Pretreatment method of cubic boron nitride micropowder and preparation method of polycrystal cubic boron nitride composite sheet

Abstract

This invention relates to a pretreatment method for cubic boron nitride (CBN) micropowder and a method for preparing polycrystalline CBN composite sheets, belonging to the technical field of polycrystalline CBN cutting tools. The pretreatment method for CBN micropowder of this invention includes the following steps: depositing a first binder for synthesizing polycrystalline CBN onto the surface of CBN micropowder particles, and then depositing a second binder for synthesizing polycrystalline CBN onto the surface of the CBN micropowder particles; the first binder is a metal binder and the second binder is a ceramic binder, or the first binder is a ceramic binder and the second binder is a metal binder. The pretreatment method for CBN micropowder of this invention can significantly improve the uniformity of particle distribution in polycrystalline CBN composite sheets and improve the stability of polycrystalline CBN composite sheets.

Description

Technical Field

[0001] This invention relates to a pretreatment method for cubic boron nitride micro powder and a preparation method for polycrystalline cubic boron nitride composite sheets, belonging to the field of polycrystalline cubic boron nitride cutting tool technology. Background Technology

[0002] Cubic boron nitride (CBN) is a superhard tool material second only to diamond in hardness, and it also possesses superior chemical inertness compared to diamond, making it particularly suitable for cutting difficult-to-machine materials. To overcome the drawbacks of CBN single crystals, such as easy cleavage and anisotropy, polycrystalline PCBN is often used as a cutting tool in practical applications. Polycrystalline cubic boron nitride composite sheets are obtained by adding metal binders, ceramic binders, or metal-ceramic composite binders, followed by mixing, granulation, cold pressing into a blank, and assembly and sintering. Compared to polycrystalline boron nitride composite sheets using metal or ceramic binders, polycrystalline cubic boron nitride composite sheets using metal-ceramic composite binders can balance wear resistance and impact toughness, exhibiting excellent turning performance. However, due to the significant differences in specific gravity among CBN, metal binders, and ceramic binders, it is difficult to achieve uniform mixing. This can easily lead to uneven particle distribution of the CBN layer in the sintered polycrystalline cubic boron nitride composite sheet, resulting in poor stability when turning workpieces with different tools using the composite sheet. Even when turning the same distance, the wear on the tool's flank face varies greatly, resulting in significant fluctuations in product quality. Summary of the Invention

[0003] The purpose of this invention is to provide a pretreatment method for cubic boron nitride micropowder used in the synthesis of polycrystalline cubic boron nitride composite sheets, which can improve the uniformity of the distribution of metal binders and ceramic binders in the CBN layer.

[0004] The present invention also provides a method for preparing polycrystalline cubic boron nitride composite sheets.

[0005] To achieve the above objectives, the technical solution adopted in the pretreatment method for cubic boron nitride micro powder of the present invention is as follows:

[0006] A pretreatment method for cubic boron nitride micropowder used in the synthesis of polycrystalline cubic boron nitride composite sheets includes the following steps: depositing a first binder for the synthesis of polycrystalline cubic boron nitride on the surface of cubic boron nitride micropowder particles, and then depositing a second binder for the synthesis of polycrystalline cubic boron nitride on the surface of cubic boron nitride micropowder particles; the first binder is a metal binder and the second binder is a ceramic binder, or the first binder is a ceramic binder and the second binder is a metal binder.

[0007] The pretreatment method of cubic boron nitride micropowder for synthesizing polycrystalline cubic boron nitride composite sheets of the present invention pre-deposits the metal binder and ceramic binder of the polycrystalline cubic boron nitride composite sheet using a metal-ceramic composite binder on the surface of the cubic boron nitride micropowder particles, which can significantly improve the uniformity of particle distribution in the polycrystalline cubic boron nitride composite sheet and improve the stability of the polycrystalline cubic boron nitride composite sheet.

[0008] The particle size of the cubic boron nitride micro powder in the required raw materials is selected according to the requirements. Furthermore, the average particle size of the cubic boron nitride micro powder is 2–6 μm.

[0009] Furthermore, the first binder is a metal binder, and the second binder is a ceramic binder.

[0010] Furthermore, the mass of the metal binder deposited on the surface of the cubic boron nitride micro powder particles is 6-10% of the mass of the cubic boron nitride micro powder, and the mass of the deposited ceramic binder is 45-55% of the mass of the cubic boron nitride micro powder.

[0011] Furthermore, the metal binder is one or any combination of aluminum, tungsten, and cobalt; the ceramic binder is one or any combination of titanium carbonitride, titanium nitride, and titanium carbide.

[0012] The technical solution adopted in the preparation method of the polycrystalline cubic boron nitride composite sheet of the present invention is as follows:

[0013] A method for preparing a polycrystalline cubic boron nitride composite sheet includes the following steps: depositing a first binder on the surface of cubic boron nitride microparticles, and then depositing a second binder on the surface of the cubic boron nitride microparticles to obtain pretreated cubic boron nitride microparticles; then assembling the pretreated cubic boron nitride microparticles with an alloy matrix and performing high-temperature and high-pressure synthesis; wherein the first binder is a metal binder and the second binder is a ceramic binder, or the first binder is a ceramic binder and the second binder is a metal binder.

[0014] The method for preparing polycrystalline cubic boron nitride composite sheets of the present invention involves pre-depositing a metal binder and a ceramic binder on the surface of cubic boron nitride microparticles, thereby achieving uniform mixing of cubic boron nitride microparticles and binders, which in turn allows for a more complete sintering reaction and a more uniform sintered product structure, thus meeting the market's urgent need to continuously improve the stability of cutting tool performance.

[0015] Furthermore, the average particle size of the cubic boron nitride micro powder is 2–6 μm.

[0016] Furthermore, the mass of the metal binder deposited on the surface of the cubic boron nitride micro powder particles is 6 to 10% of the mass of the cubic boron nitride micro powder, for example, 8%, and the mass of the deposited ceramic binder is 45 to 55% of the mass of the cubic boron nitride micro powder, for example, 50%.

[0017] Furthermore, the metal binder is one or any combination of aluminum, tungsten, and cobalt; the ceramic binder is one or any combination of titanium carbonitride, titanium nitride, and titanium carbide.

[0018] Furthermore, after assembling the pretreated cubic boron nitride micro powder with the alloy matrix, pre-pressing is performed first, followed by a vacuum degree ≤10×10 -3 Vacuum heat treatment at 700–1000℃ for 15–20 hours is followed by high-temperature and high-pressure synthesis. For example, the vacuum heat treatment temperature is 800℃. Vacuum heat treatment can achieve both purification and pre-sintering. It is understood that the assembly of the pretreated cubic boron nitride micropowder and the alloy matrix is ​​completed in a material cup. After assembly, the material cup is placed on a cold press for cold pressing to complete the pre-pressing.

[0019] Furthermore, the temperature of the high-temperature and high-pressure synthesis is ≥1200℃, and the pressure is ≥4GPa. For example, the temperature of the high-temperature and high-pressure synthesis is 1300~1350℃, and the pressure is 5~6GPa. Attached Figure Description

[0020] Figure 1 This is a morphology diagram of the CBN layer of the polycrystalline cubic boron nitride composite sheet prepared in Example 5 of the present invention;

[0021] Figure 2 This is a morphology diagram of the CBN layer in the polycrystalline cubic boron nitride composite sheet prepared in the comparative example. Detailed Implementation

[0022] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0023] Example 1

[0024] The pretreatment method for cubic boron nitride micropowder used in the synthesis of polycrystalline cubic boron nitride composite sheets in this embodiment includes the following steps:

[0025] Metallic aluminum was deposited on the surface of cubic boron nitride micro powder with an average particle size of 3 μm using physical vapor deposition, so that the mass increase of cubic boron nitride micro powder was 8% of the mass of cubic boron nitride micro powder, thus obtaining aluminum-deposited cubic boron nitride micro powder.

[0026] Then, titanium carbonitride was deposited on the surface of aluminum-deposited cubic boron nitride microparticles using physical vapor deposition, so that the mass increase of aluminum-deposited cubic boron nitride microparticles was 50% of the mass of cubic boron nitride microparticles, thus obtaining pretreated cubic boron nitride microparticles.

[0027] Example 2

[0028] The pretreatment method for cubic boron nitride micropowder used in the synthesis of polycrystalline cubic boron nitride composite sheets in this embodiment includes the following steps:

[0029] Then, titanium carbonitride was deposited on the surface of cubic boron nitride microparticles with an average particle size of 3 μm using physical vapor deposition, so that the mass increase of cubic boron nitride microparticles was 50% of the mass of cubic boron nitride microparticles, thus obtaining titanium carbonitride deposited cubic boron nitride microparticles.

[0030] Metallic aluminum was deposited on the surface of cubic boron nitride micropowder using physical vapor deposition (PVD) to increase the mass of the cubic boron nitride micropowder by 8% of the mass of the cubic boron nitride micropowder, thus obtaining pretreated cubic boron nitride micropowder.

[0031] Example 3

[0032] The pretreatment method for cubic boron nitride micropowder used in the synthesis of polycrystalline cubic boron nitride composite sheets in this embodiment includes the following steps:

[0033] Metallic aluminum was deposited on the surface of cubic boron nitride micro powder with an average particle size of 2 μm using physical vapor deposition, so that the mass increase of cubic boron nitride micro powder was 6% of the mass of cubic boron nitride micro powder, thus obtaining aluminum-deposited cubic boron nitride micro powder.

[0034] Then, titanium carbonitride was deposited on the surface of aluminum-deposited cubic boron nitride microparticles using physical vapor deposition, so that the mass increase of aluminum-deposited cubic boron nitride microparticles was 45% of the mass of cubic boron nitride microparticles, thus obtaining pretreated cubic boron nitride microparticles.

[0035] Example 4

[0036] The pretreatment method for cubic boron nitride micropowder used in the synthesis of polycrystalline cubic boron nitride composite sheets in this embodiment includes the following steps:

[0037] Metallic aluminum was deposited on the surface of cubic boron nitride micro powder with an average particle size of 6 μm using physical vapor deposition, so that the mass increase of cubic boron nitride micro powder was 10% of the mass of cubic boron nitride micro powder, thus obtaining aluminum-deposited cubic boron nitride micro powder.

[0038] Then, titanium carbonitride was deposited on the surface of aluminum-deposited cubic boron nitride microparticles using physical vapor deposition, so that the mass increase of aluminum-deposited cubic boron nitride microparticles was 55% of the mass of cubic boron nitride microparticles, thus obtaining pretreated cubic boron nitride microparticles.

[0039] Example 5

[0040] The preparation method of the polycrystalline cubic boron nitride composite sheet in this embodiment includes the following steps:

[0041] 1) Metallic aluminum was deposited on the surface of cubic boron nitride micro powder with an average particle size of 3 μm using a phase vapor deposition method, so that the mass increase of cubic boron nitride micro powder was 8% of the mass of cubic boron nitride micro powder, thus obtaining aluminum-deposited cubic boron nitride micro powder.

[0042] Then, titanium carbonitride was deposited on the surface of aluminum-deposited cubic boron nitride microparticles using a phase vapor deposition method, so that the mass increase of aluminum-deposited cubic boron nitride microparticles was 50% of the mass of cubic boron nitride microparticles, thus obtaining pretreated cubic boron nitride microparticles.

[0043] 2) Weigh 15g of the pretreated cubic boron nitride micro powder obtained in step 1) and pour it into a niobium cup. Use a press head to smooth the material, then put it into a tungsten carbide alloy matrix to complete the assembly, and perform cold pressing on a hydraulic press.

[0044] 3) Place the cold-pressed cup from step 2) into a vacuum furnace and set the vacuum level to less than 10 × 10⁻⁶. -3 Pa was subjected to vacuum heat treatment at 800℃ for 15 hours.

[0045] 4) The vacuum heat-treated cup is placed in the heating tube according to a certain assembly sequence, and then inserted into the conventionally assembled pyrophyllite block containing heating elements, conductive coils and other components. The pyrophyllite is then sintered on a six-sided press at a sintering pressure of about 5 GPa and a sintering temperature of 1300℃ to obtain a polycrystalline cubic boron nitride composite sheet.

[0046] The polycrystalline cubic boron nitride composite sheet prepared in this embodiment was processed using conventional techniques to achieve a CBN layer thickness of 0.7–1.0 mm. The overall height of the composite sheet was then processed to 1.6 mm, from which a 10 mm diameter circular piece was cut. After polishing, the morphology of the CBN layer was observed under an electron microscope as follows: Figure 1 The sintered product has a relatively uniform microstructure and a distinct network structure.

[0047] Example 6

[0048] The preparation method of the polycrystalline cubic boron nitride composite sheet in this embodiment includes the following steps:

[0049] 1) Then, titanium carbonitride was deposited on the surface of cubic boron nitride micro powder particles with an average particle size of 3 μm by vapor deposition, so that the mass increase of cubic boron nitride micro powder was 50% of the mass of cubic boron nitride micro powder, thus obtaining titanium carbonitride deposited cubic boron nitride micro powder.

[0050] Metallic aluminum was deposited on the surface of cubic boron nitride micro powder deposited by titanium carbonitride using a phase vapor deposition method, so that the mass increase of the cubic boron nitride micro powder deposited by titanium carbonitride was 8% of the mass of the cubic boron nitride micro powder, thus obtaining pretreated cubic boron nitride micro powder.

[0051] 2) Weigh 15g of the pretreated cubic boron nitride micro powder obtained in step 2) and pour it into a niobium cup. Use a press head to smooth the material, then put it into a tungsten carbide alloy matrix to complete the assembly, and perform cold pressing on a hydraulic press.

[0052] 3) Place the cold-pressed cup from step 3) into a vacuum furnace and set the vacuum level to less than 10 × 10⁻⁶. -3 Pa was subjected to vacuum heat treatment at 800℃ for 15 hours.

[0053] 4) The vacuum heat-treated cup is placed in the heating tube according to a certain assembly sequence, and then inserted into the conventionally assembled pyrophyllite block containing heating elements, conductive coils and other components. The pyrophyllite is then sintered on a six-sided press at a sintering pressure of about 5 GPa and a sintering temperature of 1300℃ to obtain a polycrystalline cubic boron nitride composite sheet.

[0054] Example 7

[0055] The preparation method of the polycrystalline cubic boron nitride composite sheet in this embodiment includes the following steps:

[0056] 1) Metallic aluminum was deposited on the surface of cubic boron nitride micro powder with an average particle size of 2 μm using a phase vapor deposition method, so that the mass increase of cubic boron nitride micro powder was 6% of the mass of cubic boron nitride micro powder, thus obtaining aluminum-deposited cubic boron nitride micro powder.

[0057] Then, titanium carbonitride was deposited on the surface of aluminum-deposited cubic boron nitride microparticles using a phase vapor deposition method, so that the mass increase of aluminum-deposited cubic boron nitride microparticles was 45% of the mass of cubic boron nitride microparticles, thus obtaining pretreated cubic boron nitride microparticles.

[0058] 2) Weigh 15g of the pretreated cubic boron nitride micro powder obtained in step 1) and pour it into a niobium cup. Use a press head to smooth the material, then put it into a tungsten carbide alloy matrix to complete the assembly, and perform cold pressing on a hydraulic press.

[0059] 3) Place the cold-pressed cup from step 2) into a vacuum furnace and set the vacuum level to less than 10 × 10⁻⁶. -3 Pa was subjected to vacuum heat treatment at a temperature of 1000℃ for 20 hours.

[0060] 4) The vacuum heat-treated cup is placed in the heating tube according to a certain assembly sequence, and then inserted into the conventionally assembled pyrophyllite block containing heating elements, conductive coils and other components. The pyrophyllite is then sintered on a six-sided press at a sintering pressure of about 6 GPa and a sintering temperature of 1350℃ to obtain a polycrystalline cubic boron nitride composite sheet.

[0061] Example 8

[0062] The preparation method of the polycrystalline cubic boron nitride composite sheet in this embodiment includes the following steps:

[0063] 1) Metallic aluminum was deposited on the surface of cubic boron nitride micro powder with an average particle size of 6 μm using a phase vapor deposition method, so that the mass increase of cubic boron nitride micro powder was 10% of the mass of cubic boron nitride micro powder, thus obtaining aluminum-deposited cubic boron nitride micro powder.

[0064] Then, titanium carbonitride was deposited on the surface of aluminum-deposited cubic boron nitride microparticles using a phase vapor deposition method, so that the mass increase of aluminum-deposited cubic boron nitride microparticles was 55% of the mass of cubic boron nitride microparticles, thus obtaining pretreated cubic boron nitride microparticles.

[0065] 2) Weigh 15g of the pretreated cubic boron nitride micro powder obtained in step 1) and pour it into a niobium cup. Use a press head to smooth the material, then put it into a tungsten carbide alloy matrix to complete the assembly, and perform cold pressing on a hydraulic press.

[0066] 3) Place the cold-pressed cup from step 2) into a vacuum furnace and set the vacuum level to less than 10 × 10⁻⁶. -3 Pa was subjected to vacuum heat treatment at a temperature of 1000℃ for 20 hours.

[0067] 4) The vacuum heat-treated cup is placed in the heating tube according to a certain assembly sequence, and then inserted into the conventionally assembled pyrophyllite block containing heating elements, conductive coils and other components. The pyrophyllite is then sintered on a six-sided press at a sintering pressure of about 6 GPa and a sintering temperature of 1350℃ to obtain a polycrystalline cubic boron nitride composite sheet.

[0068] Comparative Example

[0069] The preparation method of the polycrystalline cubic boron nitride composite sheet in this comparative example includes the following steps:

[0070] 1) Mix cubic boron nitride micro powder with an average particle size of 3 μm, aluminum powder with an average particle size of 1 μm, and titanium carbonitride powder with an average particle size of 1 μm in a mass ratio of 100:8:50 to obtain a mixture.

[0071] 2) Weigh 15g of the mixture obtained in step 1) and pour it into the niobium cup. Use the press head to smooth the material, then put it into the tungsten carbide alloy matrix to complete the assembly, and perform cold pressing on the hydraulic press.

[0072] 3) Place the cold-pressed cup from step 2) into a vacuum furnace and set the vacuum level to less than 10 × 10⁻⁶. -3 Pa was subjected to vacuum heat treatment at 800℃ for 15 hours.

[0073] 4) The vacuum heat-treated cup is placed in the heating tube according to a certain assembly sequence, and then inserted into the conventionally assembled pyrophyllite block containing heating elements, conductive coils and other components. The pyrophyllite is then sintered on a six-sided press at a sintering pressure of about 5 GPa and a sintering temperature of 1300℃ to obtain a polycrystalline cubic boron nitride composite sheet.

[0074] The morphology of the CBN layer in the polycrystalline cubic boron nitride composite sheet prepared in this comparative example was observed under an electron microscope as follows: Figure 2 The uniformity of microstructure distribution in sintered products is poor.

[0075] Experimental Example 1

[0076] The polycrystalline cubic boron nitride composite sheets prepared in Examples 5-8 and the comparative examples were tested using a four-probe resistivity meter. The resistivity was measured at 10 points along the diameter direction, with one point every 6 mm. The distribution of resistivity values ​​can reflect the conductivity and sintering uniformity of the sheets. The results are shown in Table 1.

[0077] Table 1. Resistivity test results of polycrystalline cubic boron nitride composite sheets

[0078]

[0079]

[0080] Variance is a measure of the dispersion of a set of data. The larger the variance, the greater the fluctuation and the less stable the data. The variance values ​​calculated from the resistivity data of the examples and comparative examples show that the polycrystalline cubic boron nitride composite sheet prepared in the examples has the smallest variance in its resistivity test results, indicating that it has the best stability.

[0081] Experiment Example 2

[0082] The polycrystalline cubic boron nitride composite sheets prepared in Examples 5-8 and the comparative example were used to make welding tools of fixed specifications. Continuous turning was adopted, and the cutting parameters for quenched steel were as follows: workpiece hardness 63HRC, linear speed 150m / min, depth of cut 0.2mm, feed rate 0.1mm / r, and cutting distance 4000m. The wear of the cutting tool's flank face was measured using a high-magnification microscope. The average value was obtained after five tests, and the data are shown in Table 2.

[0083] Table 2. Turning test results of polycrystalline cubic boron nitride composite sheets

[0084]

[0085] The wear on the back face shows that the variance of the five sets of wear data in Examples 5 to 8 is smaller than that in the comparative example, indicating that the products prepared in the examples have better quality stability. Examples 5, 6 and the comparative example use the same raw material ratio. From the wear data comparison, the wear resistance of Examples 5 and 6 is better than that of the comparative example. The product quality of the polycrystalline cubic boron nitride composite sheet prepared in Examples 5 to 6 is better than that of the comparative example.

Claims

1. A pretreatment method for cubic boron nitride micropowder used in the synthesis of polycrystalline cubic boron nitride composite sheets, characterized in that: The method includes the following steps: depositing a metal binder for synthesizing polycrystalline cubic boron nitride on the surface of cubic boron nitride microparticles, and then depositing a ceramic binder for synthesizing polycrystalline cubic boron nitride on the surface of the cubic boron nitride microparticles on which the metal binder is deposited; the mass of the metal binder deposited on the surface of the cubic boron nitride microparticles is 6-10% of the mass of the cubic boron nitride microparticles, and the mass of the deposited ceramic binder is 45-55% of the mass of the cubic boron nitride microparticles.

2. The pretreatment method for cubic boron nitride micropowder used in the synthesis of polycrystalline cubic boron nitride composite sheets according to claim 1, characterized in that: The average particle size of the cubic boron nitride micro powder is 2~6μm.

3. The pretreatment method for cubic boron nitride micropowder used in the synthesis of polycrystalline cubic boron nitride composite sheets according to claim 2, characterized in that: The mass of the metal binder deposited on the surface of the cubic boron nitride micro powder particles is 6-8% of the mass of the cubic boron nitride micro powder, and the mass of the ceramic binder deposited is 45-50% of the mass of the cubic boron nitride micro powder.

4. The pretreatment method for cubic boron nitride micropowder used in the synthesis of polycrystalline cubic boron nitride composite sheets according to claim 1, 2, or 3, characterized in that: The metal binder is one or any combination of aluminum, tungsten, and cobalt; the ceramic binder is one or any combination of titanium carbonitride, titanium nitride, and titanium carbide.

5. A method for preparing a polycrystalline cubic boron nitride composite sheet, characterized in that: Includes the following steps: A metal binder is deposited on the surface of cubic boron nitride micro powder particles, and then a ceramic binder is deposited on the surface of the cubic boron nitride micro powder particles on which the metal binder has been deposited, to obtain pretreated cubic boron nitride micro powder. The pretreated cubic boron nitride micro powder is then assembled with the alloy matrix and subjected to high-temperature and high-pressure synthesis. The mass of the metal binder deposited on the surface of the cubic boron nitride micro powder particles is 6-10% of the mass of the cubic boron nitride micro powder, and the mass of the deposited ceramic binder is 45-55% of the mass of the cubic boron nitride micro powder. The high-temperature and high-pressure synthesis temperature is ≥1200℃ and the pressure is ≥4GPa.

6. The method for preparing polycrystalline cubic boron nitride composite sheets according to claim 5, characterized in that: The average particle size of the cubic boron nitride micro powder is 2~6μm.

7. The method for preparing polycrystalline cubic boron nitride composite sheet according to claim 6, characterized in that: The mass of the metal binder deposited on the surface of the cubic boron nitride micro powder particles is 6-8% of the mass of the cubic boron nitride micro powder, and the mass of the ceramic binder deposited is 45-50% of the mass of the cubic boron nitride micro powder.

8. The method for preparing polycrystalline cubic boron nitride composite sheets according to claim 6 or 7, characterized in that: The metal binder is one or any combination of aluminum, tungsten, and cobalt; the ceramic binder is one or any combination of titanium carbonitride, titanium nitride, and titanium carbide.

9. The method for preparing polycrystalline cubic boron nitride composite sheets according to claim 5, 6, or 7, characterized in that: After assembling the pretreated cubic boron nitride micro powder with the alloy matrix, pre-pressing is performed first, followed by a vacuum degree ≤10×10 -3 Vacuum heat treatment for 15-20 hours at 700-1000℃ and Pa, followed by high-temperature and high-pressure synthesis.

10. The method for preparing polycrystalline cubic boron nitride composite sheets according to claim 5, 6, or 7, characterized in that: The high-temperature and high-pressure synthesis is carried out at a temperature of 1300~1350℃ and a pressure of 5~6GPa.

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