金刚石与磨料磨具工程

Study on etching of diamond monocrystal by MnO₂

XIAO Changjiang, CHEN Yiguang, LI Zhengxin

2019, 39(5): 1-6. doi: 10.13394/j.cnki.jgszz.2019.5.0001

Abstract(297)

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Abstract:
In order to compare the surface etching of diamond monocrystal, diamond is etched directly in air or with MnO₂ at different temperatures. The etching degree on the surface of diamond monocrystal was characterized by surface morphology, etching area and compressive strength of diamond single particle. The results show that both MnO₂ and air can successfully etch the surface of synthetic diamond monocrystal. With the increasing of etching temperature, the etching of diamond single crystal by air and MnO₂ intensifies. At the same temperature, when using MnO₂ as an enchant, the {111} face is more heavily etched than the {100} one; while in air, the {100} face is more heavily etched than the {111} one. After etching, the morphology of the etched diamond {100} face tends to form quadrilateral pits, while the {111} face is easy to form inverted pyramid corrosion pits. In addition, MnO₂ can promote the etching of diamond surface by expanding the etching area and decreasing the temperature of the maximum etching rate, so the compressive strength of diamond monocrystal decreases greatly.

Preparation and characterization of diamond single crystal with native rough surface

ZHAO Ziyong, LI Zhenyu, CAI Yule, CHEN Zhimin, DING Yiliang, LAI Yang, QI Lixia

2019, 39(5): 7-12. doi: 10.13394/j.cnki.jgszz.2019.5.0002

Abstract(405)

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Single crystal diamond with rough surface is obtained by adding a new type of catalyst, optimizing composition of the catalyst, adjusting reduction process, optimizing the temperature and pressure conditions in the synthetic procedure. The regulation of crystal color and surface morphology are realized. The results of scanning electron microscope (SEM) and atomic force microscope (AFM) show that there are regular wavy patterns on the surface of the crystal. Raman spectra indicates that the carbon atoms in the diamond crystal surface are in sp³ hybridization state. The test results of impact resistance and thermal impact resistance illustrate that the native roughened diamond has better thermal stability than the ordinary diamond does. In addition, the native roughened diamond has lower magnetic susceptibility and impurities in the crystal. The sawing test shows that the small diameter saw blade made of native surface roughened diamond has better sharpness and wear resistance.

Iron etching of diamond in hydrogen-free atmosphere

SHAO Zengming, SU Yanbin, ZHANG Cunsheng, WU Ruige

2019, 39(5): 13-15. doi: 10.13394/j.cnki.jgszz.2019.5.0003

Abstract(280)

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Diamond surface was etched by iron powder in hydrogen-free atmosphere. Scanning electron microscopy (SEM), laser probe analyzer (LPA) and X-ray Diffractometer (XRD) were used to characterize the surface morphology, pit depth, structure and composition of the etched diamond. The etching behavior of diamond was also analyzed.The results show that iron powder can etch diamond crystals through its catalysis in hydrogen-free atmosphere. The etching is mainly carried out on {111} and {100} surfaces of diamond, and the etching rate of {100} surfaces is higher than that of {111} surfaces. The etching mechanism is realized by the formation of Fe-C phase between iron and diamond. The etching is influenced by the content of iron phase and the structure of diamond remains unchanged after etching.

Influence of solution composition on weight increasing when electroless plating nickel onto diamond powder

FANG Lili, CHENG Bingliang, LI Yizhe

2019, 39(5): 16-21. doi: 10.13394/j.cnki.jgszz.2019.5.0004

Abstract(296)

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The influence of concentration of complexant, dispersing agent and stable agent on the weight rate of electroless nickel plating on diamond powder was investigated by means of orthogonal experiment method. The results show that the influence order of factors on weight is as follows: ammonia> citric acid> sodium citrate> thiourea> dodecyl benzene sulfonate. Considering the weight gain rate, electroless plating leakage and crystals stock, the optimal recipe of electroless nickel plating on diamond powder is nickel sulfate 25 g/L, sodium hypophosphite 33 g/L, ammonia 10-15 mL/L, citric acid 15-20 g/L, sodium citrate 10-15 g/L, thiourea 1.3-2.1 mg/L, dodecyl benzene sulfonate 1.6-2.4 g/L。

Comparison of analysis methods of boric acid in nickel plating solution

ZHAO Jun, XING Bo, JIA Hefeng, LUO Miaodi, ZHU Xiaowei

2019, 39(5): 22-25. doi: 10.13394/j.cnki.jgszz.2019.5.0005

Abstract(316)

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The accuracy, precision and detection efficiency of boric acid content analysis methods in two commonly used nickel plating solutions were compared, namely separation determination and quick determination. The results show that the accuracy and precision of bot methods can meet the requirements of production testing, but the accuracy and precision of the former are better than that of the latter, and the detection efficiency of the latter is higher.

Alumina-bonded nano-polycrystalline diamond powder synthesized by detonation sintering

YAN Xianrong, LI Xiaojie, WANG Xiaohong, YAN Honghao, FENG Bo, ZENG Zheyan

2019, 39(5): 26-32. doi: 10.13394/j.cnki.jgszz.2019.5.0006

Abstract(317)

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Alumina-bonded nano-polycrystalline diamond was synthesized by detonation sintering. The thermal stability, morphology and crystal structure are analyzed by thermogravimetric analyzer (TGA), scanning electron microscope (SEM) and transmission electron microscopes (TEM). Results show that the nano-polycrystalline diamond has good thermal stability in air with no obvious oxidation and good dispersity, the particle sizes of which are 0.5 to 0.7 μm. The nano-polycrystalline diamond is made up of large particles sized 100 to 200 nm, which are the aggregates formed by 2 to 10 nm alumina tightly bonded nano-diamond particles.

Comparative experimental study of machining quality of polycrystalline diamond

DENG Fuming, ZHANG Liyan, DENG Wenli, LIU Jialin, YANG Xuefeng, YAN Xiao, LU Xuejun

2019, 39(5): 33-38. doi: 10.13394/j.cnki.jgszz.2019.5.0007

Abstract(287)

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In order to solve the problems of surface forming and polishing of polycrystalline diamond (PCD), and improve PCD processing efficiency and surface quality, the PCD surface was machined by EDM coarse/fine discharge or diamond grinding wheel. The surface morphology, composition and microstructure of PCD were observed and analyzed by SEM, EDS, XRD and Raman spectroscopy. The microhardness and wear resistance of PCD in different processing modes were tested and analyzed. The influences of different processing methods and modes on microstructures and mechanical properties of PCD surface were investigated. Experimental results show that there are graphitizations on the PCD surface after EDM, but none on that after mechanical grinding. The microhardness and wear resistance of EDM precision machined PCD are 5 613 HV 10 and Q 5.8×10⁴while those of mechanically ground PCD are 5 727 HV 10 and Q 5.4×10⁴. There is limited difference between them. As with the EDM rough machining, the values are 4 604 HV 10 and Q 4.7×10⁴, respectively. The performance is significantly reduced.The concept of the surface metamorphic layer of PCD after discharge machining is proposed, the reasons of which are discussed.

Microstructure and properties of solid PCBN composites with different TiN contents

DENG Fuming, HE Xuehua, DENG Wenli, ZHANG Zhuowei, WANG Hao, ZHANG Peng, FENG Fei

2019, 39(5): 39-43. doi: 10.13394/j.cnki.jgszz.2019.5.0008

Abstract(290)

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The solid polycrystalline cubic boron nitride (PCBN) was sintered by CBN powders, TiN and a certain amount of Al. It was investigated that the effect of TiN contents on the microstructure and mechanical properties of the solid PCBN composites under high pressure and high temperature. The phase composition analysis, microstructure observation, density and hardness test of the sintered samples were carried out. The results show that CBN reacts with the binders of TiN and Al to form TiB₂ and AlN. TiN reacts with Al to form Al₃Ti, TiN and AlN. The TiN, AlN, TiB₂ and Al₃Ti are uniformly distributed around the CBN grain boundary and the grains are firmly bonded together, which effectively improves the bonding strength of PCBN composite. The lower content of TiN has a certain increase in the density and hardness of the solid PCBN. When the mass fractions of TiN, Al and CBN are 10%, 10% and 80%, respectively, the solid PCBN composites has the best mechanical properties.

Study on simulation prediction and control method of burns in plunge grinding

ZHU Huanhuan, LI Houjia, ZHANG Lihua, JIA Baofu

2019, 39(5): 44-49. doi: 10.13394/j.cnki.jgszz.2019.5.0009

Abstract(332)

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According to the model of grinding heat transformation and material removal, a new method for grinding burning simulation prediction and control is proposed based on monitoring power signal. The grinding power signal can be monitored by computer to control the CNC infeed process parameters and the actual grinding power is kept at 5%~15% lower than the maximum power boundary to avoid grinding burn during roughing, semi-finishing, finishing and spark-out stage. And the effectiveness and practicability of this model are proved by the grinding experiment on the inner circle of bear rings.

Burr formation simulation of end face grinding core of servo valve based on DEFORM^3D

MA Tianrong, DANG Jiaqiang, AN Qinglong

2019, 39(5): 50-56. doi: 10.13394/j.cnki.jgszz.2019.5.0010

Abstract(330)

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In order to investigate the effect of abrasive grain arrangement on the grinding burr formation, the end face grinding process of the servo valve core was simplified to design a grinding simulation with a single abrasive grain. The grinding process, in which the abrasive grains were arranged in the forms of leaf, dislocation or random, was modeled and simulated utilizing the commercial software DEFORM^3D. The side burrs under the three different abrasive grain arrangements were analyzed and the burr heights were also compared. The results show that under the leaf arrangement, there are relatively stable burrs at the contact edge between the two abrasive grains; the tracks of the two abrasive grains coincide basically and burrs are formed on both sides of the workpiece surface of plough under the dislocation arrangement; under the random arrangement, the track of the two abrasives overlaps and the extrusion characteristics of the material at the contact edge of the two abrasives are more remarkable, thus easily forming secondary burrs. The burr height can be controlled effectively when utilizing the grinding wheel with leaf arrangement.

Research and new development of GaAs substrate fabrication technology

LUO Bin, YAN Qiusheng

2019, 39(5): 57-66. doi: 10.13394/j.cnki.jgszz.2019.5.0011

Abstract(925)

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The second generation semiconductor material, gallium arsenide (GaAs), is widely used in the field of microelectronics and optoelectronic devices. It is used as the basic material for substrate epitaxial growth and device preparation. The surface integrity of GaAs wafer is required to have ultra-smooth surface and no surface/subsurface damage or residual stress. The surface flattening quality of GaAs wafer determines the subsequent epitaxial layer and ultimately affects the performance of related devices. By summarizing and analyzing the intrinsic characteristics of GaAs single crystal materials and the research progress of cutting, edge grinding, surface grinding and polishing technology, the future research direction of super smooth flattening processing technology of GaAs is prospected.

Study on high efficient lapping of calcium fluoride crystal with fixed abrasive pad

SHEN Gongming, GU Qunfei, WANG Kerong, TANG Chao, NIU Fengli, ZHU Yongwei

2019, 39(5): 67-72. doi: 10.13394/j.cnki.jgszz.2019.5.0012

Abstract(413)

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The high efficiency lapping of calcium fluoride crystal is the prerequisite of its ultra-precision polishing. Two kinds of abrasives, single crystal diamond and agglomerated diamond were chosen to prepare the fixed abrasive pad (FAP). A comparison of lapping performance between agglomerated diamond FAP and single crystal diamond FAP was made. And the role of different kinds of diamond abrasives in self-conditioning process of FAP was explored. The results show that the lapping efficiency of FAP embedded with agglomerated diamond abrasives is obviously higher than the FAP embedded with single crystal diamond. The material removal rate of FAP embedded with agglomerated diamond is more stable during the process, which means its self-conditioning performance is much better than the FAP embedded with single crystal diamond. When adopting the agglomerated diamond with a original size of 3 to 5 μm as the abrasives of FAP and a lapping load of 10 kPa, the material removal rate of calcium fluoride crystal can reach 13.0 μm/min and the average surface roughness R_a is 130.0 nm.

Effect of abrasive particle exposure height on grinding vibration of bearing steel

YANG Wei, ZHU Jianhui, SHI Chaoyu, ZHAO Yanjun, ZHAO Jiong, HUI Zhen, GUO Xuanyang

2019, 39(5): 73-78. doi: 10.13394/j.cnki.jgszz.2019.5.0013

Abstract(275)

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In order to explore the influence of grinding wheel surface abrasive state on grinding vibration and improve grinding quality, a grinding vibration model was constructed and the corresponding relationship between grinding particle state, contact rigidity and grinding vibration was deduced. Dressing-grinding experiments were carried out to analyze and verify the effects of different abrasive states on the vibration signal RMS and the surface corrugation characteristics W_a.The results show that without affecting the sharpness of the grinding wheel, the AH value of the grinding wheel representing the exposure height of abrasive particles decreases by about 58%, while the RMS value and W_a value decrease by about 47% and 57%, respectively.At the same abrasive exposure height, the ratio of abrasives passivation is about 20%, while RMS and W_a are reduced by about 22% and 30%, respectively. Meanwhile, the appropriate reduction of the abrasive exposure height and the appropriate passivation of the abrasive are helpful to increase the contact area between the abrasive and the workpiece, improve the grinding vibration and improve the grinding quality. The proposed grinding vibration model is in agreement with the experimental results.

Wear evolution of brown alumina abrasive wheel based on step grinding method

ZHU Yejun, DING Wenfeng, CHEN Zhenzhen, YI Peng, RAO Zhiwen

2019, 39(5): 79-84. doi: 10.13394/j.cnki.jgszz.2019.5.0014

Abstract(266)

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In order to increase the manufacturing efficiency and improve the surface integrity of K4125 nickel-based superalloy, the grinding method with alumina abrasive wheel was studied. The wear mechanism of the grinding wheel was investigated based on step grinding method. The results indicate that the grinding force ratio increases by 70.3% to 10.9 when the specific material removal volume increased from 100 mm³/mm to 125 mm³/mm. In addition, severe grinding chip adhesion occurs during this process, while the radial wear volume of alumina abrasive wheel increases rapidly from 18 μm to 25 μm. It is the severe wear stage. The attrition wear stage increases due to the grinding chip which formed due to the chemical reaction between the grains and workpiece. The grinding ability decreases rapidly. As a consequence, the service life of the alumina abrasive wheel is optimized as 100 mm³/mm.

Experimental study on the shearing failure of high frequency induction brazed diamond abrasive

YANG Qin, LING Jingliang, CUI Changcai, HUANG Hui

2019, 39(5): 85-91. doi: 10.13394/j.cnki.jgszz.2019.5.0015

Abstract(294)

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Four different filler alloys were selected according to the different active elements from two common solder systems of Ni base and Ag base. The diamond abrasive grains were brazed on steel with high frequency induction heating and were sheared with pushing experiment. Diamond failure process was recorded with high-speed camera in the shear process. The forces in the shear process were also recorded. The fracture features of diamond grains were observed. The diamond abrasive thermal damage and mechanical properties of filler alloys strength were also measured in this paper. The experiment results indicated that the main shear failure of diamond abrasive mainly include shear fracture and shear slip. The diamond abrasive thermal damage and mechanical strength of filler alloys have a close relationship with the abrasive failure. According to the experiment results, the established shear failure model of brazed diamond abrasive is in good agreement with the experiment results.

Surface characteristics and wire wear of electroplated diamond wire saw slicing photovoltaic polycrystalline silicon

PANG Jiwei, GAO Yufei, LI Sheng

2019, 39(5): 92-96. doi: 10.13394/j.cnki.jgszz.2019.5.0016

Abstract(339)

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The surface characteristics of photovoltaic (PV) polycrystalline silicon cut by electroplated diamond wire saw affects the fracture strength and the subsequent texture process of wafers. The experiment of electroplated diamond wire sawing PV polycrystalline silicon was conducted in order to analyze the sliced wafer surface characteristics, investigate the influence of sawing parameters on the sawn surface characteristics and reveal the wire saw wear mechanism. The results show that there are shallow ductile scratches and deep grooves formed by ductile shear micro-cutting of diamond abrasives, and fracture micro-pits left by brittle removal of materials on the sawn polysilicon surface. The relative proportion of materials brittle removal to ductile removal varies with the change of process parameters combination. Increasing the feed rate of crystals and decreasing the wire speed, the surface roughness of sliced wafer increases and the sawn surface topography gradually changes from ductile grooves to fracture micro-pits. The wear forms of electroplated diamond saw wire fabricated by nickel-coated (metallized) diamond abrasives are as follows: abrasive flattening is the main wear form in steady wear stage, and abrasives-pulled out and coating wear are the main wear forms in late-use period.

Analysis of turning temperature field of titanium alloy based on nanofluid cooling

SHAO Weifan

2019, 39(5): 97-102. doi: 10.13394/j.cnki.jgszz.2019.5.0017

Abstract(364)

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When turning titanium alloys, the high temperature in the processing zone reduces the surface quality and intensifies the wear of diamond turning tools. Cooling methods such as atomized nano-fluid injection are used to improve the turning environment, improve the processing quality of titanium alloy surface and the durability of diamond cutting tools. A Ti-6Al-4V titanium alloy material model was established based on ABAQUS simulation software. The temperature variation of chips and tools under different cooling modes was studied, and the simulation results were verified by turning experiments of titanium alloy. The results show that the cooling effect of atomized nano-fluid injection is good when turning titanium alloy. The maximum surface temperatures of chips and tools are 168 ℃ and 142 ℃, respectively, which is about 68% lower than that of common cooling mode. The simulation and experimental results of chips and tools under stable cutting state have errors within 5%, which verifies the rationality of the simulation results.

Study on stress distribution of rake face based on finite element method

WANG Yu, FAN Jiangbo, XU Changcheng, LI Rui, ZHANG Xiaolong

2019, 39(5): 103-107. doi: 10.13394/j.cnki.jgszz.2019.5.0018

Abstract(340)

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The stress distribution of the contact area between tool and chip on tool rake face when cutting is studied by finite element method. The friction coefficient and the maximum shear stress are related to the contact condition at the interface. Results show that from tool tip to the separation point of chips, the stress decreases quickly at first, then slowly, and quickly again. It is also found that the cutting depth has great influence on stress distribution, and that there is no slow decrease period of stress curve at cutting depth of 0.13 mm. Meanwhile, cutting speed has limited influence on stress distribution, contact length and chip thickness.

Application of weakening matrix additive in small diameter diamond saws

YANG Dong, CHEN Zhiqiang, WANG Xiaodong, WU Xiwang

2019, 39(5): 108-111. doi: 10.13394/j.cnki.jgszz.2019.5.0019

Abstract(299)

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Silicon-iron was added into the matrix of Fe-based metal bonded diamond saw blade as a weakening agent. The effects of the agent on the mechanical properties, sharpness and wear resistance of the matrix were investigated by using universal material testing machine, pendulum impact testing machine and automatic cutting machine. The results show that the addition of silicon-iron can reduce the flexural strength, toughness and wear resistance of the matrix, and improve the sharpness and hardness of the matrix. The appropriate mass fraction of the additive is 3% to 5%.

Ultrasonic machining technology in dental materials

LI Quanzhou, WANG Chengyong, ZHANG Yue, CHEN Zhihua, ZHAO Danna, ZHENG Lijuan, CHEN Danying, ZENG Chaofeng

2019, 39(5): 112-122. doi: 10.13394/j.cnki.jgszz.2019.5.0020

Abstract(435)

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According to the different processing materials (including tooth, jaw bone, implanted metal and various types of dental ceramics) used in the field of stomatology, this paper reviewed the up-to-date treatment methods and their equipment applying the ultrasonic machining technology (include the ultrasonic milling, the ultrasonic grinding, the ultrasonic surface finishing and the ultrasonic cutting). Its development trend was prospected.

Research status and development prospect of B₄C

ZHAO Liang, LI Yanguo, ZOU Qin, WANG Mingzhi

2019, 39(5): 123-129. doi: 10.13394/j.cnki.jgszz.2019.5.0021

Abstract(331)

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B₄C has excellent properties such as high hardness, good wear resistance, high thermal conductivity, good neutron absorption performance and stable chemical properties. It is widely used in military, nuclear, engineering and other fields. The common preparation methods include carbothermal reduction, self-propagating high-temperature synthesis, chemical vapor deposition, precursor cracking and solvothermal methods. The unique crystal structure makes the densification and sintering of B₄C powder very difficult. Adding additives can effectively promote the compact sintering process and improve the ceramic properties. In this paper, the preparation and sintering of B₄C are reviewed, and the application prospects of B₄C are prospected.

2019 Vol. 39, No. 5

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