A method for preparing diamond abrasives with a microcrystalline glass bond resistant to pure water corrosion

Abstract

This invention relates to the field of diamond abrasive technology and discloses a method for preparing diamond abrasives with a microcrystalline glass bond resistant to pure water corrosion. The method involves surface activation pretreatment of diamond micropowder to obtain activated diamond micropowder; coating the activated diamond micropowder with amorphous silica to obtain pretreated diamond micropowder; uniformly mixing the microcrystalline glass bond, pretreated diamond micropowder, and binder, followed by pressing to obtain a molded blank; and then subjecting the molded blank to gradient sintering to obtain the microcrystalline glass bonded diamond abrasive. The microcrystalline glass bond of this invention is an alkali-free formulation, which effectively improves the water and acid resistance of the composite material. Through reasonable component formulation, a high degree of compatibility with the thermal expansion coefficient of diamond is achieved, enhancing the dimensional and thermal stability of the grinding wheel during the grinding process.

Description

Technical Field

[0001] This invention relates to the field of diamond abrasive technology, and in particular to a method for preparing diamond abrasives using a microcrystalline glass bond resistant to pure water corrosion. Background Technology

[0002] Currently, diamond grinding wheels face a serious bottleneck in corrosion resistance during precision grinding applications in ultrapure water environments, such as those used for semiconductor silicon wafers and optical glass. Existing diamond grinding wheel bonding systems mainly include resin bonds, metal bonds, and traditional ceramic bonds, all of which exhibit significant defects in resistance to pure water corrosion. While resin bonds have low preparation temperatures and good self-sharpening properties, their poor corrosion resistance makes them prone to hydrolysis and swelling in pure or ultrapure water, leading to a sharp drop in strength and failing to meet the requirements for long-life grinding. Metal bonds, although possessing higher strength, are susceptible to electrochemical corrosion in pure water environments, with interfacial corrosion significantly reducing the holding force on diamond abrasive grains and increasing the abrasive grain shedding rate. Traditional ceramic bonds (silicate and borosilicate glass systems) offer good heat resistance, but generally contain alkali metal components (Na₂O₃). + K + Li + In a pure water environment, alkali metal ions are easily dissolved, which can cause hydrolysis of the glass network and loss of crystal phase, resulting in low binder strength retention and insufficient corrosion resistance life.

[0003] Microcrystalline glass binders, due to their precisely controllable coefficient of thermal expansion, excellent mechanical properties, and highly stable chemical properties, have become an indispensable core material system in high-performance diamond grinding wheels. However, existing microcrystalline glass binders still have the following problems: 1. Insufficient resistance to pure water corrosion. Traditional alkali metal-containing microcrystalline glass binders (containing Li₂O, Na₂O, K₂O, etc.) in ultrapure water environments react with alkali metal ions (Na₂O, Na₂O, K₂O, etc.). + K + Li + [SiO4] readily dissolves from the glass network, leading to hydrolytic destruction of the glass network structure, breakage of the [SiO4] network, loss of crystalline phases, and increased binder porosity. This results in decreased interfacial bonding strength and diamond abrasive grain shedding. While existing surface coating technologies can partially mitigate corrosion, they suffer from weak interfacial bonding between the coating and the substrate, complex processes, high costs, and inability to block OH groups. - Problems such as corrosion of the glass itself.

[0004] 2. The preparation process involves high temperatures, high energy consumption, and severe damage to the diamond. Traditional microcrystalline glass binders are generally prepared using a process of "high-temperature melting (>1400℃) + dry grinding + high-temperature sintering (>900℃)," resulting in low powder refinement efficiency and a wide particle size distribution (D). 90Diamond abrasives with a diameter >5 µm have poor activity, high energy consumption, and long cycle time. Furthermore, high-temperature sintering can easily lead to thermal damage to diamond abrasive grains (graphitization rate >10%), which severely restricts the long-life and high-reliability grinding applications of grinding wheels in ultrapure water environments.

[0005] 3. Uneven distribution of passivation elements and difficulty in constructing corrosion-resistant barriers. In traditional processes, passivating elements such as Cr and V are uniformly distributed in the glass matrix, making it difficult to form an enriched layer on the surface and thus unable to effectively block OH. - Penetration pathway. Even with the addition of corrosion-resistant elements, they disperse in the bulk phase due to the lack of directional migration driving force, resulting in low corrosion resistance efficiency.

[0006] Therefore, there is an urgent need for a method to prepare diamond abrasives using a microcrystalline glass bond resistant to pure water corrosion in order to solve the above-mentioned technical problems. Summary of the Invention The purpose of this invention is to address the above-mentioned technical problems by proposing a method for preparing microcrystalline glass-bonded diamond abrasives resistant to pure water corrosion. This method achieves its purpose through synergistic optimization of component design and process innovation: a one-step low-temperature precipitation of magnesium aluminum spinel crystal phase, simultaneously improving corrosion resistance and high hardness and strength mechanical load-bearing capacity; and in-situ construction of a surface passivation barrier, where Cr2O3 reacts with water to form a dense CrO(OH)2 passivation film, blocking OH... - Permeation; diamond pretreatment activation, gradient sintering process optimization, blocking OH in ultrapure water - Eroding and reinforcing the interface.

[0007] To achieve the above objectives, the present invention is implemented according to the following technical solution: A method for preparing a diamond abrasive tool with a microcrystalline glass bond resistant to pure water corrosion, comprising the following steps: S1, Diamond surface pretreatment Diamond micro powder is subjected to surface activation pretreatment to obtain activated diamond micro powder; amorphous silica is then coated on the activated diamond micro powder to obtain pretreated diamond micro powder. S2, Mixing and Molding The microcrystalline glass binder, pretreated diamond powder, and adhesive are mixed evenly and then pressed into shape to obtain a molded blank. The microcrystalline glass binder comprises the following components in the indicated mass percentages: SiO2 45-60%, Al2O3 5-15%, MgO 8-12%, B2O3 1-9%, P2O5 1-6%, V2O5 1-5%, Bi2O3 5-8%, Cr2O3 1-10%, Y2O3 2-3%, TiO2 2-4%, ZrO2 1-3%; S3, gradient sintering The preform is subjected to gradient sintering, and after sintering, a microcrystalline glass-bonded diamond abrasive is obtained.

[0008] Preferably, the surface activation pretreatment process in step S1 is as follows: 0.5~1 µm diamond micropowder is ultrasonically treated at 60°C for 30 min in a mixed acid with a volume ratio of concentrated HNO3:concentrated H2SO4 of 1:3; washed with deionized water until neutral; and dried at 80°C for 4 h to obtain activated diamond micropowder.

[0009] Preferably, the coating process in step S1 is as follows: using tetraethyl orthosilicate (TEOS) as the silicon source, ammonia water is used to catalyze hydrolysis and condensation to generate an amorphous SiO2 shell in situ on the diamond surface.

[0010] Specifically, the diamond surface pretreatment process in step S1 is as follows: S1.1 Select 0.5~1 µm diamond micro powder for surface activation pretreatment: Diamond micro powder was added to a mixed acid and ultrasonically treated at 60°C for 30 min to remove surface impurities and graphite layer; it was then washed with deionized water until neutral and dried at 80°C for 4 h to obtain activated diamond micro powder. The mass-to-volume ratio of diamond micron powder to mixed acid is 1:10 (the unit of mass-to-volume ratio is g:mL). The mixed acid includes 65-68% nitric acid and 98% sulfuric acid by mass fraction, and the volume ratio of 65-68% nitric acid to 98% sulfuric acid is 1:3 (the unit of volume ratio is mL:mL).

[0011] S1.2 The activated diamond micropowder is modified by coating it with amorphous silica (SiO2) using the sol-gel method: The raw materials for this process are: 5g of diamond micro powder obtained in step S1.1, 5~6mL of tetraethyl orthosilicate (TEOS) as the silicon source, 100mL of anhydrous ethanol as the dispersion medium, 15mL of deionized water, and 4~6mL of ammonia (25~28%) as the catalyst. The reaction process is as follows: 100 mL of anhydrous ethanol, 15 mL of deionized water, 4-6 mL of 25-28% ammonia water and 5-6 mL of tetraethyl orthosilicate are added sequentially to 5 g of diamond micropowder obtained in step S1.1. After ultrasonic dispersion for 20-30 min, the mixture is stirred at a constant temperature of 25-30℃ for 6-12 h. Then, the mixture is allowed to stand at room temperature for 12-24 h to allow the sol to fully gel. The mixture is then separated by centrifugation at 8000-10000 r / min and washed sequentially with anhydrous ethanol and deionized water until the system is neutral. The resulting powder is then vacuum dried at 60-90℃ for 6-12 h. Finally, the mixture is heat-treated by heating to 400-500℃ at a rate of 2-5℃ / min and holding for 1-3 h. After cooling in the furnace, the powder is sieved and dispersed to obtain diamond micropowder uniformly coated with silica, which is the pretreated diamond micropowder.

[0012] The process involves coating amorphous silica using a sol-gel method under ammonia catalysis. After thorough dispersion and hydrolysis-condensation reaction, a uniform amorphous SiO2 shell is generated in situ on the surface of the diamond particles, thus completing the diamond pretreatment.

[0013] The SiO2 coating layer resolves thermal expansion mismatch, provides chemical bonding sites, and effectively protects diamond from oxidation / corrosion. Simultaneously, the use of a microcrystalline glass binder in the sintering process not only significantly improves the contact tightness between diamond particles and the binder, but also further enhances the interfacial bonding force through optimized surface treatment and sintering processes, thereby effectively improving the overall performance and service life of the final composite material.

[0014] Preferably, in step S2, the mass-to-volume ratio of the microcrystalline glass binder, the pretreated diamond powder, and the adhesive is (0.9~2):(1~2.1):2, with the comparison unit being g:g:mL, wherein the adhesive is a 3~5 wt.% PVA solution.

[0015] Preferably, the total amount of B2O3, P2O5, and V2O5 in step S2 accounts for 10-16% of the total amount of the microcrystalline glass binder.

[0016] Specifically, the mixing and molding process in step S2 is as follows: The microcrystalline glass binder, pretreated diamond powder, and binder are mixed and then mixed in a planetary ball mill for 2 hours to obtain a green body mixture. The green body mixture is then pressed into a molded green body. The mass-volume ratio of the microcrystalline glass binder, pretreated diamond powder, and adhesive is (0.9~2):(1~2.1):2, with the comparison unit being g:g:mL, wherein the adhesive is a PVA solution with a concentration of 3~5 wt.%.

[0017] Preferably, the mixture is dry-pressed under a pressure of 30~35MPa, and the pressed sample is taken out after holding the pressure for 90~120s to obtain the molded blank.

[0018] Specifically, the prepared preform can be a 4mm×3.4mm×2.7mm strip sample or a Φ30mm×5mm round sample.

[0019] Preferably, the gradient sintering process in step S3 is as follows: in the first stage, the temperature is raised from room temperature to 600°C at a rate of 4-5°C / min; in the second stage, the temperature is raised from 600°C to the sintering temperature at a rate of 8-10°C / min; the sintering temperature is 750-1050°C; the temperature is held at the sintering temperature for 50-60 min; and the temperature is cooled to room temperature with the furnace after the holding period.

[0020] Specifically, the gradient sintering process in step S3 is as follows: The formed preform is placed in an alumina crucible and subjected to a gradient sintering process. The first stage involves heating from room temperature to 600℃ at a rate of 5℃ / min; the second stage involves heating from 600℃ to the sintering temperature at a rate of 8-10℃ / min. The sintering temperature is 750-1050℃, and the holding time is 50-60 min. The preform is then cooled to room temperature in the furnace. The sintering process completes densification and crystallization in a single step, eliminating the need for secondary crystallization treatment. Simultaneously, it promotes the migration and enrichment of B / P / Cr to the surface, thereby enhancing corrosion resistance.

[0021] This invention involves diamond micron powder particles → surface activation pretreatment → alkali-free microcrystalline glass binder diamond abrasive → sintering densification to form a corrosion-resistant barrier.

[0022] Preferably, the preparation method of the microcrystalline glass binder includes the following steps: St1, Raw material weighing and mixing Weigh each component raw material according to the proportion, wet grind and mix to obtain a mixture; after drying, the mixture is obtained as a dried mixture. St2, Melting and Water Quenching The dried mixture is heated to obtain a uniform melt; the melt is quickly poured into room temperature deionized water for water quenching to obtain glass fragments; the glass fragments are then dried and crushed to obtain dried glass fragments. St3, pre-calcined wet milling and refining After drying, the glass fragments are pre-fired at 350~400℃ for 1.5~2 h, and then wet-milled. The product obtained after wet milling is dried to obtain a microcrystalline glass binder.

[0023] Preferably, in step St1, the wet grinding medium is anhydrous ethanol; during the wet grinding process, the mass ratio of grinding balls:material:anhydrous ethanol is (2~3):1:1, the wet grinding speed is 200 rpm, and the wet grinding time is 2 h.

[0024] Specifically: When the ratio of grinding balls to material is 3:1, large grinding balls are used; including: 10mm grinding balls accounting for 10~30 wt.%, 8mm grinding balls accounting for 20~30 wt.%, and 5mm grinding balls accounting for 50~70 wt.%.

[0025] Grinding balls: The ratio of material to grinding balls is (2~2.5):1. Medium-sized grinding balls are used, including: 10~20 wt.% of 5mm grinding balls, 10~30 wt.% of 3mm grinding balls, and 60~80 wt.% of 1mm small grinding balls. You can choose grinding balls that are commonly used in this field, such as zirconia grinding balls or alumina grinding balls.

[0026] Preferably, in step St2, the heating process is as follows: the dried mixture is heated to 800°C at 5°C / min and held for 30 min; then heated to 1200-1250°C at 8-10°C / min and held for 1-1.5 h; then heated to 1380-1450°C at 12-15°C / min and held for 1.5-2.5 h to obtain a uniform melt.

[0027] Preferably, in step St3, the wet grinding medium is deionized water; during the wet grinding process, the mass ratio of grinding balls:material:deionized water is 3:1:1.5; the wet grinding speed is 200~250 rpm, and the wet grinding time is 1~1.5 h; the D of the microcrystalline glass binder... 90 ≤0.5 µm.

[0028] Specifically, the preparation method of the microcrystalline glass binder includes the following steps: St1, Raw material weighing and mixing The raw materials (analytical grade oxides) of each component were accurately weighed according to the proportions. They were then wet-milled using anhydrous ethanol as the medium in a planetary ball mill (the wet milling medium was anhydrous ethanol; during the wet milling process, the mass ratio of milling balls:material:anhydrous ethanol was (2~3):1:1, the wet milling speed was 200 rpm, and the wet milling time was 2 h) to obtain a mixture. After drying the mixture at 80℃ for 6 h, it was passed through a 100-mesh sieve to obtain the dried mixture for later use.

[0029] St2, Melting and Water Quenching The dried mixture was placed in a platinum crucible and heated to 800°C at 5°C / min, held for 30 min to remove residual moisture and organic matter. The temperature was then increased to 1200-1250°C at 10°C / min and held for 1-1.5 h to complete the initial melting of the oxides. The temperature was then increased to 1380-1450°C at 12-15°C / min and held for 1.5-2.5 h to obtain a homogeneous melt. The melt was then rapidly poured into deionized water at room temperature for less than 5 s to obtain glass fragments, ensuring the formation of a completely amorphous glass. Subsequently, the glass fragments were dried at 80°C for 6-8 h, pulverized using a pulverizer, and passed through a 200-mesh sieve to obtain dried glass fragments for later use.

[0030] St3, pre-calcined wet milling and refining After drying, the glass fragments are pre-fired at 350~400℃ for 1.5~2 hours to remove residual stress and adsorbed water; Pre-calcination wet milling was then performed: wet milling medium: deionized water; ball milling parameters: grinding balls:material:deionized water = 3:1:1.5, rotation speed 200~250 rpm, time 1 h; particle size control: D 90 Refine to ≤0.5 µm.

[0031] For grinding balls, any commonly used type in this field can be selected, such as agate balls. Pre-calcined wet milling improves the refining efficiency by 40% compared to direct wet milling, and significantly enhances the activity of the powder.

[0032] This invention addresses the insufficient corrosion resistance of diamond grinding wheels in ultrapure water environments by proposing an innovative comprehensive solution. It is the first to propose a technical route of "alkali-free high-polymer network + passivation element enrichment + diamond pretreatment + one-step low-temperature sintering." Through meticulous design and compositional control of the SiO2-Al2O3-MgO-B2O3-P2O5-V2O5-Bi2O3-Cr2O3-Y2O3-TiO2-ZrO2 multi-component system, a stable framework with a high degree of polymerization of [SiO4] as the main body is constructed, combined with [BO3]. - [PO4] - [VO4] - Multiple low-solubility functional units, such as [BiO6], work together to form a dense and chemically stable surface barrier layer. Simultaneously, the magnesium aluminum spinel (MgAl2O4) crystal phase precipitated from the microcrystalline glass binder significantly enhances corrosion resistance, thanks to its unique cubic crystal structure (O... 2- cubic packing, Mg 2+ Occupying tetrahedral interstitials, it can form a dense crystalline structure with good interfacial bonding with the glass matrix, improving chemical stability and exhibiting excellent mechanical properties. It is an ideal crystalline phase that effectively enhances the wear resistance and load-bearing capacity of glass-ceramics. In an ultrapure water environment, the Cr in the system... 3+ It can generate a dense passivation film of the CrO(OH)2 type in situ, effectively blocking OH. - The erosion and penetration pathways were investigated. Furthermore, by performing surface chemical activation pretreatment on the diamond abrasive to enhance its interfacial bonding with the binder, and employing a gradient sintering process, a corrosion-resistant microcrystalline glass binder was prepared, achieving a synergistic optimization between corrosion resistance and mechanical strength.

[0033] The technical solution adopted in this invention is as follows: Alkali-free formulation and crystal structure design: Alkali metal Li + / Na + Plasma disrupts the silicon-oxygen network, forming permeation channels and increasing the weight loss rate by 10 to 100 times. Through thermodynamic calculations and phase diagram analysis, it was determined that the binder components must meet the alkali-free eutectic characteristics. Based on this, a Cr-BPV-Bi enrichment layer was added to form a diffusion barrier, which reduced the ion leaching coefficient by 2 to 3 orders of magnitude. Furthermore, this formulation successfully precipitated magnesium aluminum spinel (MgAl2O4), a crystalline phase that is almost insoluble in pure water (solubility <10). -6 (mol / L).

[0034] ① Basic glass network forging: SiO2 content of 45~60 wt.% ensures the formation of a high degree of polymerization [SiO4] network, and Al2O3 is controlled at 5~15 wt.%. When Al2O3 < 5 wt.%, the network modification is insufficient and the chemical stability decreases; when Al2O3 > 15 wt.%, the proportion of [AlO6] octahedra increases, and Al-O bonds are easily hydrolyzed in pure water, becoming the corrosion initiation point.

[0035] ② Passivation elements and surface barrier construction: B2O3-P2O5-V2O5 (total 10~16 wt.%) forms a low-solubility composite network with a diffusion coefficient 1–2 orders of magnitude higher than that of the Si-O-Si network, preferentially migrating and enriching to the surface during sintering; Bi2O3 reduces surface tension, accelerating this migration process; Cr2O3 (1~10 wt.%) enriches on the surface and then undergoes in-situ oxidation upon contact with pure water to form a dense CrO(OH)2 film. These three elements synergistically construct a dual barrier of "low-solubility network + dense passivation film".

[0036] ③ Network modification and fluxing system: MgO is added as an intermediate oxide at a rate of 8-12 wt.% to adjust the coefficient of thermal expansion, lower the melting temperature, and react to generate magnesium aluminum spinel (MgAl2O4) crystal phase, thereby enhancing mechanical properties; TiO2 is added as a nucleating agent at a rate of 2-4 wt.% to lower the crystallization activation energy and promote the uniform precipitation of magnesium aluminum spinel and other crystal phases; ZrO2 is added as a nucleating agent and toughening phase at a rate of 1-3 wt.% to induce microcrack deflection and improve fracture toughness.

[0037] Mechanism of action: By precisely controlling the chemical composition and microstructure of the glass-ceramic, excellent thermal compatibility between it and diamond abrasive grains can be effectively achieved, significantly improving the service life and machining accuracy of the grinding wheel under high-speed and high-temperature environments. Simultaneously, this material exhibits outstanding mechanical strength and excellent wear resistance, further enhancing the operational stability and efficiency of the grinding wheel during heavy-duty, high-intensity grinding processes. Furthermore, the glass-ceramic binder possesses outstanding chemical corrosion resistance and strong oxidation resistance, enabling it to maintain stable performance over extended periods in various complex corrosive media such as acids and alkalis. This provides solid and reliable support for the widespread application of diamond tools in extremely harsh industrial environments. In summary, this advanced material system not only comprehensively optimizes the overall performance of diamond grinding wheels but also greatly expands their practical application range and development potential in high-precision, ultra-efficient machining fields. This invention addresses the following shortcomings in existing technologies: ① Alkali metal-containing formulations: Alkali metal ions dissolve in pure water, initiating network hydrolysis and resulting in short corrosion resistance life; ② High Al2O3 content (>15%): Easily forms [AlO6] octahedrons, becoming OH... -Attack sites accelerate corrosion; ③ Bulk distribution of passivating elements: unable to form a dense passivation film on the surface, OH - ④ High-temperature sintering process: Diamond graphitization is severe, abrasive thermal damage is large, and grinding wheel life is reduced; ⑤ Dry powder preparation: Powder activity is low, sintering temperature is high, and crystal phase control is difficult.

[0038] A novel approach is proposed to construct a multi-component system of SiO2-Al2O3-MgO-B2O3-P2O5-V2O5-Bi2O3-Cr2O3-Y2O3-TiO2-ZrO2 through synergistic innovation of alkali-free high-polymer network design and surface enrichment of passivating elements. This system utilizes SiO2 ≥ 45 wt.% to form a [SiO4] high-polymer network framework, with Al2O3 at 5~10 wt.% to avoid [AlO6] hydrolysis sites; and introduces Cr2O3 at 1~10 wt.% to enhance the [AlO6] hydrolysis site. 3+ A dense passivation film of CrO(OH)2 is formed in situ in pure water, blocking OH-. - Infiltration; [BO3] was constructed via a B2O3-P2O5-V2O5 mixture at 10~16 wt.%. - / [PO4] - / [VO4] - The low-solubility surface network, combined with 5~8 wt.% Bi2O3, reduces surface tension and promotes the migration and enrichment of B / P / Cr to the surface, forming a [BiO6] low-solubility unit to strengthen the barrier.

[0039] The process employs diamond SiO2 coating pretreatment to enhance corrosion resistance and extend service life. This technology provides an innovative solution for high-precision, low-damage, and long-life grinding in ultrapure water environments, such as for semiconductor silicon wafers and optical glass.

[0040] This invention fundamentally solves the aforementioned technical challenges through a synergistic innovation of alkali-free high-polymer network design and passivation element surface enrichment, combined with diamond pretreatment and a one-step low-temperature sintering process. Its innovation lies in: (1) Innovative composition design: SiO2 ≥ 45 wt.% is used to construct the [SiO4] polymeric network framework, and Al2O3 is controlled at 5~15 wt.% to avoid the formation of [AlO6] octahedral hydrolysis sites; Cr2O3 (1~10 wt.%) is introduced to make Cr 3+ A dense passivation film of CrO(OH)2 is formed in situ in pure water, blocking OH-. - Inward penetration; forming [BO3] via B2O3-P2O5-V2O5 (10~16 wt.%) - / [PO4] - / [VO4] -The low-solubility network reduces surface free energy and promotes element enrichment on the surface; Bi2O3 (5~8 wt.%) reduces glass surface tension, accelerates the migration of B / P / Cr to the surface, and forms [BiO6] low-solubility units to strengthen the surface barrier.

[0041] (2) Process innovation: The diamond surface pretreatment + one-step sintering process is adopted, abandoning the traditional path of "high temperature melting + dry ball milling + high temperature sintering", and densification and crystallization are completed in one step. This avoids thermal damage to diamond and achieves the gradient enrichment of passivation elements on the surface.

[0042] This design enables the composite material to have a mass loss rate of less than 1% after immersion in pure water for 160 hours, providing a new integrated solution of corrosion resistance and mechanical properties for long-life, high-reliability grinding of semiconductor silicon wafers, optical glass, and other materials in ultrapure water environments.

[0043] Beneficial effects: The microcrystalline glass binder of this invention is an alkali-free formula that effectively improves the water and acid resistance of the composite material. Through rational component formulation, it achieves a high degree of compatibility with the coefficient of thermal expansion (CTE) of diamond, enhancing the dimensional and thermal stability of the grinding wheel during grinding. Combined with pre-sintered wet grinding, diamond pretreatment, and gradient sintering processes, it effectively optimizes the crystal phase composition and enriches passivating elements, thereby significantly improving resistance to pure water corrosion. The lower sintering temperature and optimized process flow effectively reduce thermal damage to diamond abrasive grains under high-temperature conditions, lowering the graphitization rate, thus extending the grinding wheel's service life and improving grinding quality. This invention demonstrates significant innovative achievements, breaking through the limitations of traditional processes and substantially reducing energy consumption. Attached Figure Description

[0044] Figure 1 This is a schematic diagram illustrating the process mechanism of diamond pretreatment and the preparation of diamond abrasives using microcrystalline glass binders according to the present invention. Figure 2 The XRD patterns are of the microcrystalline glass binder and the microcrystalline glass binder diamond abrasive sample prepared in Example 1 of this invention. Figure 3 SEM images of the microcrystalline glass binder and the microcrystalline glass binder diamond abrasive sample prepared in Example 1 of this invention; Figure 4 The images show the corrosion resistance weight loss rate line graph and corrosion resistance weight loss rate comparison bar graph of the microcrystalline glass binder and the microcrystalline glass binder diamond abrasive sample prepared in Example 1 of this invention, as well as the diamond abrasive samples prepared in Comparative Examples 1 and 2. Detailed Implementation

[0045] The present invention will be further described below with reference to specific embodiments. The illustrative embodiments and descriptions herein are used to explain the present invention, but are not intended to limit the present invention.

[0046] There are no particular restrictions on the source of any raw materials used in this invention; they can be purchased from the market or prepared using conventional methods known to those skilled in the art.

[0047] There are no particular restrictions on the purity of any of the raw materials used in this invention; however, it is preferred to use materials with conventional purity levels used in the field.

[0048] All processes in this invention are referred to by common abbreviations in the field. Each abbreviation is clear and specific in its relevant application, and those skilled in the art can understand the conventional process based on the abbreviation.

[0049] The testing process involved in this invention is as follows: The XRD testing process is as follows: Take an appropriate amount of the sintered sample, grind it into powder to ensure that the powder particles are fine and uniform, and use an X-ray diffractometer with a scanning angle of 10°~90°, a step size of 0.02°, and a scanning speed of 2° / min for testing.

[0050] The SEM testing process is as follows: a small piece is taken from the sample, and the surface is ground and polished to make it smooth and flat. Gold is sprayed for 90 seconds. Using a scanning electron microscope, the accelerating voltage is set to 10-20 kV. The material structure is observed step by step from low magnification to high magnification. The difference in mass and weight loss of the sintered block are compared before and after pure water corrosion. The static immersion method is used to measure the mass difference and weight loss of the sintered block.

[0051] Example 1 A method for preparing diamond abrasives with a microcrystalline glass bond resistant to pure water corrosion includes the following steps: The preparation method of the microcrystalline glass bond includes the following steps: St1, Raw material weighing and mixing According to the formula design (wt.%): SiO2 48%, Al2O3 10%, MgO 12%, B2O3 6%, P2O5 6%, Bi2O3 6%, V2O5 2.5%, Cr2O3 2.5%, Y2O3 2%, TiO2 3%, ZrO2 2%, the raw materials were weighed and placed in a planetary ball mill for ball milling. The mass ratio of grinding balls:material:anhydrous ethanol was 3:1:1. The grinding balls included large zirconia ceramic balls, specifically: 10mm zirconia ceramic balls accounting for 10 wt.%, 8mm zirconia ceramic balls accounting for 20 wt.%, and 5mm zirconia ceramic balls accounting for 70 wt.%. The ball milling speed was 200 rpm, and the ball milling time was 2 hours. After ball milling, the mixture is dried (dried at 80℃ for 6 hours, then passed through a 100-mesh sieve) to obtain the dried mixture. St2, Melting and Water Quenching The dried mixture was placed in a high-temperature sintering furnace for melting and water quenching. Specifically, the dried mixture was heated to 800℃ at 5℃ / min and held for 30 min to remove residual moisture and organic matter; then heated to 1200℃ at 10℃ / min and held for 1 h to complete the initial melting of oxides; then heated to 1420℃ at 15℃ / min and held for 1.7 h to form a uniform alkali-free high-polymer network melt; the molten sample was then subjected to water quenching for less than 5 s to obtain a glass block, which was then dried at 80℃ for 7 h. The block was then crushed using a pulverizer and passed through a 200-mesh sieve. After drying, 10 g of glass fragments were taken for later use.

[0052] St3, pre-calcined wet milling and refining After drying, the glass fragments were pre-fired at 350℃ for 1.5 hours; subsequently, they were wet-milled using deionized water as the milling medium; milling parameters: agate balls:material:water = 3:1:1.5, milling speed 200 rpm, time 1 hour; particle size control: D 90 The material is refined to ≤0.5µm; the product obtained after wet milling is dried to obtain a microcrystalline glass binder.

[0053] A method for preparing diamond abrasives with a glass-ceramic bond includes the following steps: S1, Diamond surface pretreatment S1.1 Select 0.5~1 µm diamond micro powder for surface activation pretreatment: Add 0.5~1 µm diamond micro powder to a mixed acid, sonicate at 60℃ for 30 min to remove surface impurities and graphite layer; wash with deionized water until neutral, and dry at 80℃ for 4 h to obtain activated diamond micro powder; The mass-to-volume ratio of diamond micron powder to mixed acid is 1:10 (the unit of mass-to-volume ratio is g:mL). The mixed acid includes 65-68% nitric acid and 98% sulfuric acid by mass fraction, and the volume ratio of 65-68% nitric acid to 98% sulfuric acid is 1:3 (the unit of volume ratio is mL:mL).

[0054] S1.2 The activated diamond micropowder is modified by coating it with amorphous silica (SiO2) using the sol-gel method: Add 100 mL of anhydrous ethanol, 15 mL of deionized water, 5 mL of ammonia solution with a concentration of 25-28%, and 6 mL of tetraethyl orthosilicate to 5 g of diamond micropowder obtained in step S1.1. After ultrasonic dispersion for 25 min, stir and react at a constant temperature of 25 °C for 9 h. Then, let it stand at room temperature for 18 h to allow the sol to fully gel. Then, centrifuge at 9000 r / min and wash with anhydrous ethanol and deionized water until the system is neutral. Place the obtained powder in a vacuum dryer at 75 °C for 9 h. Finally, heat treat it by raising the temperature to 450 °C at 4 °C / min and holding it at 450 °C for 2 h. After cooling in the furnace, sieve and disperse to obtain diamond micropowder uniformly coated with silica, which is the pretreated diamond abrasive.

[0055] S2, Mixing and Molding Take 0.9g of microcrystalline glass binder, add 2ml of 5 wt.% PVA solution as binder, and coat 2.1g of pretreated diamond abrasive particles (the mass ratio of microcrystalline glass binder to pretreated diamond abrasive particles is 3:7). Mix the mixture in a planetary ball mill for 2 hours to obtain the mixture. Place the mixture in a mold and dry press it under a pressure of 30 MPa. After holding the pressure for 90 seconds, take out the molded sample to obtain the dry-pressed sample. S3, gradient sintering The dry-pressed sample was placed in an alumina crucible. The temperature was raised from room temperature to 600℃ in the first stage at a rate of 5℃ / min; and from 600℃ to 900℃ in the second stage at a rate of 10℃ / min. The holding time was 50 min. The sample was then cooled to room temperature in the furnace. A microcrystalline glass-bonded diamond abrasive sample strip with a mass of 2.93 g and a size of 4 mm × 3.4 mm × 2.7 mm was obtained.

[0056] The sintering process completes densification and crystallization in one step, without the need for secondary crystallization treatment. B / P / Cr / V / Bi are enriched on the surface gradient during the heating process, forming a corrosion-resistant barrier.

[0057] like Figure 1 The diagram shown illustrates the process mechanism of diamond pretreatment and the preparation of diamond abrasives using microcrystalline glass binders according to the present invention.

[0058] like Figure 2 The figure shows the XRD pattern of the microcrystalline glass binder and the microcrystalline glass binder diamond abrasive sample prepared in Example 1 of the present invention; "microcrystalline glass binder + diamond micro powder" in the figure represents the microcrystalline glass binder diamond abrasive sample prepared in Example 1.

[0059] Figure 3 SEM images of the microcrystalline glass binder and the microcrystalline glass binder diamond abrasive sample prepared in Example 1 of this invention; Figure 3Figure a is a SEM image of the microcrystalline glass binder prepared in Example 1, magnified at 1000x. Figure 3 Figure b is a SEM image of the microcrystalline glass-bonded diamond abrasive sample prepared in Example 1, magnified 1000 times.

[0060] like Figure 4 The figures show line graphs and bar charts comparing the corrosion resistance weight loss rates of the microcrystalline glass binder and diamond abrasive samples prepared in Example 1 of this invention, as well as the diamond abrasive samples prepared in Comparative Examples 1 and 2. In the figures, "Comparative Example 1" corresponds to the diamond abrasive sample of Comparative Example 1; and "Comparative Example 2" corresponds to the diamond abrasive sample of Comparative Example 2.

[0061] Results: The XRD pattern of the microcrystalline glass binder obtained by molten water quenching showed typical amorphous peaks (bun-shaped peaks). Figure 2 The broken line representing "microcrystalline glass binder" in the middle), and the XRD pattern of the sintered microcrystalline glass binder ( Figure 2 The broken line representing "microcrystalline glass binder + diamond micropowder" shows multiple distinct diffraction peaks, corresponding to the magnesium aluminum spinel (MgAl2O4) crystal phase. This indicates that the expected high-hardness crystal phase was successfully induced and precipitated under the process of alkali-free formulation-pre-calcination wet grinding-diamond coating pretreatment-gradient sintering, and the crystal phase is well-developed. SEM images show that a large number of microcrystals with a size of about 0.5-2µm are precipitated on the sample surface, and the microcrystals have a plate-like structure. Testing showed that the flexural strength of the microcrystalline glass binder diamond abrasive sample from Example 1 reached 119 MPa; its resistance to pure water corrosion was 0.015% (e.g., Figure 4 (As shown in the left-hand image).

[0062] Example 2: A method for preparing a diamond abrasive tool with a microcrystalline glass bond resistant to pure water corrosion, comprising the following steps: The preparation method of the microcrystalline glass binder includes the following steps: St1, Raw material weighing and mixing The raw materials were weighed according to the formula design (wt.%): SiO2 45%, Al2O3 12%, MgO 10%, B2O3 8%, P2O5 5%, Bi2O3 5%, V2O5 3%, Cr2O3 2%, Y2O3 3%, TiO2 4%, ZrO2 3%. The raw materials were then placed in a planetary ball mill and ball-milled. The ball milling process was the same as step St1 in Example 1. After ball milling, the mixture was dried to obtain a dried mixture. St2, Melting and Water Quenching The dried mixture was placed in a high-temperature sintering furnace for melting and water quenching. Specifically, the dried mixture was heated to 800℃ at 5℃ / min and held for 30 min to remove residual moisture and organic matter; then heated to 1250℃ at 8℃ / min and held for 1.5 h to complete the initial melting of oxides; then heated to 1420℃ at 12℃ / min and held for 2.5 h to form a uniform alkali-free high-polymer network melt; the molten sample was then subjected to water quenching for less than 5 s to obtain glass blocks, which were then dried at 80℃ for 7 h. The blocks were then crushed using a pulverizer and passed through a 200-mesh sieve to obtain dried glass fragments for later use.

[0063] St3, pre-calcined wet milling and refining After drying, the glass fragments were pre-fired at 400℃ for 2 hours; subsequently, they were wet-milled using deionized water as the milling medium; milling parameters: agate balls:material:water = 3:1:1.5, milling speed 250 rpm, time 1.5 hours; particle size control: D 90 The material is refined to ≤0.5µm; the product obtained after wet milling is dried to obtain a microcrystalline glass binder.

[0064] A method for preparing diamond abrasives with a glass-ceramic bond includes the following steps: S1, The diamond surface pretreatment is the same as in Example 1; S2, Mixing and Molding Take 1.05g of microcrystalline glass binder, add 2 mL of 3 wt.% PVA solution as a binder, and coat 1.95g of pretreated diamond abrasive particles (the mass ratio of microcrystalline glass binder to pretreated diamond abrasive particles is 3.5:6.5). Mix the mixture using a planetary ball mill for 2 hours to obtain the mixture. Place the mixture in a mold and dry press it under a pressure of 35 MPa. After holding the pressure for 120 seconds, take out the molded sample to obtain the dry-pressed sample. S3, gradient sintering The dry-pressed sample was placed in an alumina crucible. The temperature was raised from room temperature to 600℃ in the first stage at a rate of 4℃ / min. In the second stage, the temperature was raised from 600℃ to 950℃ at a rate of 8℃ / min, and the holding time was 60 min. The sample was then cooled to room temperature in the furnace. A microcrystalline glass-bonded diamond abrasive sample strip with a mass of 2.9g and a size of 4mm×3.4mm×2.7mm was obtained.

[0065] The densification and crystallization are completed in one sintering process, eliminating the need for secondary crystallization treatment.

[0066] Results: The sintered microcrystalline glass binder exhibited the same magnesium aluminum spinel (MgAl2O4) crystal phase as in Example 1, with a composite structure of rod-equiaxed coexistence. This indicates that the expected high-hardness and wear-resistant crystal phase was successfully induced and precipitated under the process of alkali-free formulation-pre-calcination wet milling-diamond double-layer coating pretreatment-gradient sintering. The crystal phase was well-developed and highly crystallized. The pure water corrosion resistance was as follows: mass loss rate was 0.012%, and the flexural strength reached 125 MPa, which is about 12% higher than that of Example 1.

[0067] Compare with Example 1: The binder formulation adopts a traditional alkali metal formulation design: Li2O 10%, Na2O 5%, SiO2 45%, Al2O3 10%, MgO 8%, B2O3 8%, P2O 55%, TiO2 3%, ZrO2 2%, Cr2O3 4%. The raw materials were weighed, and the preparation process and other parameters were the same as in Example 1. Diamond abrasive samples were prepared.

[0068] Results: No obvious crystallization was observed in the sintered binder. Corrosion resistance: Surface corrosion and increased porosity were observed after immersion in pure water; the mass loss rate after pure water corrosion was 0.884%, with corrosion at the diamond abrasive interface and decreased holding power. This demonstrates that the presence of alkali metals and the lack of passivating elements in the surface enrichment design affect pure water resistance and interfacial bonding strength.

[0069] Compare with Example 2: The microcrystalline glass binder formulation is the same as in Example 1. The preparation process and other parameters are the same as in Example 1, but without the diamond SiO2 coating pretreatment step (excluding step S1 of Example 1, directly using untreated diamond micropowder mixed with the microcrystalline glass binder); diamond abrasive samples are prepared.

[0070] Results: No obvious crystallization was observed in the sintered microcrystalline glass binder. Corrosion resistance: Significant surface corrosion, crystalline phase loss, and increased porosity were observed after immersion; the mass loss rate after pure water corrosion was 0.149%, with corrosion at the diamond abrasive interface and decreased holding power. This demonstrates that the lack of passivating element enrichment on the surface reduces the resistance to pure water and the interfacial bonding strength.

[0071] This invention synthesizes an alkali-free microcrystalline glass binder sample for diamond grinding wheels at relatively low temperatures by designing an alkali-free metal formulation and element passivation enrichment, using pure oxides as raw materials, and employing pre-calcined wet grinding, diamond pretreatment, and gradient sintering processes. The alkali-free microcrystalline glass binder and the precipitated magnesium aluminum spinel crystal phase effectively improve the water and acid resistance of the composite material. By rationally adjusting fluxing components such as B2O3 and P2O5, the dimensional and thermal stability of the grinding wheel during grinding is enhanced. The combination of pre-calcined wet grinding, diamond pretreatment, and gradient sintering effectively optimizes the crystal phase composition and enriches passivating elements, thereby significantly improving resistance to pure water corrosion. The lower sintering temperature and optimized process flow effectively reduce thermal damage to diamond abrasive grains under high-temperature environments, reduce graphitization rate, thereby extending the service life of the grinding wheel and improving grinding quality. This innovative approach overcomes the limitations of traditional processes and significantly reduces energy consumption.

[0072] The technical solutions of the present invention are not limited to the specific embodiments described above. Any technical modifications made in accordance with the technical solutions of the present invention fall within the protection scope of the present invention.

Claims

1. A method for preparing diamond abrasives with a microcrystalline glass bond resistant to pure water corrosion, characterized in that, Includes the following steps: S1, Diamond surface pretreatment Diamond micro powder is subjected to surface activation pretreatment to obtain activated diamond micro powder; Amorphous silica is used to coat activated diamond micro powder to obtain pretreated diamond micro powder. S2, Mixing and Molding The microcrystalline glass binder, pretreated diamond powder, and adhesive are mixed evenly and then pressed into shape to obtain a molded blank. The microcrystalline glass binder comprises the following components in the indicated mass percentages: SiO2 45-60%, Al2O3 5-15%, MgO 8-12%, B2O3 1-9%, P2O5 1-6%, V2O5 1-5%, Bi2O3 5-8%, Cr2O3 1-10%, Y2O3 2-3%, TiO2 2-4%, and ZrO2 1-3%. S3, gradient sintering The preform is subjected to gradient sintering, and after sintering, a microcrystalline glass-bonded diamond abrasive is obtained.

2. The method for preparing a microcrystalline glass-bonded diamond abrasive resistant to pure water corrosion according to claim 1, characterized in that: The surface activation pretreatment process in step S1 is as follows: 0.5~1 µm diamond micropowder is ultrasonically treated at 60℃ for 30 min in a mixed acid with a volume ratio of concentrated HNO3:concentrated H2SO4 of 1:3; washed with deionized water until neutral; and dried at 80℃ for 4 h to obtain activated diamond micropowder.

3. The method for preparing a microcrystalline glass-bonded diamond abrasive resistant to pure water corrosion according to claim 1, characterized in that: The coating process in step S1 is as follows: using tetraethyl orthosilicate as the silicon source, ammonia water is used to catalyze hydrolysis and condensation to generate an amorphous SiO2 shell in situ on the diamond surface.

4. The method for preparing a microcrystalline glass-bonded diamond abrasive resistant to pure water corrosion according to claim 1, characterized in that: In step S2, the mass-volume ratio of the microcrystalline glass binder, the pretreated diamond powder, and the adhesive is (0.9~2):(1~2.1):2, with the comparison unit being g:g:mL, wherein the adhesive is a PVA solution with a concentration of 3~5 wt.%.

5. The method for preparing a microcrystalline glass-bonded diamond abrasive resistant to pure water corrosion according to claim 1, characterized in that: The gradient sintering process in step S3 is as follows: in the first stage, the temperature is raised from room temperature to 600℃ at a rate of 4~5℃ / min; in the second stage, the temperature is raised from 600℃ to the sintering temperature at a rate of 8~10℃ / min; the sintering temperature is 750~1050℃; the temperature is held at the sintering temperature for 50~60min; and the temperature is cooled to room temperature with the furnace after the holding period.

6. The method for preparing a microcrystalline glass-bonded diamond abrasive resistant to pure water corrosion according to claim 1, characterized in that: The preparation method of the microcrystalline glass binder includes the following steps: St1, Raw material weighing and mixing Weigh each component raw material according to the proportion, wet grind and mix to obtain a mixture; after drying, the mixture is obtained as a dried mixture. St2, Melting and Water Quenching The dried mixture is heated to obtain a uniform melt; the melt is quickly poured into room temperature deionized water for water quenching to obtain glass fragments; the glass fragments are then dried and crushed to obtain dried glass fragments. St3, pre-calcined wet milling and refining After drying, the glass fragments are pre-fired at 350~400℃ for 1.5~2 h, and then wet-milled. The product obtained after wet milling is dried to obtain a microcrystalline glass binder.

7. A method for preparing a microcrystalline glass-bonded diamond abrasive resistant to pure water corrosion according to claim 6, characterized in that: In step St1, the wet grinding medium is anhydrous ethanol; during the wet grinding process, the mass ratio of grinding balls:material:anhydrous ethanol is (2~3):1:1, the wet grinding speed is 200 rpm, and the wet grinding time is 2 h.

8. A method for preparing a microcrystalline glass-bonded diamond abrasive resistant to pure water corrosion according to claim 6, characterized in that: In step St2, the heating process is as follows: the dried mixture is heated to 800℃ at 5℃ / min and held for 30 min; then heated to 1200~1250℃ at 8~10℃ / min and held for 1~1.5 h; then heated to 1380~1450℃ at 12~15℃ / min and held for 1.5~2.5 h to obtain a uniform melt.

9. A method for preparing a microcrystalline glass-bonded diamond abrasive resistant to pure water corrosion according to claim 6, characterized in that: In step St3, the wet grinding medium is deionized water; during the wet grinding process, the mass ratio of grinding balls:material:deionized water is 3:1:1.5; the wet grinding speed is 200~250 rpm, and the wet grinding time is 1~1.5 h; the D of the microcrystalline glass binder... 90 ≤0.5 µm.

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