金刚石与磨料磨具工程

Chemical vapor deposition of diamond microsphere: Investigation of growth dynamics

XU Shuai, LI Xiaopu, DING Yulong, WU Xiao, FAN Bo, YAN Ning

2018, 38(5): 1-5. doi: 10.13394/j.cnki.jgszz.2018.5.0001

Abstract(404)

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Abstract:
The spherical polycrystalline diamond microspheres were prepared on the monocrystalline silicon substrate by microwave plasma chemical vapor deposition. By changing the deposition pressure and temperature, the transition of diamond from graphite growth region to nanocrystalline spherical structure, and to diamond growth region with good crystallization was studied. The particle size increases with the pressure and temperature increasing, and microspheres change from sp³ and sp² coexisting phase to pure diamond phase. The formation of microspheres is mainly controlled by the secondary nucleation mechanism within a certain degree of carbon oversaturation, pressure and temperature. The microsphere grows in the orientation of <110> with the pressure and temperature increasing. The formation of diamond microspheres is controlled by (111) face defects with high density twins and stacking faults, which reveals the growth process of diamond microspheres induced by secondary nucleation mechanism and twin stacking fault mechanism in different growth regions of CVD diamond.

Study on the titanium plating on diamond surface and its bonding state in the matrix

LUO Li, ZHOU Qiang, YANG Shuzhong, WEI Shichao, CHANG Demin

2018, 38(5): 6-11. doi: 10.13394/j.cnki.jgszz.2018.5.0002

Abstract(304)

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Abstract:
The method of vacuum evaporation-diffusion plating was used to plate titanium on diamond, the effects of plating temperature and holding time on diamond surface morphology, coating thickness and coating phase were studied, and the anti-oxidation performance of Ti-coated diamond was analyzed as well as its bonding state in iron matrix. The results showed that TiC appeared at low temperature(680℃). The plating temperature increasing or the holding time prolonging, the coating became denser and thicker, titanium deposition occurred at 720℃, cracks occurred due to stress and led to the destruction of the coating at 820℃. The coating isolated the direct contact between diamond and oxygen, and the erosion of diamond by oxygen was greatly delayed. After titanium plating, the diamond achieved solidly metallurgical bonding in the matrix.

Application of TiO₂/BDD composite electrode in electrochemical oxidation treatment of pharmaceutical wastewater

ZHAO Xinyang, LI Zhiqiang, MA Yuxiang, ZHANG Kehao, HUANG Jinzhou, YUAN Xinjie, XU Yang, WANG Hailong, XI Yaohui, XU Shuai, ZHAO Yanjun, YAN Ning, WANG Zhiqiang

2018, 38(5): 12-16. doi: 10.13394/j.cnki.jgszz.2018.5.0003

Abstract(251)

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In this paper, nano TiO₂ are grown on the surface of boron-doped diamond (BDD) film using a hydrothermal method, thus fabricating a TiO₂/BDD composite electrode with photoelectric co-catalysis function. The electrochemical property of the electrode is characterized by a electrochemical workstation, and then the electrodes are used to degrade the pharmaceutical wastewater. Results show that the electrode has a wide electrochemical potential, which is 3 V, 4 V and 4 V in acidic, neutral and alkaline conditions, respectively. It also has an anodic oxidation potential of 2 V with low background current and good reversibility. The composite electrode has remarkable degrading effect on the wastewater by reducing the chemical oxygen demand from 7339 mg/L to 19 mg/L in 630 min, which means a 99.7% reduction.

Experimental study on the whole process of diamond indenting rock

YE Jichao, SHEN Lina, YANG Gansheng, SUN Jiwei

2018, 38(5): 17-20,27. doi: 10.13394/j.cnki.jgszz.2018.5.0004

Abstract(311)

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In order to explore the interaction process and phenomenon between diamond and rock, the experiment of diamond indenting the rock surface in the whole process was carried out on WDW-100 electronic universal testing machine controlled by microcomputer. The breaking law of diamond pressing into rock was summarized by its test force-deformation curve. The experimental results show that the diamond with small diamond size should be selected when the diamond is pressed into hard rock, and the diamond with large diamond size should be selected when the diamond is pressed into soft rock. The diamond indentation test can provide reference for the optimization design of the drill bit.

Preparation and property study on PCBN carcass implanted diamond composites

LIU Baochang, CAO Xin, MENG Qingnan, ZHU Pinwen, DAI Wenhao, HAN Zhe, ZHAO Xinzhe, LI Siqi

2018, 38(5): 21-27. doi: 10.13394/j.cnki.jgszz.2018.5.0005

Abstract(240)

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Abstract:
Under the conditions of 5 to 6 GPa, 1400 to 1500℃, holding for 5 minutes, diamond composite material was prepared by mixing cubic boron nitride powder, various binders, and titanium-coated diamond particles. Scanning electron microscopy (SEM), X-ray diffractometer (XRD), energy dispersive spectrometer (EDS) and Raman spectrometer were used to character the microstructure and phase composition, Its wear resistance and microhardness were tested by mechanical tests. Results show that the diamond particles are well distributed in the cubic boron nitride matrix, with well-bonded interface. There are many kinds of carbides and nitrides at the interface, such as TiB₂, TiC, and AlN which makes the material exhibit excellent physical and mechanical properties. The abrasion ratio of the composite is 37.64 times higher than that of traditional material, microhardness greater than 40 GPa, density of more than 97%, and the heat resistant up to 1148℃, which is 28% to 64% higher than traditional PDC composite.

In-lab micro drill test of brazed diamond bit

PENG Yu, YAN Hai, BU Changgen

2018, 38(5): 28-32. doi: 10.13394/j.cnki.jgszz.2018.5.0006

Abstract(293)

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Abstract:
The brazed diamond drill has been widely used because of its high lifespan and high efficiency. The geological drilling test requires a lot of manpower and material resources. In order to optimize the brazing and sintering process, the drill matrix formulations compatible with different strata are studied. φ36-7B, φ36-11B micro drills are brazed and then tested with in-lab drill to study and optimize the brazing process. Results show that the carcass and diamond are well combined in the high-temperature and low-pressure sintering environment, that φ36-7B bit has higher drilling efficiency at similar wear per unit, and that the addition of WC particles can effectively improve the wear resistance of the φ36-11B bit matrix.

Simulation and experimental research on flow field andtemperature field of diamond impregnated drill bit

LIU Baochang, CAO Xin, JI Shengli, HAN Zhe, ZHAO Xinzhe, LI Siqi

2018, 38(5): 33-38. doi: 10.13394/j.cnki.jgszz.2018.5.0007

Abstract(258)

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In order to improve the drilling efficiency of diamond drill bits, the bit structure is reasonably designed to ensure that the bit has a good cooling and chip removal ability during the drilling process, so as to avoid abnormal wear caused by excessive rise of the temperature at the bottom lip of the bit. Numerical simulation and experimental research are used to study the distribution of flow field and temperature field at the bottom of the impregnated diamond drill bit. The results show that the lateral pressure generated by the flow field has a great effect on the pressure destruction of the nozzle wall. According to numerical simulation and drilling tests, the temperature of the contact surface between the drill and the rock is related to the number of nozzles but excessive nozzles will decrease the flow rate of drilling fluid in a single nozzle and thus decrease the heat transfer efficiency at the nozzle. Therefore, the cooling effect is reduced and the drill bit wears fast.

Effect and mechanism of sintering pressure on microstructure and property of solid PCBN tools

DENG Wenli, DENG Fuming, XU Zhihao, HE Xuehua, ZHANG Peng, MA Xiangdong, CHENG Shaohua

2018, 38(5): 39-43. doi: 10.13394/j.cnki.jgszz.2018.5.0008

Abstract(371)

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The whole polycrystalline cubic boron nitride (PCBN) tools were prepared by high temperature and high pressure sintering with size 5 μm CBN and binder Al powders on the domestic cubic press.The optimum sintering parameters were obtained by testing and analyzing the wear ratio and microhardness of samples. The sintering pressure was 5.4 GPa, the sintering temperature was 1500℃ and the sintering time was 240 s with hardness of 3897HV5 (loading time 15 s). The microhardness of the sample are HV3897, and the wear ratio was 8750. SEM, TEM observation and XRD analysis show that increasing of sintering pressure can make CBN particles produce a certain plastic flow, and inhibit the surface of CBN particles to reverse into hBN during sintering process. The binder Al can react with the surface of CBN particles to form the intermediate products AlN and AlB₂, which can form a solid ceramic bond between CBN grains and eliminate the residual hBN during sintering, thus improving the performance of the integral PCBN tool.

Engineering technology of turning typical CFRP with coated cemented carbide inserts

HE Genghuang

2018, 38(5): 44-49,55. doi: 10.13394/j.cnki.jgszz.2018.5.0009

Abstract(261)

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Two coated carbide inserts with the same geometric structure but different materials were used to turn T800H bar of typical carbon fiber reinforced composites. The cutting load and tool working state are monitored by multicomponent mechanical sensors, pressure sensors and high-speed cameras in turning process. The characteristics of machined surface and chip morphology were observed and analyzed by optical scanning system and digital microscope system. Experiment shows that:When turning carbon fiber reinforced composites, each tool has a critical cutting speed v_cr. Under the conditions of the same feed f and the constant cutting depth a_p, the cutting speed v_c has little effect on the machined surface quality of the workpiece. Besides, the better quality of machined surface can be obtained by turning carbon fibers with higher hardness tools.

Research on electrochemical mechanical hybrid finishingusing high-speed abrasive particles flow

WANG Jinshan, XU Zhengyang, XU Guangchao

2018, 38(5): 50-55. doi: 10.13394/j.cnki.jgszz.2018.5.0010

Abstract(324)

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In order to deal with the finishing problems of complex profile metal parts, a new kind of electrochemical mechanical finishing (ECMF) method using high-speed abrasive flow is proposed. By means of electrochemical dissolution and tiny abrasive particles' continuous micro scratch, the surface quality of workpiece is improved. In this study, the finishing principles is discussed. Meanwhile, the effect of hybrid fishing, pure electrochemical machining and pure high-speed abrasive machining under the same condition is analyzed through comparative experiments. The single-factor method is used to test the influence of different factors on surface roughness of stainless steel workpiece. The results show that the hybrid finishing process can effectively improve the machining efficiency, reduce the surface roughness, and achieve better processing results and a smooth surface, which has a R_a of 0.17 μm obtained in 5 min.

Wear analysis of arc-sharped wheel in aspheric grinding process

CHEN Bing, LUO Liang, JIAO Haowen, LI Shichun, DENG Zhaohui, ZHAO Qingliang

2018, 38(5): 56-60. doi: 10.13394/j.cnki.jgszz.2018.5.0011

Abstract(343)

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Abstract:
Aiming at the problem that grinding wheel wear will seriously affect the aspheric grinding quality, the formulas of material removal volume and grinding wheel wear volume in aspheric grinding process are analyzed based on the motion mode of aspheric grinding.The wear law of arc-sharped diamond grinding wheel for aspheric grinding is studied by combining with grinding wheel wear test.The results show that the radial dimension of arc-sharped diamond grinding wheel decreases due to wear during aspheric grinding, and there are three main stages of its diameter change before the failure of the grinding wheel, namely rapid change stage, slow change stage and micro change stage. Besides, the holding force of the bond to diamonds in the top of arc is less than those of other diamonds because of structural characteristics of arc-sharped wheel, which leads to rapid wear of diamond abrasives and bond until the holding force is not affected by the characteristics of arc-sharped wheel. At that time, the wear process of arc-sharped wheel is similar as the wear process of the plane wheel.

Study on unit grinding force of abrasive grains in face grinding rail with brazed diamond grinding wheel

DOU Liyun, XIAO Bing, YAN Xinlin, WU Hengheng, XIAO Haozhong, ZHANG Yiquan

2018, 38(5): 61-66. doi: 10.13394/j.cnki.jgszz.2018.5.0012

Abstract(242)

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Assuming that the grit shape of brazed diamond grinding wheel is octahedron and that the grits are uniformity distributed, the contact line length between the grit and the workpiece is deduced by using the kinematic trajectory model of the grit and the finite integral method. The average thickness of the un-deformed abrasive chip is calculated by the average volume method, and then the relationship between the tangential grinding force and the unit grinding force in face grinding is deduced. The mathematical model of unit grinding force is established and verified through the rail end grinding experiment.The results show that the mathematical prediction model of unit grinding force is effective and can provide theoretical support for calculating the grinding force and temperature in subsequent end grinding.

Research on adaptive belt grinding aeroengine titanium alloy fan blades

ZHANG Hongzhi, LIANG Qiaoyun, CHEN Shengtian, WANG Jie, HUANG Yun, ZOU Lai

2018, 38(5): 67-72. doi: 10.13394/j.cnki.jgszz.2018.5.0013

Abstract(315)

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Most aeroengine blades are made of titanium alloys, which have good strength and mechanical properties, but poor machinability. The surface precision and surface quality of the blades after precision forging and precision milling need to be machined to meet the requirements of aeroengine.The machining allowance of precision forged blade is determined by the best fitting method with three coordinate measuring instrument, which is removed from the blade by adaptive abrasive belt grinding method. The results show that the grinding process can accurately remove the machining allowance of precision forged blade surface and guarantee the arc transition of blade inlet and exhaust edges. In addition, the roughness R_a values of blade surface are all below 0.4 μm.

Application of vitrified bonded diamond wheel in YG10X cemented carbide anvil grinding

LIU Wei, LIU Yibo, HUANG Xia, YIN Xiang

2018, 38(5): 73-77. doi: 10.13394/j.cnki.jgszz.2018.5.0014

Abstract(274)

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A new kind of anvil with high strength and densing was machined by self-designed vitrified bonded diamond grinding wheel that low diamond concentration was designed for flat surface processing and high concentration for circumferential surface processing, and the machining performance were compared with that by resin bond diamond wheel.The results show that the sharpness of vitrified bonded diamond wheel was higher than that of resin bond diamond wheel under the same conditions, the processing speed was faster, and the heat generated by grinding was much lower than that of resin bond wheel. In surface grinding, the better surface roughness using vitrified bond grinding wheel was obtained by ways of adjusting machining parameters and fine diamond grit. In cylindrical grinding, the processing efficiency of vitrified bond wheel was increased by about 50% compared with that of resin bond wheel and vitrified bond diamond wheel had higher cost-conformance when its concentration came to 200%.

Advances in molecular dynamics simulation of nano-manufacturing of monocrystalline materials

XIA Siwei, ZHOU Hai, XU Xiaoming, ZHANG Chunwei, CHEN Xifu, HUANG Chuanjin, XU Tongtong

2018, 38(5): 78-86. doi: 10.13394/j.cnki.jgszz.2018.5.0015

Abstract(469)

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Molecular dynamics simulation is one of the important methods to study nano-manufacturing, whose fundamental principles and methods are introduced. This paper mainly reviews the principles of monocrystalline nano-machining from five aspects by classical molecular dynamics simulations, namely, phase transformations, mechanical properties, thermodynamics properties, ambient medium effects, and subsurface damage mechanisms. Finally, some problems and future development directions in the molecular dynamics simulation are pointed out.

Observing development of diamond industry from perspective of patent application

FU Jiguang, LI Yinsuo

2018, 38(5): 87-92. doi: 10.13394/j.cnki.jgszz.2018.5.0016

Abstract(250)

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As the hardest substance known in the world, diamond is an important function material with special optic, electric, thermal and acoustic properties, and widely used in industry. This paper is based on the statistics on the patent applications of diamond materials and products, where in the analysis of the patent application situation is made from the viewpoints of age, technology and geographical distribution. The results reveal that the diamond application situation is closely related to the development and evolution of the industry pattern, and that the characteristics of the patent application situation in different stages are highly consistent with those of the industrial development specialties. Finally, from the perspective of the evolution of the patent application situation,some suggestions related to industry development are given.

2018 Vol. 38, No. 5

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