graphite crucible, covering coarse silicon powder on the surface of the strip sample, and putting the graphite crucible into a high-temperature siliconizing furnace for siliconizing treatment. The siliconizing process comprises the steps of carrying out the siliconizing reaction process under the vacuum condition at the siliconizing temperature of 1550 ℃ for 2 hours, and obtaining the siliconizing sample after siliconizing treatment. Since the melting point of silicon is 1410 ℃, at the temperature of 1550 ℃, the solid silicon powder can be completely melted to form liquid silicon, the liquid silicon reacts with the surface of the sample, and the liquid silicon reacts with B4The boron carbide on the surface of the C/graphite composite material reacts to generate silicon carbide, the liquid silicon can also react with the graphite to generate the silicon carbide, and the residual silicon exists in the formed coating, so that the silicon carbide is subjected to the siliconizing process at B4And preparing a layer of silicon carbide and silicon coating with thicker thickness on the surface of the C/graphite composite material. Therefore, the present embodiment uses the high temperature liquid siliconizing process at B4And preparing compact and hard silicon carbide and silicon coatings on the surface of the C/graphite composite material. The silicon carbide and silicon coatings are about 300-400 μm thick. And the silicon carbide and silicon coating are combined with the composite material matrix compactly. Because the silicon carbide and the silicon coating on the surface of the siliconized sample have higher hardness and higher wear resistance and good high-temperature oxidation resistance, the B can be obviously improved and enhanced4The surface hardness, the wear resistance, the high-temperature oxidation resistance and the like of the C/graphite composite material.
Example 6
The surface of the silicon carbide coating B4The preparation method of the C/graphite composite material comprises the following steps:
step 1, adopting 80 parts of micron-sized boron carbide ceramic powder, wherein the granularity of the powder is about 4 mu m; mixing boron carbide ceramic powder and graphite powder by using 20 parts of micron-sized graphite powder with the particle size of about 13 mu m, and mixing the mixture B46 parts of Al is added into the C/graphite composite powder2O3Powder and 4 parts of Y2O3The powder is used as sintering aid, and boron carbide ceramic powder, graphite powder and Al are added2O3Powder and Y2O3Putting the powder into a ball milling tank, adding 300ml of absolute ethyl alcohol and agate milling balls, mixing, mechanically milling for 24 hours to prepare slurry, and drying the slurry to obtain B4C/graphite mixed powder;
step 2, mixing and drying the mixture B obtained by mechanical ball milling4Filling the C/graphite composite powder into a graphite mold, placing the graphite mold into a hot-pressing sintering furnace for hot-pressing sintering, wherein the hot-pressing sintering temperature is 1800 ℃, the hot-pressing pressure is 30MPa, the heat preservation time is 1h, and the hot-pressing sintering is carried out under the vacuum condition, namelyPreparing B by an over-hot pressing sintering process4C/graphite composite material wafer;
step 3, preparing B by the hot-pressing sintering process4Preparing a C/graphite composite material wafer sample into a strip sample, carrying out siliconizing treatment on the strip sample, putting the strip sample into a graphite crucible, covering coarse silicon powder on the surface of the strip sample, and putting the graphite crucible into a high-temperature siliconizing furnace for siliconizing treatment, wherein the size of the strip sample is 4mm multiplied by 30 mm. The siliconizing process comprises the steps of carrying out the siliconizing reaction process under the vacuum condition at the siliconizing temperature of 1550 ℃ for 2 hours, and obtaining the siliconizing sample after siliconizing treatment. Since the melting point of silicon is 1410 ℃, at the temperature of 1550 ℃, the solid silicon powder can be completely melted to form liquid silicon, the liquid silicon reacts with the surface of the sample, and the liquid silicon reacts with B4The boron carbide on the surface of the C/graphite composite material reacts to generate silicon carbide, the liquid silicon can also react with the graphite to generate the silicon carbide, and the residual silicon exists in the formed coating, so that the silicon carbide is subjected to the siliconizing process at B4And preparing a layer of silicon carbide and silicon coating with thicker thickness on the surface of the C/graphite composite material. Therefore, the invention adopts the high-temperature liquid siliconizing process at B4And preparing compact and hard silicon carbide and silicon coatings on the surface of the C/graphite composite material. The silicon carbide and silicon coatings are about 300-400 μm thick. And the silicon carbide and silicon coating are combined with the composite material matrix compactly. Because the silicon carbide and the silicon coating on the surface of the siliconized sample have higher hardness and higher wear resistance and good high-temperature oxidation resistance, the B can be obviously improved and enhanced4The surface hardness, the wear resistance, the high-temperature oxidation resistance and the like of the C/graphite composite material.
Example 7
The surface of the silicon carbide coating B4The preparation method of the C/graphite composite material comprises the following steps:
step 1, adopting 70 parts of micron-sized boron carbide ceramic powder with the particle size of about 5 microns; mixing 30 parts of micron-sized graphite powder with the particle size of about 15 mu m, and mixing B4Adding into C/graphite composite powderAdding 5 parts of Al2O3Powder and 5 parts of Y2O3The powder is used as sintering aid, and boron carbide ceramic powder, graphite powder and Al are added2O3Powder and Y2O3Putting the powder into a ball milling tank, adding 300ml of absolute ethyl alcohol and agate milling balls, mixing, mechanically milling for 24 hours to prepare slurry, and drying the slurry to obtain B4C/graphite mixed powder;
step 2, mixing and drying the mixture B obtained by mechanical ball milling4The C/graphite composite powder is filled into a graphite mold, the graphite mold is placed into a hot-pressing sintering furnace to be subjected to a hot-pressing sintering process, the hot-pressing sintering process is carried out at 1800 ℃, the hot-pressing pressure is 30MPa, the heat preservation time is 1h, and the hot-pressing sintering process is carried out under the vacuum condition; so B is prepared by a hot-pressing sintering process4C/graphite composite material wafer;
step 3, preparing B by the hot-pressing sintering process4Preparing a C/graphite composite material wafer sample into a strip sample, wherein the size of the strip sample is 4mm multiplied by 30mm, and carrying out siliconizing treatment on the strip sample. Putting a strip sample into a graphite crucible, covering coarse silicon powder on the surface of the strip sample, putting the graphite crucible into a high-temperature siliconizing furnace for siliconizing, wherein the siliconizing process comprises the steps of siliconizing at 1550 ℃ for 2h, siliconizing reaction under vacuum, obtaining the siliconizing sample after siliconizing treatment, and completely melting solid silicon powder to form liquid silicon at the temperature of 1550 ℃ due to the melting point of silicon of 1410 ℃, reacting the liquid silicon with the surface of the sample, and reacting the liquid silicon with B4The boron carbide on the surface of the C/graphite composite material reacts to generate silicon carbide, the liquid silicon can also react with the graphite to generate the silicon carbide, and the residual silicon exists in the formed coating, so that the silicon carbide is subjected to the siliconizing process at B4A layer of silicon carbide and a silicon coating with thicker thickness is prepared on the surface of the C/graphite composite material, so the embodiment adopts a high-temperature liquid siliconizing process to prepare the coating on the surface of the material B4And preparing compact and hard silicon carbide and silicon coatings on the surface of the C/graphite composite material. The silicon carbide and silicon coatings are about 300-400 μm thick. And the silicon carbide and silicon coating and composite materialThe material matrix is combined compactly. Because the silicon carbide and the silicon coating on the surface of the siliconized sample have higher hardness and higher wear resistance and good high-temperature oxidation resistance, the B can be obviously improved and enhanced4The surface hardness, the wear resistance, the high-temperature oxidation resistance and the like of the C/graphite composite material.
Example 8
The surface of the silicon carbide coating B4The preparation method of the C/graphite composite material comprises the following steps:
step 1, 60 parts of micron-sized boron carbide ceramic powder is used as a raw material, and the granularity of the boron carbide ceramic powder is about 3 microns; 40 parts of micron-sized graphite powder with the particle size of about 12 mu m is adopted; mixing boron carbide ceramic powder and graphite powder in B4Adding 4 parts of Al into the C/graphite composite powder2O3Powder and 6 parts of Y2O3The powder is used as sintering aid, and boron carbide ceramic powder, graphite powder and Al are added2O3Powder and Y2O3Putting the powder into a ball milling tank, adding 300ml of absolute ethyl alcohol and agate milling balls, mixing, mechanically milling for 24 hours to prepare slurry, and drying the slurry to obtain B4C/graphite mixed powder;
step 2, mixing and drying the mixture B obtained by mechanical ball milling4The C/graphite composite powder is filled into a graphite mold, the graphite mold is placed into a hot-pressing sintering furnace to be subjected to a hot-pressing sintering process, the hot-pressing sintering process is carried out at 1800 ℃, the hot-pressing pressure is 30MPa, the heat preservation time is 1h, and the hot-pressing sintering process is carried out under the vacuum condition; so B is prepared by a hot-pressing sintering process4C/graphite composite material wafer;
step 3, preparing B by the hot-pressing sintering process4Preparing a C/graphite composite material wafer sample into a strip sample, wherein the size of the strip sample is 4mm multiplied by 30mm, and carrying out siliconizing treatment on the strip sample. And putting the strip sample into a graphite crucible, covering coarse silicon powder on the surface of the strip sample, and putting the graphite crucible into a high-temperature siliconizing furnace for siliconizing treatment. The siliconizing process comprises the steps of siliconizing temperature of 1550 ℃ and siliconizing time ofAnd 2h, carrying out a siliconizing reaction process under a vacuum condition, and carrying out siliconizing treatment to obtain a siliconizing sample. Since the melting point of silicon is 1410 ℃, at the temperature of 1550 ℃, the solid silicon powder can be completely melted to form liquid silicon, the liquid silicon reacts with the surface of the sample, and the liquid silicon reacts with B4The boron carbide on the surface of the C/graphite composite material reacts to generate silicon carbide, the liquid silicon can also react with the graphite to generate the silicon carbide, and the residual silicon exists in the formed coating, so that the silicon carbide is subjected to the siliconizing process at B4And preparing a layer of silicon carbide and silicon coating with thicker thickness on the surface of the C/graphite composite material. Therefore, the present embodiment uses the high temperature liquid siliconizing process at B4And preparing compact and hard silicon carbide and silicon coatings on the surface of the C/graphite composite material. The silicon carbide and silicon coatings are about 300-400 μm thick. And the silicon carbide and silicon coating are combined with the composite material matrix compactly. Because the silicon carbide and the silicon coating on the surface of the siliconized sample have higher hardness and higher wear resistance and good high-temperature oxidation resistance, the B can be obviously improved and enhanced4The surface hardness, the wear resistance, the high-temperature oxidation resistance and the like of the C/graphite composite material.
As can be seen from examples 5-8, examples 5-8 employ the hot press sintering process to prepare B4C/graphite composite material, wherein the graphite material is in B4The mass fractions of the C/graphite composite material are respectively 10wt%, 20wt%, 30wt% and 40 wt%. And through high-temperature liquid siliconizing process to B4The C/graphite composite material is subjected to a surface modification treatment process, and is subjected to a high-temperature liquid siliconizing process at the step B4The surface of the C/graphite composite material is provided with a layer of silicon carbide and a silicon coating which are thicker, dense and hard, the silicon carbide and the silicon coating are coated on the surface of the siliconizing sample, and the silicon carbide and the silicon coating have higher hardness, the Vickers hardness can reach 20GPa, and higher wear resistance, so that the B can be greatly improved and enhanced4The surface hardness and the wear resistance of the C/graphite composite material sample are improved, and the high-temperature oxidation resistance of the sample is improved. The surface modification treatment technology for the siliconizing process has the advantages of low preparation cost and simple preparation process, and the obtained siliconizing sample has high hardnessThe Vickers hardness can reach 20GPa, and the wear-resistant. The main advantages of the present invention over the existing technology are therefore:
1) in order to improve and improve the processability of the boron carbide ceramic material, a graphite material is added into the boron carbide ceramic matrix to prepare B through a hot-pressing sintering process4C/graphite composite material block. But due to B4The C/graphite composite material has low surface hardness, poor abrasion resistance and poor high-temperature oxidation resistance, so that the B which is processed and formed is required to be subjected to high-temperature oxidation4And carrying out surface modification treatment on the C/graphite composite material. Since liquid silicon can react with B4The boron carbide ceramic material on the surface of the C/graphite composite material sample and the graphite material can both react to generate silicon carbide, so the siliconizing process is adopted to carry out reaction on the B4And carrying out surface modification treatment on the C/graphite composite material. The siliconizing process technology is mature, the preparation process is simple, the preparation cost is low, and the silicon carbide and silicon coating on the surface of the siliconizing sample obtained by siliconizing treatment has high hardness, the Vickers hardness can reach 20GPa, and the siliconizing sample has high wear resistance, high-temperature oxidation resistance and the like. So adopting siliconizing process to B4The surface modification treatment of the C/graphite composite material is a very effective surface modification technology.
2) Due to the processing of B4The C/graphite composite material can be applied to the fields of high-temperature-resistant engineering, wear-resistant engineering and the like in the future, so that the B content is improved4The surface hardness, wear resistance and high temperature oxidation resistance of the C/graphite composite material are important. The object of the present invention is to provide4Machining the C/graphite composite material to obtain required parts, and machining the formed B4The C/graphite composite material adopts a high-temperature liquid siliconizing process to carry out a surface modification treatment process, and is subjected to a siliconizing surface modification treatment process at the step B4And preparing silicon carbide and silicon coatings on the surfaces of the C/graphite composite material samples. The silicon carbide and the silicon coating prepared by the siliconizing reaction have higher surface hardness, the Vickers hardness can reach 20GPa, higher wear resistance and good performanceSo that B can be remarkably improved and enhanced4The surface hardness, the wear resistance, the high-temperature oxidation resistance and the like of the C/graphite composite material. The siliconized sample obtained by the siliconizing treatment will be likely to be applied to the field of wear-resistant engineering or the field of high-temperature-resistant engineering. Therefore, the invention greatly expands B4The application range of the C/graphite composite material in the engineering field. Therefore, the invention has important research significance and practical value. The invention aims to promote and promote B4The wide application of the C/graphite composite material in the engineering field lays a foundation.
FIG. 1 shows a method provided by the present invention in B4The X-ray diffraction pattern of the silicon carbide and silicon coating prepared on the surface of the C/graphite composite material. FIG. 1 shows a process for high-temperature liquid siliconizing in B4XRD patterns of the silicon carbide and silicon coatings prepared on the surfaces of the C/graphite composite materials. As can be seen from FIG. 1, there are diffraction peaks of SiC phase and diffraction peaks of Si phase in the XRD pattern, which indicates that the coating layer on the surface of the siliconized specimen is composed of SiC and Si. This is because during the high temperature liquid siliconizing process, the liquid silicon and B4And the boron carbide on the surface of the C/graphite composite material reacts to generate a silicon carbide coating, the liquid silicon also reacts with the graphite to generate the silicon carbide coating, and the residual silicon exists in the formed coating, so that the silicon carbide and the silicon coating are generated on the surface of the siliconized sample, wherein the silicon carbide is a main component and has higher content, and the residual silicon is less in amount and lower in content. The reaction of liquid silicon with boron carbide to produce silicon carbide is shown below: 3B4C+5Si=3SiC+2SiB6Or B4C+2Si=SiC+SiB4The reaction of liquid silicon and graphite to form silicon carbide is as follows: si + C = SiC. Silicon carbide and silicon coatings can be obtained according to the above reaction. So that the high-temperature liquid siliconizing process is adopted in B4The surface of the C/graphite composite material can be prepared into a silicon carbide coating and a silicon coating.
FIG. 2 shows a method provided by the present invention in B4And scanning electron microscope photographs of the silicon carbide and silicon coatings prepared on the surfaces of the C/graphite composite materials. FIG. 2 shows the use of a heightThe warm liquid siliconizing process is in B4And scanning electron microscope photographs of the silicon carbide and silicon coatings prepared on the surfaces of the C/graphite composite materials. As can be seen from FIG. 2, in B4A layer of silicon carbide and silicon coating with certain thickness is formed on the surface of the C/graphite composite material sample, and the thickness of the silicon carbide and silicon coating is about 300-400 mu m. The silicon carbide and silicon coating is combined with the substrate compactly without gaps and cracks, and the internal tissues of the silicon carbide and silicon coating are compact without holes and gaps. And line scanning energy spectrum analysis shows that the coating mainly contains carbon element and silicon element, which shows that the coating mainly consists of silicon carbide and silicon. Through siliconizing surface modification treatment process in B4And preparing silicon carbide and silicon coatings on the surfaces of the C/graphite composite material samples. The silicon carbide and the silicon coating prepared by the siliconizing reaction have higher surface hardness, the Vickers hardness can reach 20GPa, higher wear resistance and good high-temperature oxidation resistance, so that the B can be obviously improved and enhanced4The surface hardness, the wear resistance, the high-temperature oxidation resistance and the like of the C/graphite composite material.

Claims (6)

1. B with silicon carbide and silicon coating on surface4The C/graphite composite material is characterized by comprising the following components in parts by weight:
with B4The material C is a matrix phase, and the graphite material is a machinable phase; the graphite material is in B4The mass fraction of the C/graphite composite material is 10-40 parts; b is4The mass fraction of the material C is 90-60 parts; al (Al)2O3The mass fraction of the powder is 4 to 7; y is2O3The mass fraction of the powder is 3 to 6.
2. B according to claim 1 having a surface coated with silicon carbide and silicon4C/graphite composite material, characterized in that B is4The material C adopts micron-sized boron carbide powder as a raw material, and the particle size of the powder is about 3-5 mu m; the graphite material adopts micron-sized graphite powder as a raw material, and the particle size of the powder is 10-15 mu m.
3. A composition comprising the silicon carbide and silicon coating layer according to claim 14The preparation method of the C/graphite composite material is characterized by comprising the following steps:
step one, taking 90-60 parts of micron-sized boron carbide powder as a raw material I, wherein the granularity of the boron carbide powder is 3-5 mu m; 10-40 parts of micron-sized graphite powder serving as a second raw material, wherein the granularity of the graphite powder is 10-15 mu m; mixing boron carbide powder and graphite powder in proportion to obtain B4C/graphite composite powder; in B4Adding 4 to 7 parts of Al into the C/graphite composite powder2O3Powder and 3-6 parts of Y2O3The powder is used as a sintering aid; will add Al2O3Powder and Y2O3B of the powder4Placing the C/graphite composite powder into a ball milling tank, adding 100-300ml of absolute ethyl alcohol and 20 agate milling balls with the diameter of 15mm, mixing, preparing slurry by mechanical ball milling for 24 hours, and drying the slurry to obtain B4C/graphite mixed powder;
step two, drying the B obtained in the step one4Filling the C/graphite composite powder into a graphite mold, placing the graphite mold into a hot-pressing sintering furnace to perform a hot-pressing sintering process, wherein the hot-pressing sintering temperature is 1800 ℃, the hot-pressing pressure is 30MPa, the heat preservation time is 1h, and performing hot-pressing sintering under a vacuum condition; preparing B by a hot-pressing sintering process4C/graphite composite material wafer;
step three, the B prepared in the step two4Preparing a C/graphite composite material wafer into a strip sample, carrying out siliconizing treatment on the strip sample, putting the strip sample into a graphite crucible, covering coarse silicon powder on the surface of the strip sample, putting the graphite crucible into a high-temperature siliconizing furnace for high-temperature liquid siliconizing treatment, and obtaining the siliconizing sample after siliconizing treatment; the siliconizing treatment comprises the following steps: the siliconizing temperature is 1550 ℃, the siliconizing time is 2 hours, and the siliconizing time is 1 multiplied by 10-2Carrying out siliconizing reaction under the Pa vacuum condition.
4. The surface of claim 3B with silicon carbide and silicon coating4The preparation method of the C/graphite composite material is characterized in that in the step one: the particle size of the boron carbide powder is 3-5 μm; the particle size of the graphite powder is 10-15 μm.
5. B according to claim 3 having a surface coated with silicon carbide and silicon4The preparation method of the C/graphite composite material is characterized in that in the second step, the vacuum condition is 1 multiplied by 10-2Pa。
6. B according to claim 3 having a surface coated with silicon carbide and silicon4The preparation method of the C/graphite composite material is characterized in that the C/graphite composite material is mixed according to the proportion in the step one, and B4C: graphitic material =9:1 or B4C: graphitic material =4:1 or B4C: graphitic material =7:3 or B4C: graphite material =3: 2.
CN202110464571.0A 2021-04-28 2021-04-28 B with silicon carbide and silicon coating on surface4C/graphite composite material and preparation method thereof Pending CN113105243A (en)

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