Particle toughened PcBN composite sheet and preparation process thereof

Abstract

The invention provides a particle-toughened PcBN composite sheet and a preparation method thereof. The PcBN composite sheet is prepared by sintering the following raw materials in percentage by mass: 60% of cubic boron nitride micro powder; the weight percentage ratio of the titanium nitride powder to the aluminum powder is 7: 3, and the weight percentage ratio of the titanium nitride powder to the aluminum powder is 2: 3; the content of hafnium carbide is 5-20%; the bending strength of the PcBN composite sheet is larger than or equal to 1445 MPa, and the microhardness of the PcBN composite sheet ranges from 3110 HV to 4414 HV. The invention also provides a preparation method. The impact toughness of the PcBN composite sheet prepared by introducing HfC is obviously improved, no pollutant is produced in the preparation process, industrial batch production is easy to realize, and the PcBN composite sheet is suitable for popularization.

Description

Technical Field

[0001] This invention relates to PcBN material technology, specifically a particle-toughened PcBN composite sheet and its preparation method. Background Technology

[0002] Polycrystalline cubic boron nitride (PcBN) possesses numerous advantages, including high hardness, excellent wear resistance, high thermal conductivity, thermal stability, and chemical inertness, making it the most promising tool material after synthetic diamond. It perfectly compensates for diamond's unsuitability for cutting ferrous materials and is widely used in machining various hardened steels, chilled cast iron, cemented carbide, surface-coated materials, and other high-hardness and wear-resistant materials. PcBN composite blades achieve high-speed dry cutting, ultra-long lifespan, and mirror-finish machining quality due to their ultra-high hardness. In extreme conditions such as aerospace composite materials, hardened steel molds, and wind turbine bearings, traditional cemented carbide or diamond saw blades are unsuitable due to rapid wear, thermal softening, or graphitization. Therefore, PcBN, with its hardness second only to diamond and excellent high-temperature red hardness, has become the preferred tool material. However, the high brittleness of PcBN results in its bending strength being only one-third that of cemented carbide, and it is extremely sensitive to interrupted cutting, micro-chipping, and lateral impacts. When encountering hard inclusions or sudden feed changes, the cutting teeth are prone to chipping or even complete failure. Therefore, the introduction of metal carbides (HfC) is used to improve the impact resistance and bonding strength of PcBN tools.

[0003] Traditional approaches to improving the bonding strength and impact resistance of PcBN tools can be summarized as follows: using metals or intermetallic compounds as sintering aids, relying on liquid-phase wetting to coat cBN particles, forming a tough metal film and releasing thermal stress; introducing a ceramic transition layer between cBN and the bonding phase, using a gradient design of the coefficient of thermal expansion to alleviate grain boundary stress concentration; and employing micron-nano-scale cBN blending or gradient sintering to suppress crack propagation through fine-grain strengthening and residual compressive stress on the surface. However, these methods either sacrifice hardness, cause oxidation embrittlement at high temperatures, or have narrow processing windows, making it difficult to achieve new breakthroughs in the "hardness-toughness-thermal stability" triangle.

[0004] Therefore, the research focuses on using HfC, which has a high melting point, high modulus, and excellent compatibility with cBN, to enhance the toughness of PcBN composite sheets. With a melting point as high as 3900 ℃ and Young's modulus >450 GPa, it can form an Hf-BN interface transition layer without reducing hot hardness. This layer can both pin grain boundaries to improve bonding strength and absorb impact energy through local micro-plastic deformation, opening up a new design space for the synergy of "high hardness-high toughness" in PcBN tools.

[0005] Among the published patents concerning the optimization of PcBN binder selection, Chinese patents with publication numbers CN119822849A and CN119110792A involve technologies using nitride or carbide ceramic powders as binders. Based on this approach, Chinese patent CN103030397A involves introducing TiC to toughen the material while maintaining a certain level of hardness. In these three published patents, the toughening method of "multiple carbides + multi-component binders" leads to interface disorder, insufficient high-temperature oxidation resistance, and high sintering temperatures, creating a "performance-process-cost" triangle contradiction. Summary of the Invention

[0006] To address the problems existing in the prior art, this invention provides a particle-toughened PcBN composite sheet and its preparation method. The purpose is to add ultra-high melting point ceramic HfC to a binder and utilize its high hardness, high elastic modulus, high chemical inertness, and low thermal expansion to prepare a PcBN composite sheet with high flexural strength and impact resistance.

[0007] To achieve the above objectives, the specific solution of the present invention is as follows:

[0008] The content of cubic boron nitride micro powder is 60%;

[0009] The composite binder of titanium nitride powder and aluminum powder is 20-35%, and the weight percentage of titanium nitride powder to aluminum powder in the composite binder is 7:3.

[0010] Hafnium carbide 5-20%;

[0011] And the sum of the above components is 100%;

[0012] The flexural strength of the PcBN composite sheet is ≥1445MPa, and the microhardness is 3110HV~4414HV.

[0013] Furthermore, the cubic boron nitride micro powder has a particle size of ≤3μm and a purity greater than 99.9%; the aluminum powder has a particle size of 1~2μm and a purity greater than 99.8%; the titanium nitride powder and hafnium carbide powder both have a particle size of 1~3μm and a purity ≥99.8%.

[0014] Furthermore, after being continuously impacted 60 times from a height of 133 mm by a 0.6 kg YG8 cemented carbide hammer, the composite sheet showed no through cracks on its surface.

[0015] A method for preparing the composite sheet includes the following steps:

[0016] Step 1: Weigh out cubic boron nitride micro powder, aluminum powder, titanium nitride powder and hafnium carbide powder by mass percentage, mix and dry grind, then add wetting agent and wet grind, then dry to obtain mixed powder;

[0017] Step 2: After mixing the powder described in Step 1 with the cemented carbide matrix and cold pressing it into a blank, the blank is reduced at 800°C for 90 minutes to obtain the blank to be sintered.

[0018] Step 3: The blank to be sintered described in Step 2 is loaded into a pyrophyllite block for sintering. The sintering power is 3000-3200W, the sintering pressure is 4.5-5.5GPa, the sintering temperature is 1100-1350℃, and the holding time is 6min to obtain the PcBN composite sheet.

[0019] Furthermore, in step 1, the amount of wetting agent added and the liquid-solid ratio of the mixed powder are 1g:1-1.5ml, and the wetting agent is anhydrous ethanol.

[0020] Furthermore, the cemented carbide substrate mentioned in step 2 is of type YG8.

[0021] In step 2, the pressure for cold pressing the billet is 60-100 MPa, and the holding time is 5 seconds.

[0022] Advantages of the present invention

[0023] (1) This invention significantly improves the impact toughness of PcBN composite sheets by introducing HfC. For example, in the method of Example 4, 5% HfC was added, resulting in a microhardness of 3721.45±618.95 HV and a flexural strength of 1730.53±409.16 MPa for the prepared PcBN composite sheet. The toughening effect of this PcBN composite sheet is significant. The aggregation energy of HfC enhances the penetration of the interfacial phase and the formation of a dense structure, making the alloy phase and the ceramic phase tightly bonded. After 60 impact tests, the actual density was measured by Archimedes' displacement method. Compared with the theoretical density, the relative density reached 97.37%, maintaining structural integrity and without cracks. Its average flexural strength was 1675 MPa, exceeding the flexural strength of most commercial PcBN composites.

[0024] (2) The method for preparing PcBN composite sheets of the present invention is simple and can produce PcBN composite sheets with high flexural strength and impact toughness. Moreover, the preparation process of PcBN composite sheets produces no pollutants and is an environmentally friendly technology. The composition of PcBN composite sheets is easy to control and easy to achieve industrial mass production.

[0025] (3) This invention achieves a triple breakthrough of “low cBN content - ultra-high toughness - extremely simple process” in the PcBN system for the first time through the interface densification effect induced by HfC aggregates, solving the bottleneck of high hardness and high toughness that has plagued the industry for many years, and providing a new generation of environmentally friendly superhard material platform technology for high-end manufacturing. Attached Figure Description

[0026] Figure 1XRD analysis results for cBN-28TiN-12Al composite sheet;

[0027] Figure 2 SEM image of cBN-28TiN-12Al composite sheet;

[0028] Figure 3 Impact test results for cBN-28TiN-12Al composite sheet;

[0029] Figure 4 XRD analysis results for cBN-21TiN-9Al composite sheet;

[0030] Figure 5 SEM image of cBN-21TiN-9Al composite sheet;

[0031] Figure 6 Impact test results for cBN-21TiN-9Al composite sheet;

[0032] Figure 7 XRD analysis results for cBN-14TiN-6Al composite sheet;

[0033] Figure 8 SEM image of cBN-14TiN-6Al composite sheet;

[0034] Figure 9 Impact test results for cBN-14TiN-6Al composite sheet;

[0035] Figure 10 XRD analysis results of cBN-24.5TiN-10.5Al-5HfC composite sheet;

[0036] Figure 11 SEM image of cBN-24.5TiN-10.5Al-5HfC composite sheet;

[0037] Figure 12 Impact test results for cBN-24.5TiN-10.5Al-5HfC composite sheet;

[0038] Figure 13 XRD analysis results for cBN-21TiN-9Al-10HfC composite film;

[0039] Figure 14 SEM image of cBN-21TiN-9Al-10HfC composite;

[0040] Figure 15 Impact test results for cBN-21TiN-9Al-10HfC composite sheet;

[0041] Figure 16 XRD analysis results of cBN-17.5TiN-7.5Al-15HfC composite sheet;

[0042] Figure 17 SEM image of cBN-17.5TiN-7.5Al-15HfC composite sheet;

[0043] Figure 18 Impact test results of cBN-17.5TiN-7.5Al-15HfC composite sheet;

[0044] Figure 19 XRD analysis results for cBN-14TiN-6Al-20HfC composite sheet;

[0045] Figure 20 SEM image of cBN-14TiN-6Al-20HfC composite sheet;

[0046] Figure 21 Impact test results for cBN-14TiN-6Al-20HfC composite sheet;

[0047] Figure 22 This is a comparison chart of microhardness.

[0048] Figure 23 This is a comparison chart of bending strength.

[0049] Figure 24 SEM and EDS images of the interface of the cBN-24.5TiN-10.5Al-5HfC composite sheet. Detailed Implementation

[0050] The present invention will be further explained and described below with reference to the accompanying drawings and specific embodiments. It should be noted that the specific embodiments are not intended to limit the scope of the present invention.

[0051] Example 1: Preparation of cBN-28TiN-12Al composite sheet

[0052] Step 1: Weigh out 300g of the following ingredients according to their mass percentage:

[0053] Cubic boron nitride (cBN) micro powder: purity 99.9%, particle size 1μm, accounting for 60% of the total raw material mass;

[0054] The composite binder accounts for 40% of the total raw material mass, and its composition is as follows:

[0055] Titanium nitride (TiN) powder: purity 99.8%, particle size 1μm, accounting for 70% of the composite binder mass, i.e. 28% of the total raw materials;

[0056] Aluminum (Al) powder: purity 99.8%, particle size 1μm, accounting for 30% of the composite binder mass, i.e. 12% of the total raw materials;

[0057] The above raw materials were placed in a mortar and pestle and ground for 5 minutes. Then, 400 ml of anhydrous ethanol was added as a wetting agent and ground 2-3 times. The mixture was then dried with an infrared lamp to obtain a mixed powder.

[0058] Step 2: The mixed powder described in Step 1 is mixed with the cemented carbide matrix in a molybdenum cup and then cold-pressed at 80 MPa for 5 seconds, and then reduced at 800°C for 90 minutes to obtain the blank to be sintered.

[0059] Step 3: The green body to be sintered described in Step 2 is encapsulated in a pyrophyllite block and placed in a six-sided top press for sintering under the following conditions:

[0060] Sintering power: 3000W

[0061] Sintering pressure: 5.5 GPa

[0062] Sintering temperature: 1350℃

[0063] Keep warm for: 6 minutes

[0064] After sintering, the PcBN composite sheet is obtained. Its XRD pattern is shown below. Figure 1 As shown, SEM Figure 2 As shown.

[0065] Impact performance tests were performed on the PcBN composite sheet obtained in step 3:

[0066] Using a 0.6kg YG8 carbide cylindrical hammer, the polycrystalline layer was continuously impacted 60 times from a height of 133mm by free fall. The morphology after impact is as follows. Figure 3 As shown.

[0067] The microhardness of the PcBN material prepared by the method in Example 1 is 3253.52±383.03 HV (load 20 kgf), and the flexural strength is 1614.08±209.26 MPa.

[0068] Example 2: Preparation of cBN-21TiN-9Al composite sheet

[0069] Step 1: Weigh out 300g of the following ingredients according to their mass percentage:

[0070] Cubic boron nitride (cBN) micro powder: purity 99.9%, particle size 1μm, accounting for 70% of the total raw material mass;

[0071] The composite binder accounts for 30% of the total raw material mass, and its composition is as follows:

[0072] Titanium nitride (TiN) powder: purity 99.8%, particle size 1μm, accounting for 70% of the composite binder mass, i.e. 21% of the total raw materials;

[0073] Aluminum (Al) powder: purity 99.8%, particle size 1μm, accounting for 30% of the composite binder mass, i.e. 9% of the total raw materials;

[0074] The above raw materials were placed in a mortar and pestle and ground for 5 minutes. Then, 400 ml of anhydrous ethanol was added as a wetting agent and ground 2-3 times. The mixture was then dried with an infrared lamp to obtain a mixed powder.

[0075] Step 2: The mixed powder described in Step 1 is mixed with the cemented carbide matrix in a molybdenum cup and then cold-pressed at 80 MPa for 5 seconds, and then reduced at 800°C for 90 minutes to obtain the blank to be sintered.

[0076] Step 3: The green body to be sintered described in Step 2 is encapsulated in a pyrophyllite block and placed in a six-sided top press for sintering under the following conditions:

[0077] Sintering power: 3000W

[0078] Sintering pressure: 5.5 GPa

[0079] Sintering temperature: 1350℃

[0080] Keep warm for: 6 minutes

[0081] After sintering, the PcBN composite sheet is obtained. Its XRD pattern is shown below. Figure 4 As shown, SEM Figure 5 As shown.

[0082] Impact performance tests were performed on the PcBN composite sheet obtained in step 3:

[0083] Using a 0.6kg YG8 carbide cylindrical hammer, the polycrystalline layer was continuously impacted 60 times from a height of 133mm by free fall. The morphology after impact is as follows. Figure 6 As shown.

[0084] The PcBN material prepared by the method in Example 2 has a microhardness of 3797.42±355.28 HV (load 20 kgf) and a flexural strength of 1578.43±82.67 MPa.

[0085] Example 3: Preparation of cBN-14TiN-6Al composite sheet

[0086] Step 1: Weigh out 300g of the following ingredients according to their mass percentage:

[0087] Cubic boron nitride (cBN) micro powder: purity 99.9%, particle size 1μm, accounting for 80% of the total raw material mass;

[0088] The composite binder accounts for 20% of the total raw material mass, and its composition is as follows:

[0089] Titanium nitride (TiN) powder: purity 99.8%, particle size 1μm, accounting for 70% of the composite binder mass, i.e. 14% of the total raw materials;

[0090] Aluminum (Al) powder: purity 99.8%, particle size 1μm, accounting for 30% of the composite binder mass, i.e. 6% of the total raw materials;

[0091] The above raw materials were placed in a mortar and pestle and ground for 5 minutes. Then, 400 ml of anhydrous ethanol was added as a wetting agent and ground 2-3 times. The mixture was then dried with an infrared lamp to obtain a mixed powder.

[0092] Step 2: The mixed powder described in Step 1 is mixed with the cemented carbide matrix in a molybdenum cup and then cold-pressed at 80 MPa for 5 seconds, and then reduced at 800°C for 90 minutes to obtain the blank to be sintered.

[0093] Step 3: The green body to be sintered described in Step 2 is encapsulated in a pyrophyllite block and placed in a six-sided top press for sintering under the following conditions:

[0094] Sintering power: 3000W

[0095] Sintering pressure: 5.5 GPa

[0096] Sintering temperature: 1350℃

[0097] Keep warm for: 6 minutes

[0098] After sintering, the PcBN composite sheet is obtained. Its XRD pattern is shown below. Figure 7 As shown, SEM Figure 8 As shown.

[0099] Impact performance tests were performed on the PcBN composite sheet obtained in step 3:

[0100] Using a 0.6kg YG8 carbide cylindrical hammer, the polycrystalline layer was continuously impacted 60 times from a height of 133mm by free fall. The morphology after impact is as follows. Figure 9 As shown.

[0101] The microhardness of the PcBN material prepared by the method in Example 3 is 3135±339HV (load 20kgf), and the flexural strength is 1626.72±81.96MPa.

[0102] Example 4: Preparation of cBN-24.5TiN-10.5Al-5HfC composite sheet

[0103] To illustrate the toughening effect of adding binders to HfC particles, the preparation method includes the following steps:

[0104] Step 1: Weigh out 300g of the following ingredients according to their mass percentage:

[0105] Cubic boron nitride (cBN) micro powder: purity 99.9%, particle size 1μm, accounting for 60% of the total raw material mass;

[0106] The composite binder accounts for 35% of the total raw material mass, and its composition is as follows:

[0107] Titanium nitride (TiN) powder: purity 99.8%, particle size 1μm, accounting for 70% of the composite binder mass, i.e. 24.5% of the total raw materials;

[0108] Aluminum (Al) powder: purity 99.8%, particle size 1μm, accounting for 30% of the composite binder mass, i.e. 10.5% of the total raw materials;

[0109] Hafnium carbide (HfC) additive: purity 99.8%, particle size 1μm, accounting for 5% of the total raw material mass;

[0110] The above raw materials were placed in a mortar and pestle and ground for 5 minutes. Then, 400 ml of anhydrous ethanol was added as a wetting agent and ground 2-3 times. The mixture was then dried with an infrared lamp to obtain a mixed powder.

[0111] Step 2: The mixed powder described in Step 1 is mixed with the cemented carbide matrix in a molybdenum cup and then cold-pressed at 80 MPa for 5 seconds, and then reduced at 800°C for 90 minutes to obtain the blank to be sintered.

[0112] Step 3: The green body to be sintered described in Step 2 is encapsulated in a pyrophyllite block and placed in a six-sided top press for sintering under the following conditions:

[0113] Sintering power: 3000W

[0114] Sintering pressure: 5.5 GPa

[0115] Sintering temperature: 1350℃

[0116] Keep warm for: 6 minutes

[0117] After sintering, the PcBN composite sheet is obtained. Its XRD pattern is shown below. Figure 10 As shown, SEM Figure 11 As shown.

[0118] Impact performance tests were performed on the PcBN composite sheet obtained in step 3:

[0119] Using a 0.6kg YG8 carbide cylindrical hammer, the polycrystalline layer was continuously impacted 60 times from a height of 133mm by free fall. The morphology after impact is as follows. Figure 12 As shown.

[0120] The microhardness of the PcBN material prepared by the method in Example 4 is 3721.45±618.95 HV (load 20 kgf), and the bending strength is 1813.86±190.43 MPa.

[0121] The interface morphology between the PcBN layer and the cemented carbide layer is as follows: Figure 24 As shown, the added HfC aggregates at the interface in the form of clumps, tightly connecting the alloy and ceramic phases and enhancing the interfacial bonding strength.

[0122] Example 5: Preparation of cBN-21TiN-9Al-10HfC composite sheet

[0123] To illustrate the toughening effect of adding binders to HfC particles, the preparation method includes the following steps:

[0124] Step 1: Weigh out 300g of the following ingredients according to their mass percentage:

[0125] Cubic boron nitride (cBN) micro powder: purity 99.9%, particle size 1μm, accounting for 60% of the total raw material mass;

[0126] The composite binder accounts for 30% of the total raw material mass, and its composition is as follows:

[0127] Titanium nitride (TiN) powder: purity 99.8%, particle size 1μm, accounting for 70% of the composite binder mass, i.e. 21% of the total raw materials;

[0128] Aluminum (Al) powder: purity 99.8%, particle size 1μm, accounting for 30% of the composite binder mass, i.e. 9% of the total raw materials;

[0129] Hafnium carbide (HfC) additive: purity 99.8%, particle size 1μm, accounting for 10% of the total raw material mass;

[0130] The above raw materials were placed in a mortar and pestle and ground for 5 minutes. Then, 400 ml of anhydrous ethanol was added as a wetting agent and ground 2-3 times. The mixture was then dried with an infrared lamp to obtain a mixed powder.

[0131] Step 2: The mixed powder described in Step 1 is mixed with the cemented carbide matrix in a molybdenum cup and then cold-pressed at 80 MPa for 5 seconds, and then reduced at 800°C for 90 minutes to obtain the blank to be sintered.

[0132] Step 3: The green body to be sintered described in Step 2 is encapsulated in a pyrophyllite block and placed in a six-sided top press for sintering under the following conditions:

[0133] Sintering power: 3000W

[0134] Sintering pressure: 55.5 GPa

[0135] Sintering temperature: 1350℃

[0136] Keep warm for: 6 minutes

[0137] After sintering, the PcBN composite sheet is obtained. Its XRD pattern is shown below. Figure 13 As shown, SEM Figure 14 As shown.

[0138] Impact performance tests were performed on the PcBN composite sheet obtained in step 3:

[0139] Using a 0.6kg YG8 carbide cylindrical hammer, the polycrystalline layer was continuously impacted 60 times from a height of 133mm by free fall. The morphology after impact is as follows. Figure 15 As shown.

[0140] The microhardness of the PcBN material prepared by the method in Example 5 is 4049.32±364.68 HV (load 20 kgf), and the bending strength is 1467.73±22.62 MPa.

[0141] Example 6: Preparation of cBN-17.5TiN-7.5Al-15HfC composite sheet

[0142] To illustrate the toughening effect of adding binders to HfC particles, the preparation method includes the following steps:

[0143] Step 1: Weigh out 300g of the following ingredients according to their mass percentage:

[0144] Cubic boron nitride (cBN) micro powder: purity 99.9%, particle size 1μm, accounting for 60% of the total raw material mass;

[0145] The composite binder accounts for 25% of the total raw material mass, and its composition is as follows:

[0146] Titanium nitride (TiN) powder: purity 99.8%, particle size 1μm, accounting for 70% of the composite binder mass, i.e. 17.5% of the total raw materials;

[0147] Aluminum (Al) powder: purity 99.8%, particle size 1μm, accounting for 30% of the composite binder mass, i.e. 7.5% of the total raw materials;

[0148] Hafnium carbide (HfC) additive: purity 99.8%, particle size 1μm, accounting for 15% of the total raw material mass;

[0149] The above raw materials were placed in a mortar and pestle and ground for 5 minutes. Then, 400 ml of anhydrous ethanol was added as a wetting agent and ground 2-3 times. The mixture was then dried with an infrared lamp to obtain a mixed powder.

[0150] Step 2: The mixed powder described in Step 1 is mixed with the cemented carbide matrix in a molybdenum cup and then cold-pressed at 80 MPa for 5 seconds, and then reduced at 800°C for 90 minutes to obtain the blank to be sintered.

[0151] Step 3: The green body to be sintered described in Step 2 is encapsulated in a pyrophyllite block and placed in a six-sided top press for sintering under the following conditions:

[0152] Sintering power: 3000W

[0153] Sintering pressure: 5.5 GPa

[0154] Sintering temperature: 1350℃

[0155] Keep warm for: 6 minutes

[0156] After sintering, the PcBN composite sheet is obtained. Its XRD pattern is shown below. Figure 16 As shown, SEM Figure 17 As shown.

[0157] Impact performance tests were performed on the PcBN composite sheet obtained in step 3:

[0158] Using a 0.6kg YG8 carbide cylindrical hammer, the polycrystalline layer was continuously impacted 60 times from a height of 133mm by free fall. The morphology after impact is as follows. Figure 18 As shown.

[0159] The microhardness of the PcBN material prepared by the method in Example 6 is 3806.97±693.43 HV (load 20 kgf), and the flexural strength is 1614.37±156.45 MPa.

[0160] Example 7: Preparation of cBN-17.5TiN-7.5Al-15HfC composite sheet

[0161] To illustrate the toughening effect of adding binders to HfC particles, the preparation method includes the following steps:

[0162] Step 1: Weigh out 300g of the following ingredients according to their mass percentage:

[0163] Cubic boron nitride (cBN) micro powder: purity 99.9%, particle size 1μm, accounting for 60% of the total raw material mass;

[0164] The composite binder accounts for 20% of the total raw material mass, and its composition is as follows:

[0165] Titanium nitride (TiN) powder: purity 99.8%, particle size 1μm, accounting for 70% of the composite binder mass, i.e. 14% of the total raw materials;

[0166] Aluminum (Al) powder: purity 99.8%, particle size 1μm, accounting for 30% of the composite binder mass, i.e. 6% of the total raw materials;

[0167] Hafnium carbide (HfC) additive: purity 99.8%, particle size 1μm, accounting for 20% of the total raw material mass;

[0168] The above raw materials were placed in a mortar and pestle and ground for 5 minutes. Then, 400 ml of anhydrous ethanol was added as a wetting agent and ground 2-3 times. The mixture was then dried with an infrared lamp to obtain a mixed powder.

[0169] Step 2: The mixed powder described in Step 1 is mixed with the cemented carbide matrix in a molybdenum cup and then cold-pressed at 80 MPa for 5 seconds, and then reduced at 800°C for 90 minutes to obtain the blank to be sintered.

[0170] Step 3: The green body to be sintered described in Step 2 is encapsulated in a pyrophyllite block and placed in a six-sided top press for sintering under the following conditions:

[0171] Sintering power: 3000W

[0172] Sintering pressure: 5.5 GPa

[0173] Sintering temperature: 1350℃

[0174] Keep warm for: 6 minutes

[0175] After sintering, the PcBN composite sheet is obtained. Its XRD pattern is shown below. Figure 19 As shown, SEM Figure 20 As shown.

[0176] Impact performance tests were performed on the PcBN composite sheet obtained in step 3:

[0177] Using a 0.6kg YG8 carbide cylindrical hammer, the polycrystalline layer was continuously impacted 60 times from a height of 133mm by free fall. The morphology after impact is as follows. Figure 21 As shown.

[0178] The microhardness of the PcBN material prepared by the method in Example 7 is 3548.80±286.80 HV (load 20 kgf), and the bending strength is 1653.88±149.95 MPa.

Claims

1. A particle-toughened PcBN composite sheet, characterized in that, The PcBN composite sheet is sintered from the following raw materials in the indicated mass percentages: The content of cubic boron nitride micro powder is 60%; The composite binder of titanium nitride powder and aluminum powder is 20-35%, and the weight percentage of titanium nitride powder to aluminum powder in the composite binder is 7:

3. Hafnium carbide 5-20%; And the sum of the above components is 100%; The flexural strength of the PcBN composite sheet is ≥1445MPa, and the microhardness is 3110HV~4414HV.

2. The composite sheet according to claim 1, characterized in that, The cubic boron nitride micro powder has a particle size of ≤3μm and a purity of greater than 99.9%; the aluminum powder has a particle size of 1~2μm and a purity of greater than 99.8%; the titanium nitride powder and hafnium carbide powder both have a particle size of 1~3μm and a purity of ≥99.8%.

3. The composite sheet according to claim 1 or 2, characterized in that, The composite sheet showed no through cracks after being continuously impacted 60 times from a height of 133 mm by a 0.6 kg YG8 cemented carbide hammer.

4. A method for preparing the composite sheet according to any one of claims 1 to 3, characterized in that, Includes the following steps: Step 1: Weigh out cubic boron nitride micro powder, aluminum powder, titanium nitride powder and hafnium carbide powder by mass percentage, mix and dry grind, then add wetting agent and wet grind, then dry to obtain mixed powder; Step 2: After mixing the powder described in Step 1 with the cemented carbide matrix and cold pressing it into a blank, the blank is reduced at 800°C for 90 minutes to obtain the blank to be sintered. Step 3: The blank to be sintered described in Step 2 is loaded into a pyrophyllite block for sintering. The sintering power is 3000-3200W, the sintering pressure is 4.5-5.5GPa, the sintering temperature is 1100-1350℃, and the holding time is 6min to obtain the PcBN composite sheet.

5. The method according to claim 4, characterized in that, The amount of wetting agent added in step 1 and the liquid-solid ratio of the mixed powder are 1g:1~1.5ml, and the wetting agent is anhydrous ethanol.

6. The method according to claim 4, characterized in that, The cemented carbide substrate described in step 2 is of type YG8.

7. The method according to claim 4, characterized in that, The pressure for cold pressing in step 2 is 60-100 MPa, and the holding time is 5 seconds.

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