金刚石与磨料磨具工程

2020, 40(5): 1-4.

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Comparing performance of CBN grinding wheels in high-speed grinding particulate reinforced titanium matrix composites

LI Zheng, LIU Ying, DING Wenfeng

2020, 40(5): 5-10. doi: 10.13394/j.cnki.jgszz.2020.5.0001

Abstract(434)

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To take advantages of high-speed grinding to improve the high-efficiency precision machining of particulate reinforced titanium matrix composites (PTMCs), it is necessary to further understand the grinding performance of high-speed grinding PTMCs with CBN grinding wheels. High-speed grinding PTMCs was carried out with three kinds of CBN grinding wheels, and the grinding forces, the temperature, the ground surface roughness and the ground surface topography were comparatively investigated. The results display that grinding force, temperature and ground surface roughness obtained with the brazed grinding wheel are the best, compared with those of vitrified or electroplated grinding wheels. Its grinding force and temperature are 16.2%-40.4% (normal), 25.2-44.4% (tangential) and 26.0%-74.3% lower than those of vitrified wheels, and 7.1%-31.1% (normal), 23.3-31.1% (tangential) and 14.5%-58.9% lower than those of electroplated wheels. The roughness of surface ground by brazed wheel is 0.60-0.77 μm. Therefore, the brazed grinding wheel has more advantages in high-speed grinding of PTMCs.

Study on tool wear of PCD tool in turning titanium matrix composites

PU Jianfei, HUAN Haixiang, XU Jiuhua, SU Honghua, HUO Fusong

2020, 40(5): 11-16. doi: 10.13394/j.cnki.jgszz.2020.5.0002

Abstract(326)

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PCD tool was used to cut reinforced titanium matrix composites at different cutting speeds, and the tool wear during high speed cutting was studied. The results show that the volume fraction of reinforcement phase has a significant effect on the tool durability of PCD, which is that the higher the volume fraction, the more serious the tool wear with lower tool durability. The type of reinforcement phase also has an obvious effect on the tool life, namely the effect of TiB_w on tool life greater than that of TiC_p. The wear patterns of PCD tools are similar when cutting different titanium matrix composites, which are mainly the wear of rake and back faces, accompanied by tool chipping and microcracks. The main wear mechanisms of PCD tools are abrasive wear and adhesive wear, and the higher the volume fraction of the reinforcement phase, the more obvious the adhesive wear.

Research on temperature field during grinding of low-pressure turbine blade tenon of TiAl alloys

XI Xinxin, CHEN Tao, DING Wenfeng

2020, 40(5): 17-22. doi: 10.13394/j.cnki.jgszz.2020.5.0003

Abstract(356)

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The temperature distribution, when grinding low-pressure turbine blade tenon of TiAl alloys, is complicated. To study its characteristics, the finite element analysis (FEA) method was used. The main procedure was provided, including the geometric modeling, the determination of energy partition and the selection and the load of the heat source. The feasibility of the model was verified by grinding experiment, with the error between the simulated and measured temperatures of about 15%. Results reveal that the temperature gradually increases and then stays stable. The maximum temperature value appears at the top of the tenon teeth, which is 30%~40% higher than that at the teeth root. This is attributed to the difference of thermal-conduction condition at different regions. The grinding temperature gradually increases with increasing grinding speed, workpiece infeed speed and depth of cut.

Effect of nanoparticle volume on grinding performance of titanium alloy in cryogenic air minimum quantity lubrication

WANG Xiaoming, ZHANG Jianchao, WANG Xuping, ZHANG Yanbin, LIU Bo, LUO Liang, ZHAO Wei, ZHANG Naiqing, NIE Xiaolin, LI Changhe

2020, 40(5): 23-29. doi: 10.13394/j.cnki.jgszz.2020.05.0004

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A two-step method was used to prepare alumina nanofluids with six different concentrations to perform grinding processing experiments on the titanium alloy Ti-6Al-4V. The results show that the maximum temperature in the grinding zone gradually decreases from 193.6 ℃ when the alumina volume fraction is 0.5% to a minimum value of 183.5 ℃ when it is 1.5%. When the volume fraction is further increased to 3.0%, the maximum temperature is gradually raised to 196.3 ℃. The specific grinding energy decreases from 74.8 J/mm³ to a minimum value of 64.73 J/mm³ while the volume fraction increases from 0.5% to 2.5%. When the volume fraction continues to increase to 3.0%, the specific grinding energy can rise to 69.33 J/mm³. The viscosity increases with the increase of alumina nanoparticles and reaches 235.8 MPa·s when the volume fraction is 3.0%. The contact angle decreases first with the increase of volume fraction and reaches the lowest value of 45.85° when the volume fraction is 2.5%. The dispersion of nanoparticles in the base oil affects the friction reduction and heat transfer performance of the nanofluid and thus the grinding performance.

Experimental study on turning particle reinforced titanium matrix composites

HUO Fusong, HUAN Haixiang, XU Jiuhua, SU Honghua, PU Jianfei

2020, 40(5): 30-34. doi: 10.13394/j.cnki.jgszz.2020.5.0005

Abstract(312)

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To study the effect of cutting parameters on the surface roughness of the particle-reinforced titanium matrix composites, both cutting force and cutting temperature were studied through experiments and the machinability of Ti matrix composites was explored. The results show that when turning the composites, the cutting force increases first and then decreases as the cutting speed increases; the cutting temperature increases with the increase of the cutting speed while the temperature increase becomes slower in higher speed range; the cutting force increases significantly with the increase of particle content, but the cutting temperature decreases. In conclusion, the processed surface roughness R_a can be below 0.5 μm with the cutting parameters in the range of v=80-100 m/min, a_p=0.30-0.60 mm and f=0.06-0.10 mm/r.

Optimization of edge-grinding parameters of polycrystalline diamond micro ball-end mill

DU Yuchao, LIANG Zhiqiang, CHEN Jianjun, LI Yu, MA Dan, CAO Yuxuan, LI Shidi, WANG Xibin

2020, 40(5): 35-41. doi: 10.13394/j.cnki.jgszz.2020.5.0006

Abstract(290)

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Aiming at grinding quality control problem of the 0.5 mm diameter polycrystalline diamond micro ball-end mill, based on the geometric motion principle of six-axis CNC machine, a mathematical model for the grinding of PCD micro ball-end mill is established, orthogonal experiments are carried out to study the influence of the grinding parameters on the spindle load, the surface roughness of tool rake face, and the radius of micro ball-end mill cutting edge. The results show that the grinding speed has the most significant effect on the surface roughness and spindle load, and the grinding depth has the most significant effect on the radius of the cutting edge. With the optimized process parameters, the diameter error of PCD micro ball-end mill is less than 4.0 μm, the radius of tool blunt circle is 4.5 μm, the angle error of tool is less than 1°. The edge quality is complete without obvious grinding damage defects.

Suppression and elimination of [NV] and [SiV] defects in CVD single crystal diamond

WU Xiaolei, XU Shuai, ZHAO Yanjun, WU Xiao, CHANG Haofeng, GUO Xingxing

2020, 40(5): 42-44. doi: 10.13394/j.cnki.jgszz.2020.5.0007

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Investigating the photoluminescence spectroscopy (PL) of CVD diamond with 10 ppm N₂ added in the reaction gas, it demonstrates that [NV]⁰ and [NV]^- related to N impurity and [SiV] related to Si impurity are the main defects in diamond. After high temperature and high pressure (HPHT) treatment, the [NV]⁰ peak intensity was weakened, the [NV]^- peak intensity was enhanced, the [SiV] peak intensity was significantly enhanced, and [SiV]^- broad peak appears when the N₂ content was decreased to 1 ppm and 0.5% O₂ was added in the reaction gas, the [NV]⁰ and [NV]^- peaks disappeared. When the O₂ was increased to 1%, the [SiV] peak intensity significantly decreased. As the O₂ content continued to increase, the decreasing of [SiV] peak intensity slowed down. These results demonstrated that a small amount of O₂ addition was helpful to the inhibition and elimination of N and Si impurities in CVD diamond.

Effect of pH value on dispersity of CeO₂/SiO₂ composite nanoparticles

CHEN Guomei, ZHOU Ling, NI Zifeng, XU Laijun, DU Chunkuan, CHEN Feng, SU Min, ZHAO Yongwu

2020, 40(5): 45-50. doi: 10.13394/j.cnki.jgszz.2020.5.0008

Abstract(262)

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CeO₂/SiO₂ composite nanoparticles with complete core-shell structure were prepared through homogeneous precipitation method using commercial silica sol as silicon resource. The phase composition and nanotopography of the as-prepared particles were characterized by X-ray diffraction (XRD) and transmission electron microscope (TEM), respectively. The effect of pH value on the dispersity of CeO₂/SiO₂ composite nanoparticles in water suspension was studied by the analysis of size distribution and Zeta potential. The results indicated that the as-prepared composite nanoparticles possessed a complete core-shell structure which composed by amorphous silica core and cubic fluorite ceria shell. The particle size was about 110 nm. The equipotential point of CeO₂/SiO₂ composite nanoparticles was about pH5, and its value was significantly shifted from the equipotential point of SiO₂ to the equipotential point of CeO₂. The as-prepared composite nanoparticles agglomerated easily under the acidic condition, while dispersed well under the alkaline condition.

Influence of assembly structure optimization on thickness difference uniformity and stability of PCBN polycrystalline layer

WANG Zhihui, XIE Zhigang, HE Xulin, XU Wenjuan, ZHOU Zhicheng, ZHANG Zhe, WANG Wenlong

2020, 40(5): 51-57. doi: 10.13394/j.cnki.jgszz.2020.5.0009

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By optimizing the thickness of salt tube and the material of intermediate gasket in the assembly structure of PCBN composite layer, the effects of the thickness difference, the hardness of the same position and the overall wear resistance of the polycrystalline layer were investigated under the four conditions of no optimization (A), optimization of intermediate gasket material (B), optimization of salt tube thickness (C) and joint optimization of the intermediate gasket and the thickness of salt tube (D). The results show that when the thickness of salt tube changes from 1.0 mm to 1.4 mm, and the intermediate gasket material changes from graphite to cemented carbide, the hardness and overall wear resistance of the polycrystalline layer of PCBN composite are basically unchanged under the four conditions. At the significance level of 0.05, B, C, D optimization relative to A, D optimization compared to a single factor B and C optimization, can improve the uniformity of the thickness difference of polycrystalline layer. The optimization of B, C, and D is relative to that of A, and the optimization of D is relative to that of C, which can improve the stability of the thickness difference of the polycrystalline layer. However, the D optimization compared with the B optimization does not improve the stability of the thickness difference of the polycrystalline layer.

Corrosion inhibition of imidazoline and porphyrin on hot-pressed impregnated diamond bits in NaCl solution

YAO Yuanji, PAN Bingsuo, LIU Zhijiang

2020, 40(5): 58-63. doi: 10.13394/j.cnki.jgszz.2020.05.0010

Abstract(349)

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The corrosion inhibition behavior of imidazoline and porphyrin in hot pressing impregnated diamond bit matrix material in NaCl solution with pH10 and mass fraction of 20% was studied by electrochemical method, weight loss test and Raman spectroscopy. The results show that both imidazoline and porphyrin can promote the formation of passivation films (mainly copper and iron oxides) on the surface of matrix materials, which can play a role of corrosion inhibition. Due to the hydrolysis of imidazoline under alkaline conditions, the inhibition efficiency of imidazoline in the electrochemical test is significantly less than that of porphyrin. The one-week weightlessness test shows that prolonged soaking can increase the inhibitory efficiency of imidazoline to the same level as porphyrin.

Properties of new catalyst curing phenolic resin for superhard abrasive tools

JIAN Yaliu, YUAN Tianshun, PENG Jin, ZOU Wenjun, SONG Xudong, LIU Pengzhan, WANG Junke

2020, 40(5): 64-68. doi: 10.13394/j.cnki.jgszz.2020.5.0011

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Hexamethylenetetramine (HMTA) is the most commonly used catalytic curing agent for thermoplastic phenolic resins, and is widely used in the field of abrasive grinding. However, the cured resin exhibits greater brittleness due to the methylene linkage between the aromatic nuclei in structure. In this study, the sulfonamide derivatives(PTSA) was used to replace the hexamethylenetetramine for the curing of phenolic resin. The phenolic resin cured by PTSA and HMTA was characterized and analyzed by TGA, mechanical properties and impact test. The results show that the weight loss temperature of PTSA cured phenolic resin at 10% weight loss is 396 ℃, which is 24 ℃ higher than that of HMTA cured phenolic resin, and the heat resistance is excellent. The grinding ratio of super-hard abrasives made by using PTSA cured resin as binder is 36.18% higher than that of HMTA cured resin as binder.

Effect of SiC content on cutting ability of resin diamond wire

GAO Wei, NI Jinhua, LIU Xingpeng, ZHANG Xu, MA Bojiang

2020, 40(5): 69-73. doi: 10.13394/j.cnki.jgszz.2020.05.0012

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Resin diamond wires with different SiC contents were prepared and the actual silicon wafer cutting experiments were carried out. The effect of SiC contents on the cutting ability of resin diamond wire was studied by recording the torque and cutting conditions during the cutting process. The results show that when the amount of SiC in resin liquid increases, the cutting ability of resin diamond wire increases gradually. But the cutting ability will be reduced when the content of SiC is over a certain level. In experiment, when the content of SiC in resin solution is 600 g/L, the cutting torque of resin diamond wire cutting silicon wafer is 96 N·m, and without cutting, while the cutting ability is the highest. At this time, the shore hardness of resin cured is 91 HD, SiC in resin layer are uniformly dispersed, and there are no defects such as pores.

Grinding performance of brazed CBN porous abrasive wheels based on open pore structures

DING Wenfeng, FU Yucan, ZHAO Biao, LONG Weimin, ZHONG Sujuan, SONG Xiaoguo, JIA Lianhui

2020, 40(5): 74-78. doi: 10.13394/j.cnki.jgszz.2020.5.0013

Abstract(373)

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In order to solve the problems, such as the low machining efficiency, short service life of abrasive tools, and poor ground surface quality, brazed cubic boron nitride (CBN) porous abrasive wheels coupled with high porosity, good wear resistance and excellent self-sharpening ability were fabricated. Open pore structures were designed, and then the grinding performance and wear experiments were conducted in grinding of Ti-6Al-4V titanium alloys. Grindability and ground surface quality of Ti-6Al-4V alloys affected by grinding parameters were discussed in detail. In addition, the self-sharpening ability of brazed CBN porous abrasive wheels was analyzed. Results shows that brazed CBN porous abrasive wheels featured a desired flexural strength and excellent chip storage space after optimizing the pore size of 0.6~0.8 mm and designed porosity of 40%. The brazed CBN porous abrasive wheels showed a more stable grinding force ratio from 1.5 to 2.2 with the grinding speed of 80 m/s compared to that with the grinding speed of 30 m/s. Moreover, with the increase of material removal volume, the ground surface roughness rapidly declined and stabilized due to the stabilization of the dynamic effective grains number.

Experimental study on electro-discharge dressing of super-abrasive grinding wheel using different dielectric

SHAN Zizhao, ZHOU Cong, CHEN Genyu, DAI Longzhou

2020, 40(5): 79-84. doi: 10.13394/j.cnki.jgszz.2020.5.0014

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Electro-discharge dressing of super-abrasive grinding wheel was limited by the discharge gap. It was difficult to meet the requirements of the dressing of coarse-grained wheels under traditional dielectric conditions. Based on the mechanism of electrical discharge machining (EDM) with powder mixed dielectric, a method of electrical discharge dressing (EDD) with powder mixed dielectric was presented. A comparative study on the discharge gap of compressed air, deionized water mist and powder mixed deionized water mist with different discharge parameters was carried out. Furthermore, the experiment of dressing and grinding of diamond wheel was carried out. The results show that the EDD with powder mixed dielectric has larger discharge gap, which can improve the dressing efficiency of the coarse-grained bronze bonded diamond wheel, and optimize the surface morphology, abrasive protrusion and grinding performance of the wheel after dressing. The efficiency of EDD in powder mixed dielectric is increased by 28.2%~50.0% compared with the other two kinds of dielectric under the optimal parameters of open circuit voltage of 90 V, peak current of 13.33 A and duty of 50%. The addition of SiO₂ powder makes the distribution of Si element on the surface of grinding wheel more uniform and the content higher, thus improving its wear resistance.

Experimental study on mechanical properties of cold plasma processed K9 optical

MENG Zheng, LIU Xin, LIU Jiyu, WU Mingyu, CHEN Yang

2020, 40(5): 85-89. doi: 10.13394/j.cnki.jgszz.2020.5.0015

Abstract(297)

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To explore the plasma jet to K9 optical, through the bending test and the indentation scratches test the mechanical properties of the processed K9 optical were studied. Firstly, surface properties of K9 glass/diamond materials were controlled of the K9 optical by cold plasma assisted cutting machining. And then a universal testing machine was used to test the bending strength of the plasma-treated quartz glass rod by three-point method. Finally, the critical loads of elastic-plastic transition and brittle transition are obtained by indentation and scratch test. The experimental results show that cold plasma jet for brittle materials the properties influence can be kept over 20 hours. During the loading process, the shear force and positive pressure of K9 glass treated by cold plasma are relatively stable, the friction coefficient fluctuates between 0.09 and 0.12, and the change is not obvious. And cold plasma jet for K9 glass/diamond materials friction pair can reduce the elastic-plastic transition of K9 optical critical load, ductile brittle fracture occurs when ductile brittle stress is delayed, reinforced material plasticity and reduce its brittleness.

Optimization of process parameters for lapping quartz glass with fixed abrasive

WANG Zhankui, YANG Yakun, PANG Minghua, MA Lijie, LIANG Mingchao, LI Yongfeng, SU Jianxiu

2020, 40(5): 90-95. doi: 10.13394/j.cnki.jgszz.2020.5.0016

Abstract(362)

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The material removal rate and the surface roughness were taken as indexes to evaluate quartz glass quality, and the rotating speed (A), the pressure (B) and the lapping slurry type (C) as the influencing factors were studied in the orthogonal test of grinding quartz glass with fixed abrasive. Regression analysis was carried out on the test results, and the influence rule model of three factors on the removal rate and the surface roughness of quartz glass was established. The results show that the most significant factor affecting the removal rate of quartz glass is B, followed by C and A. The most significant factor affecting the surface roughness of quartz glass is A, followed by B and C. The optimum grinding process parameters for the material removal rate are triethanolamine slurry at the rotating speed of 100 r/min and the pressure of 27.580 kPa. The optimum process parameters for the surface roughness are ethylenediamine slurry at the rotating speed of 100 r/min and the pressure of 27.580 kPa. At the same time, the relationship between the material removal rate and the rotating speed is a quadratic function, while the relationship between the material removal rate and the pressure is an exponential function, and the relationships between the surface roughness and the rotating speed & the pressure are both power functions. Triethanolamine slurry can be selected when the material removal rate is the priority objective, and ethylenediamine slurry can be selected when the surface quality is the priority objective.

Three dimensional simulation and experiment of plane grinding temperature field based on temperature matching method

JIANG Peijun

2020, 40(5): 96-101. doi: 10.13394/j.cnki.jgszz.2020.05.0017

Abstract(366)

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To accurately predict temperature field changes of the surface and subsurface workpiece, based on the principle of anti-heat source and the actually measured grinding temperature, using the temperature matching method, a heat source model of the contact zone in the real grinding process was established. Comparing with prediction results of Rayleigh heat source model, the finite element method was used to simulate the change of the grinding temperature field of the workpiece. The grinding temperature field at different depths of the workpiece in the grinding zone was measured. The results show that the heat source model based on the temperature matching method has good consistency with the measured values at different depths on the surface and subsurface. The relative error is between 3.0% and 7.5%. Compared with the Rayleigh heat source model, the distribution accuracy of predicted temperature field is improved nearly 2 times.

2020 Vol. 40, No. 5

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