金刚石与磨料磨具工程

2020, 40(6): 1-3.

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Preparation and properties of octahedral diamond single crystal

ZHANG Cunsheng, SHAO Zengming, SU Yanbin

2020, 40(6): 4-8. doi: 10.13394/j.cnki.jgszz.2020.6.0001

Abstract(213)

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Octahedral diamond single crystals with specific {111} plane were synthesized by optimizing catalyst formula, adding new catalyst, designing synthesis process and improving heat preservation chamber. The results of SEM indicate that the diamond crystal is octahedral, and the crystal has regular {111} facet. The results of Raman spectra show that the hybrid type of carbon atoms in diamond crystal is sp³ hybridization state, and that octahedral diamond has higher purity. The magnetic susceptibility test results show that the magnetic susceptibility of the octahedral diamond is lower than 1.00×10^-5 SI. The application results show that dressing tools with this diamond have better sharpness and wear resistance than that with normal diamond.

Synthesis of gem grade diamond by temperature gradient method using high temperature sintered alumina ceramics

ZHANG Kun, TIAN Yangyang, LIU Kun, ZHANG Jianhua, WANG Tao

2020, 40(6): 9-12. doi: 10.13394/j.cnki.jgszz.2020.6.0002

Abstract(197)

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Gem diamond was synthesized by temperature gradient method under high temperature and high pressure. Alumina ceramics used as insulation chamber were prepared by sintering high purity alumina powder at different temperature. The results show that with the increase of sintering temperature, the density of alumina ceramics increases, the apparent porosity decreases, the corresponding crystal growth rate increases, and the inclusions in the crystal decrease. The relative density of alumina ceramics is 97% and the apparent porosity is 0.05% when sintered at 1 650 ℃ for 4h. The high-grade diamond without any inclusions, weighing 0.40 g (2 ct) and growing at a speed of 4.0 mg/h was prepared.

Detection method based on deep learning for yellow industrial diamond

YANG Jianxin, LAN Xiaoping, WANG Bo, YAN Lei, ZHAO Zhen, FENG Yadong

2020, 40(6): 13-19. doi: 10.13394/j.cnki.jgszz.2020.6.0003

Abstract(228)

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To solve problems such as low manual testing speed, high labor intensity and limited quality consistency of yellow industrial diamond test, we proposed a testing method based on deep learning for yellow industrial diamond. Firstly, a hardware system was developed to collect the data of the yellow industrial diamond by its structural characteristics. Then, the data were pre-processed by image processing, using three basic classifiers, namely VGG-16, inception-V3 and ResNet-50 to construct three network structures respectively. The information fusion of each basic classifiers and classification decision were realized by integrating fusion method. It is confirmed by verifying test that the comprehensive recognition evaluation indicators of yellow industrial diamonds with grades of 2240, 2280 and 2290 are all over 85%. This testing method is valuable and highly practicableness.

Preparation of CVD single crystal diamond and research of its infrared property

LU Canhua, LIU Qiankun, WANG Zhitao, ZHANG Guokai, CHEN Ming, CAO Tong, ZHU Pei

2020, 40(6): 20-24. doi: 10.13394/j.cnki.jgszz.2020.6.0004

Abstract(256)

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With H₂/CH₄/N₂ as the mixed gas source, the single crystal diamonds are deposited on CVD diamond substrate using microwave plasma chemical vapor deposition method. The effect of substrate temperature on diamond crystallization quality and optical properties at a certain concentration of methane are analyzed. Optical microscope and scanning electron microscope (SEM) are used to characterize the color, the internal defect and the surface morphology of the CVD diamond samples. After polishing, the infrared transmittance of the samples is detected by the infrared Fourier transform spectrometer. The results show that the crystallization quality and the infrared transmittance is the best when the growth temperature is maintained at about 930 ℃. The infrared transmittance will reduce if the temperature is higher or lower. It also shows that the diamond grown at a slightly higher temperature has better crystallization quality and infrared transmittance performance than diamond grown at a lower temperature. The N₂ doped diamond shows a brown color and faster growth rate, the infrared transmittance performance of which will be seriously reduced.

Grinding YG8 cemented carbide with resin bond grinding wheels made of diamond agglomerate abrasive

CHEN Zhe, CHEN Chunhui, LIU Yibo, XU Yanjun, LIU Wei, HUANG Xia, LI Yapen, KONG Shuaifei

2020, 40(6): 25-30. doi: 10.13394/j.cnki.jgszz.2020.6.0005

Abstract(265)

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To explore the grinding performance of diamond agglomerate abrasive in resin bonded grinding wheels, we prepared ceramic bond diamond agglomerate abrasives with diamond concentrations of 150%, 200%, and 250%, respectively on ZLB-60 rotary granulator. The results show that the single-particle static pressure strength of diamond agglomerate abrasives was 61 N, 65 N, 36 N. We selected the agglomerate abrasive with a diamond concentration of 200% and the single-grain diamond with the same original particle size to prepare resin bond diamond grinding wheels with a diamond concentration of 100%, and conduct a YG8 cemented carbide grinding test on the grinding wheels through a self-made grinding platform. Results indicate that when the volume fraction of polycrystalline abrasive is 30%, the resin bond diamond wheel has the best grinding performance. The grinding ratio is 145.11 and the grinding efficiency is 13.64 g/h, which are increased by 152% and 40%, respectively when compared with those of the single-grain diamond wheels.

Analysis on interface microstructure of Ni-Cr filler brazed Ti coated CBN

WANG Junlin, XIAO Bing, WANG Shuyi, SU Shichao, PU Yizhi, GAO Rui

2020, 40(6): 31-35. doi: 10.13394/j.cnki.jgszz.2020.6.0006

Abstract(159)

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Ni-Cr filler was used to braze Ti coated CBN abrasive and AISI1045 steel in vacuum. SEM, EDS and XRD were used to analyze the morphology of Ti coated CBN abrasive particles after brazing, the microstructure of the interface between CBN and Ni-Cr filler, and the surface products of abrasive after brazing. During the brazing process, Ni-Cr filler climbs the CBN particles along the Ti coating and has good wettability to the abrasive. After brazing, the Ti coating on the exposed part of CBN grains transforms into Ni-Ti metal layer under the diffusion of Ni atoms. However, in the area where the grains are embedded in the filler, the Ti coating of the abrasive diffuses with CBN and Ni-Cr filler during the brazing process, forming an intermediate layer mainly composed of NiTi and Ni_0.3Ti_0.7N, which realizes the metallurgical bonding of Ti coated CBN abrasive and Ni-Cr filler.

Research on resin-bonded diamond grinding wheel based on brazing-coated diamond and its performances

LI Mingcong, XIANG Gangqiang, LI Weixiong, ZHANG Fenglin, ZHOU Yumei, LONG Weimin

2020, 40(6): 36-41. doi: 10.13394/j.cnki.jgszz.2020.6.0007

Abstract(128)

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The surfaces of two kinds of diamond abrasives, the single crystal RVD and the polycrystalline PDGF1, were coated by brazing method, and the resin-bonded diamond grinding wheels were prepared with four kinds of abrasives before and after coating. The effects of brazing process on the surface morphologies and the mechanical properties of diamond abrasives were studied, and the grinding performances of cemented carbide machined by different grinding wheels were tested. The results show that a layer of filler alloy coating can be effectively coated on the surface of diamond abrasives by brazing-coating method, and the TiC interface bonding is formed between the coating and the diamond abrasive particles. Compared with the particles before brazing-coating, the impact toughness (TI) value of the RVD abrasive particles after brazing-coating decreases by 6%, while the TI value of the PDGF1 particles after brazing-coating increases by 42%. The resin-bonded diamond wheel made of brazing-coating PDGF1 abrasives has lower grinding force and higher grinding ratio, but the resin-bonded diamond wheel made by brazing-coating RVD abrasives has the opposite result. Under the same processing parameters, the surface topographies of cemented carbide grinded by four kinds of grinding wheels are similar, and the surface roughnesses are between 0.50 μm and 0.68 μm.

Experimental research on brazed diamond grinding wheel for rail grinding performance

YAN Xinlin, XIAO Bo, GAO Xianzhe, XIAO Bing, ZHANG Yiquan

2020, 40(6): 42-46. doi: 10.13394/j.cnki.jgszz.2020.6.0008

Abstract(175)

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In view of the shortcomings of large spark and dust pollution in the grinding of rail with resin grinding wheel, a single layer brazed diamond grinding wheel used for rail grinding is designed and made. Through the grinding test, the comprehensive performance of the brazed diamond grinding wheel grinding rail is evaluated. Experimental results show that in the stable grinding stage, the grinding efficiency, grinding current and grinding spark of the diamond grinding wheel are better than that of the resin grinding wheel; the surface roughness of the workpiece after grinding by diamond grinding wheel is good, and the wear debris has no thermal deformation; the main reason of the failure of the diamond grinding wheel is the adhesion of the debris, and the abrasive particles have not been obviously worn out when they fail.

Study on development and properties of ceramic metal bond CBN block

LIU Bingheng, XIAO Bing, MENG Xianglong, ZHAO Pengcheng, WANG Shuyi

2020, 40(6): 47-50. doi: 10.13394/j.cnki.jgszz.2020.6.0009

Abstract(191)

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Resin bond wheels are mainly used for rail grinding, which have problems such as low material removal rate and high grinding temperature. Therefore, a new ceramic-metal bond CBN block was developed by using brazed super-hard abrasive technology. The grinding performance of ceramic-metal bond CBN block and resin zircon corundum was studied, such as material removal rate, chip distribution and grinding temperature. Results show that compared with the resin zirconium corundum, the ceramic-metal bond CBN block has a 124% higher material removal rate and a 15~50 ℃ lower grinding temperature peak.

Effect of colloidal graphite on properties of low temperature metal-resin composite bond

DIAO Yinyan, CUI Chong, YANG Songcan, FENG Yuanru

2020, 40(6): 51-57. doi: 10.13394/j.cnki.jgszz.2020.6.0010

Abstract(184)

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The strength, the hardness, the microstructure and the reaction bonding mechanism of the composite bond were studied by adding mass fraction of 0~0.4% trace colloidal graphite to the aluminum-based metal-resin composite bond. The results show that when the sintering temperature is 360 ℃, the holding time is 5 min, and the holding pressure is 2 100 N/cm², with the increase of the mass fraction of colloidal graphite, the density of the composite bond first decreases, then increases and finally decreases; the hardness, the strength and the elastic modulus all increase first and then decrease. When the added mass fraction of the colloidal graphite is 0.2%, the hardness and the strength of the composite bond reach the maximum values of 61.5 HRB and 250 MPa, respectively, and the density and the elastic modulus of the composite bond are moderate. Trace colloidal graphite can react with Al in the composite bond to form a small amount of Al₄C₃, which promotes the formation of three-dimensional cross network structure and improves the properties of low-temperature metal-resin composite bond.

3D simulation study on the chip formation process in high speed and ultra-high speed grinding of nickel-based superalloy

XIA Jiang, DING Wenfeng, QIU Bo, XU Jiuhua

2020, 40(6): 58-69. doi: 10.13394/j.cnki.jgszz.2020.6.0011

Abstract(232)

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A three-dimensional finite element simulation model about high speed and ultra-high speed grinding of GH4169 nickel-based superalloy with a single abrasive was established. The evolution process of chip morphology and the change rule of grinding forces under high speed and ultra-high speed grinding conditions were studied. The distribution and change of physical parameters such as stress, strain and temperature in the grinding area were observed. The influences of the grinding speed and the cutting thickness of single abrasive on the chip morphology, the chip forming frequency and the groove uplift characteristics were analyzed. The results show that the sawtooth chip is easy to appear when grinding high temperature nickel-based alloy at high speed. The grinding force changes periodically, and its period corresponds to the formation process of the chip. The temperature, the strain and the strain rate in the grinding process are mainly concentrated in the shear zone, while the stress is concentrated on two sides of the shear zone. With the increase of grinding speed, the spacing between the sawtooth decreases, the degree of serration increases, the sawtooth forming frequency increases linearly, and the groove uplift ratio increases. In addition, the critical forming chip cutting thickness of GH4169 is about 0.3 μm. When the cutting thickness is 0.8 μm, the sawtooth chip will appear. With the increase of single abrasive cutting thickness, the degree of serration will increase, but the chip forming frequency will decrease.

Simulation analysis of stress field and temperature field of cutting blades based on laser ranging and positioning

SONG Yu, MENG Guangyao, GAO Zhiyang, SHEN Yisong

2020, 40(6): 70-75. doi: 10.13394/j.cnki.jgszz.2020.6.0012

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In the automatic cutting process of casting pouring riser, the diameter of the grinding wheel is gradually reduced due to wear, which affects the positioning accuracy of the cutting process. Based on the laser distance meter, a method for automatic positioning by measuring the remaining diameter of the cutting blade after wear is proposed. ABAQUS finite element analysis software is used to design single-factor experiments to analyze the stress and temperature field before and after increasing the thickness of the cutting blade. The results of the study show that properly increasing the thickness of the cutting sheet is beneficial to avoid stress concentration and reduce the cutting temperature, and it is found that the surface morphology of the workpiece improved after the thickness of the cutting disc is increased.

Experimental research on the grinding performances of iron-based diamond wheel with biological in-process dressing

LIN Weimin, HUANG Hui, MA Fei

2020, 40(6): 76-82. doi: 10.13394/j.cnki.jgszz.2020.6.0013

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Biological in-process dressing (BID) is an environmentally friendly dressing technique for metal based grinding wheel. In this study, different concentration Fe³⁺solution containing acidithiobacillus ferrooxidans(A.f) was used as grinding fluid, comparing with water. The effects of different Fe³⁺ concentrations on the grinding force, the surface roughness of the workpiece and the exposed height of the abrasive particles on the surface of the grinding wheel were compared and analyzed when the iron-based diamond wheel ground the single crystal silicon carbide with BID. The result shows that compared with the water group, BID can significantly reduce the normal force and tangential force in the grinding process. With the increase of Fe³⁺ concentration in the biological dressing solution, the grinding force shows a downward trend, but the grinding force ratio first decreases and then slowly increases to 3.42. Biological dressing can also effectively reduce the roughness. The lowest surface roughness is 259.67 nm when the Fe³⁺ concentration in the dressing solution is 3.0 g/L. The main reason for the above results is that the exposed height of the abrasive particles in the grinding wheel can be effectively increased through biological dressing.

Review on cutting performance and wear mechanism of PCBN tools

CUI Jinmeng, MENG Dezhong, WU Zhe, YUE Wen, WANG Chengbiao

2020, 40(6): 83-91. doi: 10.13394/j.cnki.jgszz.2020.6.0014

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Polycrystalline cubic boron nitride (PCBN) tool is another kind of superhard tool after polycrystalline diamond tool. It is known as the green environmental protection tool in the 21st century for its unique advanced cutting methods such as turning instead of grinding, hard machining and dry cutting. PCBN tools are is widely used in metal cutting, which is mainly used for processing various kinds of hardened steel, wear-resistant cast iron and other iron-based materials. This paper introduces the influences of tool composition, tool geometry and cutting parameters on the cutting performance of PCBN tools. On this basis, the main wear mechanism of cutting tools in machining different materials are analyzed, and the cutting performance differences between cemented carbide and PCBN tools are also briefly compared.

Analysis and experimental research on titanium alloy cutting based on two-dimensional ultrasonic vibration assistance

DAI Bing

2020, 40(6): 92-96. doi: 10.13394/j.cnki.jgszz.2020.6.0015

Abstract(195)

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To solve the problem of poor surface quality of titanium alloy in conventional cutting, two-dimensional ultrasonic assisted cutting was applied to the processing of titanium alloy. The ultrasonic vibration cutting theory of titanium alloy was analyzed to find out the factors affecting the tool path and cutting force. The titanium alloy surface cutting experiment based on 2D ultrasonic vibration was designed to study the influences of ultrasonic vibration on cutting force, workpiece surface morphology and tool life. The results show that compared with conventional cutting, 2D ultrasonic vibration assisted cutting can effectively reduce the cutting force, reduces the impact of machining process on the tool, and improves the tool life. Under the same processing conditions, the cutting force of 2D ultrasonic vibration assisted machining is reduced by 47.7%, the average height of workpiece surface profile is reduced by 40.9%, and the service life of the tool is nearly doubled.

Study on diamond bit with right trapezoidal cutters for drilling hard-compact rocks

YE Hongyu, YANG Zhan, ZOU Shengshu, XIE Tao, PAN Jiadong

2020, 40(6): 97-101. doi: 10.13394/j.cnki.jgszz.2020.6.0016

Abstract(158)

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Deep drilling has the challenges of varied strata types and complicated lithologic characters, and the problems of low rate penetration and short bit service life in hard-compact rock drilling. To solve the above mentioned drilling difficulties, a bit with right trapezoidal cutters was provided as an extensive adapted bit. The requirements of bit structure and performance of extensive adapted bit, as well as force analysis of the right trapezoidal bit were studied. Theoretical study and drilling practice indicated that the right trapezoidal bit had reasonable bit structure, which could obtain good drilling results in rocks with drillability of 7 to 9 grades. Compared to ordinary bits, the right trapezoidal bit has similar bit service life, improving penetrating rate by 21% to 24% and reducing bit cost by 15%. Consequently, the right trapezoidal bit is comparatively better than ordinary bits.

Chip control method when machining holes with PCD tools

HUANG Zhen, DANG Zhanguo, ZHAO Zhenguo

2020, 40(6): 102-104. doi: 10.13394/j.cnki.jgszz.2020.6.0017

Abstract(163)

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The types of surface scratches on the inner surface of hole drilled with PCD tools are analyzed, as well as the reasons of their appearance to eliminate them. Experiments are implemented to test the effect of methods such as optimizing the main principal deflection angle and adding spray. Results show that in rough machining, there formed an aluminum ring chip in the hole. Then the ring chip, driven by the fine machining tool, would scratch the hole surface. It is also found that optimizing the main principal deflection angle of the edge of coarse machining tool, thus from 85° to 48°, could reduce the ring thickness and limit its appearance. Actual production proves that this method could eliminate the remaining aluminum ring in finished product and thus improve the surface quality of inner hole.

2020 Vol. 40, No. 6

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