CN115368141B

CN115368141B - alpha-SiC and amorphous silicon nitride composite ceramic brake material and preparation method thereof

Info

Publication number: CN115368141B
Application number: CN202211120763.0A
Authority: CN
Inventors: 陈灵涛; 沈益顺; 熊杰; 左劲旅
Original assignee: HUNAN BOYUN NEW MATERIALS CO Ltd
Current assignee: HUNAN BOYUN NEW MATERIALS CO Ltd
Priority date: 2022-09-15
Filing date: 2022-09-15
Publication date: 2023-07-14
Anticipated expiration: 2042-09-15
Also published as: CN115368141A

Abstract

The invention discloses an alpha-SiC and amorphous silicon nitride composite ceramic brake material and a preparation method thereof, wherein the preparation method comprises the steps of obtaining a carbon matrix by adopting a carbon fiber preform through chemical vapor deposition, preparing a silicon nitride ceramic matrix through reactive infiltration silicon and PIP, and obtaining the alpha-SiC and amorphous silicon nitride composite ceramic brake material.

Description

alpha-SiC and amorphous silicon nitride composite ceramic brake material and preparation method thereof

Technical Field

The invention relates to an alpha-SiC and amorphous silicon nitride composite ceramic brake material and a preparation method thereof, belonging to the technical field of brake material preparation.

Background

The current methods for preparing the C/SiC ceramic brake material are numerous, including a precursor impregnation cracking method (PIP), a plasma spraying method (APS), a vapor deposition method (CVI), a reaction infiltration method (RMI) and the like. The carbon ceramic brake material prepared by the PIP method has low density, larger gap and large wet brake attenuation rate. The carbon ceramic material prepared by APS and CVI has compact surface and too thin thickness to be applied to brake materials. The brake material prepared by RMI has the highest density, small void ratio and higher content of internal simple substance silicon. The simple substance silicon forms micro silicon powder in the friction process, has strong water absorption and can reduce the wet braking performance.

Disclosure of Invention

Aiming at the defects of the prior art, the first aim of the invention is to provide a preparation method of alpha-SiC and amorphous silicon nitride composite ceramic brake material.

The second object of the invention is to provide the alpha-SiC and amorphous silicon nitride composite ceramic brake material prepared by the preparation method. The ceramic brake material has the advantages of good toughness, low brake peak-to-valley ratio, no tail warping, small vibration, small abrasion and insensitivity to wet braking.

The invention relates to a preparation method of an alpha-SiC and amorphous silicon nitride composite ceramic brake material, which comprises the following steps:

step one preparation of carbon fiber preform

Alternately layering the weft-free cloth and the thin net felt, continuously needling in the X, Y direction, then performing bidirectional puncture on the weft-free cloth and the thin net felt by using asphalt-based carbon fibers in the Z direction to obtain a carbon fiber preform, and performing heat treatment on the carbon fiber preform to obtain a heat-treated carbon fiber preform; in the carbon fiber preform, the weight percentage of the non-woven cloth and the thin net felt is 58-62: 38 to 42;

preparation of step two carbon/carbon preform

Carrying out chemical vapor deposition and heat treatment on the carbon fiber preform obtained in the step one by taking propylene as a carbon source and taking nitrogen as diluent gas to obtain a carbon/carbon preform, wherein the deposition pressure is 1.4-1.8 kPa and the deposition temperature is 920-970 ℃;

step three, preparing alpha-SiC matrix by reaction infiltration

Carrying out reactive fusion siliconizing on the carbon/carbon preform obtained in the step two, carrying out heat treatment to remove silicon and carrying out SiC recrystallization to obtain a carbon ceramic material containing an alpha-SiC matrix;

preparation of silicon nitride ceramic matrix by PIP (PIP)

Adding the carbon ceramic material containing the alpha-SiC matrix obtained in the step three into an impregnant for impregnation, and then solidifying and cracking to obtain the alpha-SiC and amorphous silicon nitride composite ceramic brake material, wherein the impregnant consists of perhydro-polysilazane (PHPS) and n-hexane.

According to the preparation method, compared with the prior art, the lower weft-free cloth is adopted in the preparation process of the preform, so that the content of the thin net felt is increased, and carbon is enriched in the thin net felt layer in the chemical vapor deposition process, so that the content of pyrolytic carbon can be increased in the chemical vapor deposition process, the content of SiC is finally increased, the hardness and the strength of a matrix can be greatly increased due to the increase of the content of SiC, and the abrasion is effectively reduced; in addition, after the 2D layering and needling are completed, the Z-direction steel needle introduces the asphalt carbon fiber with high heat conduction performance into the 2D preform to form the 3D preform, so that the shearing strength and heat conduction performance between the layers of the material are improved, and the fatigue wear and the oxidative wear are reduced.

In addition, the carbon fiber preform is subjected to heat treatment, organic matters on the surface of the carbon fiber are volatilized through the heat treatment, the specific surface area is increased, the interface bonding strength of pyrolytic carbon and the carbon fiber is increased in the late Chemical Vapor Deposition (CVD) densification process, and the strength of the material is increased.

In the chemical vapor deposition process, the pyrolytic carbon is controlled to be of a smooth layer structure by controlling the temperature and the pressure in the chemical vapor deposition process, and the smooth layer structure has high carbon hardness and high strength, can effectively support silicon carbide, is not easy to break, has good lubricity and can greatly reduce material abrasion.

After the carbon/carbon preform is obtained by chemical vapor deposition, siC matrix is formed by reaction and infiltration, then silicon is removed by heat treatment, and then SiC is recrystallized, so that all SiC is converted into alpha-SiC, and the alpha-SiC silicon after the crystal form conversion has good wear resistance, can well reduce wear, but the internal gap of the material is enlarged due to recrystallization, so that the wear is increased, the water absorption of the material is enhanced, and the wet braking performance is reduced.

Of course, in the preparation process of the preform, the weight percentage of the laid cloth and the thin net felt needs to be effectively controlled, if the proportion of the laid cloth is too low, the brittleness of the subsequently prepared material is enhanced and the toughness is reduced, in the braking process, the brittle fracture or collapse of the tooth part is easily caused by impact, and if the proportion of the laid cloth is too high, larger gaps cannot be formed, the content of CVD carbon is reduced, so that the content of SiC is reduced, and the abrasion is not reduced.

In chemical vapor deposition, the pressure and temperature are not reasonably controlled, and 100% of smooth layer structure cannot be obtained, such as coarse layer structure or carbon black formation.

In the preferred scheme, in the first step, the non-woven cloth and the thin net felt are alternately paved, the interlayer density is controlled to be 11-15 layers/cm, then needling is continuously carried out in the X, Y direction, the needling row spacing and the interval are controlled to be 2.0-2.4x2.0-2.4 mm, and the needling density is controlled to be 20-25 needles/cm ² And then carrying out bidirectional puncture on the pitch-based carbon fiber in the Z direction, and controlling the row spacing and the spacing of the puncture to be 4.8-5.2 multiplied by 4.8-5.2 mm to obtain the carbon fiber preform.

In a preferred scheme, in the first step, the non-woven fabric is polypropylene-based carbon fiber (PANCF) non-woven fabric, and the thin mesh felt is polypropylene-based carbon fiber (PANCF) non-woven fabric.

In a preferred embodiment, in the first step, the temperature of the heat treatment is 2000 to 2300 ℃, preferably 2050 to 2150 ℃, and the time of the heat treatment is 2 to 3 hours, preferably 1.5 hours.

In a preferred embodiment, in the first step, the carbon fiber preform has a density of 0.50 to 0.60g/cm ³ 。

In the second step, the volume ratio of the propylene to the nitrogen is 0.8-1.2: 0.8 to 1.2.

In the second step, the deposition temperature is 930-960 ℃ and the deposition time is 230-260h.

The inventors found that controlling the deposition temperature within the above range, the resulting smooth layer structure is optimal.

In a preferred embodiment, in the second step, the temperature of the heat treatment is 1500-1800 ℃, preferably 1550-1650 ℃, and the time of the heat treatment is 1-3 hours, preferably 1.5 hours.

After chemical vapor deposition, pores are opened through heat treatment, so that the impregnation efficiency is improved in the subsequent preparation process of the carbon/carbon porous body, and in the heat treatment process, the excessive temperature is avoided so as to prevent the smooth layer structure carbon from being subjected to stress graphitization, microcracks are formed at the interface of the carbon fiber and pyrolytic carbon, the interface strength is reduced, and the fatigue wear of the material is increased.

In a preferred embodiment, in the second step, the density of the carbon/carbon preform is 1.35 to 1.40g/cm ³ 。

In the actual operation process, the carbon/carbon preform is machined according to the brake disc feed rule before reaction infiltration. Reserving (1.0+/-0.2) mm machining allowance.

In the preferred scheme, in the step three, the purity of silicon used for reaction infiltration is more than or equal to 99.0 percent, and the grain diameter is less than or equal to 400 meshes.

In a preferred scheme, in the third step, the reaction and infiltration silicon is carried out under argon atmosphere, the temperature of the reaction and infiltration silicon is 1900-2100 ℃, preferably 1850-1950 ℃, the time of the reaction and infiltration silicon is 2-3 h, preferably 2.5h, and the pressure is 0-0.005 MPa.

In a preferred scheme, in the third step, the heat treatment process is as follows: heating to 1700-1750 ℃, preserving heat for 1-2 h, controlling the pressure to 700-900 Pa, removing silicon, then filling argon to enable the pressure lifting force to be 0-0.005 MPa, continuously heating to 2000-2300 ℃, preferably 2200 ℃, preserving heat for 2-3 h, preferably 2h, and carrying out silicon carbide crystal form conversion.

The inventor finds that silicon formed in the reaction infiltration process is wrapped by silicon carbide, so that the silicon-carbon reaction is weaker, the reaction of the silicon-carbon can be reduced by controlling the furnace temperature and the furnace pressure, and the simple substance silicon can be directly overflowed from the inside of the material in a silicon vapor dynamic mode to achieve the effect of removing the silicon. If the temperature is too high, the silicon reacts with the carbon to increase the silicon carbide content, blocking the voids and being unfavorable for the impregnation of the silicon nitride in the later stage. If the temperature is too high, the silicon reacts with the carbon to increase the silicon carbide content, blocking the voids and being unfavorable for the impregnation of the silicon nitride in the later stage. If the temperature is too low, the silicon vapor overflows too slowly, and long heat treatment can degrade the mechanical properties of the material. After the elemental silicon is removed, the temperature is raised and the crystal form conversion of the silicon carbide crystal is performed at normal pressure. The temperature is too high or the furnace pressure is too low, so that the silicon carbide can be decomposed into silicon carbide and gas of silicon carbide overflows, the content of the silicon carbide is reduced, and if the temperature is too low, the crystal form conversion efficiency of the silicon carbide is low. The silicon carbide crystal forms are converted to form a compact structure, the volume is reduced, and a channel is formed for subsequent impregnation of silicon nitride.

In the actual operation process, the carbon ceramic material containing the alpha-SiC matrix is machined according to the near-ruler of the brake disc before being immersed.

In a preferred scheme, in the fourth step, in the impregnant, the mass ratio of the perhydro-polyazasilane to the n-hexane is as follows: 8-12: 0.8 to 1.2.

For the amorphous silicon nitride precursor, the invention selects the perhydro polysilazane, the ceramic yield is up to 85 percent, the material density is high, the ceramic temperature is lower, the formed amorphous silicon nitride is a hydrophobic material, the water absorption rate and the abrasive dust water absorption rate of the material can be reduced, and the wet braking performance in the friction process is not attenuated.

According to the invention, the proportion of alpha-SiC to amorphous silicon nitride is finally controlled by controlling the silicon content in the reaction-fused siliconizing body through the density of the carbon/carbon preform, wherein the alpha-SiC content is 30+/-5 percent, and the amorphous silicon nitride content is 20+/-5 percent, so that the alpha-SiC and the amorphous silicon nitride achieve the best synergistic effect, and if the alpha-SiC content is high and the amorphous silicon nitride content is low, the friction coefficient is increased, the vibration is increased and the abrasion is slightly increased. If the α -SiC content is reduced and the amorphous silicon nitride content is increased, the friction coefficient is reduced and the deceleration rate is reduced.

The perhydropolysilazanes used in the invention have a viscosity (25 ℃) of 40 to 100s, ash content (w/%)

The water content (w/%) is less than or equal to 3.0, the purity of n-hexane is less than or equal to 85%, and in the actual operation process, the perhydro-polysilazane and n-hexane are mixed and stirred for 30 minutes to obtain the impregnant.

In a preferred scheme, in the fourth step, the dipping process is that the vacuum degree of the dipping tank is smaller than or equal to 10pa, the dipping agent is sucked into the dipping tank, the dipping is carried out for 1-2 hours, preferably 2 hours, then the dipping is carried out by pressurizing to 3-5 MPa, preferably 5MPa by nitrogen, and the pressurizing dipping is carried out for 1-2 hours, preferably 2 hours.

In the fourth step, the curing temperature is 150-300 ℃, preferably 200-300 ℃, the curing time is 8-12h, and the heating rate is less than or equal to 2 ℃/min.

The inventor finds that the heating rate and the curing time of curing need to be effectively controlled, the curing time is insufficient, and the bonding strength of silicon nitride and silicon carbide can be reduced; the rate of temperature rise is too fast and microcracks can develop.

In the actual operation process, an impregnating and curing integrated tank can be adopted, after impregnation is finished, pressure is released, impregnant is discharged, and then pressure is increased, and temperature is increased for curing.

In a preferred scheme, in the fourth step, the cracking is performed under the nitrogen atmosphere, the cracking temperature is 800-1300 ℃, preferably 1050-1150 ℃, the cracking time is 1-4 h, preferably 2-3 h, and the heating rate is less than or equal to 2.5 ℃/min.

The inventors found that the cracking temperature cannot be too high, that the amorphous silicon nitride is formed at too high a temperature, that crystallization occurs, that the self-lubricating effect is reduced, that the bonding strength with silicon carbide is reduced, and that the wear is increased.

While at the preferred cracking temperature conditions, avoiding crystallization of the silicon nitride may be accomplished. The final performance is optimal.

In the actual operation process, when the cured product is transferred into a cracking furnace, the vacuum is firstly pumped for replacing nitrogen twice, and then the nitrogen is filled to micro positive pressure.

In the preferred scheme, in the fourth step, the density of the alpha-SiC and amorphous silicon nitride composite ceramic brake material is 1.90-2.0 g/cm ³ 。

The invention also provides the alpha-SiC and amorphous silicon nitride composite ceramic brake material prepared by the preparation method.

Principle and advantages

After the carbon/carbon preform is obtained by chemical vapor deposition, siC matrix is formed by reaction and infiltration, then silicon is removed by heat treatment, and simultaneously SiC is recrystallized, so that all SiC is converted into alpha-SiC, and the alpha-SiC silicon after the crystal form conversion has good wear resistance, and can well reduce wear, but the internal gap of the material is enlarged due to recrystallization, so that the wear is increased, the water absorption of the material is enhanced, and the wet braking performance is reduced.

For the prior art, the invention has the following advantages:

the silicon carbide combined with the silicon nitride composite ceramic has better thermal shock resistance and impact resistance, good toughness and difficult occurrence of brittle fracture. The wear resistance is better than that of single-phase ceramic matrix composite materials.

The RMI process has the advantages of short preparation period and low cost. The disadvantage is that the content of simple substance silicon in the prepared carbon ceramic material is high, and is generally (5-15)%. The simple substance silicon can increase the attenuation rate of the high-energy brake, and the micro silicon powder formed in the abrasive dust has strong water absorption and can increase the attenuation rate of the wet brake performance. According to the invention, after reaction infiltration, high-temperature heat treatment is performed to remove silicon and recrystallize silicon carbide, so that elemental silicon in a blank body is removed, and beta-SiC is converted into alpha-SiC with better wear resistance.

The invention adopts PIP technology to immerse the perhydro polysilazane into the silicon carbide ceramic matrix, fills the macropores left by silicon removal, so that the ceramic matrix is more compact, and the product after the perhydro polysilazane is cracked is amorphous silicon nitride, and has good hydrophobicity and toughness. The silicon carbide can be supported in the braking process, and the elasticity of the silicon carbide can be reduced when the silicon carbide is impacted, so that the silicon carbide is broken or pulled out. In addition, the amorphous silicon nitride has good self-lubricating effect, so that abrasion and vibration can be greatly reduced.

The invention increases the content of the thin net felt, and increases fiber puncture in the Z direction, so that the interlaminar shear strength of the brake material is improved from (30+/-10) MPa to (95+/-10) MPa. Solves the problem of whole block falling-off caused by fatigue and abrasion.

According to the invention, graphitization treatment is added in the preparation of the preform, because high-temperature graphitization is a defect that the surface of the fiber is uneven, and the defects are that the interface bonding strength of the carbon fiber and the CVD pyrolytic carbon is increased, so that fatigue wear can be effectively reduced.

The CVD pyrolytic carbon prepared by the method is of a smooth layer structure, has high hardness, high strength and good wear resistance, is strongly combined with the interface of the carbon fiber and the silicon carbide, has enhanced supporting effect on the silicon carbide, and reduces the abrasion of silicon carbide particles.

The silicon carbide silicon nitride composite ceramic brake material prepared by the invention has the alpha-SiC content of 30+/-5 percent, the amorphous silicon nitride content of 20+/-5 percent, the surface hardness of 91HD and the density of 1.90 ultra-thin2.1)g/cm ³ 。

The wear rate of the composite ceramic brake material prepared by the invention is less than 0.62 mu m/surface/time, the wet brake performance attenuation rate is less than 3%, the friction curve peak-to-valley ratio is less than 1.6, and the composite ceramic brake material has low speed and no vibration. Because the temperature of the friction surface in the high-energy braking process can reach more than 1200 ℃, and amorphous silicon nitride starts to crystallize at more than 1200 ℃, the crystallized silicon nitride loses toughness and self-lubricating effect, and abrasion is greatly increased, the composite ceramic brake material prepared by the invention is only suitable for the low-energy braking field of helicopters, trucks, automobiles and the like.

Drawings

FIG. 1A carbon ceramic brake disc prepared in example 1.

Detailed Description

Example 1

Step one: preparation of carbon fiber preform

Alternately laminating a layer of polypropylene-based carbon fiber (PANCF) laid cloth and a layer of polypropylene-based carbon fiber (PANCF) thin net felt (laid cloth 0) ⁰ /90 ⁰ /270 ⁰ Layering), the weight percentage of the laid cloth and the thin net felt is 60:40, controlling the interlayer density to be 12 layers/cm, continuously needling after finishing layering in X, Y direction, controlling the needling row spacing to be 2.2 multiplied by 2.2mm, and controlling the needling density to be 25 needles/cm ² After the completion, carrying out bidirectional puncture on the carbon fiber preform by using high-heat-conductivity asphalt carbon fiber (TYG) in the Z direction, wherein the line spacing and the interval of the Z-direction fiber are 5.0x5.0mm during the puncture, and the density of the obtained carbon fiber preform is 0.55g/cm ³ 。

And then carrying out heat treatment on the obtained carbon fiber preform, wherein the temperature of the heat treatment is controlled to be 2100 ℃, and the time of the heat treatment is 2 hours.

Step two, preparation of carbon/carbon preform

Taking propylene as a carbon source and nitrogen as diluent gas for the carbon fiber preform obtained in the step one, wherein the volume ratio of the propylene to the nitrogen is 1:1, performing chemical vapor deposition and heat treatment to obtain a density of 1.37g/cm ³ During the chemical vapor deposition, the deposition pressure is 1.5kPa, and the deposition temperature is 930 ℃; deposition time is 230h, the heat pointThe temperature is 1600 ℃, and the time of the heat treatment is 2 hours.

Step three, preparing alpha-SiC matrix by reaction infiltration

And (3) carrying out reactive infiltration siliconizing on the carbon/carbon prefabricated body obtained in the step (II), wherein the purity of silicon used for reactive infiltration is larger than or equal to 99.0%, the grain size is smaller than or equal to 400 meshes, the reactive infiltration siliconizing is carried out under the argon atmosphere, the temperature of the reactive infiltration siliconizing is 1900 ℃, the time of the reactive infiltration siliconizing is 2.5h, and the pressure is 0.005MPa.

And then carrying out heat treatment on the carbon ceramic material obtained by infiltration to remove silicon and simultaneously carrying out recrystallization of SiC, firstly heating to 1720 ℃, preserving heat for 2 hours, controlling the pressure to 850Pa, removing silicon, then filling argon to ensure that the pressure lifting force is 0.005MPa, continuously heating to 2200 ℃, preserving heat for 2 hours, and carrying out silicon carbide crystal form conversion.

Step four, preparation of carbon ceramic brake material

Selecting perhydro polysilazane with the viscosity (25 ℃) of 40-100 s, ash content (w/%) of less than or equal to 3.0, moisture content (w/%) of less than or equal to 1.0, and n-hexane with the purity of 85 percent, wherein the mass ratio of the perhydro polysilazane to the n-hexane is 10:1, stirring for 30 minutes to obtain an impregnant, machining the carbon ceramic material containing the alpha-SiC matrix obtained in the step three according to a brake disc rule, placing the carbon ceramic material into an impregnation curing furnace, vacuumizing (the vacuum degree is less than or equal to 10 pa), then sucking the impregnation liquid into the impregnation curing furnace to immerse a carbon ceramic blank, pressurizing to 5MPa by nitrogen after vacuum impregnation for 2 hours, and continuing impregnation for 2 hours. And then releasing pressure, discharging the impregnating solution, pressurizing to 5MPa again, heating to 250 ℃ for curing for 10 hours, and heating up at a rate less than or equal to 2 ℃/min. Transferring the cured material into a cracking furnace, vacuumizing and replacing nitrogen twice, and then charging nitrogen to micro positive pressure. The temperature was slowly raised to 1100℃for cleavage for 2 hours. The temperature rising rate is less than or equal to 2.5 ℃/min. And obtaining the silicon carbide and silicon nitride composite ceramic brake material after the cracking is completed.

The density of the material prepared was 2.05g/cm ³ alpha-SiC content 30%, amorphous silicon nitride content 21%, compressive strength 303MPa, bending strength 291MPa, and shear strength 93MPa. The friction coefficient of the carbon ceramic brake disc is 0.28, the wear rate is 0.49 mu m/surface/time, the peak-to-valley ratio of the friction curve is 1.51, and the wet braking performance attenuation rate is 0.2%.

Example 2

Step one: preparation of carbon fiber preform

Step two, preparation of carbon/carbon preform

Taking propylene as a carbon source and nitrogen as diluent gas for the carbon fiber preform obtained in the step one, wherein the volume ratio of the propylene to the nitrogen is 1:1, performing chemical vapor deposition and heat treatment to obtain a density of 1.37g/cm ³ During the chemical vapor deposition, the deposition pressure is 1.5kPa, and the deposition temperature is 930 ℃; the deposition time is 230h, the temperature of the heat treatment is 1600 ℃, and the time of the heat treatment is 2h.

Step three, preparing alpha-SiC matrix by reaction infiltration

And (3) carrying out reactive infiltration siliconizing on the carbon/carbon preform obtained in the step (II), wherein the purity of silicon used for reactive infiltration is larger than or equal to 99.0%, the particle size is smaller than or equal to 400 meshes, the reactive infiltration siliconizing is carried out under the argon atmosphere, the temperature of the reactive infiltration siliconizing is 1900 ℃, the time of the reactive infiltration siliconizing is 2 hours, and the pressure is 0.005MPa.

And then carrying out heat treatment on the carbon ceramic material obtained by infiltration to remove silicon and simultaneously carrying out recrystallization of SiC, wherein the heat treatment temperature is 1720 ℃, the pressure is 850Pa, and the time is 2h. The temperature of the SiC recrystallization is 2200 ℃, the pressure is 0.005MPa, and the time is 2 hours.

Step four, preparation of carbon ceramic brake material

The density of the material prepared was 1.98g/cm ³ alpha-SiC content 26%, amorphous silicon nitride content 25%, simple substance silicon content 1.5%, compressive strength 298MPa, bending strength 294MPa and shearing strength 93MPa. The friction coefficient of the carbon ceramic brake disc is 0.25, the wear rate is 0.41 mu m/surface/time, the peak-to-valley ratio of the friction curve is 1.44, and the wet braking performance attenuation rate is 2%.

Example 3

Step one: preparation of carbon fiber preform

Step two, preparation of carbon/carbon preform

Step three, preparing alpha-SiC matrix by reaction infiltration

And (3) carrying out reactive infiltration siliconizing on the carbon/carbon preform obtained in the step (II), wherein the purity of silicon used for reactive infiltration is larger than or equal to 99.0%, the particle size is smaller than or equal to 400 meshes, the reactive infiltration siliconizing is carried out under the argon atmosphere, the temperature of the reactive infiltration siliconizing is 1900 ℃, the time of the reactive infiltration siliconizing is 3 hours, and the pressure is 0.005MPa.

And then carrying out heat treatment on the carbon ceramic material obtained by infiltration to remove silicon and simultaneously carrying out recrystallization of SiC, wherein the temperature of the heat treatment for removing silicon is 1720 ℃, the pressure is 850Pa, and the time is 2h. The temperature of the SiC recrystallization is 2200 ℃, the pressure is 0.005MPa, and the time is 2 hours.

Step four, preparation of carbon ceramic brake material

The density of the material prepared was 2.1g/cm ³ alpha-SiC content 34%, amorphous silicon nitride content 15%, silicon content 0.5%, compressive strength 308MPa, flexural strength 288MPa, and shear strength 94MPa. The friction coefficient of the carbon ceramic brake disc is 0.31, the wear rate is 0.61 mu m/surface/time, the peak-to-valley ratio of the friction curve is 1.60, and the wet braking performance attenuation rate is 1.3%.

Table 1 comparison of example performance

Comparative example 1

Other conditions were the same as in example 1 except that the reaction infiltration time was shortened to 1h. The prepared material contains 18% of alpha-SiC, 30% of amorphous silicon nitride, 1.7% of simple substance silicon, 247MPa of compressive strength, 252MPa of bending strength and 91MPa of shearing strength. The friction coefficient of the carbon ceramic brake disc is 0.15, the deceleration rate is 2.28, the abrasion rate is 0.44 mu m/surface.times, the peak-to-valley ratio of the friction curve is 1.40, and the wet braking performance attenuation rate is 4.7%.

Comparative example 2

Other conditions were the same as in example 1 except that the reaction infiltration time was prolonged to 4 hours. The prepared material contains 43% of alpha-SiC, 5% of amorphous silicon nitride, 0.2% of simple substance silicon, 340MPa of compressive strength, 278MPa of bending strength and 94MPa of shearing strength. The friction coefficient of the carbon ceramic brake disc is 0.43, the deceleration rate is 5.23, the abrasion rate is 0.87 mu m/surface.times, the peak-to-valley ratio of the friction curve is 1.8, and the wet braking performance attenuation rate is 3%. The braking process has the phenomena of howling and vibration.

Comparative example 3

Other conditions were the same as in example 1 except that the silicon carbide recrystallization time was prolonged to 4 hours. The prepared material contains 20% of alpha-SiC, 25% of amorphous silicon nitride, 269MPa of compressive strength, 247MPa of bending strength and 78MPa of shearing strength. The friction coefficient of the carbon ceramic brake disc is 0.22, the deceleration rate is 2.73, the abrasion rate is 1.12 mu m/surface.times, the friction curve peak-to-valley ratio is 1.5, and the wet braking performance attenuation rate is 1.7%.

Comparative example 4

Other conditions were the same as in example 1 except that the silicon carbide recrystallization time was shortened to 1h. The prepared material contains 16% of alpha-SiC, 17% of beta-SiC, 15% of amorphous silicon nitride, 305MPa of compressive strength, 298MPa of bending strength and 94MPa of shearing strength. The friction coefficient of the carbon ceramic brake disc is 0.28, the deceleration rate is 3.76, the abrasion rate is 1.04 mu m/surface.times, the friction curve peak-to-valley ratio is 1.7, and the wet braking performance attenuation rate is 2.3%.

Comparative example 5

The other conditions were the same as in example 1 except that the weight percentage of the laid fabric to the thin mesh felt was 70:30. the prepared material contains 23% of alpha-SiC, 17% of amorphous silicon nitride, 0.8% of elemental silicon, 261MPa of compression strength, 228MPa of bending strength and 81MPa of shearing strength. The friction coefficient of the carbon ceramic brake disc is 0.25, the deceleration rate is 3.55, the abrasion rate is 1.14 mu m/surface-times, the friction curve peak-to-valley ratio is 1.7, and the wet braking performance attenuation rate is 5%.

Comparative example 6

Other conditions were the same as in example 1 except that the deposition pressure was 1.2kPa and the deposition temperature was 990 ℃. The prepared material contains 32% of alpha-SiC, 20% of amorphous silicon nitride, 290MPa of compressive strength, 232MPa of bending strength and 69MPa of shearing strength. The friction coefficient of the carbon ceramic brake disc is 0.31, the deceleration rate is 3.76, the abrasion rate is 1.13 mu m/surface-times, the friction curve peak-to-valley ratio is 1.7, and the wet braking performance attenuation rate is 2%.

Comparative example 7

The other strips will be the same as in example 1, with no subsequent treatment after reactive-melt siliconizing. The prepared material contains 36% of beta-SiC, 2% of amorphous silicon nitride, 7% of simple substance silicon, 308MPa of compression strength, 292MPa of bending strength and 94MPa of shearing strength. The friction coefficient of the carbon ceramic brake disc is 0.32, the deceleration rate is 3.76, the wear rate is 0.89 mu m/surface.times, the friction curve peak-to-valley ratio is 1.8, and the wet braking performance attenuation rate is 40%.

Comparative example 8

The other strips will be the same as in example 1 except that the temperature is 1850 ℃ during the desilication heat treatment. The prepared material contains 20% of alpha-SiC, 28% of amorphous silicon nitride, 267MPa of compressive strength, 274MPa of bending strength and 69MPa of shearing strength. The friction coefficient of the carbon ceramic brake disc is 0.22, the deceleration rate is 2.81, the abrasion rate is 1.20 mu m/surface-times, the friction curve peak-to-valley ratio is 1.6, and the wet braking performance attenuation rate is 1.2%.

Table 2 comparative example performance comparison

Claims

1. A preparation method of an alpha-SiC and amorphous silicon nitride composite ceramic brake material is characterized by comprising the following steps of: the method comprises the following steps:

step one preparation of carbon fiber preform

Alternately layering the weft-free cloth and the thin net felt, continuously needling in the X, Y direction, then performing bidirectional puncture on the weft-free cloth and the thin net felt by using asphalt-based carbon fibers in the Z direction to obtain a carbon fiber preform, and performing heat treatment on the carbon fiber preform to obtain a heat-treated carbon fiber preform; in the carbon fiber preform, the weight percentage of the non-woven cloth to the thin net felt is 58-62: 38-42;

preparation of step two carbon/carbon preform

Carrying out chemical vapor deposition and heat treatment on the carbon fiber preform obtained in the step one by taking propylene as a carbon source and nitrogen as a diluent gas to obtain a carbon/carbon preform, wherein the deposition pressure is 1.4-1.8 kPa and the deposition temperature is 920-970 ℃ during the chemical vapor deposition;

step three, preparing alpha-SiC matrix by reaction infiltration

the reaction and infiltration are carried out in an argon atmosphere, the temperature of the reaction and infiltration is 1900-2100 ℃, the time of the reaction and infiltration is 2-3 h, and the pressure is 0-0.005 MPa;

the heat treatment process comprises the following steps: firstly heating to 1700-1750 ℃, preserving heat for 1-2 h, controlling the pressure to 700-900 Pa, removing silicon, then filling argon to enable the pressure to rise to 0-0.005 MPa, continuously heating to 2000-2300 ℃, preserving heat for 2-3 h, and carrying out silicon carbide crystal form conversion;

preparation of silicon nitride ceramic matrix by PIP (PIP)

And (3) adding the carbon ceramic material containing the alpha-SiC matrix obtained in the step (III) into an impregnant for impregnation, and then curing and cracking to obtain the alpha-SiC and amorphous silicon nitride composite ceramic brake material, wherein the impregnant consists of perhydro polysilazane and n-hexane.

2. The method for preparing the alpha-SiC and amorphous silicon nitride composite ceramic brake material according to claim 1, which is characterized in that:

alternately laying the laid cloth and the thin net felt, controlling the interlayer density to be 11-15 layers/cm, continuously needling in the X, Y direction, controlling the needling row spacing and the pitch to be 2.0-2.4 multiplied by 2.0-2.4 mm, and controlling the needling density to be 20-25 needles/cm ² Then, bi-directionally puncturing is carried out by using pitch-based carbon fibers in the Z direction, and the row spacing and the spacing of puncturing are controlled to be 4.8-5.2 multiplied by 4.8-5.2 mm, so that a carbon fiber preform is obtained;

in the first step, the non-woven cloth is polypropylene-based carbon fiber non-woven cloth, and the thin net felt is polypropylene-based carbon fiber non-woven cloth.

3. The method for preparing the alpha-SiC and amorphous silicon nitride composite ceramic brake material according to claim 1, which is characterized in that:

in the first step, the temperature of the heat treatment is 2000-2300 ℃, the time of the heat treatment is 2-3 hours,

in the first step, the density of the carbon fiber preform is 0.50-0.60 g/cm ³ 。

4. The method for preparing the alpha-SiC and amorphous silicon nitride composite ceramic brake material according to claim 1, which is characterized in that:

in the second step, the volume ratio of the propylene to the nitrogen is 0.8-1.2: 0.8-1.2;

in the second step, the deposition temperature is 930-960 ℃ and the deposition time is 230-260h during the chemical vapor deposition.

5. The method for preparing the alpha-SiC and amorphous silicon nitride composite ceramic brake material according to claim 1, which is characterized in that:

in the second step, the temperature of the heat treatment is 1500-1800 ℃, the time of the heat treatment is 1-3 hours,

in the second step, the density of the carbon/carbon preform is 1.35-1.40 g/cm ³ 。

6. The method for preparing the alpha-SiC and amorphous silicon nitride composite ceramic brake material according to claim 1, which is characterized in that:

in the third step, the purity of the silicon used for reaction infiltration is more than or equal to 99.0 percent, and the grain diameter is less than or equal to 400 meshes.

7. The method for preparing the alpha-SiC and amorphous silicon nitride composite ceramic brake material according to claim 1, which is characterized in that:

in the fourth step, in the impregnant, the mass ratio of the perhydro-polyazasilane to the n-hexane is 8-12: 0.8-1.2;

and step four, the dipping process is that firstly, vacuumizing until the vacuum degree of a dipping tank is less than or equal to 10pa, sucking the dipping agent into the dipping tank, dipping for 1-2 hours in vacuum, and then pressurizing to 3-5 MPa through nitrogen, and pressurizing and dipping for 1-2 hours.

8. The method for preparing the alpha-SiC and amorphous silicon nitride composite ceramic brake material according to claim 1, which is characterized in that:

in the fourth step, the curing temperature is 150-300 ℃, the curing time is 8-12h, the heating rate is less than or equal to 2 ℃/min,

in the fourth step, the cracking is carried out in a nitrogen atmosphere, the cracking temperature is 800-1300 ℃, the cracking time is 1-4 hours, and the heating rate is less than or equal to 2.5 ℃/min;

step fourWherein the density of the alpha-SiC and amorphous silicon nitride composite ceramic brake material is 1.90-2.0 g/cm ³ 。

9. An α -SiC and amorphous silicon nitride composite ceramic brake material prepared by the method according to any one of claims 1 to 8.