金刚石与磨料磨具工程

Synthesizing bulk polycrystalline diamond by method of direct phase transition

WANG Haikuo, ZHANG Xiangfa, WEI Xing, WANG Yongkai, REN Ying, ZHAO Haijun, LU Canhua, LIU Qiankun

2018, 38(1): 1-6. doi: 10.13394/j.cnkij.gszz.2018.1.0001

Abstract(326)

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Pure-phase bulk polycrystalline diamonds are prepared through direct phase transition at ultrahigh pressure and high temperature. The phase composition and microstructure of the pure-phase bulk polycrystalline diamonds are studied by SEM, XRD and Raman spectrum. It is found that with different raw materials and different conditions, diamond samples have different colors and different grain sizes but they are all pure-phase polycrystalline diamonds.The average grain sizes for yellow-transparent and green samples are about 25 nm and 35 μm, respectively. The size of synthesized diamond blocks is φ6 mm×6 mm. The Vicker's hardness of yellow-transparent polycrystalline diamond, HV, is 130-270 GPa at the load of 3 N. According to China National Quality Supervision & Inspection Center for Abrasives, the abrasion ratio of yellow-transparent sample is 1.658×10⁶, which is 25 times higher than that of commercial Co-based PCD used on oil bits. TG/DSC shows that the thermal stability of the yellow-transparent sample is almost the same as that of carat-level single-crystal diamond.Contrast grinding test, using NPD to grind against carat-level single-crystal diamond, shows that the abrasion ratio for the nano-structured polycrystalline diamond is 2.5, which demonstrates that the abrasion performance of NPD is much better than that of carat-level single-crystal diamond.

Synthesis and performance of nano-polycrystalline diamond

TANG Hu, WANG Mingzhi, KANG Ning, JIA Guang, JIAO Xiaochen, GOU Huiyang

2018, 38(1): 7-15,27. doi: 10.13394/j.cnkij.gszz.2018.1.0002

Abstract(730)

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Traditional polycrystalline diamond (PCD) has been widely used in the fields of mechanical processing and mineral exploration. However, due to the existence of binders or sintering aids, the deterioration of mechanical properties greatly limits its applications. Nano-polycrystalline diamond (NPD), which is non-adhesive with ultra-fine grain size and strong grain boundary, performs excellent properties superior to those of traditional PCD and single diamond in the field of high precision machining hard materials, etc. Hereby, the synthesis routes and mechanical properties of NPD are reviewed. The method and technology of preparing NPD from different carbon precursors under high temperature and high pressure (HPHT) are introduced. It is focused on the technology of direct converting graphite and carbon onions to NPD, which will provide reference for further research on its synthesis and application.

Recent progress of free-standing diamond films prepared by DC arc plasma jet method

LI Chengming, CHEN Liangxian, LIU Jinlong, WEI Junjun, HEI Lifu, LV Fanxiu

2018, 38(1): 16-27. doi: 10.13394/j.cnkij.gszz.2018.1.0003

Abstract(404)

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In this paper, the recent progress of free-standing diamond films prepared by DC (direct current) arc plasma jet is reviewed from arc characteristics, diamond crystal quality, mechanical properties, optical properties and thermal properties. The results shows that the crystalline quality and stress state of diamond films are different in various regions of arc, and that Ti transition layer can reduce the residual stress of diamond. The fracture toughness of diamond is up to 10.99 MPa·m^1/2 by four-point bending method. In a certain temperature range, the change tendency of the absorption coefficient and temperature is independent of the crystalline quality and thickness of diamond films. The better optical properties of diamond films are, the higher thermal conductivity is. The thermal conductivity of nucleation surface is slightly higher than that of growth surface. When temperature is more than 500 K, the thermal conductivity of polycrystalline diamond films could approach that of single crystal.

Process of depositing diamond coating on diamond-impregnated cemented carbide

JIAN Xiaogang, HUANG Zhuo

2018, 38(1): 28-31. doi: 10.13394/j.cnkij.gszz.2018.1.0004

Abstract(309)

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To enhance the bonding strength between diamond coating and matrix, chemical vapor deposition was used to deposit diamond coatings on ordinary and diamond-impregnated cemented carbides, separately. SEM, Raman and indentation tests were used to analyze and compare the coatings. Results show that both homoepitaxial and heteroepitaxial growths of diamond coating could be found on the diamond-impregnated cemented carbide substrate, and that the coating deposited on diamond-impregnated cemented carbide substrate performs high diamond nucleation rate, uniform crystal size, and flat coating surface. It is also found that the bonding strength between diamond coating and diamond-impregnated cemented carbide is higher than that between coating and ordinary substrate, which will greatly expand the application of diamond coating.

Modification design and performance analysis of Cu-Sn-Ti solder

GAO Xianzhe, XIAO Bing, GUAN Haijun, XIAO Bo

2018, 38(1): 32-36,40. doi: 10.13394/j.cnkij.gszz.2018.1.0005

Abstract(420)

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The pre-mixed filler metal is made by adding Fe, Al and Si elements in the Cu-Sn-Ti pre-alloy filler metal. 17 kinds of proportioning schemes are determined by using the extreme vertex mixture design method with both upper and lower bounds. The mechanical properties of the solders were evaluated by the shear test. The interface of the matrix, the morphology of diamond and the interface of diamond were analyzed by SEM, EDS and Raman. The test results show that the shear strength of the pre-mixed filler metal decreases obviously when the mass fraction of Cu-Sn-Ti is below 95%, and the mass fraction of each addition should be under 2%. The premixed solder made of Fe, Al, Si with the same mass fraction of 1.7% added in Cu-Sn-Ti have better comprehensive performance, the melting point and the flow ability are suitable, the abrasive grain edge is good, the diamond is not damaged and the dendritic compact TiC is formed on the interface of diamond.

TiN graphene crystals on the surface of CBN by microwave-salt molten treatment

LIANG Baoyan, HAN Danhui, ZHANG Wangxi, WANG Yanzhi, YANG Li, ZHANG Zongchao

2018, 38(1): 37-40. doi: 10.13394/j.cnkij.gszz.2018.1.0006

Abstract(314)

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Titanium nitride on the surface of cubic boron nitride (CBN) was obtained by heat treatment of Ti and CBN with microwave and salt molten. Chemical compositions, phase compositions and microstructures were analyzed and characterized using XRD, SEM and EDS methods. The results show that TiN, Ti₂N, TiN_0.3 and TiB₂ organization were formed on the surface of CBN by molten-salt treatment. The coating of CBN with a coarser size had a thickness of about 2.8 μm. There were many micro pores on this coating. Flower bud nanometer coating was formed on the fine-grained CBN surface. This coating had many titanium nitride nano-rods and nano sheets. In addition to, some TiN graphene crystals, 40-90 nm thick were obtained among CBN particles.

Sinter Fe-Cu-WC based metal bonding agent by using microwave pressureless method

YE Xiaolei, GUO Shenghui, GAO Jiyun, YANG Li, WANG Liang, HOU Ming, GUO Yu

2018, 38(1): 41-44,54. doi: 10.13394/j.cnkij.gszz.2018.1.0007

Abstract(363)

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Metal powders, such as Fe, Cu, Sn and WC, were used to prepare metal bond by conventional and microwave pressureless-sintering. The effects of different sintering processes on the densification and impact toughness of metal bonds were studied. SEM was used to observe the microstructure of the bond. Research indicates that compared with conventional pressureless sintering, microwave pressureless sintering improves the relative density and mechanical properties of the metal bond. The relative density and bending strength of the two bonds both reach the maximum at 900℃, which is 90.6%, 93.9% and 753 MPa, 816 MPa, respectively. It can be seen from the microstructure that microwave pressureless sintering can make the elements uniformly distributed and reduce the porosity of the bond. In addition, at the same level of performance, microwave pressureless sintering can reduce sintering temperature, thus effectively avoiding its damages to diamond strength.

Influence of brazing process on 75Ni8 gang saw steel's brazing properties

YU Xuezong, LONG Weimin, GAO Ya

2018, 38(1): 45-49. doi: 10.13394/j.cnkij.gszz.2018.1.0008

Abstract(240)

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The mechanical properties and microstructures of 75Ni8 gang saw steel are investigated by changing the brazing processes. The experiments select 7 kinds of brazing materials for induction brazing. The mechanical properties and microstructure are analyzed by using mechanical test machine, impact tester, Vickers hardness tester, metallographic microscope and so on. The results show that the shear strength of sandwich HL861 brazed joint is the highest, reaching 164.87 MPa, and that the impact toughness of CT737 is the highest, reaching 50.08 J/cm². The Vickers hardness of the 75Ni8 base material area near the brazing seam is decreased rapidly, whose nadir is 1 176 MPa, while the original Vickers hardness is 4 468.91 MPa. The metallographic observation finds that the organization of the 75Ni8 base material near the brazing seam is coarse and the original is fine and uniform. The organization and property of 75Ni8 gang saw after welding are influenced by temperature.When the heating time becomes longer and the tempering temperature exceeds 600℃, the microstructure changes to the tempered troostite.

Experimental research on metal-based diamond composites by 3D printing

YANG Zhan, TAN Songcheng, YANG Kaihua

2018, 38(1): 50-54. doi: 10.13394/j.cnkij.gszz.2018.1.0009

Abstract(366)

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The traditional manufacturing methods of metal matrix diamond composite tools usually have some typical disadvantages, such as lower holding strength of metal matrix to diamond grits, shorter protrusion height of diamond grits, and it is hardly to produce some specially designed diamond tools with complex structures. While 3D printing technology could provide a new development opportunity for the design and manufacture of metal-based diamond composites and diamond tools. By theoretical analyses, optimizations from metal materials, selective laser melting (SLM) forming process and diamond parameters were conducted. Based on this, the feasibility test and focused test about metal based diamond composites and diamond tools made with SLM were carried out. The results indicated that the use of SLM forming technology can improve the performance of metal-based diamond composites. However, there are still some deficiencies in the application of the new technology, which should be overcome in further researches.

Development and drilling performance of the brazed Ti-coated diamond drill bits

GUAN Haijun, XIAO Bing, GAO Xianzhe, XIAO Bo, LIU Sixing

2018, 38(1): 55-58,64. doi: 10.13394/j.cnkij.gszz.2018.1.0010

Abstract(295)

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Using Ni-Cr and Cu-Sn-Ti solders to produce the brazed Ti-coated and uncoated diamond drills, the performances of four types of diamond drill bits were investigated through the drilling test of vitrified brick. The results show that the average life of Ti-coated diamond drill using Ni-Cr solder brazing decreased by 41.7% compared with the uncoated diamond drilll. The average life of Ti-coated diamond drill and uncoated diamond drill using Cu-Sn-Ti solder brazing are basically the same, but the drilling efficiency of Ti-coated diamond drill is significantly higher.Finally, the mechanism of the above conclusion is analyzed.

Analysis and optimization on cross section profile of fused silica grinding wheel

ZHOU Lian, XIE Ruiqing, CHEN Xianhua, LIU Mincai, WANG Jian

2018, 38(1): 59-64. doi: 10.13394/j.cnkij.gszz.2018.1.0011

Abstract(350)

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In order to improve the grinding quality of fused silica optics and reduce the depth of subsurface defect (SSD), the experiment of grinding fused silica and theoretical analysis were carried out by parallel diamond grinding wheels with straight edge and circular edge. The stress concentration on the straight edge of wheel was the main cause of deep defects like continuous white line, whose depth was about 22 μm. To relieve the stress concentration, a combined cross section profile with circular edges was designed. The propounded dressing method was verified by wheel dressing experiment. After grinding using the latter wheel, the deep defect was constrained remarkably, and the depth of SSD was below 2.5 μm. The purpose of low defect grinding of fused silica optics was achieved.

Principle and application of orderly arranging grain technology of superabrasives

FENG Chuangju, CUI Zhongming, HE Qingshan, WANG Xing, YANG Moxi

2018, 38(1): 65-72,77. doi: 10.13394/j.cnkij.gszz.2018.1.0012

Abstract(537)

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The grinding tools arranged in order of superhard abrasives are the new varieties of the series of grinding tools,their working surfaces have grinding edges which are arranged in a regular pattern. Compared with the traditional abrasive tools, they have the advantages of large chip space, sharpness of grinding edge, small grinding force and low grinding temperature.They have a good application potential in high precision machining.Nevertheless, it's still a difficult problem to achieve arrangement of abrasive grains efficiently and accurately. Therefore, it is urgent to develop new layout technology to overcome these problems.This paper introduces the basic theory of orderly arrangement of abrasives, the structure, main manufacturing methods, research and development of abrasive tools, analyzes the influence of layout way on grinding performance, and forecasts its future development direction.

Process of mechanical polishing yttrium aluminum garnet crystals

SUN Zhiming, JIN Zhuji, HAN Xiaolong, FAN Kangnan, SI Likun

2018, 38(1): 73-77. doi: 10.13394/j.cnkij.gszz.2018.1.0013

Abstract(311)

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Yttrium aluminum garnet (YAG) is a kind of excellent laser crystal, while it is a hard-brittle material with Mohs hardness of 8.5. In order to remove the defects such as scratches and pits easily produced during the polishing, copper plate was used as rough polishing and the effect of load and rotational speed on the flatness and surface roughness RMS was studied. Results show that copper plate can obviously improve the surface defects of YAG, and that the optimized parameters are rotation speed 70 r/min, load 15 kPa for 45 min. Then IC1000 was used to further reduce crystal surface roughness, and the best process are rotational speed 9 r/min and polishing pressure 15 kPa for 30 min polishing. At such condition, the flatness can reach around 100 nm and the surface roughness RMS can reach around 0.9 nm, with no scratches and pits observed under the stereo microscope. The proposed process could be a good reference for YAG polishing.

Effect of electrolytic magnetic composite machining on properties of magnetic abrasive particles

KANG Lu, CHEN Yan, QIAN Zhikun, DU Zhaowei, HAN Bing

2018, 38(1): 78-81. doi: 10.13394/j.cnkij.gszz.2018.1.0014

Abstract(333)

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When the nickel base superalloy and other materials are machined by simple magnetic grinding process, the failure of magnetic abrasive particles seriously affect the grinding effect of the magnetic grinding process. In order to solve this technical problem, electrochemistry is combined with the abrasive finishing technology.Eelctrolytic processing is used to form a softer passivation film on the workpiece, and then the surface is machined by magnetic abrasive finishing.The compositions of the magnetic abrasive particles after the composite processing are analyzed by electron microscopy, the relative mass fraction of aluminum decreases from 27.60% to 23.48%. It effectively reduced the loss of abrasive phase components in magnetic abrasive grains, delags the failure time and improves the utilization and service life of magnetic abrasive grains, thus ensures the machining quality of workpieces.

Experimental study on magnetorheological dynamic plane polishing with microstructure polishing disk

DONG Min, LU Jiabin, PAN Jisheng, YAN Qiusheng

2018, 38(1): 82-88. doi: 10.13394/j.cnkij.gszz.2018.1.0015

Abstract(343)

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In order to improve the plane polishing efficiency of the cluster magnetorheological, some polishing disks with different microstructures were proposed to increase the hydrodynamic pressure of the plane polishing. Polishing experiments and polishing force characteristic experiments were carried out on the plane polishing disk and polishing disks with different microstructures such as holes, V-shaped grooves, U-shaped grooves and rectangular grooves on the surface. The influences of machining gap and workpiece rotation speed on the polishing effects were studied. The results show that the microstructures on the surface of the polishing disk have a great influence on the material removal rates of the workpiece. The material removal rates of the various disks are V-shaped disk>U-shaped disk>plane disk>hole-shaped disk>rectangular disk. The material removal rate of V-shaped disk is 25% greater than that of the plane disk. However, the disk structures have little effects on the surface roughnesses and all the polishing disks with different microstructures can obtain nano-scale (less than R_a 8 nm) surface. In this test, the better polishing effect can be obtained under the condition of the polishing gap 0.9-1.0 mm and the workpiece speed 550 r/min.

Mechanism and experimental study of cluster magnetorheological polishing with dynamic magnetic

GUO Mingliang, YAN Qiusheng, PAN Jisheng, XIAO Xiaolan

2018, 38(1): 89-93,97. doi: 10.13394/j.cnkij.gszz.2018.1.0016

Abstract(277)

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The machining mechanism of cluster magnetorheological plane finishing and the action mechanism of dynamic magnetic fields were analyzed. The magnetorheological polishing experiments of dynamic magnetic field on silicon substrate were carried out. Results show that the dynamic magnetic field can make the distorted polishing pad self-repair in time, and that the abrasives have frequent dynamic behavior. It overcomes the shortcomings of distorted pads repairing and abrasive agglomeration under the static magnetic field. The material removal process is stable and the polishing effect is better. Under the dynamic magnetic fields, different polishing methods make big different effect on the polishing results. In multi workpieces synchronous polishing, the high speed self rotation of the large size tool head makes the workpieces have higher line speed, and the abrasives has a stronger effect on the surface defect removal of the mono crystalline silicon substrate. After 5 h polishing, the surface of the silicon wafer is super smooth, and its roughness R_a is reduced from 0.48 μm to 3.3 nm.

2018, 38(1): 94-96.

Abstract(121)

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2018, 38(1): 97-97.

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2018 Vol. 38, No. 1

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