Method for preparing diamond grinding wheel through binding agent doped with rare earth material

Abstract

The invention discloses a method for preparing a diamond grinding wheel through a binding agent doped with a rare earth material, and particularly relates to the technical field of diamond grinding wheels, and the method comprises the steps of S1, diamond abrasive particle pretreatment, S2, composite binding agent preparation, S3, gradient charging and S4, spark plasma sintering. According to the method, abrasive particle concentration and density gradient distribution is formed on a grinding wheel working layer through a gradient charging process, and a reinforced reaction layer is formed on a diamond-binding agent interface in combination with a rare earth additive, so that remarkable improvement of the grinding efficiency, great reduction of the abrasive particle falling-off rate and optimization of comprehensive mechanical properties are synergistically realized; and meanwhile, the impact resistance and the heat dissipation capacity are enhanced through the edge strengthening area and the multi-stage pore structure, and the application scene in the high-hardness material machining field is effectively expanded.

Description

Technical Field

[0001] The present invention relates to the technical field of diamond grinding wheels, and more particularly to a method for preparing a diamond grinding wheel using a binder doped with a rare earth material. Background Art

[0002] A diamond grinding wheel is a circular bonded abrasive tool with diamond abrasive as its main component. It is usually composed of diamond abrasive, a binder (such as metal powder, resin powder, ceramic or electroplated metal) and a matrix. Its structure includes three parts: a diamond abrasive layer, a transition layer and a matrix.

[0003] However, the existing diamond grinding wheels use a uniform loading process, which results in a uniform distribution of abrasive grains and binders in the working layer, causing the outer layer abrasive grains to wear and fall off easily, the inner layer utilization rate to be low, and poor heat dissipation and chip removal, which in turn affects the accuracy. At the same time, the binder lacks effective interface strengthening means, and the bonding strength between ordinary binders and diamond abrasive grains is insufficient. Products with added rare earths are also difficult to form a stable strengthening layer due to structural and particle size design defects. Coupled with the unreasonable pore structure, the existing technology ultimately suffers from multiple defects such as low grinding efficiency, easy shedding of abrasive grains, short life, poor accuracy, and limited application.

[0004] In view of the above situation, the present invention provides a method for preparing a diamond grinding wheel using a binder doped with rare earth materials. Summary of the Invention

[0005] In order to overcome the above-mentioned defects of the prior art, the present invention provides a method for preparing a diamond grinding wheel using a binder doped with a rare earth material to solve the problems raised in the above-mentioned background technology.

[0006] To achieve the above object, the present invention provides the following technical solution: a method for preparing a diamond grinding wheel using a binder doped with a rare earth material, specifically comprising the following steps: S1, pre-treating diamond abrasive grains, chemically plating a nickel-phosphorus-rare earth composite layer on the diamond surface, wherein the rare earth element content in the composite layer is 1.0-2.5wt% and the coating thickness is 0.5-1.2μm; S2. Preparation of composite binder: Mix the following components by weight: The metal phase is 60-70%, specifically iron-cobalt-chromium alloy powder, wherein iron:cobalt:chromium = 4-6:2-4:1-3; The ceramic phase is 25-35%, specifically a mixture of hexagonal boron nitride and nano-alumina in a ratio of 6-8:2-4; 3-5% reinforcement phase, specifically carbon nanofibers with an aspect ratio greater than 15; Rare earth additives 0.3-0.8%, specifically a nano core-shell structure composed of lanthanum oxide as the core and cerium oxide as the shell, with a core diameter of 150-250nm and a shell thickness of 30-60nm; S3, gradient loading, arranging the diamond abrasives treated in step S1 and the composite binder prepared in step S2 according to a concentration gradient, with the outer working layer concentration being 70-80%, the inner layer concentration being 45-55%, and the transition zone concentration decreasing continuously from the outer layer to the inner layer; S4, spark plasma sintering, performing three-stage temperature-controlled sintering on the mixture after gradient loading in step S3 under a vacuum environment, specifically including: Interface activation stage, temperature is 300-500℃, applied pressure is 50-60MPa, time is 8-12min; During the ceramic skeleton formation stage, the temperature is 600-700°C, the applied pressure is 75-85 MPa, and the temperature is 4-6 minutes; During the metal infiltration stage, the temperature is 750-850°C, the applied pressure is 25-35 MPa, and the temperature is 2-4 minutes.

[0007] Preferably, the chemical plating solution in step S1 comprises the following components in parts by weight: 20-30 parts of a nickel ion source, 25-35 parts of a reducing agent, sodium hypophosphite, 4-8 parts of a rare earth compound, wherein the molar ratio of lanthanum nitrate to cerium chloride is 1:0.5-1.5, and 15-25 parts of a complexing agent, sodium citrate; The plating temperature is 80-90°C and the pH value is 8.5-9.5.

[0008] Preferably, in step S2, the particle size of the iron-cobalt-chromium alloy powder in the metal phase is ≤15 μm, the diameter of the hexagonal boron nitride flakes in the ceramic phase is 5-20 μm and the thickness is 0.2-1 μm, and the particle size of the nano-alumina is 30-80 nm.

[0009] Preferably, the rare earth additive preparation method in step S2 is: Lanthanum nitrate solution is co-precipitated with a precipitant to generate a lanthanum hydroxide core, and then a cerium oxide shell is coated on the core surface by a hydrothermal method at a calcination temperature of 450-550° C. The precipitant includes but is not limited to ammonia water, potassium hydroxide and sodium hydroxide.

[0010] Preferably, in step S3, centrifugal magnetic control assembly is used to achieve gradient arrangement, with a centrifugal speed of 2000-3000 rpm and a magnetic field strength of 0.5-1.2T.

[0011] Preferably, in step S4, spark plasma sintering adopts a pulse current mode with a pulse frequency of 50-100 Hz, an on-off ratio of 8:2-9:1, a peak voltage of 3-5 V, and a current density of 100-150 A / cm²; During the sintering process, a mixed protective gas of argon and hydrogen was introduced, wherein the ratio of argon to hydrogen was 95:5 and the gas flow rate was 10-20 mL / min. After the metal infiltration stage is completed, the temperature is lowered to 300°C at a rate of 8-12°C / min and then cooled naturally.

[0012] Preferably, in the composite binder of step S2, the particle sizes of the metal phase, ceramic phase, reinforcing phase and rare earth additive must satisfy the following coordination relationship: Metal phase and ceramic phase: The average particle size of the metal phase is 1.4-3.3 times the average particle size of the ceramic phase; Ceramic phase and reinforcement phase: The average particle size of the ceramic phase is 200-400 times the diameter of the reinforcement phase carbon nanofiber; Rare earth additives and metal phase: The average particle size of the rare earth additive cannot exceed one tenth of the average particle size of the metal phase.

[0013] The present invention also provides a diamond grinding wheel prepared by the above method, wherein a stepped reaction layer exists at the diamond-binder interface, and the reaction layer is generated by the reaction between the rare earth additive and the diamond interface during the S4 sintering process, comprising: The inner layer is specifically a lanthanum carbide / cerium carbide compound layer generated by in-situ reaction of rare earth additives, with a thickness of 50-100 nm; The outer layer is specifically a (iron, cobalt, chromium)-carbon-lanthanum / cerium solid solution layer formed by the coordinated infiltration of rare earth additives with a core-shell structure and metals, with a thickness of 150-250nm.

[0014] Preferably, there is a multi-level pore structure in the binder, the primary pores are the gaps between hexagonal boron nitride sheets, with a size of 2-5 μm, the secondary pores are directional channels formed by the decomposition of the pore-forming agent, with a size of 20-50 μm, and the tertiary pores are carbon nanofiber extraction holes, with a size of 0.1-0.5 μm.

[0015] Preferably, the protrusion of the abrasive grains on the outer edge of the working layer of the diamond grinding wheel is 25-35% higher than that of the inner layer, the gradient change rate of the abrasive grain spacing is 5-8% / mm, and the density of the working layer of the grinding wheel is gradient distributed, with the outer layer density being 4.5-5.0 g / cm³ and the inner layer density being 3.5-4.0 g / cm³; The edge of the working layer of the diamond grinding wheel is provided with a gradient strengthening zone with a width of 1-3 mm. In this zone, the metal phase content gradient increases to 65-75%, and the diamond concentration gradient increases to 80-90%.

[0016] The technical effects and advantages of the present invention are as follows: The present invention adopts a gradient charging process to form a unique concentration and density gradient distribution in the working layer of the diamond grinding wheel. The high-concentration abrasive grains in the outer layer ensure efficient cutting, while the low-density structure in the inner layer improves chip removal and heat dissipation performance. At the same time, the precise control of the gradient change rate of the abrasive grain spacing and the amount of abrasive grain protrusion ensures that the grinding wheel always remains sharp during the grinding process. Compared with traditional uniform structure grinding wheels, the grinding efficiency is significantly improved, the processing time is effectively shortened, and the production efficiency is improved. The present invention adds a rare earth additive to the composite binder. After spark plasma sintering, a stepped reaction layer of a lanthanum carbide / cerium carbide compound layer and a solid solution layer is formed at the diamond-binder interface, greatly enhancing the interfacial bonding strength between the diamond abrasive grains and the binder. The multi-level pore structure and edge reinforcement zone design in the binder further optimize stress distribution and reduce abrasive grain shedding. Compared with grinding wheels without rare earth additives, the service life is greatly extended, effectively reducing the cost of use. The present invention forms a synergistic effect with the gradient charging and rare earth modification processes through precise particle size matching of the metal phase, ceramic phase, reinforcing phase and rare earth additives, giving the grinding wheel excellent comprehensive performance. It has good toughness while maintaining high hardness and wear resistance, and can meet the needs of efficient grinding of high-hardness materials such as cemented carbide. It broadens the application field of the grinding wheel and has broad application prospects in industries such as mechanical processing and precision manufacturing. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is the overall flow chart of the present invention. DETAILED DESCRIPTION

[0018] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention. Example 1

[0019] This embodiment provides a method for preparing a diamond grinding wheel using a binder doped with a rare earth material, which specifically includes the following steps: S1. Pretreatment of diamond abrasive grains: Plating the diamond abrasive grains in a chemical plating solution containing 20 parts of a nickel ion source, 25 parts of a reducing agent, sodium hypophosphite, 4 parts of a rare earth compound having a molar ratio of lanthanum nitrate to cerium chloride of 1:0.5, and 15 parts of a complexing agent, sodium citrate, at 80° C. and a pH value of 8.5 to obtain a nickel-phosphorus-rare earth composite layer having a rare earth element content of 1.0 wt% and a coating thickness of 0.5 μm; S2. Preparation of composite binder: 60% metal phase, 25% ceramic phase, 3% reinforcement phase and 0.3% rare earth additive are mixed by weight. Specifically: The metal phase is iron-cobalt-chromium alloy powder, wherein iron:cobalt:chromium = 4:2:1, and the particle size is 10 μm; The ceramic phase is a mixture of hexagonal boron nitride and nano-alumina in a ratio of 6:2. The hexagonal boron nitride flakes have a diameter of 5 μm and a thickness of 0.2 μm, and the nano-alumina particle size is 30 nm. The reinforcement phase is carbon nanofiber with an aspect ratio of 20; The rare earth additive is a nano core-shell structure with a lanthanum oxide core and a cerium oxide shell, with a core diameter of 150nm and a shell thickness of 30nm; S3, gradient loading, using centrifugal magnetic control assembly, centrifugal speed 2000rpm, magnetic field strength 0.5T, arrange the treated diamond abrasive and composite binder, the working layer concentration is 70% in the outer layer, 45% in the inner layer, and the transition zone concentration continuously decreases; S4: Spark plasma sintering (SPS) was performed in a three-stage vacuum sintering process using a pulsed current mode (pulse frequency 50 Hz, on-off ratio 8:2, peak voltage 3 V, current density 100 A / cm²). The interface activation stage was at 400°C, 50 MPa, and 10 minutes; the ceramic skeleton formation stage was at 650°C, 75 MPa, and 5 minutes; and the metal infiltration stage was at 800°C, 25 MPa, and 3 minutes. During sintering, an argon-hydrogen mixed gas (Ar:H2 = 95:5, flow rate 10 mL / min) was introduced. After metal infiltration, the temperature was lowered at 8°C / min to 300°C and naturally cooled. Example 2

[0020] This embodiment provides a method for preparing a diamond grinding wheel using a binder doped with a rare earth material, which specifically includes the following steps: S1. Pretreatment of diamond abrasive grains: Plating the diamond abrasive grains in a chemical plating solution containing 25 parts of a nickel ion source, 30 parts of a reducing agent, sodium hypophosphite, 6 parts of a rare earth compound having a molar ratio of 1:1 between lanthanum nitrate and cerium chloride, and 20 parts of a complexing agent, sodium citrate. Plating was performed at 85° C. and a pH value of 9.0 to obtain a nickel-phosphorus-rare earth composite layer having a rare earth element content of 1.8 wt % and a coating thickness of 0.9 μm. S2. Preparation of composite binder: 65% metal phase, 30% ceramic phase, 4% reinforcement phase and 0.5% rare earth additive are mixed by weight. Specifically: The metal phase is iron-cobalt-chromium alloy powder, wherein iron:cobalt:chromium = 5:3:2, and the particle size is 12 μm; The ceramic phase is a mixture of hexagonal boron nitride and nano-alumina in a ratio of 7:3. The hexagonal boron nitride flakes have a diameter of 12 μm and a thickness of 0.6 μm, and the nano-alumina particle size is 50 nm. The reinforcement phase is carbon nanofiber with an aspect ratio of 25; The rare earth additive is a nano-core-shell structure with a lanthanum oxide core and a cerium oxide shell, with a core diameter of 200nm and a shell thickness of 45nm; S3, gradient loading, using centrifugal magnetic control assembly, centrifugal speed 2500rpm, magnetic field strength 0.8T, arrange the treated diamond abrasive and composite binder, the working layer concentration is 75% in the outer layer, 50% in the inner layer, and the transition zone concentration decreases continuously; S4: Spark plasma sintering (SPS) was performed in a three-stage vacuum sintering process using a pulsed current mode (pulse frequency 80 Hz, on-off ratio 8.5:1.5, peak voltage 4 V, current density 120 A / cm²). The interface activation stage was set at 450°C, 55 MPa, and 10 minutes; the ceramic skeleton formation stage was set at 680°C, 80 MPa, and 5 minutes; and the metal infiltration stage was set at 830°C, 30 MPa, and 3 minutes. During sintering, a protective gas mixture of argon and hydrogen (Ar:H2 = 95:5, flow rate 15 mL / min) was introduced. After metal infiltration, the temperature was lowered at a rate of 10°C / min to 300°C with natural cooling. Example

[0021] This embodiment provides a method for preparing a diamond grinding wheel using a binder doped with a rare earth material, which specifically includes the following steps: S1. Pretreatment of diamond abrasive grains: Plating the diamond abrasive grains in a chemical plating solution containing 30 parts of a nickel ion source, 35 parts of a reducing agent, sodium hypophosphite, 8 parts of a rare earth compound having a molar ratio of lanthanum nitrate to cerium chloride of 1:1.5, and 25 parts of a complexing agent, sodium citrate, at 90° C. and a pH of 9.5 to obtain a nickel-phosphorus-rare earth composite layer having a rare earth element content of 2.5 wt % and a coating thickness of 1.2 μm; S2. Preparation of composite binder: 70% metal phase, 35% ceramic phase, 5% reinforcement phase and 0.8% rare earth additive are mixed by weight. Specifically: The metal phase is iron-cobalt-chromium alloy powder, wherein iron:cobalt:chromium = 6:4:3, particle size 15μm; The ceramic phase is a mixture of hexagonal boron nitride and nano-alumina in the ratio of 8:4. The hexagonal boron nitride flakes have a diameter of 20 μm and a thickness of 1 μm, and the nano-alumina particle size is 80 nm. The reinforcement phase is carbon nanofiber with an aspect ratio of 30; The rare earth additive is a nano-core-shell structure with a lanthanum oxide core and a cerium oxide shell, with a core diameter of 250nm and a shell thickness of 60nm; S3, gradient loading, using centrifugal magnetic control assembly, centrifugal speed 3000rpm, magnetic field strength 1.2T, arrange the treated diamond abrasive and composite binder, the working layer concentration is 80% in the outer layer, 55% in the inner layer, and the transition zone concentration continuously decreases; S4: Spark plasma sintering (SPS) was performed in a three-stage vacuum sintering process using a pulsed current mode (pulse frequency 100 Hz, on-off ratio 9:1, peak voltage 5 V, current density 150 A / cm²). The sintering temperature was 500°C, 60 MPa, and 12 minutes for the interface activation stage; 700°C, 85 MPa, and 6 minutes for the ceramic skeleton formation stage; and 850°C, 35 MPa, and 4 minutes for the metal infiltration stage. During sintering, an argon-hydrogen mixed gas (Ar:H2 = 95:5, flow rate 20 mL / min) was introduced. After metal infiltration, the temperature was lowered at a rate of 12°C / min to 300°C and then naturally cooled.

[0022] Comparative Example 1 This embodiment provides a method for preparing a diamond grinding wheel using a binder doped with a rare earth material, which specifically includes the following steps: S1, diamond abrasive pretreatment, the specific steps are the same as those in Example 1; S2. Preparation of composite binder, the specific steps are the same as those in Example 1; S3, gradient charging, using a common mixing method without gradient arrangement, uniformly mixing the treated diamond abrasive grains and the composite binder, with a working layer concentration of 60%, and other conditions being the same as in Example 1; S4: Spark plasma sintering. The specific steps are the same as those in Example 1.

[0023] Comparative Example 2 This embodiment provides a method for preparing a diamond grinding wheel using a binder doped with a rare earth material, which specifically includes the following steps: S1, diamond abrasive pretreatment, the specific steps are the same as those in Example 1; S2. Preparation of composite binder: the ratio and parameters of metal phase, ceramic phase and reinforcement phase are the same as those in Example 1, but the rare earth additive is deleted and the proportion of metal phase is adjusted to 60.3%; S3, gradient loading, the specific steps are the same as in Example 1 The diamond grinding wheels prepared in Examples 1-3 and Comparative Examples 1-2 were subjected to performance tests respectively, and the test methods were as follows: Abrasive particle distribution and density detection: Use an electron microscope to observe the distribution of abrasive particles at different positions of the working layer, and measure the protrusion and spacing of the abrasive particles; use a density meter to measure the density of the outer layer, inner layer and transition zone of the working layer; Pore ​​structure analysis: Scanning electron microscopy was used to observe the pore structure in the binder and measure the pore size and distribution at each level; Edge strengthening zone detection: Use an energy spectrum analyzer to detect the metal phase and diamond concentration distribution in the edge strengthening zone and measure the width of the strengthening zone; Mechanical properties test: Hardness is measured by Rockwell hardness tester, impact toughness is tested by impact tester; flexural strength and elastic modulus are measured by universal material testing machine; Grinding performance test: Under the same grinding conditions (workpiece material is cemented carbide, the same grinding equipment), the grinding ratio, grinding efficiency, self-sharpening index and abrasive shedding rate of the grinding wheel are tested.

[0024] After the above steps are tested, the specific results are shown in the following table: Example 1 Example 2 Example 3 Comparative Example 1 (no gradient charging) Comparative Example 2 (without rare earth additive) Outer edge abrasive protrusion ratio 25% 28% 32% 10% 15% Grain spacing gradient change rate 5% / mm 6.5% / mm 7.8% / mm No gradient 3% / mm Outer layer density (g / cm³) 4.5 4.7 5.0 4.0 3.8 Inner layer density (g / cm³) 3.5 3.7 4.0 3.8 3.6 Primary pore size (μm) 2 - 5 2 - 5 2 - 5 2 - 5 2 - 5 Secondary pore size (μm) 20 - 50 20 - 50 20 - 50 20 - 50 20 - 50 Tertiary pore size (μm) 0.1 - 0.5 0.1 - 0.5 0.1 - 0.5 0.1 - 0.5 0.1 - 0.5 Edge reinforcement area width (mm) 1 2 3 No obvious enhanced area 0.5 Metal phase content in strengthening zone 65% 70% 75% - 60% Diamond concentration in the strengthening area 80% 85% 90% - 70% Rockwell hardness (HRB) 95 100 105 6 88 Impact toughness (J / cm²) 8 10 12 85 7 Flexural strength (MPa) 300 380 450 250 260 Elastic modulus (GPa) 180 220 250 160 170 Grinding ratio 1500 1800 2000 800 900 Grinding efficiency (mm³ / mm・s) 80 90 100 50 55 Self-sharpening index 0.8 1.0 1.2 0.5 0.6 Abrasive shedding rate 5% 4% 3% 12% 10% From the above table data, we can see that: In Examples 1-3, the protrusion of the outer edge of the working layer is 25%-32% higher than that of the inner layer, the gradient change rate of the abrasive spacing is 5%-7.8% / mm, the outer layer density is 4.5-5.0 g / cm³, and the inner layer density is 3.5-4.0 g / cm³, forming a clear gradient distribution. In contrast, the abrasive particles in Comparative Example 1 are evenly distributed, with only 10% protrusion at the outer edge and no density gradient (4.0 g / cm³ in the outer layer and 3.8 g / cm³ in the inner layer), indicating that the gradient loading directly affects the arrangement and density distribution of the abrasive particles. Examples 1-3 have edge reinforcement zone widths of 1-3 mm, metal phase content of 65%-75%, diamond concentration of 80%-90%, Rockwell hardness of 95-105, and flexural strength of 300-450 MPa, while Comparative Example 1 has no obvious reinforcement zone, hardness of 85 HRB, and flexural strength of 250 MPa, indicating that gradient charging is the core process for forming edge reinforcement structure and improving mechanical properties; Examples 1-3 have a grinding ratio of 1500-2000, a grinding efficiency of 80-100 mm³ / mm・s, a self-sharpening index of 0.8-1.2, and a grain shedding rate of 3%-5%, while Comparative Example 1 has a grinding ratio of 800, an efficiency of 50 mm³ / mm・s, and a grain shedding rate of 12%, verifying that gradient loading can significantly improve the cutting efficiency and durability of the grinding wheel; In Examples 1-3, a stepped reaction layer (lanthanum carbide / cerium carbide layer + solid solution layer) was formed at the diamond-binder interface, with an impact toughness of 8-12 J / cm² and an elastic modulus of 180-250 GPa. In Comparative Example 2, there was no reaction layer, with an impact toughness of 7 J / cm² and an elastic modulus of 170 GPa. This indicates that rare earth participates in the interfacial reaction, enhancing the toughness and stiffness of the binder. The grinding ratio of Examples 1-3 increased from 1500 to 2000 with the increase of rare earth content (0.3%-0.8%), the self-sharpening index increased from 0.8 to 1.2, and the abrasive grain shedding rate decreased to 3%. In contrast, the grinding ratio of Comparative Example 2 was 900, the self-sharpening index was 0.6, and the shedding rate was 10%, indicating that the rare earth additive optimizes the self-sharpening and anti-shedding ability of the grinding wheel by regulating the interface bonding strength.

[0025] In summary, gradient charging is the key process for achieving abrasive / density gradient distribution and forming edge reinforcement zone, which directly determines the grinding efficiency and impact resistance of the grinding wheel. Rare earth additives form a strengthening layer by participating in the interface reaction, significantly improving the mechanical properties of the binder and the grinding ratio of the grinding wheel, and reducing the abrasive grain shedding rate. Compared with traditional uniform charging or rare earth-free formula, the grinding ratio of the grinding wheel of the present invention is increased by 50%-150%, and the abrasive grain shedding rate is reduced by 50%-75%, which proves the synergistic effect of gradient design and rare earth modification.

[0026] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a diamond grinding wheel using a binder doped with a rare earth material, characterized in that: The specific steps include: S1, pre-treating diamond abrasive grains, chemically plating a nickel-phosphorus-rare earth composite layer on the diamond surface, wherein the rare earth element content in the composite layer is 1.0-2.5wt% and the coating thickness is 0.5-1.2μm; S2. Preparation of composite binder: Mix the following components by weight: The metal phase is 60-70%, specifically iron-cobalt-chromium alloy powder, wherein iron:cobalt:chromium = 4-6:2-4:1-3; The ceramic phase is 25-35%, specifically a mixture of hexagonal boron nitride and nano-alumina in a ratio of 6-8:2-4; 3-5% reinforcement phase, specifically carbon nanofibers with an aspect ratio greater than 15; Rare earth additives 0.3-0.8%, specifically a nano core-shell structure composed of lanthanum oxide as the core and cerium oxide as the shell, with a core diameter of 150-250nm and a shell thickness of 30-60nm; S3, gradient loading, arranging the diamond abrasives treated in step S1 and the composite binder prepared in step S2 according to a concentration gradient, with the outer working layer concentration being 70-80%, the inner layer concentration being 45-55%, and the transition zone concentration decreasing continuously from the outer layer to the inner layer; S4, spark plasma sintering, is to perform three-stage temperature-controlled sintering on the mixture after gradient loading in step S3 under a vacuum environment, specifically including: Interface activation stage, temperature is 300-500℃, applied pressure is 50-60MPa, time is 8-12min; During the ceramic skeleton formation stage, the temperature is 600-700°C, the applied pressure is 75-85 MPa, and the temperature is 4-6 min; During the metal infiltration stage, the temperature is 750-850°C, the applied pressure is 25-35 MPa, and the temperature is 2-4 minutes.

2. The method for preparing a diamond grinding wheel using a rare earth material-doped binder according to claim 1, wherein: The chemical plating solution in step S1 comprises the following components in parts by weight: 20-30 parts of a nickel ion source, 25-35 parts of a reducing agent, sodium hypophosphite, 4-8 parts of a rare earth compound, wherein the molar ratio of lanthanum nitrate to cerium chloride is 1:0.5-1.5, and 15-25 parts of a complexing agent, sodium citrate; The plating temperature is 80-90°C and the pH value is 8.5-9.

5.

3. The method for preparing a diamond grinding wheel using a rare earth material-doped binder according to claim 2, wherein: In step S2, the particle size of the iron-cobalt-chromium alloy powder in the metal phase is ≤15 μm, the diameter of the hexagonal boron nitride flakes in the ceramic phase is 5-20 μm and the thickness is 0.2-1 μm, and the particle size of the nano-alumina is 30-80 nm.

4. The method for preparing a diamond grinding wheel using a rare earth material-doped binder according to claim 3, wherein: The preparation method of the rare earth additive in step S2 is: Lanthanum nitrate solution is co-precipitated with a precipitant to generate a lanthanum hydroxide core, and then a cerium oxide shell is coated on the core surface by a hydrothermal method at a calcination temperature of 450-550° C. The precipitant includes but is not limited to ammonia water, potassium hydroxide and sodium hydroxide.

5. The method for preparing a diamond grinding wheel using a rare earth material-doped binder according to claim 4, wherein: In step S3, centrifugal magnetic control assembly is used to achieve gradient arrangement, with a centrifugal speed of 2000-3000 rpm and a magnetic field strength of 0.5-1.2T.

6. The method for preparing a diamond grinding wheel using a rare earth material-doped binder according to claim 5, wherein: In step S4, spark plasma sintering adopts a pulse current mode with a pulse frequency of 50-100 Hz, an on-off ratio of 8:2-9:1, a peak voltage of 3-5 V, and a current density of 100-150 A / cm²; During the sintering process, a mixed protective gas of argon and hydrogen was introduced, wherein the ratio of argon to hydrogen was 95:5 and the gas flow rate was 10-20 mL / min. After the metal infiltration stage is completed, the temperature is lowered to 300°C at a rate of 8-12°C / min and then cooled naturally.

7. The method for preparing a diamond grinding wheel using a rare earth material-doped binder according to claim 6, wherein: In the composite binder of step S2, the particle sizes of the metal phase, ceramic phase, reinforcement phase and rare earth additive must satisfy the following coordination relationship: Metal phase and ceramic phase: The average particle size of the metal phase is 1.4-3.3 times the average particle size of the ceramic phase; Ceramic phase and reinforcement phase: The average particle size of the ceramic phase is 200-400 times the diameter of the reinforcement phase carbon nanofiber; Rare earth additives and metal phase: The average particle size of the rare earth additive cannot exceed one tenth of the average particle size of the metal phase.

8. A diamond grinding wheel prepared by the method according to claim 7, characterized in that: There is a stepped reaction layer at the diamond-binder interface. This reaction layer is generated by the reaction between the rare earth additive and the diamond interface during the S4 sintering process, including: The inner layer is specifically a lanthanum carbide / cerium carbide compound layer generated by in-situ reaction of rare earth additives, with a thickness of 50-100 nm; The outer layer is specifically a (iron, cobalt, chromium)-carbon-lanthanum / cerium solid solution layer formed by the coordinated infiltration of rare earth additives with a core-shell structure and metals, with a thickness of 150-250nm.

9. The diamond grinding wheel according to claim 8, characterized in that: There is a multi-level pore structure in the binder. The primary pores are the gaps between hexagonal boron nitride sheets, with a size of 2-5 μm. The secondary pores are directional channels formed by the decomposition of the pore-forming agent, with a size of 20-50 μm. The tertiary pores are the carbon nanofiber extraction holes, with a size of 0.1-0.5 μm.

10. The diamond grinding wheel according to claim 9, characterized in that: The protrusion of the abrasive grains on the outer edge of the working layer of the diamond grinding wheel is 25-35% higher than that on the inner layer, and the gradient change rate of the abrasive grain spacing is 5-8% / mm. The density of the working layer of the grinding wheel is gradient distributed, with the outer layer density being 4.5-5.0g / cm³ and the inner layer density being 3.5-4.0g / cm³. The edge of the working layer of the diamond grinding wheel is provided with a gradient strengthening zone with a width of 1-3 mm. In this zone, the metal phase content gradient increases to 65-75%, and the diamond concentration gradient increases to 80-90%.

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