金刚石与磨料磨具工程

Influence of dual-substrate structure on growth of single crystal diamond by MPCVD

XIA Yuhao, LI Yanchun, GENG Chuanwen, LI Fanghui, MA Zhibin

2018, 38(3): 1-5. doi: 10.13394/j.cnki.jgszz.2018.3.0001

Abstract(341)

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Abstract:
A novel structure of double substrates is put forward for a microwave plasma chemical vapor deposition equipment which is used to grow single crystal diamond. Optical Emission Spectrometer (OES) is used to diagnose the intensity of the groups in the plasma, while Raman Spectra and Scanning Electron Microscopy are used to analyze Raman displacement and surface appearance of the single crystal diamond. The effects of the double substrates on OES of the plasma and the growth of single crystal diamond have been studied. The results show that the plasma power density can be enhanced with double substrates. The intensity of OES can be improved with double substrates and resulting in a higher growth rate of single crystal diamond at the same diamond deposition parameters. The single crystal diamond deposited has characteristic of less Raman displacement, smaller full width at half maximum of Raman spectrum and less impurity phases.

A survey of surface modification of synthetic diamond

HAN Ping, GUO Yueping, WANG Shufang, LI Zhengxin

2018, 38(3): 6-10. doi: 10.13394/j.cnki.jgszz.2018.3.0002

Abstract(622)

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Abstract:
Three main methods for surface modification of synthetic diamond are reviewed. The first one is metallization of diamond surface, such as physical or chemical vapor deposition, electroless plating, electroplating, vacuum micro-evaporation, salt bath plating, etc. The treated diamonds are mainly used in diamond tools and electronic packaging materials. The second one is the treatment of coupling agent or surfactant, which improves the interfacial properties between diamond and organic system. The technology is applied in diamond powder dispersion and resin grinding wheels. The last one is the functionalization of diamond film and nano diamonds, which is applied on materials used in industries such as electrochemistry, biosensors, electrodes and so on. The essay provides reference for the research and application of diamond surface modification.

Preparation and properties of boron doped diamond films

XU Qingbo, WANG Chuanxin, WANG Tao, DAI Kai, XIA Shuping

2018, 38(3): 11-15,20. doi: 10.13394/j.cnki.jgszz.2018.3.0003

Abstract(464)

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Abstract:
Boron doped diamond films were deposited on the silicon substrate by hot-filament chemical vapour deposition (HFCVD). The effects of boron source flow on the conductivity, grain size, crystal direction and residual stress of boron doped diamond films were investigated. The results show that the resistance of diamond films decreases rapidly with increasing boron flux. After a certain flow rate, the defects and impurities increase and hinder the further decline of resistance. The boron flow increases gradually in 0-25 mL/min, and the average grain size of the diamond film increases from 3.5 to 8.3 μm. The boron element promotes the growth of (111) crystal surface. When the boron flow rate continues to increase to 35 mL/min, the promotion effect on the (111) crystal surface weakens and the grain size decreases. Therefore, the surface defects increase and the integrity is lost. The X-ray diffraction analysis shows that with the increase of boron flow, the diffraction peak area ratios of the diamond film (111) surface and (110) surface increase first and then decrease, and that the maximum value is reached when the boron flow rate is 20 mL/min. The residual stress of boron doped diamond film is compressive stress. When the flow rate of boron source is less than 10 mL/min, the stress decreases with the increase of flow rate, and the stress increases with the increase of flow rate when the flow rate is more than 30 mL/min.

Remove cobalt to enhance performance of polycrystalline diamond compact

QIN Weili, HENG Jun, PIAN Xiaoxuan, LI Zhengxin, LI Xiaolong

2018, 38(3): 16-20. doi: 10.13394/j.cnki.jgszz.2018.3.0004

Abstract(306)

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Abstract:
Based on the common PDC preparation, synthetic polycrystalline diamond was treated by cobalt removal, reassembled and then synthesized again. Tests indicate that new PDC has better performance on abrasion resistance, impact resistance and heat resistance. The average volume abrasion ratio reached 5.20×10⁶, about 40% higher than that of normal products; the reducing of cobalt bond in diamond layer does not decrease the impact resistance; heat resistance is greatly improved. The cobalt removal could effectively reduce the cobalt content in the diamond layer, and improve the uniformity of bond distribution by inhibiting of local accumulation of the bond. Eventually, there appear more D-D bonds in diamond layer, thus improving the wear resistance of PDC product.

Heat-treated substrate facilitates interrupted cutting of PCD tools

SU Yanbin, SHAO Huili, WU Ruige

2018, 38(3): 21-23,35. doi: 10.13394/j.cnki.jgszz.2018.3.0005

Abstract(267)

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Abstract:
Polycrystalline diamond (PCD) tools have poor thermal toughness, thus less used in interrupted machining with impact. To improve the performance of PCD tools, the substrate was heat-treated to strengthen its bond with PCD and new PCD tools were made to test their life and surface wear after interrupted cutting aluminum alloy. The results indicate that modified substrates have better bond with diamond layer than the normal ones, thus improving the impact toughness of the tools. Tests show that there is no edge breakage on new PCD tools after cutting 128 min, while the wear condition is still acceptable. In conclusion, PCD tools with heat-treated substrate are suitable for interrupted cutting.

Study on the characteristics of PCBN materials at home and abroad

XIE Hui, FENG Fei, XU Zhihao, DENG Fuming

2018, 38(3): 24-29. doi: 10.13394/j.cnki.jgszz.2018.3.0006

Abstract(301)

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Abstract:
The main developments and research of polycrystalline cubic boron nitride (PCBN) products are reviewed based on categories, binders, microstructure homogeneity and impact toughness. Moreover, new materials such as nano-polycrystalline CBN and non-binder PCBN are introduced, including characteristics and future applications.

Performance of orderly-arrangement hot-pressed impregnated diamond bit

ZHANG Dingyuan, PAN Bingsuo

2018, 38(3): 30-35. doi: 10.13394/j.cnki.jgszz.2018.3.0007

Abstract(344)

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Abstract:
Dispensing and hot-press were adopted to make impregnate bits with orderly arranging diamond grits. The surface morphology of the drill bit was observed by the shape analyzer and the drilling performance was studied through laboratory drilling experiments. The results show that the drilling efficiency of the ordered drill bit is 23% higher than that of the random arrangement bit under the same number of input feet, and the diamond particle edge height of the ordered arrangement bit is 1 times as high as that of the random arrangement bit. The matrix wear of the ordered arrangement bit is in favor of the tadpole shape that helps the diamond particles self sharpening. The diamond surface of the ordered drill bit appears to be slightly broken, compared with the two kinds of extreme wear morphology of the random drills, the orderly arrangement advantage in the drilling process is obvious.

Stress analysis and process parameters optimization of circular saw blade during quenching process

ZHANG Bainian, ZHANG Jinsheng, JU Junwei, CHEN Xiaotao

2018, 38(3): 36-41. doi: 10.13394/j.cnki.jgszz.2018.3.0008

Abstract(269)

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Abstract:
Aiming at the problem that the deformation of the φ600 mm circular saw blade is large after quenching and thus affecting the performance of saw blade, the distribution characteristics of the quenching residual stress are analyzed based on the numerical calculation method. The results show that the effective residual stress of the circular saw blade is tensile stress during the whole quenching process. After quenching, the stress near the center hole is the biggest, followed by that near the outer tooth, and the stress in the middle is the smallest.The austenite forming temperature and holding time are selected as the optimizing variables, and the quenching residual stress as the target function. The response surface optimization method is used to optimize the quenching parameters of the circular saw blade. The results show that the minimum residual stress is 199 MPa when the austenite formation temperature is 837℃ and the holding time is 5 min.

Composite holes by spiral milling at low stiffness have higher accuracy

GAO Hang, YAO Shunming, BAO Yongjie, LIU Xuchao

2018, 38(3): 42-47. doi: 10.13394/j.cnki.jgszz.2018.3.0009

Abstract(285)

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Abstract:
To solve the problems of machining composite components, such as narrow space, poor accessibility and low accuracy, electroplated diamond abrasives are used to spirally drill the material at low stiffness based on micro-edge cutting principle. Theoretical analysis on cutting length of abrasive and comparative test show that the cutting force of diamond tools is generally lower than 60 N, that the maximum of which is 30% lower than that of ordinary cemented carbide tools; and that there is no bur nor burn on the edge drilled by diamond tools. In conclusion, micro-edge cutting could decrease the force and burs, thus improving accuracy.

Temperature change of Si₃N₄ ceramics by ultrasonic assisted milling

CAO Youwei, QIAO Guochao, ZHANG Xuyao

2018, 38(3): 48-52,69. doi: 10.13394/j.cnki.jgszz.2018.3.0010

Abstract(306)

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Abstract:
In order to explore the change of milling temperature in the ultrasonic assisted milling of silicon nitride ceramics, improve the quality of ceramic processing and reduce its thermal damage, the effect of spindle speed, feed speed, cutting depth and hyper vibration on the milling temperature was studied by single factor experiment method with FLIR SC325 infrared thermal imager as measuring tool. The results show that the highest temperature of the milling decreases gradually with the increase of the spindle speed, and that the faster the feed speed, the shorter the processing time and lower peak temperature in the same cutting length. The effect of cutting depth on the highest temperature of milling is periodic. The highest temperature of ultrasonic milling is slightly higher than that of common milling under the condition of dry grinding without coolant.

Research on tool wear of PCD in high speed dry cutting bronze alloy

YANG Haijun, DONG Hai, WANG Lei, ZHU Yuanqi

2018, 38(3): 53-57. doi: 10.13394/j.cnki.jgszz.2018.3.0011

Abstract(369)

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Abstract:
The dry cutting experiment of tin bronze alloy at high speed with PCD tools is carried out. The tool wear morphology was observed by the Scanning Electron Microscopy (SEM) and the chemical composition of wear area was detected with the aid of X- ray Energy Dispersive Spectrometer (EDS), and the mechanisms of tool wear were studied. The results show that the wear morphology of PCD tools is characterized by the flaking on the rake face and the slight breakage on the flank surface. At the same time, it is also accompanied by brittle failure under the impact of mechanical stress and thermal stress, resulting the breakage of the cutting edge, overall fracture of cutting edge and large-scale flaking of the rake and flank face. The oxidation wear and diffusion wear under high temperatures are the main reasons of tool wear.

Analysis on numerical prediction models of surface topography in rotational grinding

CAO Zhihe, LIN Bin, ZHOU Ping, KANG Renke

2018, 38(3): 58-63. doi: 10.13394/j.cnki.jgszz.2018.3.0012

Abstract(246)

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Rotational grinding is widely used in grinding hard brittle material such as silicon, glass and ceramics. The prediction of grinding surface topography is important for mechanism research and process optimization. Based on analyses and experiment validations of current models, the problems of these models are analyzed and the promotions put forward:When simulating ultra-precision grinding, it is necessary to modify the amount of effective grains; The recovery of workpiece, the cutting edge radius of grains and the critical cutting depth of chip formation are factors that need further attention. The result could promote acknowledge of grinding mechanism and process, and thus promoting the efficiency of rotational grinding.

Model of temperature field on ground surface based on grinding force

HE Yuhui, FENG Ke, TANG Chu, TANG Jinyuan

2018, 38(3): 64-69. doi: 10.13394/j.cnki.jgszz.2018.3.0013

Abstract(394)

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Abstract:
To study the mechanism of grinding force and improve the machining quality, a theoretical model is established based on grinding force analysis after discussing the surface temperature of workpiece. The grinding force is divided into two parts, namely cutting force and friction force to study their relationship with processing parameters. The calculated tangential forces, combined with their relations with heat source intensity, are used to establish the theoretical model of highest temperature on ground surface. The constants are confirmed by grinding tests on 45 steel and thus confirming the model. Results show that the surface temperature increases with the increase of cutting depth, infeed speed and wheel speed, and that the maximum relative error between the surface temperatures of model and experiment is 5.04%, while average relative error is 2.47%. In conclusion, theoretical model based on grinding force could be used to analyze the temperature filed on ground surface and improve the surface quality.

Experimental study on micro-abrasive slurry jet for polishing mold steel

WANG Rongjuan, WANG Chengyong, WEN Wu, CHEN Zhihua

2018, 38(3): 70-74. doi: 10.13394/j.cnki.jgszz.2018.3.0014

Abstract(273)

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Abstract:
Polishing mold steel by using micro abrasive slurry jet (MASJ) is analyzed as well as the relationship between the processing parameters and the surface quality of workpiece. Results indicate that the abrasive size is proportional to the surface roughness, and is not related with the initial R_a value of the workpiece. In the case of remaining other parameters unchanged, there is an optimal combination of travel speed 4 mm/s, working pressure 0.7 MPa, stand-off distance 5 mm and abrasive concentration 75 g/L to achieve optimized surface quality of workpiece. It is also found that polish quality of alumina is higher than that of silicon carbide, and that the larger the nozzle diameter, the smaller the surface R_a value. The surface roughness value is minimum when the polishing pitch is 1.25D.

Application of high efficiency polishing technology in manufacturing aero-engine components

WANG Bin, HE Jian, YU Jie, PEI Runsen, DAI Chenwei

2018, 38(3): 75-80. doi: 10.13394/j.cnki.jgszz.2018.3.0015

Abstract(341)

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Abstract:
Polishing, which generally works as the final process to improve the workpiece surface quality, has been applied widely in the aero-engine manufacturing, because of its high material removal efficiency and high quality of surface. In this article, the general principle of polishing is introduced. Then, the comprehensive development results were analyzed from the aspects of polishing machine, abrasive grits and polishing solvent. Finally, the applications of high efficiency polishing technology in the field of typical aero-engine component manufacturing, e. g. blade, blisk, axle and cartridge receiver, are stated.

Chemical mechanical planarization of copper sheet with high radius-thickness ratio

WAN Ce, JIN Zhuji, WU Di, LIU Zuotao, SI Likun

2018, 38(3): 81-85. doi: 10.13394/j.cnki.jgszz.2018.3.0016

Abstract(359)

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Abstract:
Using sodium hypochlorite as oxidizer, calgon as complexing agent, OP-10 emulsifier as surface active agent and silica sol as abrasive to make up slurry (pH 9), chemical mechanical polishing of large diameter thickness ratio copper sheet after coarse polishing was carried out. The surface roughness and the flatness of the copper sheet before and after polishing were measured. The elements on the surface of the copper sheet were analyzed by X-ray spectrometer, and the surface phase and residual stress of the copper sheet were analyzed by the X-ray diffractometer. Results show that the flatness PV of the copper sheet is reduced from 4.813 μm before polishing to 2.917 μm after polishing, and the surface roughness R_a decreases from 31.373 nm to 3.776 nm. There is no obvious change in the elemental composition and the phase of the surface of the copper sheet before and after polishing, and the chemical and mechanical effects have reached the balance. The mechanical action of the abrasive and the polishing pad can quickly remove the oxide layer on the surface of the copper sheet. The chemical mechanical polishing can significantly reduce the residual stress on the surface of copper after rough polishing.

Testing and evaluation of PDC real drilling performance

SUN Rongjun, GU Shuancheng, SHI Zhijun, ZHANG Youzhen, ZHANG Xianzhen

2018, 38(3): 86-90. doi: 10.13394/j.cnki.jgszz.2018.3.0017

Abstract(336)

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Abstract:
Based on summarizing and analyzing the PDC performance testing methods at home and abroad, the wear ratio, impact toughness and thermal stability of five PDC products of different manufacturers were tested, evaluated and optimized by conventional testing methods. The actual drilling performance test was carried out on the micro drilling test platform with the two selected PDC bits. The results show that the drilling efficiency attenuation coefficient and the average peak value of drilling efficiency are used to evaluate the PDC real drilling performance. The method is scientific, the data is accurate and the result is practical. It can be used as the reference basis for selection of PDC bit teeth for coal mine drilling.

2018 Vol. 38, No. 3

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