金刚石与磨料磨具工程

Study on diamond film growth by hot filament CVD in confined space

DAI Kai, WANG Chuanxin, XU Qingbo, WANG Tao

2018, 38(4): 1-5. doi: 10.13394/j.cnki.jgszz.2018.4.0001

Abstract(378)

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Abstract:
In order to increase the growth rate of diamond film deposition by hot filament CVD, the filament, the substrate and the gas were limited in a narrow space with a self-made semi-enclosed space restraint device. Acetone and hydrogen were used as the reaction gas source. The deposited diamond films under different gas flow rates were characterized by SEM and Raman spectroscopy. Results showed that the deposition rate could be significantly improved by restraint device. In this experiment, the maximum deposition rate of 6.31 μm/h was obtained at a gas flow rate of 230 sccm, which was nearly two times that of the unconstrained method. As gas flow rate increased, the deposition rate increased first and then decreased. The grain size was micron level at gas flow 86 to 115 sccm, while it changed to nano size at gas flow 115 to 575 sccm. The Raman spectroscopy showed that the quality of the constrained deposited film was generally better, and gradually decreased with the increase of gas flow rate.

Performance characterization of cryogenic treated diamond particles

LIU Baochang, CAO Xin, ZHANG Chi, MENG Qingnan, LI Chuang

2018, 38(4): 6-10. doi: 10.13394/j.cnki.jgszz.2018.4.0002

Abstract(296)

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Abstract:
Three kinds of synthetic diamond with different particle sizes were treated by cryogenic treatment, and the diamond particles before and after treatment were analyzed by Raman spectrum, fluorescence spectrum and static press tester. The results showed that the average static pressure strength of diamond 30/35 was increased by about 23.2%, while the internal residual stress was reduced by 25.93%. In conclusion, cryogenic treatment could reduce the magnetic properties of synthetic diamond particles and repair their defects. It also helped to release the internal residual stress and increase the static pressure strength.

Research progress of microstructures and plastic deformation mechanisms for nano polycrystalline diamond

HE Genchun, XU Chao, LIU Chunmei

2018, 38(4): 11-19. doi: 10.13394/j.cnki.jgszz.2018.4.0003

Abstract(408)

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Nano polycrystalline diamond is a kind of material formed by direct bonding of diamond grains with grain sizes less than 100 nm. The hardness of nano polycrystalline diamond synthesized by the direct transformation of graphite at high temperature and high pressure can reach 120-145 GPa, and the hardness of the nano twinned diamond with high density twins directly transferred from onion carbon reaches 200 GPa, which is much higher than the hardness of natural single crystal diamond. Nano polycrystalline diamond has excellent properties due to its microstructures, and the investigations on the mechanism of its plastic deformation will be beneficial to the design and synthesis of nanostructured superhard materials with higher performance. In this paper, the research progress of the microstructures and the plastic deformation mechanisms of nano polycrystalline diamond at home and abroad are reviewed, and the experimental and theoretical research on the mechanisms for the plastic deformation of nano polycrystalline diamond are introduced and evaluated, which will provide reference for further research and application of nano polycrystalline diamond.

Research progress of preparation methods of diamond-based MEMS

LU Yunxiang, MAN Weidong, LUO Hongtai, CHEN Menghuan, CHEN Peiqin

2018, 38(4): 20-26. doi: 10.13394/j.cnki.jgszz.2018.4.0004

Abstract(362)

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Due to its unique physical, chemical, and electrical properties and the feasibility of growing in the form of thin films, diamond is an ideal material for manufacturing reliable and long-life micro-electromechanical/nanoelectromechanical systems (MEMS/NEMS). In recent years, the development of chemical vapor deposition of diamond thin film has promoted the application of diamond in MEMS and realized a new era of development of diamond-based MEMS and NEMS. However, due to the difficulty in precise processing, diamond has not yet been widely applied in NEMS/MEMS. In this article,the current research progress of diamond-based MEMS is introduced, as well as the processing methods of diamond-based MEMS system. The prospect of diamond application in MEMS is proposed.

Application of diamond surface pretreatment technology on diamond bits

XU Liang, LIU Yibo, XU Qiang, YANG Lin

2018, 38(4): 27-29,35. doi: 10.13394/j.cnki.jgszz.2018.4.0005

Abstract(430)

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Abstract:
This paper introduces two kinds of diamond surface pretreatment technologies, namely titanium coating and pit treatment, which are commonly used in diamond tool manufacturing. The efficiency and life of 2 bits made of pretreated and conventional diamonds when drilling reinforced concrete are compared and analyzed. Drilling experiments show that compared with that of conventional bit, the life of the bit made of Ti-coated diamond can be increased by more than 30%, and that the service life and drilling efficiency of bits made of pit-treated diamonds are increased by 35% and 10% respectively with lower concentration of added diamond. Therefore, pit treatment is a rapidly developing technology at present.

Preparing diamond bit with Cu-Mn damping alloy in matrix and drilling test

LIU Baochang, HAN Zhe, LI Siqi, ZHAO Xinzhe, LI Chuang, CAO Xin

2018, 38(4): 30-35. doi: 10.13394/j.cnki.jgszz.2018.4.0006

Abstract(300)

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Harmful vibration often occurs in the drilling process of impregnated diamond bit, which greatly affects the stability of drilling. Copper-manganese damping alloy can dissipate vibration energy and achieve the purpose of damping vibration. Therefore, copper-manganese powder is used to replace 663 bronze powder in 63^# formula to make matrix sample and hence diamond bit. The results of mechanical properties test and fracture morphology analysis show that compared with 63^# formula sample, the matrix sample with 40wt% copper-manganese powder has uniform microstructure, compact structure and 14.7% hardness increase. The wear ratio of impregnated diamond bit increases by 13.2%, and the bending strength decreases by 22.4%. The drilling test results show that the drilling performance of Cu-Mn formula drill bit with 40wt% Cu-Mn is similar to that of 63^# diamond drill bit, while the drilling vibration acceleration amplitude is reduced by 4.3%. Therefore, drilling damping performance is improved, and the drilling process is more stable.

Application of Cu-P pre-alloyed powder in the carcass of diamond tools

YU Qi, MA Jia, LONG Weimin, ZHONG Sujuan, DING Tianran, YU Xinquan

2018, 38(4): 36-40. doi: 10.13394/j.cnki.jgszz.2018.4.0007

Abstract(297)

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The carcass of diamond tools, which contained Cu-P pre-alloyed powder by hot pressing sintering process, was studied. The powder took through the instantaneous liquid brazing copper and iron based powder, improving the density, hardness and strength of the carcass. Cu-P pre-alloyed powder could improve the wettability and binding force of copper and iron powders, and form brittle phases at grain boundaries, thus increasing the brittleness of carcass and the sharpness of diamond tools. Cu-P pre-alloyed powder have broad prospects in the manufacturing of diamond tools.

Effect of dewaxing process on carbon and oxygen content in ultra-fine pre-alloyed matrix

YAO Jiongbin, LIU Yibo

2018, 38(4): 41-44. doi: 10.13394/j.cnki.jgszz.2018.4.0008

Abstract(255)

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Abstract:
In order to improve the fluidity and cold pressure performance of superfine pre-alloyed powder, granulating agent should be added to the granulation of superfine pre-alloyed powder, and then the granulating agent is removed by reduction dewaxing process and heat preservation dewaxing process. The results show that no matter which dewaxing process after granulation, there will be granulating agent residues in the matrix after sintering, which will increase the carbon content.The mass fraction of carbon and oxygen in the matrix is the lowest in the reduction dewaxing process, which are 0.048% and 0.22% respectively, but the carbon content in the furnace preservation heat dewaxing process can also reach the level of the reduction dewaxing process by increasing the heat preservation time.In the process of heat preservation and dewaxing of the furnace, the oxygen content of the sample does not decrease with the increasing of the holding time. It is only related to the sintering condition. The reduction atmosphere in the graphite mold at high temperature makes the oxygen content of the sample lower.The two kinds of dewaxing methods have little effect on the flexural strength and Rockwell hardness of the superfine FeCoCu pre-alloyed powder matrix.

Effects of pre-alloyed CSB-2 powder addition and sintering temperature onphysical property of hot-pressed iron-rich diamond bit matrix

AI Kun, LI Jingyi, DUAN Longchen, JIA Yongjiang, TAN Songcheng, FANG Xiaohong

2018, 38(4): 45-49. doi: 10.13394/j.cnki.jgszz.2018.4.0009

Abstract(314)

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With the advantages of low cost and high drilling speed, the hot-pressed iron-rich based diamond bit has been deeply studied and applied in recent years. Compared to the same formula of the hot-pressed iron-rich matrix, the effect of the pre-alloyed CSB-2 addition and sintering temperature on the physical properties of diamond bit matrix were studied by compactness, microhardness, flexural strength and impact toughness tests. Results indicated that matrix performance of the added CSB-2 powder was better than that of the elemental mixed powders. With the increase of mass fraction of CSB-2, the compactness, microhardness, flexural strength and impact toughness of the matrix were increased by 7.68%, 27.99%, 94.43% and 312.82% respectively. At the same time, the pre-alloying of matrix formula could reduce the hot-pressing temperature. To obtain a good application performance, the optimum addition of CSB-2 should be higher than 30% and the preferred sintering temperature should range from 940℃ to 980℃.

Evolution of microstructure and high temperature hardness in WC_xTaC-Co cemented carbides

LIN Liangliang

2018, 38(4): 50-55,60. doi: 10.13394/j.cnki.jgszz.2018.4.0010

Abstract(381)

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Influence of TaC addition with 0.00% to 3.00% (mass fraction) on the microstructure, mechanical performance and high temperature hardness was investigated through SEM, XRD, EPMA analysis and mechanical tests including high temperature hardness measurement. The results show that when the mass fraction of TaC is less than 0.50%, TaC is mainly dissolved in the bond phase, strengthening the solid solution and inhibiting the grain growth, and the Vickers hardness and the bending strength of the alloy at room temperature are obviously improved. When the mass fraction of TaC increases from 0.50% to 3.00%, the unevenly distributed (Ta, W) C precipitated phase begins to appear in the structure, and the Vickers hardness of the alloy at room temperature increased slowly, while the bending strength increased slowly and then decreased. The addition of TaC helped to enhance the hardness of cemented carbide at high temperature, and the effect of improvement was positively related to the amount of TaC added. At 1000℃, the high temperature hardness of the alloy without TaC was only 802 MPa, while the alloy with a mass fraction of 1.50% TaC improved the hardness of the alloy at high temperature, and its high temperature hardness could reach 1 025 MPa.

Microstructure and mechanical property of CVD MT-Ti(C, N) coating with different C/N ratios

ZOU Lingli

2018, 38(4): 56-60. doi: 10.13394/j.cnki.jgszz.2018.4.0011

Abstract(309)

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Thin films of MT-Ti(C, N) with different nitrogen and carbon contents were prepared on cemented carbide substrates using the chemical vapour deposition. It was found that carbon source had decisive effect on the ratios of C/N, and that the microstructure of MT-Ti(C, N) varied as the ratios of C/N changed, which was analyzed by SEM, TEM and EDS. The results showed that C₂H₄ gas could help to increase the ratio of C/N compared to mono CH₃CN, and that as the ratios of C/N increased, the grain size of MT-Ti(C, N) decreased. It was also shown that the ratios of C/N played an important role in the corresponding scratch resistance and nanohardness.

Effect of particle size and content of silicon powder on microstructure and properties of SiC ceramic materials

MA Lijun, LI Wenfeng, HUANG Qingfei, XIE Yubo, HOU Yonggai

2018, 38(4): 61-63,71. doi: 10.13394/j.cnki.jgszz.2018.4.0012

Abstract(434)

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Si powders with average particle sizes of 75 μm and 48 μm respectively and mass fraction from 0% to 8% were added to the SiC ceramic materials which were sintered at 1550℃ for 3 h. The effects of particle size and addition amount of Si powder on sintering properties, mechanical properties and microstructures of SiC ceramics were studied. The results show that the addition of Si powder with different particle size and content can improve the microstructure of SiC ceramic material and improve its sintering and mechanical properties. Within a certain range, the smaller particle size of Si powder is more conducive to the formation of uniform and compact SiC sintered body, and greatly improves the performance of SiC ceramic material. When the particle size of Si powder is 48 μm and the mass fraction is 4%, the sintering and mechanical properties of SiC ceramics are better, whose volume density and apparent porosity are 2.58 g/cm³ and 13.5% respectively, with flexural strength and hardness 25 MPa and 115 HRB respectively.

Simulation and experimental study on diamond stick superfinishing bearing raceway made of zirconia ceramic

LI Songhua, WANG Weidong, WU Yuhou, SUN Jian, HAN Tao

2018, 38(4): 64-71. doi: 10.13394/j.cnki.jgszz.2018.4.0013

Abstract(290)

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Finite element model of zirconia ceramic bearing raceway superfinishing with diamond stick was established by ABAQUS software, and its machining mechanism was analyzed. The surface roughness and surface morphology of the raceway after superfinishing were obtained by finishing zirconia ceramic bearing raceway with diamond stick. The effect of superfinishing stress on surface quality of zirconia ceramic bearing raceway was studied. The results show that as the tangential velocity increases from 150 m/min to 450 m/min, the surface stress decreases and the surface roughness decreases from 0.091 2 μm to 0.059 3 μm and then increases. As the stick stress increases from 0.2 MPa to 0.8 MPa, the surface stress increases, and the surface roughness decreases from 0.194 2 μm to 0.032 2 μm. When the swing speed of long and short stroke of diamond stick increases, the surface stress of bearing raceway increases, and the surface roughness increases from 0.071 6 μm to 0.085 8 μm and 0.062 7 μm to 0.100 8 μm, respectively. It is helpful to improve the machining quality by properly increasing the tangential speed, the stick pressure and the long-stroke swing speed of the workpiece and reducing the short-stroke swing speed.

Research and development of intelligent grinding process software for machine tool spindle

GE Zhiguang, DENG Zhaohui, LIU Wei, WAN Linlin, PENG Keli, LV Lishu

2018, 38(4): 72-76,82. doi: 10.13394/j.cnki.jgszz.2018.4.0014

Abstract(369)

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To study the intelligent reasoning of the process to grind machine tool spindle, a grinding process software is developed to satisfy its intelligent manufacturing. The software includes several modules, such as the basic database of the intelligent grinding process for machine tool spindle, the process database, the optimized examples of process & intelligent reasoning, and the automatic numerical control & programming. Experiment on the CNC outer grinding machine shows that the software could significantly improve the accuracy of the decision making of the spindle numerical control grinding process up to 96%, and that the decision time is reduced by 50%, thus improving the processing efficiency.

Theoretical study on trajectory of swinging plane lapping and polishing

YAN Zhen, FANG Congfu, LIU Chong

2018, 38(4): 77-82. doi: 10.13394/j.cnki.jgszz.2018.4.0015

Abstract(351)

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To analyze the influences of swinging motion parameters on lapping and polishing trajectory in plan lapping and polishing with swinging motion, a model on movement trajectory is established, and the quantitative evaluation method of trajectory non-uniformity is used. The results show that the swinging amplitude and the swinging angle have an obvious influence on the trajectory non-uniformity, while the swinging angular velocity has little effect on trajectory non-uniformity except that the swinging angular frequency takes a special value. The trajectory non-uniformity can be well improved when the swinging amplitude is 15 mm and the swinging angle is 30°, whose value can be reduced to 0.058. If the values of the eccentricity and swinging motion parameters are improperly selected, the value of trajectory non-uniformity can be up to 0.284.

Standard of grinding wheel used on rail grinding

ZHANG Guowen, HE Chunjiang, ZHANG Jing, PEI Dingfeng

2018, 38(4): 83-86. doi: 10.13394/j.cnki.jgszz.2018.4.0016

Abstract(411)

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Based on the background of formulating China railway standard Q/CR 1-2014 "Technical specifications for the procurement of grinding wheel for the rail grinding train", the paper introduces main contents and formulation principle of the standard and emphatically expounds the source and basis of data. It also explains the selection of main parameters such as rail grinding performance, turning performance, static balance performance parameters of the grinding analytical standard, and gives a scientific evaluation for the rationality of the standard.

2018 Vol. 38, No. 4

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