A method for in-situ generating boron carbide-based wear-resistant ceramic material with uniform carbon distribution, boron carbide-based wear-resistant ceramic material and application thereof

Abstract

The application discloses a method for generating boron carbide-based wear-resistant ceramic material with uniform carbon distribution in situ, the boron carbide-based wear-resistant ceramic material and application thereof, and the method comprises the following steps: adding superfine TiC and B4C to generate elemental carbon and TiB2 in situ through hot-pressing sintering; and promoting the full reaction of the TiC and the B4C and the uniform distribution of the elemental carbon through a multi-step hot-pressing sintering process, so that the elemental carbon in the boron carbide composite ceramic sintered through the hot-pressing sintering is small and uniformly distributed. Meanwhile, the TiB2 generated in situ is uniformly distributed in the boron carbide composite ceramic, so that the fracture toughness of the ceramic is improved.

Description

Technical Field

[0001] This invention belongs to the field of composite ceramic material preparation technology, specifically relating to a method for in-situ generating boron carbide-based wear-resistant ceramic materials with uniform carbon distribution, boron carbide-based wear-resistant ceramic materials and their applications. Background Technology

[0002] Boron carbide ceramics are advanced structural ceramics with a hardness second only to diamond and cubic boron nitride. They possess characteristics such as low density, high elastic modulus, high wear resistance, high neutron absorption cross section, and low coefficient of thermal expansion, making them widely used in machining, nuclear industry, defense, and aerospace. However, the strong covalent bond crystal structure makes it difficult to achieve densification during sintering of boron carbide ceramics. Adding sintering aids (TiB2, SiC, Al2O3, CrB2) to improve the sintering performance of boron carbide ceramics is a good approach. Among these, TiB2 can improve the electrical conductivity of boron carbide ceramics, which is of great significance for improving the machinability of wire EDM and reducing processing costs.

[0003] Although boron carbide ceramics can form a lubricating H3BO3 friction layer in air due to tribochemical reactions, the self-lubricating effect is difficult to achieve through tribochemical reactions in the vacuum or inert atmospheres of aerospace applications. Secondary phases with self-lubricating properties, such as graphite, can effectively reduce the coefficient of friction and improve wear resistance of ceramics. In-situ generation of elemental carbon and TiB2 from B4C and TiC is an ideal method for reinforcing boron carbide-based ceramics; however, the complex mixing process can lead to crystal contamination by external factors, and the voids in the ceramic matrix cannot be filled by directly added elemental carbon at high temperatures. Furthermore, B4C and TiC react rapidly in the 1000℃~1400℃ range, leading to the segregation of elemental carbon, which affects the density and wear resistance of the boron-titanium boride composite ceramic material and reduces its stability. Therefore, there is an urgent need to find a method for preparing boron carbide-based composite ceramics that can generate uniform carbon distribution in situ. Summary of the Invention

[0004] The purpose of this section is to outline some aspects of embodiments of the present invention and to briefly describe some preferred embodiments. Simplifications or omissions may be made in this section, as well as in the abstract and title of this application, to avoid obscuring the purpose of these documents; however, such simplifications or omissions should not be construed as limiting the scope of the invention.

[0005] In view of the problems existing in the above and / or prior art, the present invention is proposed.

[0006] Therefore, the purpose of this invention is to overcome the shortcomings of the prior art and provide a method for in-situ generating boron carbide-based wear-resistant ceramic materials with uniform carbon distribution.

[0007] To solve the above-mentioned technical problems, the present invention provides the following technical solution: including, B4C and TiC are mixed and ball-milled to obtain a composite powder slurry with a B4C content of 70-95% and a TiC content of 5-30%. The composite powder slurry is dried, ground, and sieved to obtain mixed powder particles. Mixed powder particles are subjected to multi-step hot pressing sintering. During the sintering process, the temperature is raised to the sintering temperature in stages. After reaching the sintering temperature, the temperature is held for 1 to 5 minutes. The sample is cooled with the furnace while being subjected to pressure treatment. When the pressure is released, a boron carbide-based wear-resistant ceramic material with uniform carbon distribution is generated in situ. The sintering process involves staged heating to the sintering temperature. In the first stage, the temperature is increased from room temperature to 950-1060 ℃ at a heating rate of 80-120 ℃ / min. In the second stage, the temperature is increased from 950-1060 ℃ to 1350-1450 ℃ at a heating rate of 1-5 ℃ / min. In the third stage, the temperature is increased from 1350-1450 ℃ to the sintering temperature of 2000-2100 ℃ at a heating rate of 15-30 ℃ / min.

[0008] As a preferred embodiment of the method for in-situ generating boron carbide-based wear-resistant ceramic material with uniform carbon distribution according to the present invention, wherein: the purity of B4C is >99wt% and the average particle size is ≤1.5 μm, and the purity of TiC is >98wt% and the average particle size is <0.5 μm.

[0009] As a preferred embodiment of the method for in-situ generating boron carbide-based wear-resistant ceramic materials with uniform carbon distribution according to the present invention, the ball milling speed of the B4C and TiC mixed ball mill is 270~320 rpm, the ball milling time is >20h, and the ball milling medium is 8~12 B4C grinding balls with a diameter of 10mm.

[0010] As a preferred embodiment of the method for in-situ generating boron carbide-based wear-resistant ceramic materials with uniform carbon distribution according to the present invention, wherein: the composite powder slurry is dried, ground and sieved to obtain mixed powder particles, wherein the drying method of the composite powder slurry includes drying at 80~100℃ for 2~3 hours and then placing it in a drying oven and drying at 130~170℃ for 8~12 hours.

[0011] As a preferred embodiment of the method for in-situ generating boron carbide-based wear-resistant ceramic materials with uniform carbon distribution according to the present invention, wherein the grinding and sieving is performed through a 200-mesh sieve.

[0012] As a preferred embodiment of the method for in-situ generating boron carbide-based wear-resistant ceramic materials with uniform carbon distribution according to the present invention, the hot pressing sintering process involves starting to pressurize the sintering furnace at 150~550°C, loading it to a sintering pressure of 25~35 MPa at 1000~1150°C, and then increasing the temperature to a sintering temperature of 2000~2100°C.

[0013] In a preferred embodiment of the method for in-situ generating boron carbide-based wear-resistant ceramic material with uniform carbon distribution according to the present invention, the pressure holding time is 80~120 min.

[0014] Another object of the present invention is to provide a boron carbide-based wear-resistant ceramic material with in-situ uniform carbon distribution, wherein the boron carbide-based wear-resistant ceramic material is composed of uniformly distributed elemental C, B4C, and TiB2, and has the following characteristics. (i) Free carbon volume fraction is 0.33 ~ 11.43 vol.%; (ii) Fracture toughness is 3.31~3.75 MPa·m1 / 2; (iii) Using Al2O3 balls as the friction pair, with a load of 6 N, a reciprocating frequency of 300 r / min, a reciprocating distance of 5 mm, and a total sliding distance of 90 m, the wear rate was 3.81 × 10⁻⁶. -6 ~4.25×10 -6 mm 3 ·N -1 ·m -1 .

[0015] Another objective of this invention is to provide an application of boron carbide-based wear-resistant ceramic material with in-situ uniform carbon distribution in machining, nuclear industry, defense and military industry, and aerospace.

[0016] Beneficial effects of this invention: This invention utilizes the reaction B4C + 2TiC = 2TiB2 + 3C under high-temperature hot pressing. By introducing nanoscale TiC and employing a multi-step hot pressing sintering method, it avoids the segregation of elemental carbon in boron carbide-based composite ceramics, ultimately generating boron carbide-based composite ceramics with uniform distribution of elemental carbon in situ. This invention increases the uniformity of the composite ceramic matrix composition through a multi-step hot pressing sintering process. Simultaneously, the formation of a graphite lubricating layer during friction reduces the coefficient of friction and enhances wear resistance; the in-situ generated TiB2 gives the composite ceramic higher fracture toughness. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein: Figure 1 The scanning electron microscope image of the boron carbide-based composite ceramic prepared in Example 1 of the present invention and the X-ray energy dispersive spectroscopy elemental analysis of the carbon distribution in the corresponding region are shown.

[0018] Figure 2 The scanning electron microscope image of the boron carbide-based composite ceramic prepared in Comparative Example 1 of this invention and the X-ray energy dispersive elemental analysis of the carbon distribution in the corresponding region are shown.

[0019] Figure 3 The scanning electron microscope image of the boron carbide-based composite ceramic prepared in Example 2 of the present invention and the X-ray energy dispersive spectroscopy elemental analysis of the carbon distribution in the corresponding region are shown. Detailed Implementation

[0020] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification.

[0021] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0022] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0023] Unless otherwise specified, all raw materials used in this invention are commercially available in the art. Among them, B4C has a purity greater than 99 wt% and an average particle size less than or equal to 1.5 μm; TiC has a purity greater than 98 wt% and an average particle size less than 0.5 μm.

[0024] Example 1 This embodiment provides a method for in-situ generating boron carbide-based wear-resistant ceramic materials with uniform carbon distribution, specifically:

[0025] 1) Weigh 25.5g of B4C and 4.5g of TiC to obtain a mixed raw material with B4C content of 85% and TiC content of 15%. Place it in a polytetrafluoroethylene bottle, add 150 mL of anhydrous ethanol and 10 B4C particles with a diameter of 10 mm, and ball mill the mixture at a speed of 300 r / min for 32 h to obtain a composite powder slurry. 2) After the composite powder slurry is dried at 90℃ for 2 hours, it is placed in a drying oven and dried at 160℃ for 10 hours to obtain agglomerated powder. The powder is then ground and crushed, and passed through a 200-mesh sieve to obtain mixed powder particles.

[0026] 3) The mixed powder particles were subjected to multi-step hot pressing sintering. In the first stage, the temperature was increased from room temperature to 1000℃ at a heating rate of 100℃ / min. In the second stage, the temperature was increased from 1000℃ to 1400℃ at a heating rate of 2℃ / min. In the third stage, the temperature was increased from 1400℃ to the sintering temperature of 2050℃ at a heating rate of 20℃ / min. The hot pressing sintering furnace was pressurized at 500℃ and loaded to the sintering pressure of 30 MPa at around 1100℃. As the temperature rose to the sintering temperature of 2050℃, the heating power was cut off after holding at that temperature for 3 min. The sample was cooled with the furnace and then subjected to a pressure holding treatment for 100 min. After that, the pressure was released to obtain the boron carbide-based composite ceramic of this embodiment.

[0027] Figure 1 Scanning electron microscopy (SEM) images and EDS analysis of carbon element distribution in the corresponding regions of the boron carbide-based composite ceramic material prepared in this embodiment are shown. The images reveal that the sintered body has relatively few pores, and the white TiB2 particles are less than 2 μm in diameter and relatively uniformly distributed. The elemental carbon generated in situ during multi-step hot-pressing sintering is uniformly distributed within the ceramic matrix, without significant agglomeration.

[0028] The boron carbide-based composite ceramic material obtained in this embodiment, measured by Vickers hardness indentation, has a fracture toughness of 3.60 MPa·m. 1 / 2 ; Under test conditions of room temperature, using Al2O3 spheres as the friction pair, a load of 6 N, a reciprocating frequency of 300 r / min, a reciprocating distance of 5 mm, and a total sliding distance of 90 m, the wear rate of the composite ceramic was measured to be 4.07 × 10⁻⁶. -6 mm 3 ·N -1 ·m -1 .

[0029] Comparative Example 1 The difference between this comparative example and Example 1 is that the hot pressing and sintering process of the mixed powder particles in step 3) is adjusted to a two-stage heating process. Specifically: The mixed powder particles obtained by the treatment in steps 1) and 2) of Example 1 were subjected to hot pressing sintering. The temperature was increased from room temperature to 1800°C at a rate of 100°C / min, and then increased from 1800°C to sintering temperature of 2050°C at a rate of 30°C / min. When the hot pressing temperature reached 500°C, the pressure was slowly increased until the sintering pressure was reached at about 1500°C. The experimental sintering pressure was 30 MPa. The holding time was 3 min. After the holding time was completed, the heating power was cut off, and then the pressure was released and the furnace was cooled to obtain the boron carbide-based composite ceramic of this comparative example.

[0030] Figure 2Scanning electron microscopy (SEM) images and EDS analysis of carbon element distribution in the corresponding regions of the boron carbide-based composite ceramic material prepared in this comparative example are shown. The images reveal significant porosity in the sintered body, with white TiB2 particles agglomerated and exceeding 4 μm in diameter. The elemental carbon generated in situ during hot-pressing sintering exhibits marked segregation within the ceramic matrix, concentrating near the reacted TiB2 particles.

[0031] The boron carbide-based composite ceramic material obtained in this embodiment was tested, and its fracture toughness was measured to be 3.31 MPa·m using the Vickers hardness indentation method. 1 / 2 ; Under test conditions of room temperature, using Al2O3 spheres as the friction pair, a load of 6 N, a reciprocating frequency of 300 r / min, a reciprocating distance of 5 mm, and a total sliding distance of 90 m, the wear rate of the composite ceramic was measured to be 5.79 × 10⁻⁶. -6 mm 3 ·N -1 ·m -1 .

[0032] Example 2 1) Weigh 24g of B4C and 6g of TiC to obtain a mixed raw material with a B4C content of 80% and a TiC content of 20%. Place it in a polytetrafluoroethylene bottle, add 150 mL of anhydrous ethanol and 10 B4C particles with a diameter of 10 mm, and ball mill the mixture at a speed of 300 r / min for 32 h to obtain a composite powder slurry. 2) After the composite powder slurry is dried at 90℃ for 2 hours, it is placed in a drying oven and dried at 160℃ for 10 hours to obtain agglomerated powder. The powder is then ground and crushed, and passed through a 200-mesh sieve to obtain mixed powder particles.

[0033] 3) The mixed powder particles were subjected to multi-step hot pressing sintering. In the first stage, the temperature was increased from room temperature to 1000℃ at a heating rate of 100℃ / min. In the second stage, the temperature was increased from 1000℃ to 1400℃ at a heating rate of 3℃ / min. In the third stage, the temperature was increased from 1400℃ to the sintering temperature of 2050℃ at a heating rate of 20℃ / min. The hot pressing sintering furnace was pressurized at 500℃ and loaded to the sintering pressure of 30 MPa at around 1100℃. As the temperature rose to the sintering temperature of 2050℃, the heating power was cut off after holding at that temperature for 3 min. The sample was cooled with the furnace and then subjected to a pressure holding treatment for 100 min. After that, the pressure was released to obtain the boron carbide-based composite ceramic of this embodiment.

[0034] Figure 3Scanning electron microscopy (SEM) images and EDS analysis of carbon element distribution in the corresponding regions of the boron carbide-based composite ceramic material prepared in this embodiment are shown. The images reveal that the sintered body has relatively few pores, and the white TiB2 particles have a diameter no greater than 3 μm and are relatively uniformly distributed. The elemental carbon generated in situ during multi-step hot-pressing sintering is uniformly distributed in the ceramic matrix, without significant agglomeration.

[0035] The boron carbide-based composite ceramic material obtained in this embodiment was tested and found to have a fracture toughness of 3.47 MPa·m using the Vickers hardness indentation method. 1 / 2 ; Under test conditions of room temperature, using Al2O3 spheres as the friction pair, a load of 6 N, a reciprocating frequency of 300 r / min, a reciprocating distance of 5 mm, and a total sliding distance of 90 m, the wear rate of the composite ceramic was measured to be 3.92 × 10⁻⁶. -6 mm 3 ·N -1 ·m -1 .

[0036] Comparative Example 2 The difference between this comparative example and Example 2 is that the hot pressing and sintering process of the mixed powder particles in step 3) is adjusted to a single-stage heating process. Specifically: The mixed powder particles obtained by the treatment in steps 1) and 2) of Example 2 were subjected to hot pressing sintering. The temperature was increased from room temperature to sintering temperature of 2050°C at a heating rate of 30°C / min. When the hot pressing temperature reached 500°C, the pressure was slowly increased until the sintering pressure was reached at about 1500°C. The experimental sintering pressure was 30 MPa. The holding time was 3 min. After the holding time was completed, the heating power was cut off, and then the pressure was released and the furnace was cooled to obtain the boron carbide-based composite ceramic of this comparative example.

[0037] The resulting sintered body exhibited significant porosity, with TiB2 particles agglomerated and having a diameter greater than 5 μm. The elemental carbon generated in situ during hot pressing sintering showed obvious segregation in the ceramic matrix, concentrating near the TiB2 particles generated in the reaction.

[0038] The boron carbide-based composite ceramic material obtained in this embodiment, measured by Vickers hardness indentation, has a fracture toughness of 3.26 MPa·m. 1 / 2 ; Under test conditions of room temperature, using Al2O3 spheres as the friction pair, a load of 6 N, a reciprocating frequency of 300 r / min, a reciprocating distance of 5 mm, and a total sliding distance of 90 m, the wear rate of the composite ceramic was measured to be 5.89 × 10⁻⁶. -6 mm 3 ·N -1 ·m -1 .

[0039] The relevant performance indicators of the boron carbide-based composite ceramic materials prepared by the comparative examples and comparative examples are shown in Table 1.

[0040] Table 1

[0041] From the appendix Figure 1 ~Appendix Figure 3 As can be seen from the comparative data in Table 1, the boron carbide-based wear-resistant ceramic material prepared by the multi-step hot-pressing sintering process and in-situ reaction control strategy of this application has good comprehensive performance. This application utilizes the reaction B4C + 2TiC = 2TiB2 + 3C to achieve in-situ carbon precipitation, and matches the reaction rate with the carbon generation path through multi-step heating. However, Comparative Example 1 (two-stage heating) and Comparative Example 2 (single-stage heating) did not control the heating rate of the key reaction zone, resulting in the concentrated burst of the B4C and TiC reaction. The generated elemental carbon agglomerates because it cannot be dispersed in time, leading to performance degradation.

[0042] Furthermore, this application achieves a match between the reaction rate and the carbon diffusion rate by precisely controlling the heating rate at each stage, so that the carbon generated in situ is uniformly dispersed in the matrix. The temperature ranges and heating rates are not set arbitrarily, but are precisely controlled based on reaction kinetics, diffusion thermodynamics and sintering densification laws. When the heating rate or sintering termination temperature exceeds the range specified in this application, the material properties will deteriorate significantly.

[0043] In summary, this invention utilizes the reaction B4C + 2TiC = 2TiB2 + 3C under high-temperature hot pressing. By introducing nanoscale TiC and employing a multi-step hot pressing sintering method, it avoids the segregation of elemental carbon in boron carbide-based composite ceramics, ultimately generating boron carbide-based composite ceramics with uniform distribution of elemental carbon in situ. This invention increases the uniformity of the composite ceramic matrix composition through a multi-step hot pressing sintering process. Simultaneously, the formation of a graphite lubricating layer during friction reduces the coefficient of friction and enhances wear resistance; the in-situ generated TiB2 gives the composite ceramic higher fracture toughness.

[0044] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for in-situ generation of boron carbide-based wear-resistant ceramic materials with uniform carbon distribution, characterized in that: include, B4C and TiC are mixed and ball-milled to obtain a composite powder slurry with a B4C content of 70-95% and a TiC content of 5-30%. The composite powder slurry is dried, ground, and sieved to obtain mixed powder particles. Mixed powder particles are subjected to multi-step hot pressing sintering. During the sintering process, the temperature is raised to the sintering temperature in stages. After reaching the sintering temperature, the temperature is held for 1 to 5 minutes. The sample is cooled with the furnace while being subjected to pressure treatment. When the pressure is released, a boron carbide-based wear-resistant ceramic material with uniform carbon distribution is generated in situ. The sintering process involves staged heating to the sintering temperature. In the first stage, the temperature is increased from room temperature to 950-1060 ℃ at a heating rate of 80-120 ℃ / min. In the second stage, the temperature is increased from 950-1060 ℃ to 1350-1450 ℃ at a heating rate of 1-5 ℃ / min. In the third stage, the temperature is increased from 1350-1450 ℃ to the sintering temperature of 2000-2100 ℃ at a heating rate of 15-30 ℃ / min.

2. The method for in-situ generation of boron carbide-based wear-resistant ceramic material with uniform carbon distribution as described in claim 1, characterized in that: The purity of B4C is >99wt% and the average particle size is ≤1.5 μm, and the purity of TiC is >98wt% and the average particle size is <0.5 μm.

3. The method for in-situ generation of boron carbide-based wear-resistant ceramic materials with uniform carbon distribution as described in claim 1, characterized in that: The ball mill for the B4C and TiC mixture is operated at a speed of 270-320 rpm for a time of >20 h, and the grinding media consists of 8-12 B4C grinding balls with a diameter of 10 mm.

4. The method for in-situ generation of boron carbide-based wear-resistant ceramic materials with uniform carbon distribution as described in claim 1, characterized in that: The composite powder slurry is dried, ground, and sieved to obtain mixed powder particles. The drying method of the composite powder slurry includes drying at 80~100℃ for 2~3 hours and then placing it in a drying oven and drying at 130~170℃ for 8~12 hours.

5. The method for in-situ generation of boron carbide-based wear-resistant ceramic materials with uniform carbon distribution as described in claim 4, characterized in that: The grinding and sieving process involves passing the material through a 200-mesh sieve.

6. The method for in-situ generation of boron carbide-based wear-resistant ceramic material with uniform carbon distribution as described in claim 1, characterized in that: The hot pressing sintering process involves starting to pressurize the sintering furnace at 150~550℃, and then loading it to a sintering pressure of 25~35 MPa at 1000~1150℃, with the temperature rising to a sintering temperature of 2000~2100℃.

7. The method for in-situ generation of boron carbide-based wear-resistant ceramic material with uniform carbon distribution as described in claim 6, characterized in that: The pressure holding time is 80~120 minutes.

8. The boron carbide-based wear-resistant ceramic material prepared by the method according to any one of claims 1 to 7, characterized in that: The boron carbide-based wear-resistant ceramic material is composed of uniformly distributed elemental C, B4C, and TiB2.

9. The boron carbide-based wear-resistant ceramic material as described in claim 8, characterized in that: The boron carbide-based wear-resistant ceramic material described above has the following characteristics: (i) Free carbon volume fraction is 0.33 ~ 11.43 vol.%; (ii) Fracture toughness is 3.31~3.75 MPa·m1 / 2; (iii) Using Al2O3 balls as the friction pair, with a load of 6 N, a reciprocating frequency of 300 r / min, a reciprocating distance of 5 mm, and a total sliding distance of 90 m, the wear rate was 3.81 × 10⁻⁶. -6 ~4.25×10 -6 mm 3 ·N -1 ·m -1 .

10. The application of the boron carbide-based wear-resistant ceramic material as described in claim 9 in machining, nuclear industry, national defense and military industry and aerospace.

Images