金刚石与磨料磨具工程

2021, 41(1): 1-4.

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A new pretreatment method of pre-fixing seeds based on diamond-particles-impregnated cemented carbide substrate

JIAN Xiaogang, MA Qianli, TANG Jinyao, HU Jibo

2021, 41(1): 5-11. doi: 10.13394/j.cnki.jgszz.2021.1.0001

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To further improve the quality of the diamond coatings deposited on diamond-particles-impregnated cemented carbide substrate, a pretreatment method of pre-fixing seeds is proposed. The substrate is attached with titanium powder and then seeded, and finally pre-fixed by microwave. The quality and bonding performance of the diamond film prepared by this method and the original conventional method are compared with SEM, Raman spectroscopy, and indentation experiments. The results show that after the pretreatment method of pre-fixing seeds, the diamond nucleation density at low temperature is about 1.5 times higher than that of the coating after conventional pretreatment, and that the uniformity and flatness of the coating are significantly improved. It can be seen that the purity index and crystallinity index of diamond have been improved about 30% and the internal stress of the coating has been decreased by 50% through the analysis with Raman spectroscopy. The indentation comparison experiment confirms that the bonding strength has been improved to a certain extent.

Influence of deposition pressure on micron-nanometer transition of diamond film

FAN Bingqing, WANG Chuanxin, XU Yuanzhao, HUANG Kai

2021, 41(1): 12-16. doi: 10.13394/j.cnki.jgszz.2021.1.0002

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The effect of argon concentration on the grain size of diamond film at different pressures was studied by hot fibre chemical vapor deposition (CVD) device, and the critical value of the size transition at different pressures was analyzed. The diamond films were analyzed by SEM and Raman spectroscopy. Results show that with the increase of argon volume fraction, the grain size of diamond film will be smaller and smaller, but the argon volume fraction required for the conversion of diamond film from micron to nanometer varies at different pressures. As the pressure decreases, the concentration of argon scale required for the transition decreases gradually. In the range of 2 kPa to 500 Pa, the argon proportion required for the transition is progressively reduced. The volume fraction of Ar decreases from 60.0% at 2.0 kPa to 52.5% at 1.5 kPa, then 32.5% at 1.0 kPa and finally 20.0% at 0.5 kPa. The quality and internal stress of the diamond films obtained at the critical points are also different. With the decrease of air pressure, the quality of the film increases and so does the internal stress.

Effect of tungsten surface laser treatment on adhesion of diamond film

HUANG Yihao, MA Zhibin

2021, 41(1): 17-20. doi: 10.13394/j.cnki.jgszz.2021.1.0003

Abstract(177)

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Diamond film is deposited in CH₄/H₂ system by microwave plasma chemical vapor deposition (MPCVD). Plasma parameters are measured by emission spectrometer. The internal stress of the grown diamond film is measured by Raman spectrometer. The surface and section morphology of the grown diamond film are measured by SEM. The influence of tungsten surface laser treatment on the adhesion of diamond film is explored through thermal shock test. The results show that laser treatment can release the stress of diamond film and enhance the adhesion between tungsten and diamond film;with the premise that the adhesion between tungsten and diamond film is greatly improved and the surface damage of tungsten slice is as small as possible, the cutting depth of tungsten slice surface is more appropriate at 0.035 mm.

Comparison of compositions and pressure transmission performances of two kinds of pyrophyllites used in cubic press

JIANG Mingquan, WANG Yipeng, YANG Gongzhang, HE Duanwei

2021, 41(1): 21-26. doi: 10.13394/j.cnki.jgszz.2021.1.0004

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Two kinds of pyrophyllites from South Africa and China were analyzed by scanning electron microscope energy dispersive spectroscopy (EDS) and X-ray powder diffraction (XRD). The main chemical compositions and phase compositions of pyrophyllite were obtained. The pressure of synthesis chamber was calibrated by high-pressure phase transformation of Bi, Tl and Ba. The results show that the South African pyrophyllite ore is illite-type pyrophyllite, and the Chinese pyrophyllite ore is diaspore-type pyrophyllite. The mass fraction of SiO₂ in the South African pyrophyllite ore treated at 900 ℃ is approximately 4.50% higher than that of the Chinese one, and the pressure generation efficiency of the two pyrophyllite powder briquettes is basically the same. In the pressure calibration test of Bi, Tl, Ba, the forward displacements of the right, the front and the upper cylinders of the press, the South African pyrophyllite as medium, under 10~50 MPa oil pressure are about 0.33 mm larger than those of the Chinese pyrophyllite. Before and after 20~50 MPa oil pressure test, the densities of the South Africa pyrophyllite raw ore and powder briquette are 0.055~0.081 g/cm³ lower than those of the Chinese pyrophyllite ore block and powder briquette. The preparation plan of the South African pyrophyllite powder briquette is optimized to make the density reach the same level as the currently widely used pyrophyllite powder briquette, which can replace its Chinese counterpart.

A new assembling method to sinter pure PcBN material

DENG Fuming, WANG Hao, SONG Meijiao, WANG Han, YANG Xing, ZHANG Peng

2021, 41(1): 27-31. doi: 10.13394/j.cnki.jgszz.2021.1.0005

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A new assembling method was used in pure polycrystalline cubic boron nitride (PcBN) HPHT synthesis chamber. The cBN powder with particle size of 10 μm was used as the raw material. Scanning electron microscope (SEM) and X-ray diffraction (XRD) were used to analyze the microstructure and the phase of the sintered body, and the compactness, the microhardness and the compressive strength were tested as well. Results show that pure PcBN with good properties could be obtained at a relatively lower sintering temperature by using this new assembly method. It is also found that the sample sintered at 7.5 GPa and 1 700 ℃ has the best microstructure density and that its hardness reached 3 992.7 Hv, which is higher than that of the traditional PcBN material. A large number of cBN-cBN particle bonds were formed in the sample, which effectively improves the comprehensive properties of the sintered body.

Microstructure analysis of W-coated diamond brazing with Ni-Cr active filler

SU Shichao, XIAO Bing, WANG Shuyi, WANG Junlin, XIAO Hongzhi

2021, 41(1): 32-37. doi: 10.13394/j.cnki.jgszz.2021.1.0006

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Under vacuum condition of 1 030 ℃ for 20 min, W-coated diamond was heated and brazed with Ni-Cr alloy powder. X-ray diffraction (XRD) was used to analyze the phase changes of W-coated diamond before and after heating. Scanning electron microscope (SEM) and energy dispersive spectrometer (EDS) were used to analyze the interface microstructure, the new phase, the morphology and that the element distribution. The results show that the coating phases of W-coated diamond change from W₂C and W before heating to a large amount of WC and a small amount of W₂C after heating, and that the coating does not fall off. After the W-coated diamond is brazed, there forms a small amount of NiW phase formed in the coating and the filler metal, the columnar Cr₇C₃ at the interface of W-coated diamond/Ni-Cr alloy, and the Cr-based intermetallic compound at the interface of steel substrate/Ni-Cr alloy.

Comparative study on ultra-thin diamond saw blades made by SLS and FDMS

ZHANG Shaohe, SU Zhou, LIU Leilei, KONG Xiangwang, HE Tao

2021, 41(1): 38-43. doi: 10.13394/j.cnki.jgszz.2021.1.0007

Abstract(197)

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Additive manufacturing for diamond tools is introduced into ultra-thin diamond saw blades, using the fused deposition molding sintering (FDMS). The application of selective laser sintering (SLS) and the FDMS in manufacturing ultra-thin diamond saw blades are introduced in detail. And they are compared from the perspectives of basic equipment, process principles and steps, materials, costs, and applications in production. The results show that both the processes possess the ability to manufacture diamond ultra-thin slices with strikingly high precision and excellent performance under the condition of selecting suitable materials. SLS is characterized by high energy consumption and cost, simple process and one-time finished manufacturing, suiting for the research and development of ultra-thin diamond saw blades. FDMS process has many complicated links, and each parameter of the link needs to be optimized separately. However, it is convenient for mass production of products with consistent performance.

Wear analysis of CVD diamond tool in micro-milling AA356 aluminum alloy

ZHANG Yabo, BAI Qingshun, HE Xin, QING Lingbo, YUE Songjie, LIU Xin

2021, 41(1): 44-50. doi: 10.13394/j.cnki.jgszz.2021.1.0008

Abstract(217)

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AA356 aluminum alloy has been widely used in aerospace and other fields. However, it is faced with severe tool wear in the process of micro machining and the relevant mechanism is not clear. To reveal the influence mechanism of cutting parameters on the tool wear of CVD diamond tool micro milling AA356 aluminum alloy, micro machining experiments were carried out with orthogonal test design and response surface method. The prediction equation of tool wear was established by using least square method and the particle swarm optimization algorithm. Besides, the mechanism of tool wear and the effect of cutting parameters for tool wear were analyzed. The results show that the main wear mechanisms of micro-tool are coating delamination and adhesive wear induced by complex cutting loads. The main factor of influencing tool wear is the axial cutting depth, followed by the feed speed and the effect of spindle speed on tool wear is minimal. A strong coupling effect can be found between the spindle speed and the feed speed.

Experimental research on single abrasive grain scratch SiC_f/SiC ceramic matrix composite

ZHOU Wenwen, WANG Jianqing, ZHAO Jing, LIU Yao

2021, 41(1): 51-57. doi: 10.13394/j.cnki.jgszz.2021.1.0009

Abstract(259)

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To study the mechanism of SiC fiber (SiC_f) reinforced SiC ceramic matrix composite (SiC_f/SiC) grinding damage, a test platform was built to carry out single abrasive particle scratch tests. The scratch force was measured and the surface damage form was observed. The influence of shape of the abrasive particle, scratch depth and SiC_f orientation on the grinding mechanism was studied. The test results show that the scratch damage of SiC_f/SiC mainly includes matrix collapse, extension, cracks, fractures and pullouts of fiber. In the process of scratching SiC_f/SiC composite material, the scratching force of sharp abrasive particles is smaller, and the surface damage range of the entire scratch caused by sharp abrasive is smaller than that of the scratch caused by flat abrasive particles. However, when the flat abrasive particles are scratching and the fiber orientation is γ=0°, there are fewer damages such as fiber fracture and fiber pull-out in the scratched morphology.

Power spectrum density characterization of grinding wheel surface in ultrasonic vibration spiral grinding

WANG Qiuyan, LIANG Zhiqiang, BAI Shuowei, WU Yongbo, JIA Shun

2021, 41(1): 58-64. doi: 10.13394/j.cnki.jgszz.2021.1.0010

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During the ultrasonic vibration spiral grinding process, the surface topography of the grinding wheel varies complicatedly. To accurately characterize the characters of the grinding wheel surface, a power spectral density (PSD) analysis method was adopted by decomposing the microstructure of the grinding wheel surface into harmonics of different frequencies, amplitudes and phases. The wear behaviors of the grinding surfaces after conventional grinding and ultrasonic vibration grinding in different grinding stages were compared and analyzed by using the PSD analysis. The results show that the slope k of the surface PSD curve of the grinding wheel gradually decreases with the increase of the grinding stage, which means that a smaller k represents more serious surface wear of the grinding wheels. Moreover, in the early wear stage, the slope k of the ultrasonic grinding wheel surface is significantly larger than that of the conventional grinding wheel surface, but in the later wear stage, the decline rate of the slope k of the ultrasonic grinding wheel surface is significantly higher than that of the conventional grinding wheel surface. This trend reveals the variation of the effective number of abrasive grains and the wheel loading on the grinding wheel surface under two different grinding methods. Further analysis reveals that the ground flat and pulled-outs of the abrasive grains decrease the proportion of the power spectral density of them, and the wheel loading increases the overall energy value of the PSD curve. In the early wear stages, the number of effective abrasive grains on the ultrasonic vibration grinding wheel surface was larger than that of the conventional grinding surface, whereas in the later stages, the grinding wheel loading in ultrasonic vibration grinding is more significant.

Experimental analysis of residual stress and hardness of 18CrNiMo7-6 steel in high speed cylindrical grinding

ZHANG Yinxia, YUAN Shaoshuai, WANG Zile, YANG Xin, GAO Wei

2021, 41(1): 65-70. doi: 10.13394/j.cnki.jgszz.2021.1.0011

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For 18CrNiMo7-6 carburized steel workpiece, a single factor test was designed studying the wheel speed, the workpiece speed, the feed rate and the abrasive size. X-ray residual stress analyzer and micro hardness tester are used to detect the residual stress and hardness. The results show that high-speed cylindrical grinding can introduce residual compressive stress to the surface of the workpiece, and that the compressive stress in the X direction is less than that in the Y direction. Meanwhile, high-speed cylindrical grinding can improve the surface hardness of the workpiece. With the increase of wheel speed, the compressive stress increases first and then tends to be stable, while the hardness decreases first and then increases and the minimum value is obtained when the speed is 75 m/s. With the increase of workpiece speed, the change of residual compressive stress and hardness is not monotonic. The feed rate has a great influence on the compressive stress and hardness of the workpiece surface, which are reduced in general after linear fitting. Grinding wheels with different CBN abrasive grain sizes produce different compressive stress and hardness on the surface of the workpiece, namely: M10/20 produces the largest, followed by 120/140, and then 230/270 the smallest. On the surface of the workpiece, the hardness is low when there is tensile stress, and the hardness is high when there is compressive stress.

Reduce grinding energy consumption by modified particle swarm optimization based on dynamic inertia weigh

ZHANG Kun, TIAN Yebing, CONG Jianchen, LIU Yanhou, YAN Ning, LU Tao

2021, 41(1): 71-75. doi: 10.13394/j.cnki.jgszz.2021.1.0012

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A three-layer back propagation (BP) neural network was used to establish a grinding energy consumption prediction model. 125 single-factor experiments were designed with the grinding wheel linear velocity, feed rate and grinding depth of cut as the influencing factors. 75 sets of experimental data were obtained as the training samples and test samples of the prediction model. Particle swarm optimization algorithm was improved by using adaptive dynamic inertia weight (adaption particle swarm optimization, APSO), and the prediction of BP neural network was used as fitness function. The optimal process parameters were obtained by iterative optimization aiming at minimum energy consumption. The results show that the prediction model is accurate and the optimized process parameters can effectively reduce the grinding energy consumption.

Defect detection method of abrasive block based on machine vision

JIA Po, TIAN Jianyan, YANG Yingbo, PENG Hongli, YANG Shengqiang

2021, 41(1): 76-82. doi: 10.13394/j.cnki.jgszz.2021.1.0013

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To detect the roundness and the black core defects of sintered spherical abrasive block, a defect detection method based on machine vision was proposed. Firstly, an image acquisition system of the abrasive block was built by using single chip microcomputer, stepping motor, sampling disc, digital microscope and upper computer to realize the continuous acquisition of the abrasive block images. Secondly, the image graying, the threshold segmentation and the morphological processing were used to extract the abrasive block area and the black core defect area. Thirdly, the roundness of the abrasive block area and the size of the black core defect were calculated. Finally, the detection threshold of the abrasive block defect was determined through the detection test. The results show that the method can digitally detect the roundness and the black core defects of sintered spherical abrasive block. It can also analyze the problems of in the preparation process of the abrasive block, thus providing feedback basis for the improvement of the abrasive block preparation method.

Effect of 1, 2, 4 -triazole and benzotriazole on chemical-mechanical polishing of 316L stainless steel

WANG Hao, CHEN Guomei, NI Zifeng, QIAN Shanhua, BIAN Da, ZHAO Yongwu

2021, 41(1): 83-88. doi: 10.13394/j.cnki.jgszz.2021.1.0014

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Experiments of chemical mechanical polishing 316L stainless steel were conducted under acid condition, with 1, 2, 4-triazole (TAZ) or benzotriazole (BTA) as the corrosion inhibitor, to study the effect of TAZ and BTA and the mechanisms. The polished surfaces of 316L stainless steel were observed by using a white light interferometer. The structures of the inhibitors were characterized with an infrared spectrometer. The hydrophobic property of the passivation membrane on the surface was surveyed by measuring the contact angle.The effect and the type of inhibitor were analyzed by using an electrochemical workstation. The results show that the material removal rate of the steel decreases with the increase of the TAZ or BTA content. The minimum surface roughness of polished steel is 2.64 nm when adding 3mmol/L TAZ or 2.53 nm when adding 2 mmol/L BTA. It is found that both inhibitors contain N-functional groups, which will strengthen the hydrophobicity of the passivation membrane generated on the surface of 316L stainless steel and reduce the density of the corrosion current. However, the membrane generated when using TAZ is weaker. Both inhibitors are anodic-suppressed ones.

Simulation study on influence mechanism of abrasive radius on diamond grinding

ZHANG Tongqi, YUE Xiaobin, LEI Dajiang, YANG Ning

2021, 41(1): 89-94. doi: 10.13394/j.cnki.jgszz.2021.1.0015

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To analyze the influence mechanism of diamond grain size change on the grinding quality of diamond material, a molecular dynamics method was used to establish the grinding model of spherical rigid diamond grain grinding diamond workpiece, and the grinding force variation law, the stress and the phase transformation distribution under different abrasive grain radii were studied. The results show that when the abrasive grain radius increases from 6a to 20a (a is the lattice constant of diamond), the average normal force and the average tangential force increase linearly, but the increment of the average normal force is 3 times of that of the average tangential force. The shear effect between the abrasive grain and the workpiece is smaller and compared extrusion and friction, and the fluctuation amplitude of the grinding force becomes larger, which indicates that the dislocation formation of workpiece is more severe. At the same time, the strong compressive stress zone formed under the abrasive grain expands and so do the concentrated tensile stress zone caused by friction in the area behind the abrasive grain and the amorphous transformation zone.The number of the defects behind the grinding zone increases, and the machined surface quality of the workpiece becomes worse. When the indentation depth of the abrasive grains with radii of 10a, 15a and 20a is 2 nm, the microhardness of the workpiece surface after abrasive grains scribing is 2.8%, 9.6% and 18.3% lower than that without abrasive grain scribing, respectively. The increase of the abrasive radius will significantly reduce the surface mechanical properties of the workpiece.

Experimental study on selection of PDC cutting teeth based on thermal performance analysis

WANG Chuanliu

2021, 41(1): 95-100. doi: 10.13394/j.cnki.jgszz.2021.1.0016

Abstract(212)

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To improve the reliability of the PDC cutting teeth selection, from the perspective of thermal performance, the PDC cutting teeth of different manufacturers were analyzed by the laser Raman spectroscopy at room temperature and high temperature and the thermogravimetry analysis. Combined with high temperature wear ratio test, the residual stress, the graphitization transformation, the thermal stability and the high temperature wear resistance of the PDC cutting teeth were analyzed to comprehensively evaluate the performance of the PDC cutting teeth of different manufacturers. At the same time, four-wing arc angle PDC bits with diameter of 94 mm was made and the field drilling test were carried out. The results show that the field test results are basically consistent with the results of the PDC cutting teeth thermal performance testing and analysis. The PDC cutting teeth with excellent thermal performance have high wear ratio at high temperature and excellent drilling performance, with an average aging of 25.0 m/h and an average life of 266 m. Compared with other PDC cutting teeth whose thermal properties are slightly worse, their performances are improved in varying degrees. Therefore, it is helpful to improve the accuracy of the PDC cutting tooth selection by improving and supplementing the macro detection method of PDC from the micro point of view.

Operation of Chinese superhard industry in 2019

SUN Zhaoda, LI Zhihong, ZHAO Xinghao, LI Lijuan, ZHANG Beibei

2021, 41(1): 101-104. doi: 10.13394/j.cnki.jgszz.2021.1.0018

Abstract(199)

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The development of Chinese superhard material industry in 2019 was analyzed with the collected statistics of the industry. It is believed that the industry is in its limited development, whose main economic indicators all turn down, especially the total profit decreasing as much as 34%. However, there are some specific products at good situations, such as gem diamond, composite superhard material and resin-bond grinding wheels, with sale growths all over 10%.

2021 Vol. 41, No. 1

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