阅读说明：本技术 一种ZrB2增韧聚晶立方氮化硼复合片的制备方法 (ZrB2Preparation method of toughened polycrystalline cubic boron nitride composite sheet ) 是由 莫培程 陈家荣 陈超 骆颖 张延军 王文龙 张喆 潘晓毅 于 2021-11-25 设计创作，主要内容包括：本发明公开了一种ZrB-(2)增韧聚晶立方氮化硼复合片的制备方法,包括：按重量百分比计,称取17～35％的结合剂、1～5％的氮化铝和余量的立方氮化硼混合均匀后置于高温真空环境中净化,所得混合粉料和硬质合金基体置于保温传压介质中,进行高温高压合成,即得；其中,所述的结合剂由碳化硼、锆粉和硅粉按1：3.5～4.5：1～2的重量比组成。本发明以碳化硼、锆粉和硅粉为结合剂,在高温高压烧结过程中和立方氮化硼发生化学反应原位生成新物相二硼化锆、碳化锆以及碳化硅,从而牢固的粘结立方氮化硼颗粒；同时加入的少量氮化铝使烧结体快速致密化和抑制cBN颗粒发生相变的作用,使合成得到的具有优良的韧性和耐磨性。(The invention discloses a ZrB 2 The preparation method of the toughened polycrystalline cubic boron nitride composite sheet comprises the following steps: weighing 17-35% of a binding agent, 1-5% of aluminum nitride and the balance of cubic boron nitride, uniformly mixing, then placing in a high-temperature vacuum environment for purification, placing the obtained mixed powder and a hard alloy matrix in a heat-preservation pressure-transmission medium, and carrying out high-temperature high-pressure synthesis to obtain the high-temperature high-pressure composite material; wherein, the bonding agent is prepared from boron carbide, zirconium powder and silicon powder according to the proportion of 1: 3.5-4.5: 1 to 2 by weight. The invention takes boron carbide, zirconium powder and silicon powder as binding agents, and the boron carbide, the zirconium powder and the silicon powder are subjected to chemical reaction with cubic boron nitride in the high-temperature high-pressure sintering process to generate new phases of zirconium diboride, zirconium carbide and silicon diboride in situSilicon carbide to firmly bond the cubic boron nitride particles; meanwhile, a small amount of aluminum nitride is added to rapidly densify the sintered body and inhibit the cBN particles from phase change, so that the sintered body has excellent toughness and wear resistance.)

1. ZrB₂The preparation method of the toughened polycrystalline cubic boron nitride composite sheet is characterized by weighing 17-35% of a binding agent, 1-5% of aluminum nitride and the balance of cubic boron nitride in percentage by weight, uniformly mixing, and then purifying in a high-temperature vacuum environment to obtain mixed powder; putting the obtained mixed powder and a hard alloy matrix into a heat-preservation pressure-transmitting medium, and carrying out high-temperature high-pressure synthesis to obtain ZrB₂Toughening the polycrystalline cubic boron nitride composite sheet; wherein, the bonding agent is prepared from boron carbide, zirconium powder and silicon powder according to the proportion of 1: 3.5-4.5: 1 to 2 by weight.

2. The method as claimed in claim 1, wherein the binder is selected from the group consisting of boron carbide, zirconium powder and silicon powder in a ratio of 1: 4: 1.5 in weight ratio.

3. The method according to claim 1, wherein the cubic boron nitride powder is composed of nickel-plated cubic boron nitride and non-plated cubic boron nitride.

4. The method according to claim 3, wherein the cubic boron nitride is prepared from nickel-plated cubic boron nitride and non-plated cubic boron nitride in a ratio of 1: 2 to 5 by weight.

5. The preparation method according to any one of claims 1 to 4, wherein the particle sizes of the cubic boron nitride, the boron carbide, the zirconium powder and the silicon powder are all in the micron order.

6. The method according to claim 5, wherein the average particle size of the cubic boron nitride is 1 to 22 μm, and the average particle size of the boron carbide, the zirconium powder and the silicon powder is 1 to 10 μm.

7. The method according to any one of claims 1 to 4, wherein the particle size of the aluminum nitride is in the order of nanometers.

8. The method according to claim 7, wherein the aluminum nitride has an average particle diameter of 50 to 500 nm.

9. The method according to any one of claims 1 to 4, wherein the high-temperature vacuum environment has a temperature of 800 to 1200 ℃ and a pressure of 10 ℃^-1～10^-3Environment of Pa.

10. The preparation method according to any one of claims 1 to 4, wherein the process conditions of the high-temperature high-pressure synthesis are as follows: the pressure is 4.5-5.5 GPa, the temperature is 1400-1750 ℃, and the time is 10-15 min.

Technical Field

The invention relates to a superhard composite material, in particular to ZrB₂A preparation method of a toughened polycrystalline cubic boron nitride composite sheet.

Background

The Polycrystalline Cubic Boron Nitride (PCBN) composite sheet is formed by sintering cubic boron nitride (cBN) micro powder, a binding agent and a hard alloy matrix at high temperature and high pressure, has higher hardness and wear resistance, and simultaneously has better heat resistance and chemical inertia than diamond, and is particularly suitable for cutting quenched steel, cast iron, powder metallurgy materials, heat-resistant alloys and other iron-based materials.

PCBN composite sheets are manufactured and the performance of the PCBN composite sheets is researched in various countries around the world, the PCBN composite sheets produced abroad at present are serialized, the application specialization is brought, and the specifications of the composite sheets tend to be large-sized. Most PCBN composite sheets used in the cutting aspect of difficult-to-process materials in the automobile industry, aerospace and the like in China still depend on import.

The bonding agent plays an important role in the synthesis process of the PCBN composite sheet, and the reasonable addition of the bonding agent can not only reduce the sintering temperature and pressure, but also improve the sintering performance. The metal ceramic is used as the binding agent, the advantages of the metal binding agent and the ceramic binding agent are integrated, meanwhile, chemical reactions occur between the binding agents and between the binding agent and the cBN particles, and the generated new physical phase can better bond the cBN particles, so that the aim of improving the strength, toughness and hardness of the PCBN cutter is fulfilled, and the method has practical significance for developing a novel high-performance PCBN cutter.

Publication No. CN 110625123A discloses a high-performance polycrystalline diamond compact, which comprises a hard alloy substrate, and a silicon carbide-diamond transition layer and a polycrystalline diamond layer on the surface of the hard alloy substrate, wherein the polycrystalline diamond layer is composed of the following raw materials in percentage by weight: the diamond micro powder accounts for 90-95%, the bonding agent accounts for 5-10%, and the bonding agent consists of the following raw materials in percentage by weight: 90-95% of metal elements, 3-6% of non-metal elements, 1.5-3% of inorganic non-metal whiskers and 0.5-1% of rare earth elements; wherein the metal elements comprise the following raw materials in percentage by weight: 84-90% of Co powder, 5-7% of Ni powder, 2-3% of Cr powder, 1-2% of Ti powder, 1-2% of Zr powder, 0.5-1% of W powder and 0.5-1% of Mo powder; the nonmetal element is one or a mixture of two of Si and B, and when the nonmetal element is a mixture of two of Si and B, the weight percentage of B in the mixture is 5-10%. According to the invention, the silicon carbide-diamond gradient transition layer is deposited on the surface of the hard alloy substrate by a chemical vapor deposition method so as to effectively inhibit the cobalt element of the hard alloy substrate from diffusing to the polycrystalline diamond layer, so that the service life of the polycrystalline diamond layer is greatly prolonged while the excellent performance is ensured. On the other hand, due to the thermal expansion coefficient of the silicon carbide (1.8X 10)^-3K) between the cemented carbide (4.8 x 10)^-3K) and polycrystalline diamond (1.5X 10)^-3and/K), the stress between the polycrystalline diamond layer and the hard alloy substrate is relieved, and the bonding strength between the hard alloy substrate and the polycrystalline diamond is improved. However, the composition of the binder in the invention is complex, and the preparation needs to adopt a chemical vapor deposition method to ensure the performance and the service life of the obtained composite sheet product, and the process is complex.

Disclosure of Invention

The invention aims to solve the technical problem of providing ZrB with simple bonding agent composition, simple preparation process and excellent performance₂A preparation method of a toughened polycrystalline cubic boron nitride composite sheet.

In order to solve the technical problems, the invention adopts the following technical scheme:

ZrB₂Preparation of toughened polycrystalline cubic boron nitride composite sheetThe method comprises the following steps: weighing 17-35% of a bonding agent, 1-5% of aluminum nitride (AlN) and the balance of cubic boron nitride, uniformly mixing, and then placing in a high-temperature vacuum environment for purification to obtain mixed powder; putting the obtained mixed powder and a hard alloy matrix into a heat-preservation pressure-transmitting medium, and carrying out high-temperature high-pressure synthesis to obtain ZrB₂Toughening the polycrystalline cubic boron nitride composite sheet; wherein the binder is boron carbide (B)₄C) Zirconium powder (Zr) and silicon powder (Si) are mixed according to a ratio of 1: 3.5-4.5: 1 to 2 by weight.

In the preparation method, the boron carbide, the zirconium powder and the silicon powder can be added to generate new phases of zirconium diboride, zirconium carbide and silicon carbide in a system, the new phases can firmly bond cubic boron nitride particles, and the prepared PCBN composite sheet has high hardness, good strength, excellent toughness and wear resistance by matching with the addition of aluminum nitride. However, the addition ratio of boron carbide, zirconium powder and silicon powder has an important influence on whether new phases of zirconium diboride, zirconium carbide and silicon carbide can be generated, and further, the weight ratio of boron carbide, zirconium powder and silicon powder is preferably 1: 4: 1.5.

in the preparation method of the invention, the cubic boron nitride is preferably composed of nickel-plated cubic boron nitride micro powder and non-plated cubic boron nitride, and further preferably composed of nickel-plated cubic boron nitride micro powder and non-plated cubic boron nitride according to a ratio of 1: 2-5, more preferably nickel-plated cubic boron nitride micro powder and non-plated cubic boron nitride according to a weight ratio of 1: 4 in a weight ratio.

In the preparation method, the grain sizes of the cubic boron nitride, the boron carbide, the zirconium powder, the silicon powder and the aluminum nitride are all conventional choices in the prior art. The particle size of the cubic boron nitride, the boron carbide, the zirconium powder and the silicon powder is usually micron-sized, preferably, the average particle size of the cubic boron nitride is 1-22 μm, the average particle size of the boron carbide, the zirconium powder and the silicon powder is 1-10 μm, wherein the average particle size of the boron carbide is more preferably 5-10 μm, and the average particle size of the zirconium powder and the silicon powder is more preferably 1-5 μm. The particle size of the aluminum nitride is preferably on the order of nanometers, and the average particle size of the aluminum nitride is more preferably 50 to 500 nm.

In the preparation method, the binder, the aluminum nitride and the balance of the cubic boron nitride are uniformly mixed by adopting the conventional method, such as a ball milling method and the like.

In the preparation method, the operation of purifying in the high-temperature vacuum environment is the same as that in the prior art, and the temperature is preferably 800-1200 ℃ and the pressure is preferably 10 in the preparation method^-1～10^-3Purifying for 1-3 h in the environment of Pa.

In the preparation method of the invention, the heat-preservation pressure-transfer medium and the subsequent high-temperature high-pressure synthesis are the same as those in the prior art, specifically, the heat-preservation pressure-transfer medium is usually pyrophyllite, and the process conditions of the high-temperature high-pressure synthesis are preferably as follows: the pressure is 4.5-5.5 GPa, the temperature is 1400-1750 ℃, and the time is 10-15 min.

Compared with the prior art, the invention takes boron carbide, zirconium powder and silicon powder as binding agents, and the boron carbide, zirconium carbide and silicon powder are subjected to chemical reaction with cubic boron nitride in the high-temperature high-pressure sintering process to generate new physical phases of zirconium diboride, zirconium carbide and silicon carbide in situ, thereby firmly bonding cubic boron nitride particles; meanwhile, a small amount of added aluminum nitride serving as a melting sintering aid can flow in a system to enable the sintered body to be rapidly densified and accelerate sintering, and the aluminum nitride can also play a role in inhibiting the phase change of cBN particles, so that the PCBN composite sheet obtained by synthesis is high in hardness, good in strength and excellent in toughness and wear resistance.

Drawings

Fig. 1 is an SEM image of a cross-section of a composite sheet obtained in example 1 of the present invention after etching for 60 seconds with hydrofluoric acid having a solute mass fraction of 40%.

FIG. 2 is an SEM image of a cross section of a composite sheet obtained in example 2 of the present invention after etching for 60 seconds with hydrofluoric acid having a solute mass fraction of 40%.

Detailed Description

In order to better explain the technical solution of the present invention, the present invention is further described in detail with reference to the following examples, but the embodiments of the present invention are not limited thereto.

Example 1

1) Preparing materials: proportionally preparing cBN and B₄C、Zr, Si, and AlN.

Wherein the grain diameter of the cubic boron nitride micro powder is 4-8 μm, and the nickel-plated cubic boron nitride micro powder and the non-plated cubic boron nitride micro powder are mixed according to the weight ratio of 1: 4, accounting for 80 percent of the total weight of the powder; the average particle size of boron carbide powder is 5 microns, the average particle size of zirconium powder is 3 microns, the average particle size of silicon powder is 3 microns, and the weight ratio of boron carbide to zirconium powder to silicon powder is 1: 4: 1.5, the three account for 17 percent of the total weight of the powder; the average particle size of the aluminum nitride powder is 50nm and accounts for 3 percent of the total weight of the powder.

2) Mixing materials: and (2) taking ethanol as a mixed medium, and placing the powder into a ball mill for ball milling, wherein the ball-material ratio is 3: 1, the rotating speed is 150r/min, and the time is 2 h; then drying the mixture for 12 hours at the temperature of 80 ℃, sieving the dried mixture by a 100-mesh sieve, and collecting undersize products.

3) High-temperature vacuum treatment: placing the collected undersize into a container at 1000 deg.C and vacuum degree of 10^-2And (5) purifying for 1h in a Pa environment, and cooling to obtain mixed powder for later use.

4) Assembling: the hard alloy matrix is a commercially available model YG12 with a diameter matched with the inner diameter of the molybdenum cup, and the specification isThe (high) molybdenum cup is filled with 4g of mixed powder, and the mixed powder is laid flat and compacted, then is put into a hard alloy matrix, and is covered with a cup cover.

5) Synthesizing: placing the covered molybdenum cup into a pyrophyllite block, and carrying out high-temperature high-pressure synthesis, wherein the high-temperature high-pressure synthesis process conditions are as follows: maintaining the pressure at 5.5GPa and the temperature at 1500 ℃ for 12min to obtain ZrB₂Toughening polycrystalline cubic boron nitride composite sheets.

An SEM image of a cross section of the composite sheet obtained in this example after etching with hydrofluoric acid having a solute mass fraction of 40% for 60 seconds is shown in fig. 1. From fig. 1, it can be seen that the binder is uniformly distributed around the cBN particles and rod-like grains are generated, indicating that the compact has better strength and toughness.

Comparative examples 1 to 1

Example 1 was repeated, except that step 1) was formulated according to the following formulation:

cBN：ZrB₂：SiC：ZrC：AlN＝80：13：2.5：1.5：3。

comparative examples 1 to 2

Example 1 was repeated, except that in step 1), the weight ratio of boron carbide, zirconium powder and silicon powder was 1: 3: 1.5.

comparative examples 1 to 3

Example 1 was repeated, except that in step 1), the weight ratio of boron carbide, zirconium powder and silicon powder was 1: 3: 2.5.

comparative examples 1 to 4

Example 1 was repeated, except that in step 1), the weight ratio of boron carbide, zirconium powder and silicon powder was 1: 4: 2.5.

example 2:

1) preparing materials: proportionally preparing cBN and B₄C. Zr, Si, and AlN.

Wherein the grain diameter of the cubic boron nitride micro powder is 4-8 μm, and the nickel-plated cubic boron nitride micro powder and the non-plated cubic boron nitride micro powder are mixed according to the weight ratio of 1: 4, accounting for 70 percent of the total weight of the powder; the average particle size of boron carbide powder is 5 microns, the average particle size of zirconium powder is 3 microns, the average particle size of silicon powder is 3 microns, and the weight ratio of boron carbide to zirconium powder to silicon powder is 1: 4: 1.5, the three account for 26 percent of the total weight of the powder; the average particle size of the aluminum nitride powder is 50nm and accounts for 4 percent of the total weight of the powder.

2) Mixing materials: and (2) taking ethanol as a mixed medium, and placing the powder into a ball mill for ball milling, wherein the ball-material ratio is 3: 1, the rotating speed is 150r/min, and the time is 2 h; then drying the mixture for 12 hours at the temperature of 80 ℃, sieving the dried mixture by a 100-mesh sieve, and collecting undersize products.

3) High-temperature vacuum treatment: placing the collected undersize into a container at 1100 deg.C and vacuum degree of 10^-2And (5) purifying for 1h in a Pa environment, and cooling to obtain mixed powder for later use.

4) Assembling: the hard alloy matrix is a commercially available model YG12 with a diameter matched with the inner diameter of the molybdenum cup, and the specification isFilling the mixed powder into a high molybdenum cup4g, paving, compacting, putting the hard alloy substrate, and covering a cup cover.

5) Synthesizing: placing the covered molybdenum cup into a pyrophyllite block, and carrying out high-temperature high-pressure synthesis, wherein the high-temperature high-pressure synthesis process conditions are as follows: maintaining the pressure at 5.5GPa and the temperature at 1450 ℃ for 12min to obtain ZrB₂Toughening polycrystalline cubic boron nitride composite sheets.

An SEM image of a cross section of the composite sheet obtained in this example after etching for 60 seconds with hydrofluoric acid having a solute mass fraction of 40% is shown in fig. 2. From fig. 2, it can be observed that the binder is uniformly distributed around the cBN particles and rod-like grains are generated, indicating that the compact has better strength and toughness.

Comparative example 2-1

Example 2 was repeated, except that step 1) was formulated according to the following formulation:

cBN：ZrB₂：SiC：ZrC：AlN＝70：20：4：3：3。

example 3

1) Preparing materials: proportionally preparing cBN and B₄C. Zr, Si, and AlN.

Wherein the grain diameter of the cubic boron nitride micro powder is 4-8 μm, and the nickel-plated cubic boron nitride micro powder and the non-plated cubic boron nitride micro powder are mixed according to the weight ratio of 1: 4, accounting for 60 percent of the total weight of the powder; the average particle size of boron carbide powder is 5 microns, the average particle size of zirconium powder is 3 microns, the average particle size of silicon powder is 3 microns, and the weight ratio of boron carbide to zirconium powder to silicon powder is 1: 4: 1.5, the three account for 35 percent of the total weight of the powder; the average particle size of the aluminum nitride powder is 50nm and accounts for 5 percent of the total weight of the powder.

2) Mixing materials: and (2) taking ethanol as a mixed medium, and placing the powder into a ball mill for ball milling, wherein the ball-material ratio is 3: 1, the rotating speed is 150r/min, and the time is 2 h; then drying the mixture for 12 hours at the temperature of 60 ℃, sieving the dried mixture by a 100-mesh sieve, and collecting undersize products.

3) High-temperature vacuum treatment: placing the collected undersize into a container at 850 deg.C and 10 deg.C^-1Purifying for 3 hours in a Pa environment, and cooling to obtain mixed powder for later use;

4) assembling: the model is a commercially available model with the diameter matched with the inner diameter of the molybdenum cupYG12 as the base body of cemented carbideThe (high) molybdenum cup is filled with 4g of mixed powder, and the mixed powder is laid flat and compacted, then is put into a hard alloy matrix, and is covered with a cup cover.

5) Synthesizing: placing the covered molybdenum cup into a pyrophyllite block, and carrying out high-temperature high-pressure synthesis, wherein the high-temperature high-pressure synthesis process conditions are as follows: maintaining the pressure at 5.5GPa and the temperature at 1400 ℃ for 15min to obtain ZrB₂Toughening polycrystalline cubic boron nitride composite sheets.

Comparative example 3

Example 3 was repeated, except that step 1) was formulated according to the following formulation:

cBN：ZrB₂：SiC：ZrC：AlN＝60：26：5：4：5。

example 4

Example 1 was repeated, except that in step 1), the weight ratio of boron carbide, zirconium powder and silicon powder was 1: 3.5: 2.

example 5

Example 1 was repeated, except that in step 1), the weight ratio of boron carbide, zirconium powder and silicon powder was 1: 4.5: 1.5.

the composite sheets prepared in the above examples and comparative examples were measured for their properties, and the results are shown in table 1 below.

TABLE 1

As shown by the test results of examples and comparative examples, cBN, ZrB were used₂The strength, toughness and wear resistance of the composite sheet synthesized by the powder obtained by mixing SiC, ZrC and AlN and the matrix are all far lower than those of the composite sheet of the new phase generated by in-situ synthesis by adopting the method.