金刚石与磨料磨具工程

Highly efficient polishing of polycrystalline CVD diamond via atmosphere inductively coupled plasma

XIAO Yuxi, LI Xinyu, ZHANG Yongjie, DENG Hui

2024, 44(5): 553-562. doi: 10.13394/j.cnki.jgszz.2023.0281

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Objectives: As a typical difficult-to-machine material, polycrystalline CVD diamond often requires sophisticated and time-consuming polishing methods to achieve a smooth surface. In this study, a non-contact polishing method based on atmospheric inductively coupled plasma is investigated for the polishing of polycrystalline CVD diamond. Several indicators, including surface roughness, surface chemical composition, inner crystal structure, and material removal rate (MRR), are measured during the polishing process to evaluate the surface quality and polishing efficiency. Methods: The atmospheric inductively coupled plasma device, consisting of a plasma working zone, radio frequency (RF) power, electric sparker, RF match, mass flow controller, and water cooler, is used for polishing experiments. Oxygen is used as a reaction gas and added to the pure argon plasma, generating highly active oxygen radicals. The polycrystalline CVD diamond sample is fully exposed to oxygen-containing plasma irradiation to gain sufficient activation energy and react with the oxygen radicals. Once the processing is completed, the RF power is turned off, the oxygen supply is stopped, and the diamond is raised and cooled with pure argon shielding to protect the sample from being etched by ambient oxygen at high temperatures. Laser scanning confocal microscopy and scanning electron microscopy (SEM) are used to observe the diamond morphology, while the S_a roughness at different scales is characterized by scanning white interferometry and atomic force microscopy (AFM). The material removal rate is measured using an ultra-precision balance, and surface temperature is detected by an infrared imager. Raman spectroscopy and X-ray diffraction (XRD) are separately used to characterize the surface chemical composition and crystal orientation of the diamond before and after polishing. Results: The results of diamond treatment under different plasma irradiation conditions show that pure argon plasma tends to deteriorate the surface quality, while oxygen-containing plasma achieves significant polishing performance, removing grain tips and protruding structures. The morphology evolution of diamonds during the polishing process reveals that the initial surface is extremely rough, with severe surface irregularities and angular grain structures. After exposure to oxygen-containing plasma, the elevated grain structures are gradually removed, and the sharp edges are rounded. As the plasma irradiation time increases, some protruding sites are further eliminated, revealing the remaining cavities formed during the crystal growth process. Ultimately, the various crystal grains on the diamond surface maintain a consistent height, forming a relatively smooth surface. The fluctuating grain boundaries, which are widespread among the crystal grains, inhibit the formation of a smoother surface. The polishing effect can be explained by the principle of plasma-based atom-selective etching (PASE). During the polishing process, carbon atoms with different bonding states are randomly distributed on the diamond surface. Among them, carbon atoms at the grain tips, which only bond with atoms below and possess less stable bonds compared to those in the substrate, have lower activation energy. Consequently, tip carbon atoms preferentially react with active oxygen radicals due to their lower activation energy, accounting for the removal of grain tips during the initial polishing stage. As the polishing process continues, carbon atoms with fewer covalent bonds fade away, and the bonding states become equivalent in local areas, contributing to a progressively smoother surface. However, carbon atoms at the crystal boundary zones have complex arrangements and bonding characteristics, which restrict the differential removal of carbon atoms and hinder the overall polishing effect. The roughness evolution results show that the final S_a roughness of polycrystalline CVD diamond is reduced to 93.70 nm over a 400 μm × 400 μm area and 21.40 nm over a 20 μm × 20 μm area after polishing for 30 minutes. In some smooth areas, the roughness is as low as 2.53 nm, while in the crystal boundary zones, it reaches 31.30 nm. The presence of the crystal boundary zone hinders the global polishing performance. After 30 minutes of polishing, the surface roughness stabilizes, with the MRR also stabilizing at 34.4 μm/min. Surface composition analysis indicates a tensile stress of 1.5309 GPa on the diamond surface, and the polishing process dose not introduce new stress or amorphous carbon contaminants. XRD spectra show that there is no change in the crystal grain orientation of the diamond before and after polishing, demonstrating that PASE acts on all crystal planes of polycrystalline diamond (PCD) without preference for any specific crystal plane. Conclusions: Atmospheric inductively coupled plasma (ICP) can be used to efficiently smooth polycrystalline CVD diamond based on the principle of PASE. During the polishing process, oxygen is introduced as a reaction gas, generating oxygen radicals that selectively etch the diamond by preferentially removing carbon atoms with low activation energy, thus rapidly smoothing the surface. The S_a roughness of diamond is reduced from 10.10 μm (400 μm × 400 μm) and 338.00 nm (20 μm × 20 μm) to 93.70 nm and 21.40 nm, respectively, after 30 minutes of polishing. As polishing progresses, the MRR sharply decreases and eventually stabilizes at around 34.4 μm/min. The surface chemical composition and crystal grain orientation of polycrystalline CVD diamond remain consistent before and after polishing. Overall, atmospheric ICP can be an efficient pre-polishing method to significantly improve the overall polishing efficiency of polycrystalline CVD diamond.

Research status of thermal damage inhibition technology for diamond

ZHANG Jianhua, LI Ang, HU Tingting, DU Quanbin, CUI Bing, ZHANG Liyan, WANG Lei, MAO Wangjun

2024, 44(5): 563-574. doi: 10.13394/j.cnki.jgszz.2023.0166

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Significance: As the hardest material, diamond is widely used in various cutting and grinding tools. During the preparation process of diamond tools, thermal damage to diamonds is almost inevitable. The thermal damage to diamonds primarily includes graphitization, breakage, cracking, and chemical erosion. Graphitization of diamonds is a lattice transformation process of C atoms essentially, which requires sufficient energy to overcome the energy barrier. Consequently, during the preparation process of diamond tools, diamonds undergo varying degrees of graphitization due to high temperatures and catalyst elements. Breakage and cracking of diamonds primarily orginate from thermal mismatch between the diamond and the matrix metal, including its carbides, where carbides act as inducers of local residual stress, facilitating crack propagation. Chemical erosion of diamonds mainly refers to the process in which C atoms on the surface of diamonds react with active elements through diffusion during the sintering process, therefore deteriorating the diamonds. However, due to the poor wettability of diamonds, it often necessitates the addition of active elements such as Ti, Cr, V, etc., to react with diamonds and improve the holding force. Current suppression technologies for diamond thermal damage can be roughly divided into surface coating of diamonds, adjustment of matrix material properties, and optimization of forming technology. Progress: Diamond surface coating utilizes the unbonded atoms present on the diamond surface, which can react with certain elements at sufficiently high temperatures to form carbides, thereby enhancing the wettability between the matrix metal and the diamonds. Depending on the type of coating, it can generally be classified into metal and non-metal coatings. Metal coatings not only fill and repair defects in diamonds but also improve the bonding strength between the metal and diamonds. Common coating metals include Ni, Ti, W, Cr, and alloys are also selected as coating materials. For non-metal coatings, elements such as B and Si are typically chosen, as they can form carbide layers on the diamond surface, protect the diamond structure, reduce diamond oxidation, and prevent diamonds from being eroded and damaged by strong carbon elements in the matrix material. The choice of matrix material plays a crucial role in mitigating thermal damage to diamonds. Low-melting-point matrix materials can effectively reduce sintering temperature and inhibit the graphitization of diamonds consequently. Furthermore, incorporating appropriate active elements into the matrix material can enhance the interfacial strength between diamond and the matrix, thereby improving the performance of diamond tools. Currently, the modulation of matrix material properties is primarily focused on alloy optimization and composite material development. Alloy optimization aims to reduce diamond thermal damage by refining the alloy composition of the matrix material. Researchers have experimented with elements such as Si, Hf, and Zr, discovering that these elements can mitigate the erosion of diamonds by active elements and reduce diamond thermal damage. Additionally, amorphous Ni-based alloys, due to their low melting point and narrow melting range, have been used as brazing materials to enhance the performance of diamond tools. Composite material development seeks to improve mechanical properties while utilizing suitable reinforcing phases to absorb catalytic elements within the matrix, thereby reducing diamond graphitization. Additionally, reinforcing phases could optimize the diamond interface condition, leading to both increased interfacial strength and reduced diamond thermal damage. Molding technology significantly impacts the lifespan and performance of diamond tools, particularly through parameters such as molding temperature, soaking time, molding pressure, and atmosphere. Molding temperature and soaking time determine grain growth in the matrix, diamond thermal damage, and the interfacial growth between diamond and the matrix. Molding pressure affects the density of the matrix material, which in turn influences its mechanical properties. The atmosphere, typically vacuum or protective, must be carefully controlled, as even trace amounts of moisture or oxygen could lead to diamond oxidation, degrading tool performance and lifespan. Diamond tools are typically manufactured through methods such as hot-press sintering and brazing, while additive manufacturing is emerging as a promising direction in tool fabrication. Conclusions and Prospects: Future research to mitigate diamond thermal damage could focus on three main areas: theoretical analysis of diamond interfaces at the microscale, the establishment of a guidance system matching diamond tool matrix materials with service environments, and investigation of the mechanical behavior of diamonds interfaced during the molding process.

Preparation and performance characterization of (Ti,Nb) C_x composite material

ZOU Qin, REN Yu, LI Yanguo, REN Haibo

2024, 44(5): 575-580. doi: 10.13394/j.cnki.jgszz.2023.0164

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Objectives: The aim was to prepare a variety of non-stoichiometric (Ti, Nb)C_x PCD tool binder composites using TiC and transition metal Nb by mechanical alloying (MA) technology. The effects of different sintering temperatures and Nb contents on the phase compositions, microstructures, and mechanical properties of the composites were investigated to provide a scientific basis for optimizing the properties of PCD tool binders. The specific tasks included preparing (Ti, Nb)C_x composites with varying ratios, analyzing their solid-solution behavior at different temperatures, and evaluating their hardness and fracture toughness. Methods: High purity TiC and Nb powders were selected as raw materials for the experiment, and the MA technology was used to achieve uniform mixing of the two materials. In order to investigate the effect of sintering temperature on the properties of composite materials, various sintering temperatures ranging from 1300 to 1700 ℃ were set. The sintered samples were subjected to phase analysis using an X-ray diffractometer, and the data were analyzed using Jade software. Subsequently, the fracture morphology of the sintered body was observed using scanning electron microscopy (SEM), and the hardness and fracture toughness of the composite materials were measured using a Vickers hardness tester. Results: Within the sintering temperature range of 1300 to 1700 ℃, the solid-solution degree of TiC and Nb gradually increases with the increase in temperature. At higher temperatures, the diffusion between TiC and Nb accelerates, forming a more stable solid-solution, and the phase composition tends to stabilize. At the same sintering temperature, the hardness of the (Ti, Nb)C_x composite increases gradually with the increase in Nb content, indicating that the introduction of Nb enhances the overall hardness of the composite. Especially when the sintering temperature is 1600 ℃, the (Ti, Nb)C_0.50.5 composite exhibits the best mechanical properties with a hardness of 23.0 GPa and fracture toughness of 7.20 MPa·m^1/2. The results show that under these temperature and ratio conditions, the composite achieves the best solid-solution state, has fewer internal defects, moderate grain size, and optimal mechanical properties. Conclusions: The sintering temperature and Nb content have significant impacts on the phase composition and mechanical properties of (Ti,Nb)C_x composite materials. Controlling these two parameters can optimize the hardness and toughness of the composite materials, thereby enhancing their application potential in PCD cutting tools. The higher sintering temperature is conducive to the full solid-solution of TiC and Nb, forming a more stable crystalline phase structure and improving the mechanical properties of the material. Future research could explore the influences of introducing other transition group metals on the properties of composite materials in order to develop higher-performance PCD tool binders. Others: Although the main objective of this study is to optimize the performance of (Ti,Nb)C_x PCD tool binders, the mechanical alloying techniques and analytical methods used in this research have the potential for broader applications. The mechanical alloying technology is not only suitable for the development of PCD tool materials but also for the preparation of other high-performance composite materials. At the same time, the combination of X-ray diffraction analysis and scanning electron microscopy provides valuable data support for the field of materials science, which helps deepen the understanding of the microstructure and phase composition of materials, thereby promoting research progress in the field.

Effect of metal coated FeCuNi powder on properties of diamond tool matrix

CAO Xinmin, BAO Li, LI Zhen, CHENG Chuanwei, CHEN Peng, PAN Jianjun, YU Qi, YU Xinquan, CHEN Shengchao

2024, 44(5): 581-587. doi: 10.13394/j.cnki.jgszz.2022.0174

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Objectives: Diamond tools are widely used in fields such as oil drilling, geological exploration, and stone processing, among which sintered metal bond diamond tools have become the most representative due to their wide applicability and strong durability. Cobalt (Co) has become the preferred material for preparing diamond tools due to its excellent physical properties, but its price is relatively expensive. As market competition gradually intensifies, the application range of Co is becoming limited. It has been found that Fe-based pre-alloy powder has similar properties to Co and can be used as an important way to reduce costs. However, Fe-based diamond tools face problems such as high sintering temperature, narrow controllable process range, easy erosion of diamond, weak holding force, and the tendency for the matrix to burn during production. Additionally, the Sn element is prone to segregation and loss during long-term sintering in the furnace, resulting in unstable performance of diamond tools. This article describes the preparation of FeCuNi-Cu/Sn/Bi alloy powder using a multi-layer coating process to improve the densification of diamond matrix sintering and reduce component segregation. Methods: Co powder, Cu powder, Fe powder, Sn powder, Ni powder, and FeCuNi alloy powder were selected, and Cu, Sn, and Bi were respectively plated onto the surface of FeCuNi alloy powder by chemical methods, forming a uniform coating on the surface. Metal powder and diamond were mixed using a three-dimensional mixer for 2 hours. After mixing, the required weight of uniform powder was weighed, and sample blocks with dimensions of 4 mm × 8 mm × 40 mm were prepared using a hot press sintering machine. The mold material was graphite, and 4 sample blocks were prepared for each group. The experiment was repeated twice. For the tested materials, Rockwell hardness was measured, as well as the three-point bending strength. The microstructure and energy spectrum were analyzed using an electron microscope, and the changes in composition, structure, and mechanical properties of the tire body with fewer joints under different processes were compared and analyzed. Four formulations of sintered diamond tool bodies were designed, and their physical properties were tested. Eight samples were prepared for each formulation. After removing the maximum and minimum values, the average value of the data was calculated for analysis. Results: The hardness of the coated alloy powder formulation body decreased from 110 HRB to 106 HRB, but the decrease was less than 4%, indicating that the hardness remained similar. After adding the coated alloy powder, the flexural strength of the tire body increased by more than 10%. Specifically, for the formulation containing FeCuNi-Bi powder, the flexural strength increased from 945 MPa to 1,120 MPa, an increase of nearly 20%. The improvement was due to the even distribution of low-melting point elements coated on the surface of the alloy powder, which reduced the porosity of the matrix during the sintering process, thereby improving the bending strength of the matrix. Analysis of the microstructure of the four sintered tire bodies revealed that Sn in the original formula reacted with metal elements such as Cu in the tire body, gradually forming CuSn alloy. The distribution of Sn was uneven, and segregation was severe. As the sintering temperature increased, some CuSn alloys with higher Sn content began to melt. However, the wettability between the liquid CuSn alloy and Co or Fe particles was poor, and the distribution in the tire body was discontinuous. The vast majority of the CuSn liquid phase could not penetrate the Co and Fe skeleton phases to form a network connection. Under the interaction of sintering temperature and pressure, a strong and dense bond could not be formed, resulting in an uneven microstructure of the tire body and negatively affecting the performance and application of diamond tools. After adding FeCuNi-Cu/Sn/Bi alloy powder to the formula, the distribution of the coated alloy powder was relatively uniform. During sintering, Sn and Bi on the surface of FeCuNi alloy powder particles melted first, reacting with Cu to form liquid phases such as Cu-Sn and Cu-Bi. These phases gradually diffused along the FeCuNi alloy powder particles from the outside to the inside, entering the gaps between Fe, Ni, FeCuNi and other particles. Ultimately, Cu-Sn and Cu-Bi alloys formed a continuous network structure, encapsulating and bonding particles such as FeCuNi, Fe, and Ni, making the composition and microstructure distribution of the diamond tool bodies more uniform and dense, thus avoiding component segregation. Conclusions: FeCuNi-Cu/Sn/Bi alloy powder was prepared by chemically plating Cu, Sn, and Bi onto the surface of FeCuNi alloy powder. After adding the metal-coated alloy powder to the formula, the microstructure of the matrix was refined, and both hardness and strength were improved. The FeCuNi-Cu/Sn/Bi alloy powder, using coating technology, was sintered to obtain a denser matrix with higher diamond holding force and better mechanical properties.

Diamond particle clarity detection method based on CBAM-ResNet50

FEI Wenqian, ZHAO Fengxia, DU Quanbin, WANG Qinghai

2024, 44(5): 588-598. doi: 10.13394/j.cnki.jgszz.2023.0153

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Objectives: With the improvement of production technology, the traditional diamond particle cleanliness detection method can no longer meet the requirements of high precision, high quality and high automation in the diamond industry due to its low efficiency and poor accuracy. The rapid development of computer technology, optical, and electronic technologies has led to the widespread application of visual inspection and deep learning in image classification and detection, providing new methods for diamond clarity detection. Therefore, based on transfer learning and combined with the convolutional block attention module (CBAM) attention mechanism and the feature pyramid network (FPN) structure, an improved ResNet50 diamond particle clarity detection algorithm, CBAM-ResNet50, is proposed. Methods: The CBAM-RESnet50 clarity detection algorithm uses ResNet50 as the backbone network and adds CBAM to each layer of the backbone network to improve the feature extraction ability of the model. In addition, the FPN structure is integrated into Layer 3 and Layer 4 of the backbone network, where part of the extracted features are aggregated to address the issues of losing features of small and medium-sized targets during the sampling process. At the same time, the transfer learning method is introduced to optimize the model's initial parameters with a cross-entropy loss function, thereby improving the generalization ability and robustness of the model. Moreover, multi-angle diamond images are collected on a diamond clarity detection device, a diamond particle clarity dataset is established, and the improved CBAM-ResNet50 network model is experimentally compared and verified using the data set. Results: Firstly, when compared with other classic mainstream network models, the accuracy of the CBAM-ResNet50 model during training is 99.2%, and the precision is 99.7%, ourperforming the classification results of other network models and significantly improving the identification ability for diamond particle clarity detection. The average detection time of the CBAM-ResNet50 model is 0.01629s, which meets the real-time requirements for industrial detection. Secondly, the CBAM-ResNet50 model is evaluated and ablated on diamond particles of various grades. The results show that the CBAM-ResNet50 model achieves an accuracy of over 99.2%, a classification recall rate of over 98.7%, specificity of over 99.7%, and an F1 score of over 99.2% for classifying diamonds of different grades. The ablation experiment results show that adding the CBAM attention mechanism and FPN feature fusion module significantly improves the classification performance of different grades of diamond particles. The ResNet50+CBAM model achieves a classification accuracy and recall rate of 100.0% for A and E grade diamonds, indicating that the CBAM module helps focus the network's attention on the black impurity features inside the diamond particles, reduces attention to irrelevant information, and improves classification accuracy. The CBAM-ResNet50, with the addition of the FPN feature fusion module, further enhances the classification accuracy and recall rate for B, C, and D grade diamonds. This improvement suggests that the FPN fuses both high-level and low-level feature information, enriching the small target features in the feature map, and enhances classification performance for B, C, and D grade diamonds with similar characteristics. Conclusions: Deep learning technology has been applied to the cleanliness detection of diamond particles, with the ResNet50 network, known for its strong feature extraction ability, serving as the backbone model. Based on the cleanliness features in diamond particle images, the CBAM attention mechanism, the FPN feature fusion module, transfer learning, and the entropy loss function are respectively integrated to address the challenges of insufficient feature extraction, the loss of small target features, and limited generalization in network models. By comparing experiments with other mainstream networks and conducting network ablation experiments, the impact of various improvements on the performance of the diamond particle cleanliness classification network is studied, confirming the effectiveness of the improved network model.

Mechanical properties and rock-breaking effects of ridge-shaped PDC teeth

XIE Zhitao, ZHAO Yuxuan, GUO Yong, WU Desheng, LI Yadong

2024, 44(5): 599-606. doi: 10.13394/j.cnki.jgszz.2023.0172

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Objectives: With the depletion of easily recoverable oil reservoirs, the focus of oil and gas exploration and development in China has shifted to "two deeps and non-conventional" oil and gas fields. This transformation is not only accompanied by a significant increase in well depth and more complex formation challenges but also presents more stringent requirements for the design and construction of drilling engineering, which directly leads to a significant extension of the drilling cycle. The length of the drilling cycle is a key factor in determining drilling costs. Therefore, for a long time, scholars have been committed to improving the mechanical penetration rate and the durability of polycrystalline diamond composite (PDC) bits. The main purpose of this study is to analyze geological characteristics in depth, accurately match and optimize the design of special-shaped teeth in PDC drill bits, in order to significantly reduce the risk of drill bit failure and greatly improve mechanical drilling speed and footage. Given the wide application of PDC bits in hard rock drilling and their key impact on the cost and efficiency of drilling operations, this study focuses on the design and optimization of ridge-shaped PDC teeth, aiming to explore more suitable tooth structures for specific geological conditions through scientific testing and comparative analysis. This will promote innovation and efficiency improvements in drilling technology. Methods: Based on round teeth, the wear resistance, impact resistance, and rock-breaking effect of three types of ridge-shaped teeth were systematically tested. First, the wear resistance and impact resistance of three typical ridge-shaped PDC teeth—namely the 165 axe-shaped, 135 axe-shaped, and three-edged cutters—were tested to quantitatively evaluate their mechanical properties. Subsequently, granite was selected as the representative rock sample, and the single-tooth cutting tests were conducted with three different penetration depths to simulate the cutting effect under various drilling pressures during actual drilling. Additionally, a full-size bit simulation drilling test was designed to evaluate the drilling performance of each tooth shape under different pressures, and the data were compared with those of round teeth. This series of tests aimed to fully reveal the advantages and disadvantages of ridge-shaped PDC teeth in terms of wear resistance, impact resistance, and rock-breaking effectiveness. Results: The test results show that the three ridge-shaped PDC cutters significantly outperform the round teeth in terms of wear resistance. The 135 axe-shaped cutter, with the smallest ridge angle, exhibited the greatest improvement in wear resistance, indicating that the ridge design enhances the durability of PDC cutters and bits. In terms of impact resistance, the 165 axe-shaped cutter and the three-edged cutter performed excellently and could effectively withstand high impact loads, while the 135 axe-shaped cutter had relatively weaker impact resistance due to insufficient support at the impact point. Further analysis of the cutting force data revealed that the tangential force and normal forces of ridge-shaped cutters were lower than those of round cutters at the same cutting depth. The smaller the ridge angle, the smaller the cutting force, which indicates that the ridge design helps reduce cutting resistance and improve drilling efficiency. The full-size drill bit simulation drilling test results showed that the 135 axe-shaped cutter achieved the fastest mechanical drilling speed and is suitable for high-pressure operations. The three-edged cutter performed better in the low-pressure range (≤ 20 kN), while the round teeth had the slowest drilling speed and a lower suitable drilling pressure range. Additionally, the variation in ridge tooth angle not only affects the impact resistance but also directly influences the rock-breaking effect by altering the stress distribution within the rock. Conclusions: Through systematic testing and comparative analysis, this study has verified the significant advantages of ridge-shaped PDC cutters in improving drilling efficiency and reducing the risk of drill bit failure. Specifically, the ridge design effectively enhances the wear resistance and impact resistance of the drill bit while reducing cutting force and increasing mechanical drilling speed. The performance differences of the various ridge-shaped cutters under different drilling pressure conditions provide a scientific basis for the flexible selection of drill bit types based on formation conditions during drilling operations. In the future, further optimization of ridge-shaped PDC cutter designs, especially for specific formation conditions, will be an important direction for improving mechanical drilling speeds and reducing operational costs.

Research of brittle-plastic behavior of SiCp/Al composites based on nano-indentation/scratch

LIU Yamei, WANG Jiali, GU Yan, WU Shuang, LI Zhen

2024, 44(5): 607-620. doi: 10.13394/j.cnki.jgszz.2023.0165

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Objectives: SiCp/Al composite is a kind of particle-reinforced metal matrix composite, which offers high specific strength and low density. It is widely used in electronic packaging, aerospace and automobile manufacturing. Although the presence of a large number of SiC particles improves the mechanical properties of the material, it also presents significant challenges in processing. As the volume fraction of SiCp/Al composite material increases, its mechanical parameters such as hardness improve, but a large number of surface defects appear during processing.To improve the surface machining quality and select better machining parameters, it is crucial to investigate the mechanical properties and the removal mechanism of SiCp/Al composites with medium or high volume fraction. Methods: Nanoindentation is a commonly used method for testing hardness, which can quantitatively characterize the hardness, elastic modulus and other mechanical parameters of materials. It provides a theoretical basis for predicting machined surface roughness. The load-depth curves of SiCp/Al composites under specific indentation load and rate can be obtained through nanoindentation experiments. The hardness and elastic modulus of SiCp/Al composites are determined using the Oliver-Pharr method. Due to the presence of a large number of SiC particles in the SiCp/Al composite, different failure behaviors are observed when the diamond indenters applies loads to the SiC particles, Al matrix, and two-phase interfaces, resulting in significant differences in measured hardness and elastic modulus. After the indentation experiment, scanning electron microscope (SEM) is used to observe the indentation surface morphology, and the ABAQUS finite element software is used to simulate the indentation process of SiCp/Al composites. The reasons for the differences in mechanical properties are then analyzed based on the finite element simulation results and the experimental indentation surface defects. Results: It is found that when the diamond indenter acts on SiC particles, the experimental values of hardness and elastic modulus of the material are the largest, with average values of 22.75 GPa and 190.78 GPa, respectively. When the indenter acts on the matrix phase, the average values of hardness and elastic modulus are 1.39 GPa and 66.52 GPa, respectively. For the interface between the two phases, the average hardness and elastic modulus measured are 4.62 GPa and 84.38 GPa, respectively. Additionally, the nanoscratch experiment simplifies the complex interaction between abrasive particles and the workpiece during grinding. It explores the brittle-plastic transformation behavior and potensial surface defects of the material surface by applying loads to the workpiece. This is an effective method for studying the material removal form. The hardness and elastic modulus values obtained from the nanoindentation experiment are introduced into the scratch finite element simulation. A variable load of 0 to 400 mN is applied to the SiCp/Al composite, with the scratch speed fixed at 0.05 mm/s. The results show that the removal form of the material changes with the load during the scraping, ploughing and cutting stages. The matrix phase undergoes plastic plastic flow, causing plastic ridge accumulation with coating phenomenon, while the SiC particles are removed by brittle mechanisms such as debonding, breaking, and pulling out. Conclusions: In the indentation experiment, secondary indentation of SiC particles in SiCp/Al composites results in significant differences between the mechanical properties of SiC particles and the theoretical mechanical properties of SiC crystals. Due to fracture and breakage of the particles during the loading process of the diamond indenter, the test results tend to be exaggerated. As the scratch load increases, the removal form of SiCp/Al composites with a volume fraction of 45% replies more on the plastic removal of the matrix phase, while the removal form of SiC particles is mainly brittle. The brittle-plastic behavior of the material surface during machining, as analyzed by the nanoindentation/scratch experiments, provides a theoretical basis for predicting the material's surface quality during machining.

CVD matching analysis of worm grinding and dressing roller based on sector concentric-ring model

LEI Laigui, CHEN Enhou, ZHAO Yanjun, WANG Wei, WU Jialu, GU Longhui, WU Wushan, LI Yuan

2024, 44(5): 621-631. doi: 10.13394/j.cnki.jgszz.2023.0230

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Objectives: As the core component of major equipment, the tooth surface accuracy of gears is ultimately guaranteed by the gear grinding process. The electroplated worm grinding roller is an indispensable precision machining tool for dressing worm grinding wheels, which indirectly plays a decisive role in the machining quality and manufacturing cost of gears. However, the tooth shape of the electroplated worm grinding roller is triangular, which leads to several issues: the adhesion difficulty of abrasive particles at the top of the tooth increases significantly, the distribution of abrasive particles becomes sparse, and the dressing condition deteriorates. The isolated abrasive particles at the top of the tooth resemble a cantilever beam structure and are easily dislodged during the dressing process. As a result, the abrasive particles at the top of the roller tooth fail earlier than those on the sides of the tooth, leading to premature roller wear and scrapping, which seriously affects the manufacturing cost of the gear. To address these issues effectively, this study uses CVD (chemical vapor deposition) reinforced material embedded composite electroplating technology to manufacture worm grinding rollers, guided by the CVD matching theory to improve the grinding stability of the rollers. Methods: First, the equivalent wear model of CVD and diamond abrasive particles is established. Then, the abrasive particle distribution theory model of electroplating worm grinding and dressing rollers is developed using the sector concentric ring model. Next, the CVD matching model is derived through rigorous mathematical formulation. However, since the theoretical model of abrasive particle distribution is complex and difficult to solve, the assignment method is used for more detailed theoretical analysis. Finally, the accuracy of the model is verified through practical applications. Results: (1) The CVD matching quality is closely related to several parameters, such as the relative material properties, electroplating process level, diamond abrasive crystal type characteristics, and roller structure. Among these, material properties, electroplating process level, and abrasive crystal type are relatively fixed. Therefore, in practical engineering applications, emphasis should be placed on the relationship between the number of CVD inserts and the geometric parameters of the worm gear grinding roller structure. (2) When the CVD material is determined, the matching number is primarily influenced by the roller module, with a certain linear negative correlation to the roller module. Additionally, there is a weak negative correlation with the radius R of the CVD arc of the roller, while the relationship with the pressure angle of the machined gear is not significant. (3) When the modulus m_n and the arc radius R are both 0.80 mm, the matching number K of CVD in the roller is most suitable between 40 and 50 grains. When the pressure angle or tooth tip arc is too small, the number of CVD inlays should be appropriately increased. Generally, the change in the number of CVD inserts due to the pressure angle is no more than 10%. At the same pressure angle, when R is 0.50, 0.20, and 0.10 mm, the K value is 1.3, 2.2, and 3.3 times that when R is 0.80 mm. (4) The application verification of the trimming roller shows that when the CVD embedding quantity K reaches ROUNDUP (K_min) or more, the service life of the trimming roller remains largely unchanged with the increase of K. Conversely, when K is reduced, the service life of the trimming roller decreases significantly. When the CVD quantity K decreases by 15%, the service life of the trimming roller is reduced by 17.6%. (5) When dressing the grinding wheel under the same dressing process parameters, the service life of the dressing roller is judged based on the number of dressing cycles after which either grinding burn or tooth profile accuracy deviation occurs. A slight difference of 5% is observed between the actual verification results and the theoretical model results. Based on this, the CVD matching quantity of the roller can be designed according to theoretical calculation results in engineering practice. This ensures proper matching of the tooth tip and side loss of the roller while allowing for a repair margin for failed rollers, effectively reducing tool manufacturing costs. Conclusions: The fan-shaped concentric ring CVD matching model simulates the actual distribution of abrasive particles and CVD inserts in worm grinding rollers and introduces the relative wear performance index between diamond abrasive particles and CVD materials. The established model effectively predicts the top and side wear of CVD grinding rollers, enabling the calculation of the appropriate number of CVD inserts. This helps guide the design of worm gear grinding rollers. The model's accuracy is verified through practical applications, and its results can be applied to optimize the grinding process, reduce tool manufacturing costs, and improve the stability and efficiency of worm gear production.

Simulation and experimental analysis of composite chamfering of superhard cutting tools based on edge grinding technology

LI He, SHI Guangfeng, LV Hongbing, YANG Yongming, LI Sheng, ZHU Lichun

2024, 44(5): 632-643. doi: 10.13394/j.cnki.jgszz.2023.0223

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Objectives: Circular edge chamfering PCD turning tools often feature a chamfered surface at the cutting edge to enhance tool durability. However, the arc at the tool tip causes a large amount of chip accumulation in front of the tool, making chip discharge difficult. This leads to increased cutting temperatures, accelerated tool wear, and reduced surface brightness of the workpiece. To improve the brightness of circular edge chamfering PCD turning tools when processing non-ferrous metals and enhance the tool's durability, a composite chamfering structure is created by performing secondary chamfering on the basis of the circular edge chamfering tool. Methods: Using CATIA software and based on the actual grinding process of the PCD chamfering tool by the COBORN RG9 grinder, the grinding wheel is positioned at different points along the tool's moving path using the trajectory discrete envelope method. The unmachined tool is enveloped, and the overlap between the grinding wheel and the tool is removed, resulting in a three-dimensional approximate model of the composite chamfering tool. By extracting point coordinates, performing curve fitting, surface fitting, surface joining, and other methods, a three-dimensional model of the composite chamfering tool with a cylindrical back surface is established. Deform V11.0 software is then used to simulate the 3D cutting of the PCD composite chamfering tool, calculating the root-mean-square value of the cutting force and the mean cutting temperature under different cutting depths and second-order chamfering widths, as well as under different cutting depths and second-order chamfering angles. The analysis focuses on selecting the second-order chamfering width for different cutting depths when the first-order chamfering width is fixed, and choosing the second-order chamfering angle for different cutting depths when the second-order chamfering width is fixed. Based on this analysis, the effects of different inclination angles on the machining performance of the composite chamfering tool—such as chip flow changes, tool temperature variations, and tool wear—are analyzed. Finally, cutting experiments comparing the PCD composite chamfering tool and the PCD first-order chamfering tool are conducted to analyze changes in cutting temperature under different cutting depths, surface roughness of the workpiece over different processing times, and the final wear states of the two tools. Results: The simulation analysis results show that: (1) When the first-order chamfering width is constant and the cutting depth is smaller than the first-order chamfering width, the second-order chamfering width should be greater than the cutting depth. (2) If the cutting depth is large (even close to the first-order chamfering width), the second-order chamfering width should be smaller than the cutting depth. (3) When the cutting depth is small and does not exceed the second-order chamfering area, a larger second-order chamfering angle should be selected. (4) When the cutting depth is large, a smaller second-order chamfering angle should be selected. When cutting at an oblique angle, as the inclination angle of the tool gradually increases, interference with chip removal generally increases. The wear and tool temperature of the composite chamfered turning tool generally increase, but when the inclination angle is 10°, wear and temperature of the tool are lower, and chip removal interference is minimized. (5) When cutting at an oblique angle, as the inclination angle of the tool gradually increases, chip removal interference generally shows an increasing trend. However, at a 10° inclination angle, tool wear and temperature are lower, and chip removal interference is reduced. Specific experimental results of PCD tools show that, at the same cutting depth, the cutting temperature of the PCD composite chamfering tool is lower than that of the PCD first-order chamfering tool. Furthermore, when the cutting depth is 0.14 mm and the workpiece is turned for 30 minutes, as processing time increases, the surface roughness of the workpiece processed by the PCD composite chamfering tool remians lower than that of the PCD first-order chamfering tool. Conclusions: The composite chamfering of the PCD tool improves the brightness of the workpiece when the cutting depth is greater. The final wear state of the tool indicates that the PCD composite chamfering tool has a better smoothing effect during cutting than the PCD first-order chamfering tool, resulting in higher workpiece brightness and better wear resistance.

Principle of self-assembly of abrasive balls on surface of grinding wheels into phyllotaxis arrangement

LI Shengze, LYU Yushan, LI Xingshan, NAN Jiehong

2024, 44(5): 644-651. doi: 10.13394/j.cnki.jgszz.2023.0184

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Abstract:
Objectives: Compared with traditional abrasive random arrangement grinding wheels, structured grinding wheels offer better chip space and grinding efficiency during the grinding process. At present, the manufacturing methods for structured grinding wheels mainly include metal sintering, electroplating, mechanical dressing, laser etching, and other processing techniques. However, these processing methods generally face several issues, such as low arrangement efficiency, poor positioning accuracy of abrasive particles, and complex manufacturing processes. To address these problems, this paper proposes a method for preparing an abrasive orderly grinding wheel by the orderly accumulation of abrasive balls in a bounded space. Methods: Phyllotactic arrangement refers to the arrangement of biological tissue units in space, such as rotation, opposition, and clustering, to provide an optimal growth environment for plant grains. The spiral arrangement achieves geometric spatial complementarity and maximizes the filling effect, with the left and right spirals formed by the arrangement satisfying the mathematical law of the Fibonacci sequence or its derived series. This paper, based on the theory of phyllotactic arrangement and the study of sphere packing structures in bounded spaces, establishes the basic theory for the self-assembly of abrasive spheres into an orderly arrangement on a grinding wheel. Results: Based on the growth structure characteristics of plant primordia, the constraint barrel in the device is designed to with a hemispherical bottom and a cylindrical top. To ensure that the abrasive balls on the surface of the grinding wheel are arranged in a single layer, the distance between the cylindrical part of the constraint bucket and the grinding wheel matrix is always equal to the diameter of a spherical particle. During the self-assembly process, the motion of the constraint barrel is used to mechanically disturb the absive balls. Due to the effects of gravity, interaction forces, and friction between the grinding balls, the arrangement structure of the grinding balls in the device gradually changes from random disorder to stable order. Once the structure stabilizes, the abrasive balls are fixed to the grinding wheel. Using the evaluation method of cylindrical phyllotaxis structure, multiple parallel oblique lines can be observed, and the distance between continuously growing primordia can be determined, allowing the relevant parameters of the phyllotaxis structure to be calculated. From the cylindrical coordinate expansion diagram and the cylindrical arrangement diagram, it is evident that multiple parallel left and right diagonals resemble the phyllotactic structure. Therefore, the structural parameters were verified and calculated. Conclusions: Abrasive ball-ordered grinding wheels with different grinding wheel matrix sizes were successfully prepared through self-assembly experiments. The abrasive ball arrangement structure was measured using corresponding measuring instruments to verify the accuracy of the self-assembly motion simulation results and the feasibility of the method. The influence of size changes on the structural parameters of the abrasive ball arrangement was discussed. The results indicate that the phyllotactic arrangement of spherical abrasives on the surface of the grinding wheel matrix can be achieved using the self-assembly method. When the diameter of the spherical abrasives is constant, the phyllotaxis coefficient of the arrangement structure formed by spherical abrasives on the surface of the grinding wheel substrate decreases with the increase of the diameter of the grinding wheel substrate. Conversely, when the diameter of the grinding wheel matrix is constant, the phyllotaxis coefficient of the phyllotaxis arrangement structure formed by the spherical abrasives on the surface of the grinding wheel substrate improves with the increase in the diameter of the abrasive balls.

The selection and simplification of physical models for simulation of abrasive flow machining uniformity

SHI Sufang, ZHANG Baocai, WANG Xiayu, WANG Xinchang

2024, 44(5): 652-664. doi: 10.13394/j.cnki.jgszz.2023.0267

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Objectives: With the rapid development of electric vehicles (EVs), the maximum rotational speed of EV motors has reached up to 20 000 r/min. Precision polishing of gear surfaces after grinding has become a promising method for improving the noise, vibration, and harshness (NVH) performance of EVs. Abrasive Flow Machining (AFM) is one of the key technologies for efficiently polishing complex gear tooth surfaces. Fixture design plays a critical role in achieving process objectives, reducing surface ripple and roughness, and minimizing damage to the tooth surface accuracy. This article addresses the trade-off between selecting physical models and balancing the accuracy and computational cost of simulation results. It analyzes the impact of different simulation models on the results, providing guidance for AFM fixture design and offering practical experience for fixture optimization in AFM gear processing. Methods: Simulations are conducted using media with different viscosities, viscosity models, and flow models, within the simplest and most typical slit model. Fluid pressure distribution, velocity vectors, wall shear, and streamline distribution cloud mapsare analyzed to reflect machining uniformity. Based on the conclusions drawn from slit model simulations, the simplest Newtonian fluid—water—is selected as the medium for AFM gear shaft processing simulations. The focus is on the uniformity of streamline distribution in the machining area to optimize fixture design. Results: The analysis of slit model simulation results reveals that different physical models have varying impacts on the outcomes: (1) The selection of viscosity models decisively affects the pressure distribution of low-viscosity media. The type of viscosity and turbulence models has little impact on pressure distribution, but it significantly affects the velocity vector, wall shear, and streamline distribution within the abrasive cylinder. (2) For low-viscosity media: implementing a non-Newtonian fluid model has a significant impact on the pressure distribution. Different flow models show marked differences only in wall shear force distributions. Various viscosity models yield different cloud map distributions, but they produce numerically similar values. (3) For high-viscosity media: simulations with non-Newtonian and Newtonian fluid models show consistent results. However, different flow models greatly influence the results, while various viscosity models lead to changes in all simulation results, except for pressure distribution and streamlines within the slit. Despite these variations, the streamline distribution in the processing area remains largely unchanged. Based on the consistency of streamline distribution, fixture design optimization for the AFM gear shaft is carried out, successfully achieving the goal of eliminating gear "ghost frequencies". Conclusions: Despite variations in the physical models, the simulation results exhibit similar trends in distribution, enabling consistent streamline distribution in the processing area. For low-viscosity media, a non-Newtonian fluid viscosity model with laminar flow simulation can be used, and the selection of viscosity models can be simplified based on the rheological characteristics of the actual abrasive flow medium. For high-viscosity media, setting appropriate viscosity values and using laminar flow simulation with a Newtonian fluid model yields consistent pressure and streamline distribution in the processing area, similar to adding viscosity and turbulence models. The slit model simulation results and AFM gear shaft processing tests both demonstrate that streamline information derived from simple physical models can significantly assist in AFM fixture design. In cases where the physical properties of the abrasive flow medium are uncertain—especially in complex flow paths prone to divergence—using the simplest Newtonian fluid, such as water, with laminar flow simulation can provide a reasonable streamline distribution in the processing area. This approach aids in the analysis of processing uniformity, significantly reduces simulation difficulty and costs, and accelerates the fixture design cycle, ultimately enhancing optimization efficiency.

Comparison of erosion resistance of hard and brittle materials processed by low-temperature micro-abrasive gas jet

XU Pengchong, SUN Yuli, ZHANG Guiguan, KANG Shijie, LU Wenzhuang, SUN Yebin, ZUO Dunwen

2024, 44(5): 665-674. doi: 10.13394/j.cnki.jgszz.2023.0220

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Objectives: During low-temperature micro-abrasive air jet machining, the mechanical properties of materials undergo changes, making the material more prone to brittleness and erosion removal. Comparative experiments were conducted on the low-temperature micro-abrasive air jet machining of hard and brittle materials to investigate their machining performance at low temperatures and to indentify materials with better erosion resistance under such conditions. Methods: Low-temperature micro-abrasive air jet machining comparative experiments were conducted on five materials: silicon carbide (SiC), silicon nitride (Si₃N₄), yttrium-stabilized zirconia (YSZ), 99% alumina (Al₂O₃), and quartz glass. First, the materials were pretreated using the same surface treatment method, and a material removal model was established to identify the factors affecting the changes in low-temperature properties. Next, micro-abrasive air jet machining experiments were performed at 77 K to investigate the effects of different process parameters—including machining pressure, impact machining angle, and machining time—on erosion removal rates, low-temperature erosion groove three-dimensional morphology, and surface profiles of the five materials. Finally, the three-dimensional morphology of the low-temperature erosion grooves and the surface profiles of the materials were compared and analyzed to evaluate the erosion resistance of each material during low-temperature machining. Results: The processing performance of the five materials at low-temperatures showed the following trends: (1) As the processing pressure increased, the surface groove volumes of all five materials gradually increased. However, the surface groove volumes of Si₃N₄ and SiC did not increase significantly. (2) As the impact angle increased, the surface groove volumes of all five materials also gradually increased. The groove volume reached its maximum value when the impact angle approached a vertical processing angle. Si₃N₄ exhibited the smallest low-temperature erosion groove volume under these conditions. (3) All five materials exhibited increased brittleness at low temperatures, with minimal plastic deformation due to their high hardness. At smaller impact angles, surface material removal was limited, resulting in smaller low-temperature erosion grooves. As the impact angle increased, material removal transitioned from plastic deformation to surface fracture. At the maximum impact angle (90°), the material removal became most evident, and the erosion groove reached their largest volume, exhibiting a typical brittle removal mode. (4) Under the same processing parameters, the erosion removal rates of the five materials increased sequentially. The erosion removal rate of silicon nitride was the smallest, with a maximum low-temperature erosion groove depth of only 20 μm. Silicon carbide's erosion removal rate was similar to that of silicon nitride material, but the erosion removal rate of quartz glass material was the highest, considerably exceeding that of the other four materials. (5) As the number of machining cycles increased, the surface groove volumes for all five materials also gradually increased. (6) The groove shape formed on the surface of silicon nitride was not obvious, consisting mainly of small pits that could not form complete microchannels. Additionally, the surface of silicon nitride remained relatively flat, with minimal material removal, resulting in the smallest depth of the low-temperature erosion grooves. (7) After the erosion processing, quartz glass formed an obvious "U"-shaped groove, which could be clearly observed under a microscope. In contrast, the grooves of the other four materials had no fixed shape and appeared relatively flat. Upon magnification, small "U"-shaped grooves and similar "V"-shaped grooves were observed locally on the surfaces of the four materials, indicating that the morphological changes during erosion processing were relatively complex. Conclusions: The low-temperature micro-abrasive air jet machining comparative experiment was used to analyze the material erosion removal rates, three-dimensional morphology, and surface profiles of low-temperature erosion grooves. Among the five hard and brittle materials tested, silicon nitride material exhibited the smallest erosion groove volume, the lowest erosion removal rate, and the highest erosion resistance. These findings provide a foundation for future research into low-temperature micro-abrasive air jet technology for masks.

Composition design and optimization of electrochemical mechanical polishing slurry for single crystal SiC

GU Zhibin, WANG Haoxiang, SONG Xin, KANG Renke, GAO Shang

2024, 44(5): 675-684. doi: 10.13394/j.cnki.jgszz.2023.0246

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Objectives: Single crystal silicon carbide (SiC) is known for its high hardness and high chemical inertness, making it chanllenging to process effectively using traditional chemical mechanical polishing (CMP) methods. CMP often struggles to balance processing efficiency and surface quality for SiC. Electrochemical mechanical polishing (ECMP) is an effective method to achieve high material removal rates (MRR) and excellent surface quality when processing SiC. This study explores the main components and optimal ratios of SiC ECMP slurry through process testing. Methods: Using MRR and surface roughness as evaluation indicators, the types of conductive medium and abrasive particles in the ECMP slurry are first determined through single-factor experiments. Then, the influences of the conductive medium types, abrasive particle concentration, and the pH value of the polishing slurry, on both MRR and surface roughness, are analyzed to identify the optimal slurry parameters. Results: The results of the experiments indicate that when NaCl is used as the conductive medium and SiO₂ as the polishing abrasive, SiC achieves both good polishing efficiency and surface quality. The increase in NaCl concentration enhances the electrochemical oxidation of SiC, leading to an increase in MRR and surface roughness. As the concentration of abrasives increases, the surface conductivity of SiC improves, boosting both material removal efficiency and surface roughness. However, after reaching a certain abrasive concentration, the oxidation state of SiC stabilizes, and both MRR and surface roughness tend to reach a constant value. When the polishing slurry is acidic, electrochemical oxidation of SiC is inhibited, leading to a reduced MRR. Conversely, when the slurry is alkaline, abrasive particles undergo chemical reactions, resulting in poor polishing surface quality. A neutral slurry effectively balances both MRR and surface quality. The optimal slurry paramaters for achieving this balance are a NaCl concentration of 0.6 mol/L, a SiO₂ mass fraction of 6%, and a pH value of 7. Under these conditions, the MRR and surface roughness of SiC polishing were found to be 2.388 μm/h and 0.514 nm, respectively. Conclusions: The low oxidation rate of SiC, due to its high chemical inertness, is a key factor limiting the polishing efficiency in traditional CMP methods. ECMP overcomes this limitation by replacing chemical oxidation with electrochemical oxidation, allowing for both high polishing efficiency and superior surface quality of SiC.

Experiments on relative angles of grinding two sides of involute pole groups

LIU Jie, JIAO Anyuan, BO Qifan, DING Yunlong, CHEN Yan

2024, 44(5): 685-694. doi: 10.13394/j.cnki.jgszz.2023.0185

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Objectives : Titanium alloys are increasingly widely used in the aerospace field, and their research and development significantly influence the advancement of military aircraft, civil aviation, engines, and other high-tech equipment. However, titanium alloy are challenging to machine due to theri small deformation coefficient, low thermal conductivity, and the high temperatures generated during traditional cutting methods, which leads to tool wear. As a result, parts often have low precision, and surface quality is generally poor. This study proposes a double-sided magnetic abrasive finishing (MAF) method using opposing magnetic pole sets with adjustable relative angles to address surface defects—such as bumps, scratches, and microcracks—on the surface of titanium alloy TC4 and to improve its grinding efficiency. Methods: This study compares three types of lined magnets and introduces an involute-lined magnet design. Based on this design, opposing magnetic pole sets are used to generate an initial relative angle between them. The effects of different relative angles on double-sided MAF are tested to determine whether this method can improve the magnetic induction intensity and promote a more uniform distribution of abrasives. The results show that this approach addresses the challenges of poor abrasive fluidity and the inability of abrasives to tumble effectively. Additionally, the simultaneous grinding of both sides of the workpiece enhances processing efficiency, effectively removes the surface defects of the workpiece, and improves the grinding efficiency and surface quality. Results: The application of involute-lined magnets with a relative angle for double-sided MAF yields improved processing results under the following test conditions: magnetic pole group speed of 600 r/min, processing gap of 2 mm, magnetic abrasives size of 150 μm, and a relative angle of 10°. After 30 minutes of grinding, the surface roughness of the front side of the titanium alloy is reduced from R_a 0.458 μm to R_a 0.116 μm, and the surface height variation decreases from 43.3 μm to 7.8 μm. The reverse side also shows improvements, with surface roughness decreasing from R_a 0.434 μm to R_a 0.111 μm, and surface height variation reducing from 44.2 μm to 8.4 μm. Conclusions: The use of involute-lined magnets to create a relative angle for double-sided grinding effectively improves surface defects, such as scratches and grooves, on the workpiece. This method also significantly enhances grinding efficiency compared to single-sided grinding. The involute arrangement of magnets minimizes variations in magnetic induction intensity, which improves grinding efficiency and ensures a more uniform distribution of the magnetic field. This uniformity results in better adsorption of magnetic abrasives and enhanced grinding quality. When grinding at a relative angle of 10°, the magnetic field gradient changes significantly, covering a wider area with stronger magnetic induction. This variation in magnetic field gradient faciliates the tumbling of magnetic abrasives and the timely renewal of cutting edges, ultimately improving processing performance.

Current Issue
2024, Volume 44, Issue 5

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Current Issue 2024, Volume 44, Issue 5

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Current Issue
2024, Volume 44, Issue 5