金刚石与磨料磨具工程

Stability and process control of single-diamond grinding based on clustering of processing morphology data

XU Xinyu, HE Xiansong, CHEN Zhaojie, ZHANG Jingying, YANG Linfeng, XIE Jin

2025, 45(1): 1-11. doi: 10.13394/j.cnki.jgszz.2024.0013

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Objectives In the precision grinding process of hard mold steel workpieces, the subtle changes in machining depth can significantly cause dynamic changes in the magnitude and the direction of grinding forces, which directly lead to unstable machining conditions and affect machining accuracy and surface quality. To this end, the data clustering analysis is used to analyze the machining morphology data of the workpiece, and the stable single-point grinding of the workpiece is achieved through process control. Methods Using large particle diamond single-point grinding for hard mold steel, the dynamic characteristics and the stability of the grinding process are analyzed based on the morphology characteristics of the diamond processing surface. The influences of the process parameters on diamond processing efficiency and surface quality are explored to achieve high-efficiency and high-quality diamond grinding. Firstly, the dynamic modeling of the single point diamond grinding system is carried out, and the grinding vibration signal is measured by an accelerometer. The working mode analysis is performed to solve the natural frequency and the damping ratio of the machining system. Then, using a laser confocal microscope to obtain surface waviness and surface roughness data under different processing conditions, the feed depth and the wheel speed are correlated with the data clustering under stable conditions, and matched with the blade diagram area under stable grinding conditions to fit the stiffness and the grinding force coefficients of the processing system. A real-time control area for feed depth and the wheel speed during the stable grinding process is constructed. Finally, the machining efficiency and the quality of the mold steel are verified and analyzed through grinding experiments. Results The modal analysis of the grinding process and the clustering matching of the machined surface morphology features can map the machining process parameters in the stable domain of the grinding process. The working mode analysis method is applied to the stability analysis of single-point diamond grinding die steel, and the natural frequency and the damping ratio of the process system can be obtained under the working state. The natural frequency of the single-point diamond grinding die steel process system is f_n = 363 Hz, and the damping ratio ξ = 0.027. The clustering analysis method is applied to the machining state classification, and the machining surface can be divided into stable machining and unstable machining according to the internal relationship between the surface waviness W_a and surface roughness R_a data. The surface morphologies of the two types of machining are obviously different. The surface of the stable processing state is smooth and flat, while the surface of the unstable processing state has a large area of plastic deformation and a large number of burrs. The surface machining quality of single-point diamond grinding die steel differs greatly under stable and unstable machining conditions. The average surface waviness W_a of single-point diamond grinding mold steel in the stable processing state is 0.635 μm, and the average surface roughness R_a is 0.143 μm. The average surface waviness W_a in the unstable state is 1.203 μm, and the average surface roughness R_a is 0.267 μm, which is about twice that of the stable state. The experimental points after clustering analysis are matched to the relevant areas on the grinding stability lobe diagram, and the experimental verification is carried out to obtain the system stiffness coefficient k = 7 × 10⁶ N/m and the grinding force coefficient k_m' = 3 × 10¹⁵ N/m³ of the single-point diamond grinding die steel process system. Conclusions In the stable processing state, the single-point diamond grinding die steel can achieve a greater material removal rate while ensuring the surface quality as much as possible, thus improving the processing efficiency. In the case of the same amount of material removal, the surface roughness R_a of the stable region processing state is reduced by 74% on average compared with that of the unstable region processing state, which realizes the high-efficiency and the high-surface-quality machining of high-hardness metal materials.

Effect of TiH₂ addition on grinding performance of Cu₃Sn intermetalliccompound diamond wheels

HE Keqiao, CHEN Shuaipeng, KANG Xiyue, HE Yuehui

2025, 45(1): 12-20. doi: 10.13394/j.cnki.jgszz.2023.0261

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Objectives With the development of the modern manufacturing industry, the requirements for material machining accuracy and surface quality are increases continuously. For the precision grinding of high hardness and high wear-resistant materials, superhard material grinding wheels are required to possess high processing efficiency and durability. Intermetallic compound bond diamond grinding wheels have the wear resistance of metal grinding wheels and the self-sharpness of ceramic grinding wheels simultaneously, but they still lacks of sharpness or shape retention when machining hard and brittle materials at high loads and high speeds. To improve the sharpness and shape retention of Cu₃Sn intermetallic compound diamond grinding wheels, this study investigates the addition of TiH₂. Cu₃Sn ball-milling powders, diamond grinding blocks, and grinding wheels with different TiH₂ additions are prepared. Methods The effects of TiH₂ addition on the grinding performance of Cu₃Sn intermetallic diamond grinding wheels are investigated using testing and analyzing the micro-morphology, oxygen content, physical phase composition, thermal effect, and mechanical properties. Results (1) TiH₂ was added to the Cu₃Sn intermetallic compound bond, and the mixture is ball milled together. TiH₂ inhibits the increase in oxygen content, which improves the properties of the ball-milled bond powder and facilitated the sintering process. When TiH₂ is added with a mass fraction of 2.0%, the oxygen content is reduced from 0.67% to a minimum value of 0.51%. (2) TiH₂ decomposes into Ti and H₂ during the sintering process, and Ti could react with the C atoms on the surface of the diamond to form a Ti—C bond. This chemical bonding between the metal bond and diamonds could increased the bonding strength. TiH₂ could improve the mechanical properties of diamond grinding blocks, but a larger amount of TiH₂ increased the pores in the metal bond, which reduced its strength. When TiH₂ mass fraction is 1.5%, the flexural strength reaches the maximum value of 80.74 MPa, and the addition of 2.0% TiH₂ increased the Rockwell hardness to reaches a maximum value of 109.88 HRB. (3) Adding of an appropriate amount of TiH₂ forms a chemical metallurgical bond between diamonds and the bonding agent, which strengthens the holding force of the bonding agent to the diamonds, increases the protrusion height and chip space on the working surface, and improves the sharpness of the grinding wheel. At the same time, it can avoid the premature shedding of diamonds, reducing the consumption of the working layer and improving the shape retention of the grinding wheel. The grinding wheels prepared by adding a certain amount of TiH₂ prior to the ball milling treatment of Cu₃Sn bond powder exhibited better grinding performance. Both sharpness and shape retention are enhanced. When grinding YG8 cemented carbide, the addition of 2.0% TiH₂ enhanced the fastest feed rate of the grinding wheel from 0.020 mm/feed to 0.035 mm/feed. Meanwhile, the grinding ratio of the wheel reached a maximum value of 172.03, which is enhanced by 237% compared with the specimen without TiH₂ addition. Conclusions In this paper, TiH₂ is added to Cu₃Sn intermetallic compounds by ball milling, and the oxygen content of the bond powder is reduced. At the same time, the carbide-formation element Ti reacts with the diamond to form a chemical metallurgical bond, which improves the bonding strength between the diamond and the bonding agent. This results in improved grinding performance of the diamond wheel and provides a reference for the design and development of diamond grinding wheels with high sharpness and high conformal retention.

Tribological performances of alternating multilayer diamond films on Si₃N₄ ceramic substrates

WANG He, ZHAO Haigen, YAN Guangyu

2025, 45(1): 21-30. doi: 10.13394/j.cnki.jgszz.2023.0269

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Objectives With the development of science and technology, silicon nitride ceramics have excellent physical and chemical properties such as high strength, high hardness, high temperature resistance, corrosion resistance, and wear resistance. They can maintain good mechanical properties and chemical stability under harsh working conditions, and have been widely used in many fields. However, silicon nitride has great brittleness, low toughness, and poor plastic deformation ability, which makes it prone to cracking and brittle fracture under the action of stress. At the same time, the friction coefficient of silicon nitride ceramics, as wear-resistant devices, is high under dry friction conditions, and the loss caused by friction and wear will reduce its accuracy and affect the working stability of parts. The diamond film has the properties such as high hardness, low thermal expansion coefficient, low friction coefficient, and excellent chemical stability, making it an excellent anti-wear and wear-resistant film material. However, the two common single-layer diamond films have their own shortcomings. Therefore, diamond films with multilayer structures are designed and prepared on silicon nitride substrates to improve the tribological properties of silicon nitride ceramics. Methods The single-layer and alternate multilayer diamond films with different structures were designed and prepared on silicon nitride ceramic substrates by hot filament chemical vapor deposition (HFCVD) technique. The surface and the cross-section morphology, crystal quality, crystal orientation, surface roughness, and phase compositions of single and alternate multilayer diamond films were analyzed by scanning electron microscope, X-ray diffractometer, atomic force microscope, and Raman spectroscopy. Results (1) For alternating multilayer films, the surfaces exhibit clustered nano-diamonds. When the number of alternations is small, the interlayer thickness is thick, the thin film is clearly layered, the layers are tightly connected, the surface roughness is small, and the film quality is good. When the number of alternations is more, the interlayer thickness is thin, the film does not have obvious layering, the surface roughness is large, and the film quality is poor. The Raman spectra of the alternating multilayer structures are similar to those of the nano-diamond film, with a higher content of trans-polyacetylene and non-diamond phases in the film. (2) For alternating multilayer structured films, the friction coefficients are generally lower than those of single-layer diamond films. When the number of alternations is small, the surface roughness of the film is reduced by the nano-diamond layer on the surface, and the tightly connected micro/nano interlocking structures and the micro-diamond layer at the bottom enhance the cohesion and bonding force of the film. The friction process of the film is stable, the wear rate of the film is low, and there is less film detachment during the friction process. When the number of alternations is high, the quality of the film is poor, and during the friction process, the film falls off and breaks, and the debris enters the friction surface of the film. The friction coefficient fluctuates greatly, and the wear rate of the film is high. When the number of alternations is 4 and the number of film layers is 8, the film has the lowest average friction coefficient and wear rate, which are 0.016 and 1.04×10⁻⁷ mm³/(N·m), respectively. Conclusions The surface morphology of diamond films has a significant impact on their tribological properties. The sharp (111) edge of the micro diamond film surface generates a strong plowing effect when interacting with the grinding ball, making it easier for diamond abrasive particles and debris to enter the grinding surface, resulting in an increase in friction coefficient and wear rate. The nano-grain size on the surface of the nano-diamond film is relatively small and has no sharp edges, which reduces the friction coefficient of the film. However, its bonding ability with the substrate is poor, and the partial detachment of the film under the shear stress increases the wear rate. The friction coefficient and the wear rate of alternating multilayer structures are generally reduced compared to single-layer diamond films. The reason is that the nano-diamond layer on the surface of the alternating structure reduces the surface roughness of the film, enhances its toughness, and the columnar growth of micro-diamond grains at the bottom of the film enhances the bonding performance between the film and the substrate, making the film less prone to peeling during friction. The crystalline quality of alternating multilayer thin films with thin interlayer thickness is poor, and the film rupture and peeling are prone to occur during the friction process, thereby increasing the friction coefficient and the wear rate. A reasonable alternating multilayer structure design can significantly reduce the maximum friction coefficient, the average friction coefficient, and the wear rate of the film during the friction process, reduce the plowing effect between the film and the wear pair, and reduce the wear scar area, thus improving the wear resistance of the film.

Effect of TiN-Al system binder ratio on structure and properties of PcBN

TANG Lihui, XIAO Changjiang, ZHANG Qunfei, ZHENG Haoyu, LI Zhengxin

2025, 45(1): 31-36. doi: 10.13394/j.cnki.jgszz.2023.0284

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Objectives Al and TiN are commonly used components in PcBN synthesis under high temperature and high pressure. But the existing literature studying the TiN-Al bonding system always focuses on the single property variation, such as relative density, hardness, fracture toughness, impact resistance or abrasion resistance, rather than the comprehensive performance when analyzing the samples. In this paper, the TiN-Al ratio and its effect on the structure and the comprehensive performance of PcBN is explored. Methods The raw materials for the experiment are cBN powder sized 0.5-1.0 µm and binders of TiN powder sized of 2-10 µm and Al powder sized 1-2 µm. The high-temperature and high-pressure preparation conditions are provided by a hydraulic cubic press. The sintering pressure is 5.5 GPa and the sintering temperature is 1400 ℃, with a holding time of 10 minutes to obtain the PcBN sample. After grinding, polishing and other processing steps, the material properties are tested. The phase is analyzed using an X-ray diffractometer. The binding of cBN particles with the binder and its microscopic morphology are observed using a scanning electron microscope. The actual density, the microhardness and the fracture toughness of the samples are tested separately. The wear ratio of the specimens are measured under the following conditions: an 80-mesh grit SiC grinding wheel for counter grinding, axial force of 300 N and spindle speed of 300 r/min. The wear ratio of the samples is quantified by the ratio of the wheel wear to the PcBN wear. Results It is observed that the prepared PcBN consists of 4 phases: BN, AlN, TiN, and TiB₂. As the proportion of Al increases, the diffraction peak intensities of AlN and TiB₂ gradually become stronger while that of TiN gradually decreases. When the content of Al increases, the number of pores decreases to zero and the material become denser. The relative density of the samples reaches its maximum value of 99.02% at 9% TiN and 16% Al. The hardness, the fracture toughness and the abrasion resistance of PcBN increase initially and then decrease as TiN content increases. Conclusions The binding agents TiN and Al react with cBN, forming four phases: BN, TiB₂, TiN and AlN. As the Al ratio increases, the proportions of AlN and TiB₂ increase while that of TiN decreases. The comprehensive performance of PcBN is the best when the mass ratio of TiN∶Al in the binding agent is 9∶16, leading to uniform distribution of cBN and binder and ensuring a dense PcBN sintered body. At this condition, the relative density, the Vickers hardness, the fracture toughness and the wear ratio of the PcBN sample reach the maximum values, which are 99.02%, 4664 HV, 6.60 MPa·m^1/2 and 7340, respectively.

Effect of doped elements X (B, Al, Sn, Co) on binding performance of IDB-X/Diamond interface

JIAN Xiaogang, YAO Wenshan, ZHANG Yi, LIANG Xiaowei, HU Jibo, CHEN Zhe, CHEN Maolin

2025, 45(1): 37-45. doi: 10.13394/j.cnki.jgszz.2023.0068

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Objectives At present, resource exploration and mining continue to expand to deep underground. Impregnated diamond bits (IDB) with excellent performance have become the main tool for deep underground drilling. Our research group has found that depositing a layer of CVD diamond coating in situ on the surface of IDB can achieve homogeneous epitaxial growth and heterogeneous epitaxial growth of diamond coatings, which can improve the working life of IDB. This article is based on the first principles of quantum mechanics and uses the CASTEP computational tool to study the influence mechanism of X (X = B, Al, Sn, Co) elements commonly used in the IDB on the interfacial bonding performance of CVD diamond coatings on IDB from a microscopic perspective. It provides a theoretical reference and basis for further optimizing the formulation of drill bit substrates and improving the interfacial bonding strength between the film and substrate. Methods This article uses the CASTEP module of the quantum mechanics computing software Materials Studio to study the influence mechanism of X (X = B, Al, Sn, Co) elements commonly used in IDB on the interfacial bonding performance of CVD diamond coatings on IDB from a microscopic perspective. Firstly, establish [100] crystal orientation, 3×3 size IDB, and CVD diamond coating supercell models, with dimensions of 7.54 Å × 7.54 Å × 3.56 Å along the X, Y, and Z directions. After adding a vacuum layer with a thickness of 12 Å, the IDB model and CVD diamond coating model are obtained. Then, replace the C atoms at specific locations on the surface of the IDB model with X (X = B, Al, Sn, Co) atoms. Afterwards, the IDB-X substrate is combined with the CVD diamond coating model along the [100] crystal plane to establish an IDB-X/Diamond film substrate interface model. After testing, the film-substrate interface spacing is set to 2 Å. Next, the CASTEP module is used to optimize the IDB-X/Diamond film-substrate interface model doped with X (X = B, Al, Sn, Co) atoms. The properties of the four film-substrate interface models are analyzed from the aspects of film-substrate interface binding energy, differential charge density, and Mulliken population. Finally, verification is conducted with indentation experiments. Results (1) From the perspective of film-substrate interface binding energy, the binding energies of B, Al, Co, and Sn atom doping are 11.68, 9.94, 7.38, and 6.85 J/m², respectively. Based on the weakening phase Co of the film-substrate interface binding energy, the film-substrate interface binding energy doped with B and Al atoms is significantly higher than that of Co atoms, indicating that the B and Al elements in the substrate are beneficial for improving the film-substrate interface binding energy. The film-substrate interface binding energy doped with Sn atoms is similar to that of Co atoms, indicating that the Sn element in the substrate also weakens the bonding strength between the film and substrate. (2) From the perspective of differential charge density, the charges of B, Al, Sn, and Co atoms all tend to transfer to the surrounding C atoms, especially to the C1−C3 atoms in CVD diamond coatings, and the tendency to transfer charges to C1 atoms is more pronounced. This indicates that the four doped atoms have a stronger effect on the charges generated by the C atoms in the film. The density of charge transfer from B atom to C1−C3 atom is relatively high, which reflects the strong charge interaction between B atom and C1−C3 atom. The tendency of Al atoms to transfer charges is mainly concentrated in C1 and C2 atoms, and the tendency to transfer charges to C3 atoms is not obvious, indicating that the bonding between Al atoms and C1 and C2 atoms may be stronger. The tendency of Sn atoms to transfer charges to C1 atoms is obvious, but the tendency to transfer charges to C2 and C3 atoms is slightly weaker, indicating that the charge interaction force between Sn atoms and C atoms in the substrate is weak. Co atoms have a weak tendency to transfer charges to C1 and C3 atoms, while their tendency to transfer charges to C2 atoms is not significant, indicating that the charge interaction between Co atoms and the film and substrate is weak. (3) From the perspective of atomic and chemical bond Mulliken population, B, Al, Sn, and Co all lose electrons and carry positive charges, with charge loss numbers of 0.59e, 1.89e, 2.06e, and 1.71e, respectively. Meanwhile, the C1−C3 atoms near the four doping elements all receive negative charges, indicating significant charge transfer between the four doped atoms and C1−C3 atoms. This suggests the existence of four types of bonding interactions between the film-substrate interface interface: C—B, C—Al, C—Sn, and C—Co. The effective utilization rates of the lost charges of B, Al, Sn, and Co atoms by C1~C3 atoms are 98%, 58%, 43%, and 39%, respectively. The Mulliken population of the C—B bond is the largest and the bond length is the smallest, followed by the Mulliken population of the C—Al bond. The Mulliken populations of the C—Sn bond and C—Co bond are relatively small. (4) From the indentation experiment, it can be seen that the indentation of diamond films pretreated with B and Al elements is shallow and the pit area is small, indicating that the film-substrate interface binding strength of IDB-B/Diamond and IDB-Al/Diamond is high. Among them, the indentation pit area of diamond films pretreated with B element is the smallest, indicating that B element is most conducive to enhancing the film-substrate interface binding strength, followed by Al element. The diamond coatings pretreated with Sn and Co elements have deeper indentation and a larger indentation pit area, indicating poor film-substrate interface effect of IDB-Sn/Diamond and IDB-Co/Diamond. Conclusions (1) From the perspective of energy, the binding energy of the film-substrate interface doped with four elements is W_ad-B (11.68 J/m²)>W_ad-Al(9.94 J/m²)>W_ad-Co (7.38 J/m²)>W_ad-Sn (6.85 J/m²). Based on the weakening phase of the film-substrate interface binding energy of the Co element, the doping of B and Al elements are conducive to improving the film-substrate interface bonding strength. The film-substrate interface binding energy of Sn element doped is similar to that of Co element, indicating that Sn element doped also weakens the film-substrate interface bonding strength. (2) From the perspective of charge, the charges of B and Al atoms mainly transfer to the C1−C3 atoms near the doping site, with effective charge utilization rates of 98% and 58%, respectively. In addition, the Mulliken populations of C−B and C−Al bonds are relatively high, indicating that the bonding between B and Al atoms and C1−C3 atoms is strong, playing the role of film substrate connection nodes and improving the film substrate interface binding strength. The effective charge utilization rates of Sn and Co atoms are both less than 50%, indicating that a large amount of charge is transferred to other C atoms at the film substrate interface except for C1−C3 atoms, resulting in weak bonding between Sn and Co atoms and C1−C3 atoms. At the same time, other C atoms repel each other due to the charge obtained, weakening the film substrate interface binding strength. (3) From the indentation experiment, it can be seen that the film-substrate interface bonding strength of B element-induced crystal pretreatment is the highest, followed by Al element, while Sn and Co elements are relatively poor.

Effect of Ti powder particle sizes and raw material ratio on properties of Ti-coated diamond powder

HAN Ming, ZHAO Andong, LI Liang

2025, 45(1): 46-55. doi: 10.13394/j.cnki.jgszz.2023.0252

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Objectives Titanium plating on the surface of diamond powder can improve its wettability to the bonding agent, and the preparation process of the titanium-plated metal layer is of great significance to the industrial application of diamond powder. The effect of particle size and raw material ratio of Ti powder on the properties of Ti coated diamond powder is analyzed. Methods Different particle sizes (60 mesh coarse powder, ~250 μm and 325 mesh fine powder, ~45 μm) and raw material ratios are compared, and so are the vacuum and protective atmosphere titanium plating process. The experiments involve diamond particles, fine titanium powder, and titanium powder. The materials are immersed in hydrochloric acid and washed twice with acetone. Four ratios (5:3, 2:1, 1:1, 1:2) are set based on the mass ratio of diamond and titanium powder. The materials are sintered under vacuum or Ar protective atmospheres, and the Ti powder slag and Ti-coated diamond particles are separated. Results The chemical composition of titanium-coated diamond powders is characterized by XRD as diamond, Ti, and TiC transition layers. The morphology of titanium coated diamond powders and the distribution of elements on the surface are analyzed by SEM, which shows that Ti coating on the surface of diamond particles could be achieved with different ratios and Ti powder particle sizes. The Raman spectra of fine Ti-coated diamond contain characteristic peaks of diamond and Ti, while those of coarse Ti-coated diamond and Ti-coated diamond synthesized in a vacuum atmosphere are affected by the ratio of raw materials. The UV-visible absorption spectra show that there are obvious absorption peaks in the wavelength region of 228-234 nm and 328-350 nm for Ti-coated diamond, respectively. The weight loss rates of vacuum-synthesized titanium-coated diamond and fine-grained Ti-coated diamond are lower than those of coarse-grained Ti-coated diamond. Conclusions Combined with the results of Raman spectra, ultraviolet absorption spectra, and thermal analyses, the performance of fine Ti-coated diamonds under argon atmosphere protection is better than that of coarse Ti powder-coated diamonds and vacuum atmosphere-coated diamonds.

Effect of brazing process on microstructure and properties of brazed diamond interface

CUI Bing, JIANG Xue, DU Quanbin, XU Fan, YAN Peipei, WANG Lei, ZHANG Liyan

2025, 45(1): 56-66. doi: 10.13394/j.cnki.jgszz.2024.0026

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Objectives Diamond tools are widely used in various fields. Copper-based brazing materials are used for brazing diamond tools. In response to the problems of low-temperature phase flow and low bonding strength of copper-based brazing materials at high temperatures, different brazing temperatures and brazing times are designed, and the WC/Cu-Sn-Ti composite brazing material is used for vacuum induction brazing to study the changes in microstructure and mechanical properties of brazed joints. Methods The brazing samples were made of HWD40 diamond with a particle size code of 35/40, a 45 steel matrix, and WC/Cu-Sn-Ti composite brazing filler metal. The vacuum degree was 1×10⁻³ Pa, the brazing temperature were 950, 980, 1 010, 1 040 and 1 070 ℃, and the brazing time was 10, 15, 20 and 25 min, respectively. The SEM observation and XRD phase analysis were carried out on different samples after brazing. At the same time, friction and wear tests were carried out on brazing samples at different temperatures and different holding times to obtain the grinding amount and diamond drop rate of the samples, so as to analyze the mechanical properties of the joint structures. Results (1) Under the conditions of a brazing temperature of 980 ℃ and a holding time of 15 min, the line scan analysis is conducted on the elements at the brazed diamond interface. It is found that the W element is enriched near the brazed diamond interface, possibly due to the diffusion of elements in WC. The XRD phase analysis showes the formation of TiC and W₂C compounds at the diamond interface, which can improve the wettability between the diamond and brazing material, and enhance the adhesion of the brazing material to the diamond. In order to further determine the formation of TiC, the sample is subjected to aqua regia etching, and the surface of the diamond particle is analyzed by SEM and EDS to determine that the TiC is formed by the metallurgical reaction between the active element Ti and the C element on the diamond surface. (2) To investigate the effect of the brazing process on the surface morphology of brazed diamond, the morphology of the diamond surface is analyzed at different brazing temperatures with a holding time of 15 minutes. It is found that the diamond surface has obvious pores and cracks at a brazing temperature of 950 ℃. When the brazing temperature is raised to 980 ℃, the cutting edge of the diamond remaines intact, and the diamond is exposed the most. As the brazing temperature continues to rise, the diamond graphitization phenomenon in the brazed sample becomes severe. Therefore, the brazing process with a holding time of 15 minutes and a brazing temperature of 980 ℃ has the best effect. (3) Raman analysis is performed on the samples at 950, 1 010, and 1 070 ℃ to calculate the ratios of the diamond peak and graphite peak in the samples. It is found that when the temperature increases from 950 ℃ to 1 070 ℃, the temperature increases by 12%, and the degree of graphitization of diamond increases by 90%. At the same time, when the brazing temperature is 980 ℃, the main wear form of the diamond is flat and micro-damage, and the diamond shedding rate is 0. (4) To further compare the effect of insulation time on the performance of brazed joints, friction and wear tests are conducted on samples with different insulation times at the optimal brazing temperature of 980 ℃. It is found that as the insulation time increases, the number of diamond drops increases from 0 to 3. However, if the insulation time is too long, the diamond particles suffer thermal damage. When the brazed sample with an insulation time of 15 minutes is used to grind marble, the marble grinding volume of the sample is 36.154 mm³, and the grinding performance of the sample is the best. Conclusions The compound layer at the interface between the diamond particles and the WC/Cu-Sn-Ti composite brazing is uniform, continuous and dense. A thin and continuous layered TiC and a small amount of W₂C phase are formed on the surface of diamond particles, which improves the bonding strength between the diamond and steel substrate. Under the conditions of a brazing temperature of 980 ℃ and a holding time of 15 min, the friction coefficient of diamond particles in the grinding process is small, the grinding amount of the marble workpiece is large, and the diamond particle shedding rate is low. By reasonably controlling the brazing temperature and holding time, the efficiency and quality of diamond-abrasive tools in the processing of marble and other materials can be improved, the shedding rate of diamond particles can be reduced, and the service life of abrasive tools can be extended. At a brazing temperature of 980 °C and a holding time of 15 minutes, the diamond particles exhibit a low friction coefficient during the grinding process, a high grinding volume on marble workpieces, and a low diamond drop-out rate. By controlling the brazing temperature and holding time, the efficiency and quality of diamond grinding tools in processing materials such as marble can be improved, reducing the diamond particle drop-out rate and extending the tool's service life. The WC/Cu-Sn-Ti brazing material was used for vacuum brazing of diamond. The effects of brazing temperature and holding time on the morphology, the interfacial structure, and mechanical properties of brazed diamond were studied using a scanning electron microscope, X-ray diffractometer, energy spectrum analysis, and shear and grinding experiments. The results show that the compound layer formed at the composite brazing interface between diamond particles and WC/Cu-Sn-Ti is uniform, continuous and dense, and a thin and continuous layered TiC and a small amount of W₂C phases are formed on the surface of diamond particles, which improves the bonding strength between the diamond and steel matrix. As the brazing temperature increases and the holding time prolongs, the interface defects of brazing gradually decrease, and the degree of diamond graphitization increases. Under the brazing temperature of 980 ℃ and a holding time of 15 minutes, the friction force and the coefficient of friction of diamond particles during the grinding process are relatively small, resulting in the largest grinding volume for the marble workpiece and the lowest detachment rate of diamond particles.

Grinding power model for flute grinding of solid tools based on equivalent chip thickness

REN Lei, PAN Jiangtao, XIANG Daohui, MA Junjin, CUI Xiaobin

2025, 45(1): 67-74. doi: 10.13394/j.cnki.jgszz.2024.0003

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Objectives During the flute grinding process of solid tools, the majority of grinding power is converted into grinding heat. Excessive grinding power can cause a rapid temperature rise on the surface of the contact area between the grinding wheel and the tool, which can easily lead to grinding burns and eventually tool failure. A grinding power model for flute grinding of solid tools is proposed based on equivalent chip thickness, aiming to achieve precise prediction and control of grinding power for flute grinding. Methods A kinematic model for flute grinding is established using homogeneous coordinate transformation. On this basis, according to the theory of conjugate surfaces, the instantaneous contact line between the grinding wheel surface and the flute surface during the grinding process is obtained, and the grinding wheel is discretized into a set of equally thick grinding wheel slices. The grinding contact arc length is obtained by calculating the intersection points between the grinding wheel slices and the tool cylindrical surface. Flute grinding is regarded as external cylindrical grinding with a special contact zone shape. By introducing the contact-area-shape coefficient to define the equivalent grinding depth and the equivalent feed rate of each grinding wheel slice, the formula for calculating the equivalent grinding layer thickness of flute grinding is derived. When the linear speed of the grinding wheel, the axial feed speed of the workpiece, and the grinding contact arc length of each grinding wheel slice are known, the equivalent chip thickness of each grinding wheel slice can be calculated as long as the shape coefficient of the contact area is given. The cross-section profiles of the chute are discretized into small triangles, and the area of the cross-section profile of the chute is obtained by calculating the area of each triangle. The material removal rate of the chute during grinding is determined by combining the axial feed velocity of the workpiece. According to the principle of conservation of material removal rate, the formula for the shape coefficient of the contact area is derived. Based on the mathematical relationship between the local grinding power of each grinding wheel slice and the thickness of the equivalent grinding layer, the empirical model for flute grinding power is established. The experimental verification of the model is carried out on an ANCA MX7 CNC tool grinding machine. The flute with a spiral angle of 30° is ground on a cemented carbide rod with a metal-bonded diamond wheel. The spindle power data of the machine tool PLC is recorded using the data recording function of iGrind grinding software. The spindle power includes grinding power and spindle idle power, so grinding power is obtained by subtracting idle power from spindle power. Twenty sets of grinding experiments are carried out under different grinding parameters, and an overdetermined equation set is established by substituting the grinding power data of four sets of experiments into the power model. By solving this equation system, the two empirical constants in the model are obtained. Then, the grinding power model is used to predict the grinding powers of twenty sets of grinding experiments, and the predicted grinding powers are compared with the actual grinding powers. Results The comparison results show that the predicted grinding powers are close to the actual grinding powers, and the maximum relative error of the predicted grinding power is less than 15%. The equivalent chip thickness of each wheel slice and the grinding power per unit width vary gradually along the width of the grinding wheel, and the maximum equivalent chip thickness and the maximum grinding power per unit width exist at the edge of the grinding wheel. Conclusions The proposed grinding power model based on equivalent chip thickness can precisely predict the grinding power during the flute grinding process of solid tools, and obtain the distribution of grinding power in the width direction of the grinding wheel. The grinding power can be precisely controlled by adjusting grinding parameters with this model, and the maximum equivalent chip thickness and the maximum grinding power per unit width exist at the edge of the grinding wheel during the grinding process of the chute, which will lead to non-uniform wear in the direction of the width of the grinding wheel.

Influencing factors of power consumption in grinding iron ore with diamond cutter head

DING Caizhi, ZHUANG Shiyong, SONG Leibo, DENG Yong, WANG Huanyu, GU Lu

2025, 45(1): 75-85. doi: 10.13394/j.cnki.jgszz.2024.0031

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Objectives The existing mining equipments, such as coal mining machines, excavators, tunneling machines, and diamond tools, are combined to form a new mining equipment called the“grinding mining machine”, which is used for grinding mining. The main advantage of grinding mining applied in metal mines is that it greatly simplifies the mining process. However, whether it can be popularized and applied depends on whether its operating cost is close to or lower than the mining cost of drilling and blasting methods. Among these, the energy consumption cost of grinding mining machine operation is one of the most critical control indicators. The existing cutter heads of diamond tools, such as diamond circular saw blades and diamond grinding wheels, are used to grind iron ore. The relationship between grinding power consumption and the type of diamond cutter heads, the rock characteristics of iron ore, and the grinding operation parameters are studied. The factors affecting the grinding efficiency and the cost of the grinding mining machine are explored to find a reasonable range of values that can adapt to different situations. Methods An experimental platform was built, and two types of diamond circular saw blades and two types of diamond grinding wheels were used to conduct grinding experiments on two types of iron ore samples. There were a total of six experimental schemes, and power consumption experimental data were obtained for different blade heads and their grinding line speeds, grinding thicknesses, grinding widths, grinding movement rates, etc. Based on this, the rated grinding efficiency, the rated motor power consumption, and the rated grinding power consumption were calculated. The main influencing factors of power consumption in grinding iron ores with diamond cutter heads were analyzed by comparing the above data. Results According to the experimental data and the calculation analysis of the six experimental schemes, the following results were obtained: (1) The average rated motor power consumption of the magnetic iron zone of ore 1, the quartz zone, and the magnetic iron zone of ore 2 are 50.41, 36.05, and 15.17 (kW·h)/t, respectively. This indicates that the rock characteristics of ore, such as uniaxial compressive strength, quartz content, and particle size, have a significant impact on power consumption during grinding. The higher the uniaxial compressive strength of the ore, the higher the quartz content and the smaller the quartz particle size, the higher the power consumption of grinding the ore. (2) Two different types of diamond circular saw blades and two types of diamond grinding wheels were used to conduct grinding experiments on two different iron ore samples. Compared with other types of diamond heads, the use of sharp diamond heads with added iron sheets can significantly reduce power consumption during ore grinding operations. (3) Under the condition of constant rated power of the main motor, the grinding efficiency of the grinding wheel can be improved, and the power consumption of the motor can be reduced by optimizing the width and the diameter of the grinding wheel. (4) The single grinding movement distance Δs is closely related to grinding efficiency and directly related to the diamond cutting depth Δh. When the Δs value ranges from 6.01 to 14.35, 3.23 to 9.96, 4.14 to 15.04, 26.44 to 32.09, 1.62 to 5.37, and 2.02 to 5.64 μm in the six experimental schemes of M1 to M6, the grinding power consumption can be effectively reduced by adjusting the Δs value. When the Δs values of M1 to M6 are 14.35, 6.65, 15.04, 32.09, 5.37, and 3.22 μm, respectively, the grinding power consumption is the lowest. However, to determine the most suitable Δs value, it is necessary to comprehensively consider factors such as the size and the structure of the diamond tool, the performance of the cutting head, the characteristics of the ore rock, the operating parameters, and the force situation of the cutting head, in order to find a reasonable range of values that can adapt to different situations. Additionally, according to the force analysis of the diamond cutter head grinding ore and the phenomena observed in the experiment, selecting the appropriate grinding movement direction is conducive to pulp collection and maximizes the gain effect of tangential pushing on the cutting force. Conclusions The energy consumption of diamond cutter heads grinding ores should be optimized in two aspects: the manufacturing technology and the use parameters of the cutter heads. In terms of diamond cutter head manufacturing technology, optimization should be carried out from the aspects of diamond grade, diamond particle size, and matrix compositions, formula, processing technology, as well as the size design, shape and arrangement of diamond cutting heads. Cutting heads that are both sharp and durable for grinding different types of ores should be developed to reduce energy consumption and operating costs. In terms of using operational parameters, further optimization research should be conducted on grinding size parameters and dynamic parameters to improve grinding efficiency, reduce grinding energy consumption and operational costs, and provide experimental and theoretical basis for the manufacturing of grinding and mining machines. The core technology of the grinding mining machine lies in the manufacturing technology of the grinding drum, and optimizing diamond cutter head grinding ores is fundamental to improving the grinding drum manufacturing technology.

Mechanical lapping and polishing process of polycrystalline diamond wafers

LI Jiao, ZHANG Xiaoqiu, WANG Ziguang, ZHANG Xin, ZHANG Yu

2025, 45(1): 86-92. doi: 10.13394/j.cnki.jgszz.2024.0017

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Objectives Diamond is a critical material potentially or already applied in infrared windows, electronic components and acoustic devices for its excellent optical transmittance, high eletron mobility and high breakdown voltage. Mechanical lapping is one of the mainstream methods for diamond planarization. However, it is more difficult to mechanically planarize polycrystalline diamond due to the grains and the boundaries which may lead to defects and internal stress release. Variable-parameter mechanical lapping are conducted on polycrystalline diamond to investigate the effects of abrasive grain size, lapping pressure and abrasive concentration on material removal rate (R_MRR) and surface roughness R_a. Methods A group of {100} polycrystalline diamond wafers are attached to a load plate with lapping fluid speed of 8 mL/min, rotational speed of 30 r/min and orbital speed of 45 r/min. The grain size (W7～W50), the concentration of fluid (3%～6%) and the loading pressure (0.1～0.4 MPa) are tested for a reasonable process. A surface profiler is used to observe the morphology of three equal division points (800 μm×800 μm) on diamond surface along the diagonal of the 5 mm×5 mm×1 mm wafer. The average roughness are used to characterize the lapping effect. Results It is found that the R_MRR increases with the increase of grain size, reaching its maximum of 25.210 μm/h with grain size of W50 and R_a of 240 nm. But there appears micro cracks on diamond surface. The R_MRR slightly increases as the grain concentration increases from 3% to 5% but decreases at concentration of 6%, varying around 11 μm/h. The MRR also increases from ～8 μm/h to ～17 μm/h as the lapping pressure increases from 0.1 MPa to 0.4 MPa. Conversely, the surface roughness decrease from 240 nm to 100 nm with finer abrasive, which is a dominant factor affecting the surafce quality. The surface roughness also decreases first but increases then with higher lapping pressure and abrasive concentration. Conclusion The optimal process parameters for polycrystalline diamond wafer are determined, namely the lapping pressure of 0.3 MPa, the abrasive grain size of W10 and the lapping fluid concentration of 4%, where the processed polycrytalline diamond wafer achieves the best surface quality of R_a ～96 nm and a corresponding R_MRR of 7.097 μm/h.

Force of dressing grinding wheels by diamond rollers with orderly arrangement grains

ZHANG Rui, ZHOU Shuaikang, ZHAO Huadong, ZHU Zhenwei, HE Honghui, LIU Chang

2025, 45(1): 93-101. doi: 10.13394/j.cnki.jgszz.2024.0004

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Objectives With the increasing improvement of science and technology and industrial levels, the modern manufacturing industry has higher and higher precision requirements for grinding processing, and the grinding quality can be improved by enhancing the ability of diamond dressing rollers. However, the current research on the grinding dressing process is mostly based on experiments. Since grinding is a high-speed and complex machining process, the dressing experimental cost of diamond rollers is higher. Therefore, this paper explores the influence of surface diamond grain arrangement on the dressing ability of diamond rollers through finite element simulation, and designs experiments to verify the reliability of the simulation results. Methods The finite element analysis software Abaqus is used to carry out kinematic simulation of the dressing grinding process of the roller. First of all, in order to simulate the randomness of the real abrasive grain shape, the sphere method of plane-cutting cubes is used to obtain a more realistic abrasive grain model. Algorithms are designed for the coordinates of abrasive grains in three types of arrangement: array, misalignment, and leaf sequence, to achieve the accurate arrangement of abrasive grains on the surface of the roller model. The Johnson-Holmquist-2 (JH-2) intrinsic parameters model of 99.5% alumina ceramics is used to approximately characterize the damage evolution of white corundum grinding wheels during dressing. To verify the accuracy of the results obtained through this simulation method, dressing experiments are set up to form a control with the simulation group. Results Taking the dressing force generated in the dressing process as the evaluation index, the simulation and experimental results are analyzed: (1) A comparative analysis of the data obtained from the simulation is carried out, and it is found that diamond wheels with surface abrasive grains arranged in an array manner would generate a larger dressing force during the dressing process, followed by the staggered-arrangement wheels, and the diamond wheels with a leaf-sequence arrangement would have the smallest dressing force. In other words, the arrangement of abrasive grains on the surface of the diamond dressing wheel affects the dressing force. (2) The dressing force results obtained from the experiments also show that under these three arrangements, the dressing force generated by the array roller is the largest, and the dressing force generated by the leaf sequence is the smallest. (3) Comparing the dressing force data obtained from the simulation and experiment, it can be seen that the fluctuation of the dressing force obtained from the experiment is smaller than that of the simulation. The maximum error of both normal dressing force is 12.87%, and the maximum error of tangential dressing force is 17.16%. Conclusions (1) Comparing the dressing force results of the simulation and experiment, it is found that the fluctuation of the experimental data is smaller than that of the simulation results. This is due to the fact that the abrasive grains in the simulation are generated randomly. Even if two neighboring abrasive grains differ in parameters such as protruding height, effective action area, and the angle of abrasive grains' vertices, the fluctuation of the dressing force is still larger under the state of smooth grinding. The diamond rollers used in the experiments have undergone surface reshaping treatment, and the parameters such as the emergence height and vertex angle of the abrasive grains on the surface are more consistent with the simulation model. As a result, the fluctuation of the dressing force is smaller and smoother. The dressing force measured in the experiment is smaller compared with the simulation, which indicates that the dressing roller can be shaped to make the dressing process smoother and improve its dressing ability. (2) The reason for the difference in dressing force of diamond wheels with different arrangements of abrasive grains: Under the condition of the same concentration of abrasive grains on the surface, the abrasive grains of the roller with an array arrangement result in fewer effective abrasive grains due to a large number of overlapping grinding trajectories. In contrast, the leaf-sequence arrangement has the unique characteristic where each abrasive grain is located on a circumference that is different from that of any other abrasive grain. Therefore, the trajectory lines of each abrasive grain on it do not overlap, resulting in the largest number of effective abrasive grains and the smallest dressing force. (3) The similarity between the simulation and the dressing force obtained from the experiment verifies the reliability of the simulation of the dressing process of the wheel by finite element analysis. It also proves the feasibility of replacing the material properties of the white corundum grinding wheel with the JH-2 intrinsic parameter of alumina ceramics with 99.5% content in the kinetic simulation.

Analysis of flow field characteristics of silicon carbide CMP under ultrasonic action

WANG Zexiao, YE Linzheng, ZHU Xijing, LIU Yao, CHUAI Shida, LV Boyang, WANG Dong

2025, 45(1): 102-112. doi: 10.13394/j.cnki.jgszz.2023.0273

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Objectives Silicon carbide faces challenges such as low polishing efficiency and poor surface quality during processing. The ultrasonic-assisted CMP (UCMP) processing technology is used to smooth and non-destructive polishing the SiC surface, and the influence of ultrasonic assistance on the CMP flow field is deeply investigated in order to improve the polishing effect of SiC. Methods (1) COMSOL Multiphysics is used to conduct CFD simulation on the polishing flow field of the silicon carbide UCMP process, aiming to explore the influences of factors such as ultrasonic frequency, ultrasonic amplitude, and liquid film thickness on the polishing flow field. A model is constructed to study the polishing flow field characteristics under ultrasonic vibration, based on an achievable k−ε model to analyze the polishing flow field characteristics under ultrasonic action. (2) The influences of ultrasonic frequency, ultrasonic amplitude, and liquid film thickness on velocity and pressure in the polishing flow field are studied by the finite element method. (3) The CMP and UCMP comparative experiments are conducted to compare the polishing effects of SiC wafers under the two processes. Results The ultrasonic frequency has a significant impact on the flow field of the polishing solution, and it has a significant promoting effect on the flow field of the polishing solution. As the ultrasound frequency increases from 20 kHz to 40 kHz, the maximum velocity of the flow field increases from 324.10 m/s to 698.20 m/s, and the maximum pressure increases from 177.00 MPa to 1580.00 MPa. Compared with CMP, the polishing quality of the SiC wafer after UCMP is better, with a minimum surface roughness R_a of 3.2 nm and a higher material removal rate of 324.23 nm/h. Conclusions The UCMP process is used to process the SiC surface, and the positive effect of ultrasound-assisted polishing flow field is verified through theoretical analysis and experimental verification. The relationship between the ultrasonic frequency and the polishing flow field characteristics has been clarified, providing data support for further optimizing UCMP process parameters. The UCMP process has significant advantages in improving the polishing quality and material removal rate of SiC, and is expected to be widely applied in the field of silicon carbide material processing. Further research can be conducted on the influence of other factors on the UCMP process effect to achieve more ideal processing results.

Study on dispersion of abrasive particles in electro Fenton CMP slurry and design of green polishing fluid in neutral environment

CHENG Feng, WANG Zirui, ZHU Rui, WANG Yongguang, PENG Yang, ZHANG Tianyu, ZHAO Dong, FAN Cheng

2025, 45(1): 113-121. doi: 10.13394/j.cnki.jgszz.2023.0242

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Objectives In the process of GaN ultra-precision polishing, diamond abrasives tend to agglomerate, leading to an increase in the average particle size of abrasives in the polishing slurry, which negatively impacts the surface precision of GaN. The addition of Fe²⁺ in the Fenton reaction exacerbates this phenomenon. To address this issue, adding electrolytes to the polishing slurry has proven effective in mitigating the agglomeration and sedimentation of abrasives. To compare the effects of STPP, NaCl, and Na₂SO₄ on the dispersion stability of diamond abrasives during the Fenton reaction, the citric acid and the sodium hydroxide are used as pH regulators to investigate the Fenton reaction of green polishing solution at different pH values. The effects on the anti-settling ability of diamond abrasive particles, the Zeta potential of polishing slurry, and the polishing solution abrasive particle size are studied, and the polishing effect on the GaN wafer is verified. Methods Nano-diamond abrasive particles with an average particle size of 180 nm were added to deionized water, and H₂O₂ with a mass fraction of 5% and FeSO₄·7H₂O with a mass of 0.2 g were added as the original reactants of the Fenton reaction. Then, NaCl, Na₂SO₄ and STPP electrolytes with a mass fraction of 1% were added to prepare three groups of Fenton reaction polishing slurry, which were compared with the original Fenton reaction polishing slurry without any additional electrolyte. After thorough stirring for 5 minutes and ultrasonic dispersion for 10 minutes, citric acid and sodium hydroxide were used to adjust the pH values of all four slurries to 3. At the same time, the polishing slurry with STPP electrolyte at a pH value of 6 was prepared, and the influence of pH value on the anti-settling effect of diamond abrasive particles under STPP electrolyte was preliminarily investigated as the control group. The above five groups of polishing slurries were added to glass bottles for particle settling experiments, and the dispersion stability of diamond abrasive particles in different groups of polishing slurry was observed. The Zetasizer Nano ZS90 nanometer particle size potential analyzer was used to measure the Zeta potential and the particle size of the five groups of polishing slurries before and after the addition of a pH regulator. Finally, the ECMP experiment was carried out to study the effects of green polishing slurries on material removal rate and surface roughness at different pH values. Results (1) When the pH value is 3, the original Fenton polishing slurry and the polishing slurries with NaCl and Na₂SO₄ electrolytes have weaker anti-settling ability compared to the polishing slurry with STPP added, and the effect of improving the anti-settling ability of diamond abrasives is not obvious. The first three groups of polishing slurries exhibit an obvious delamination phenomenon at the bottom within the first 10 minutes. This indicates that STPP can improve the anti-settling ability of diamond abrasives in Fenton reaction polishing slurry. Furthermore, comparing the polishing slurry samples with STPP added at pH values of 3 and 6, it is found that the anti-settling ability of diamond in the polishing slurry with a pH value of 3 is significantly lower than that in the sample with a pH value of 6, indicating that STPP can improve the anti-settling ability of diamond abrasives in an environment with a pH value of 6. (2) The addition of NaCl and Na₂SO₄ electrolytes results in a smaller absolute Zeta potential and poorer stability of the polishing slurry, while the addition of STPP greatly increases the dispersion stability of diamond abrasives in the Fenton reaction polishing slurry. At the same time, after adjusting the pH value to 3, the absolute values of the Zeta potential of all polishing slurries slightly decrease compared to before pH adjustment, indicating a decrease in the stability of the polishing slurry. That is, the addition of acidic electrolytes may reduce the stability of the polishing slurry. (3) When the surface of GaN is processed with the polishing slurry containing STPP, there are almost no deep scratches caused by abrasive agglomeration compared with other comparison groups. The surface quality of the processed GaN is the best, with a surface roughness R_a as low as 0.449 nm, and the material removal rate is much higher than that of the control group, reaching up to 705.3 nm/h. Conclusions The Fenton reaction utilizes Fe²⁺ to react with H₂O₂ to generate hydroxyl radicals (·OH) with strong oxidizing properties. With the addition of STPP, Fe²⁺in the solution forms a relatively stable complex Fe²⁺-STPP with STPP, and which quickly reacts with H₂O₂ to form Fe³⁺-STPP and ·OH after the addition of H₂O₂, effectively avoiding the presence of a large amount of free Fe³⁺ and the precipitation of Fe(OH)₃. Adding STPP to the Fenton reaction polishing slurry with diamond as abrasive particles can broaden the pH range of the Fenton reaction polishing slurry, breaking the limit of pH≤3, and preventing the precipitation of iron flocs in the polishing slurry in a neutral environment. Meanwhile, STPP can enhance the anti-settling ability of diamond abrasives in the Fenton reaction polishing slurry in a neutral environment, and the alkaline pH regulator weakens the anti-settling ability of diamond abrasives in polishing slurry more significantly than the acidic pH regulator.

Parameter calibration of a discrete element simulation model for dry lightweight heterogeneous media

LIANG Zhiqiang, LI Xiuhong, WANG Xingfu, LI Wenhui, YANG Shengqiang, LIANG Zhenhua

2025, 45(1): 122-133. doi: 10.13394/j.cnki.jgszz.2024.0016

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Objectives Dry light-shaped medium is a type of machining medium commonly used in the rolling finishing process. Its shape varies, making it difficult to test and calibrate the contact parameters used in discrete element simulation, which affects the accuracy of the simulation. In this study, walnut shell medium is taken as the research object, and the intrinsic parameters and contact parameters of walnut shell medium are tested based on the basic parameter measurement methods of granular material, both domestically and internationally. The friction coefficient between the medium is calibrated with the accumulation angle obtained by the experiment as the response value, in order to provide parameter support for the discrete element simulation of dry light-shaped medium roller grinding. Methods The density of walnut shell medium is obtained using oil discharge method and the measuring cylinder method. The elastic/shear modulus is measured by the texture analyzer. The shape characteristic parameters are measured by the PartAn 3D particle dynamic image analyzer, and the shapes are classified by the multi-dimensional method. Based on the strong correlation between two-dimensional and three-dimensional shape characteristic parameters, a single particle simulation model of 24 types of dry-shaped media is constructed, and the dry-shaped media are bonded into particle plates. The collision recovery coefficient between the dry-shaped media is measured by the inclined plate collision experiment. The static friction coefficient, rolling friction coefficient, and collision recovery coefficient between the dry-shaped medium and acrylic are obtained using a self-made contact parameter measuring device. Taking the actual packing angle as the test object and the friction coefficient between the walnut shell media as the factor, a two-factor five-level rotation orthogonal test is carried out to establish the second-order regression equation of the friction coefficient and packing angle. The actual packing angle, as the target value, is optimized. The discrete element simulation and experiment are combined to determine the best parameter combination of the static friction coefficient and the dynamic friction coefficient between the dry-shaped media. Results (1) The physical experiment results show that the real density of walnut shell medium is 1024 kg/m³, the packing density is 642 kg/m³, and the shear modulus is 9.219 × 10⁷ Pa. (2) The collision recovery coefficient between the walnut shell medium and the acrylic plate is 0.246, the static friction coefficient is 0.422, the rolling friction coefficient is 0.175 and the collision recovery coefficient between the walnut shell medium is 0.340. (3) The actual stacking angle is the target value for optimization, and the optimal parameter combination of friction coefficient between dry-shaped media is determined by combining discrete element simulation and experiment: the static friction coefficient between walnut shell media is 0.829, and the rolling friction coefficient is 0.191. (4) The stacking test is carried out on the stacking angle under different baffle lifting speeds, and the relative error between the simulated and actual stacking angle is less than 4%, which proves that the parameter combination can be effectively used for EDEM simulation process analysis. Conclusions In this paper, the relevant parameters of walnut shell medium are measured and calibrated by combining experiment and simulation. Based on the multidimensional shape classification and the strong correlation between two-dimensional and three-dimensional morphological features, a single particle simulation model of dry-shaped medium can be effectively constructed. In this way, the calibrated walnut shell medium particle model can more truly simulate the interaction between walnut shell medium, parts, and processing equipment, and analyze and predict from a microscopic point of view. In the future, this method can be used for parameter testing and calibration of shaped media such as corncob and olive shell, thereby expanding the application range of the dry-shaped media calibration method.

Optimization of magnetic compound fluid polishing process parameters for PMMA workpieces based on grey relational analysis

WANG Youliang, GAO Xichun, ZHANG Wenjuan

2025, 45(1): 134-142. doi: 10.13394/j.cnki.jgszz.2023.0282

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Objectives MCF polishing technology has become an advanced ultra-precision machining method. To address the issue of different process parameters in achieving optimal surface quality or maximum processing efficiency in MCF polishing technology, it is necessary to accurately control the range of each process parameter and deeply understand the impact of different process parameters on MCF polishing performance. Methods The process parameters of the MCF polishing tool are optimized based on grey relation analysis (GRA) to meet the requirements of minimum surface roughness while improving material removal efficiency. Under the given experimental conditions, it is verified that the optimized MCF polishing tool has excellent polishing performance, and the mechanism of the influences of various process parameters on the polishing performance of the MCF polishing tool is analyzed in detail. Firstly, a three-factor four-level PMMA workpiece polishing experiment is designed using the orthogonal test method, and the influence mechanism of each factor on MCF polishing performance is analyzed. Afterwards, the GRA method is used to optimize multi-objective factors, and the optimization scheme of process parameters with the best polishing effect is determined. Finally, the optimized process parameters are used to verify the polishing of the workpiece, and the surface morphology and the contour of the workpiece are obtained. Results When the magnetic induction intensity B = 0.5 T, the diameter of carbonyl iron powder D_CIP = 7 μm, and the diameter of abrasive particle D_AP = 3 μm, the surface finishing ability of the MCF polishing tool is the best. When the magnetic induction intensity B = 0.5 T, the diameter of carbonyl iron powder D_cip = 7 μm, and the diameter of abrasive particle D_AP = 7 μm, the material removal efficiency of the MCF polishing tool is the highest. The magnetic induction intensity has the greatest impact on the polishing quality and the material removal efficiency of the MCF polishing tool, followed by the diameter of carbonyl iron powder, while the effect of the diameter of the abrasive particle is relatively small. During the polishing process, abrasive particle with a smaller diameter make the surface of the workpiece smoother, but the processing efficiency is lower. The polishing effect of abrasive particles with a larger diameter is uneven, but the processing efficiency is higher. The grey correlation degree of each orthogonal experimental group is calculated based on GRA, and the multi-objective factors were optimized to obtain the optimal combination of process parameters, comprehensively considering the workpiece surface quality and processing efficiency, that is, when the magnetic induction intensity B = 0.5 T, the diameter of carbonyl iron powder D_CIP = 7 μm, and the diameter of abrasive particle D_AP = 3 μm, the MCF polishing tools achieve the best comprehensive polishing performance. Under the given conditions, the PMMA workpiece is polished by using the optimal process parameter, reducing the surface roughness of the workpiece from 477 nm to 14 nm, with a surface roughness reduction rate of 97.06%, which is 3.49 percentage points higher than that before optimization. The material removal rate reaches 2.088×10⁸ $ \mathrm{\mu } $m³/min, which is 3.5% higher than that without optimization. Conclusions The process parameter combination obtained through GRA optimization not only meets the requirements for high surface quality of the workpiece, but also significantly improves the material removal rate of the MCF polishing tool. After GRA optimization, the polishing ability of the MCF polishing tool is significantly enhanced.

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2025 Vol. 45, No. 1

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Current Issue 2025 Vol. 45, No. 1

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Current Issue
2025 Vol. 45, No. 1