Multi-wire swing reciprocating sawing technology is the main machining method used to cut sapphire crystal bars into wafer substrates, while normal force is an important index that reflects the processing stability. In this paper, the normal force (Fn) during multi-wire swing reciprocating wire saw cutting sapphire crystal bars was measured, and the change in normal force at different positions and cutting depths of the sapphire crystal bars was tracked. The influence of various process parameters on the stability of the machining process was tracked by using the rangeability of normal force Fn as the index. The experimental results show that Fn is closely correlated with the reciprocating motion of the wire saw and the rocking motion of the workpiece, and ΔFn in the front of the sapphire crystal bar is significantly different from that in the middle and back. Process parameters such as the wire saw speed（vs）, maximum swing angle (θmax), single piece wire consumption (Md), tensioning force (Fw), and total cutting time (T) have different effects on ΔFn. The fluctuation degree of ΔFnis closely related to the wear of the wire saw.
Abstract: The effects of boron concentration and deposition pressure on the microstructure and electrochemical oxidation performance of Ti/BDD electrodes during HFCVD growth were systematically investigated. The electrode's surface morphology, composition, and electrochemical performance were characterized by scanning electron microscope (SEM), Raman spectroscopy, ultraviolet spectrophotometry, and an electrochemical workstation. Tetracycline served as a simulated pollutant to evaluate the electrochemical oxidation degradation performance of BDD electrodes fabricated with different boron concentrations and deposition pressures. As air pressure increases, the grain quality of the diamond gradually decreases, yet boron atom doping enhances the grain quality of the diamond. Under high boron concentration and low pressure conditions, the boron atom concentration on the diamond film's surface is elevated. BDD electrodes with larger grain sizes and higher boron atom concentrations, prepared under these conditions, exhibit superior electrochemical performance, increased degradation efficiency, and reduced degradation energy consumption.
Abstract: Based on the microwave plasma module of multiphysics simulation software COMSOL Multiphysics, a numerical model of hydrogen plasma inside a MPCVD reactor was built. The effect of different height differences Δh between the circular molybdenum support added on the outer side of the substrate and the substrate on the plasma distribution at the surface of the substrate was investigated. The uniformity of plasma distribution was quantitatively analyzed by coefficient of variation, and the microstructure of diamond coating surface was characterized by SEM. The results show that when Δh=0 mm, the uniformity of plasma distribution is the best, the coefficient of variation is 3.998%, and the uniformity of grain distribution and size of diamond coating is significantly improved compared with that without molybdenum support. When Δh< 0 mm, the uniformity of plasma distribution increases with the increase of Δh, and the coefficient of variation decreases from 10.265% to 3.998%. When Δh>0 mm, the uniformity of plasma distribution does not increased but decreases, and the coefficient of variation increases to 10.048%. In addition, when Δh=−2.0 mm, the plasma density on the substrate surface decreases by about 20%, which is not conducive to the growth of diamond coating.
Abstract: Using copper-boron alloy as the metal matrix and different-sized diamond particles through 110 μm, 230 μm to 550 μm as reinforcement, the diamond/copper-boron alloy composites were prepared via gas pressure infiltration technology under 1100 ℃ and 10 MPa gas pressure. The influences of the size of diamond particles on the configuration, interlayer phase distribution, and thermophysical properties of the composites were investigated. The results show that with the increase of particle size, there is a benefit of better interface bonding, and the thermal conductivity of the diamond/copper-boron composite is enhanced while the thermal expansion coefficient decreases. When the diamond particle size is 500 μm, the best performance of the composite is obtained. The thermal conductivity is 680.3 W/(m·K), and the thermal expansion coefficient increases from 4.095×10−6 K−1 to 7.139×10−6 K−1.
Abstract: The monolithic PcBN composite tool materials were prepared at 5.5 GPa and 1450 ℃ with different contents of Ti3AlC2 as the binder phase. The effects of different mass fractions of Ti3AlC2 on the phase composition, microstructure, and mechanical properties of PcBN tool materials were studied. The results show that Ti3AlC2 can decompose completely to form TiC and Al-Ti alloys under high temperature and high pressure, and reacts with cBN to form AlN, TiB2, and TiC0.7N0.3 phases. TiC, AlN, TiB2, and TiC0.7N0.3 are uniformly distributed around the cBN and tightly bonded to the cBN, thereby improving the mechanical properties of PcBN. When the mass fraction of Ti3AlC2 is 25 %, the relative density, bending strength, fracture toughness, and wear ratio of PcBN reach the maximum values, which are 98.9%, 592 MPa, 6.87 MPa·m1/2and 7 350, respectively. When the mass fraction of Ti3AlC2 is 20%, the microhardness of PcBN reaches the maximum value of 4 786.7 HV.
Abstract: Polycrystalline cubic boron nitride composites were prepared under high-temperature and high-pressure conditions. The effects of bonding agent ratio and cBN particle size on the composition, microstructure, microhardness, and abrasive ratios of the PcBN composites were investigated using X-ray diffraction (XRD), field scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS). The experimental results showed that the PcBN composites performed better under sintering conditions of 5.5 GPa, 1400 ℃, and a 10-minute holding time, achieving a hardness of up to 22.7 GPa and an abrasion ratio of 149.2 at V(TiN0.3)∶V(AlN)=70∶30. Moreover, when the particle size combination of cBN in PcBN composites is (0.5～1) μm:(2～5) μm:(5～10) μm = 3:5:2, the packing density between particles reaches its peak, resulting in optimal performance.
Abstract: To improve the performance of PcBN composites prepared under high temperature and high pressure, mixed cBN particle sizes ranging from 0 to 0.5 μm and 0.5 to 1.0 μm were used as the raw material, Al-Ti-Al2O3 was used as the binder and the carbon nanotubes with different contents were added. The PcBN composites were prepared by sintering under high temperature and high pressure conditions. The effect of carbon nanotube content on the structure and properties of PcBN composites was investigated. The results show that there is no chemical reaction between PcBN and carbon nanotubes after the addition of carbon nanotubes, and the carbon nanotubes exist in the form of reinforcement inside the composite. The composite material is relatively dense, and the relative density of PcBN increases first and then decreases with the addition of carbon nanotubes. When the mass fraction of carbon nanotubes added is 1.5%, the relative density of PcBN reaches its maximum value of 97.9%, while PcBN has the maximum microhardness and fracture toughness of 3 892 HV and 6.82 MPa·m1/2, respectively. When the mass fraction of carbon nanotubes added is 1.0%, PcBN has the maximum bending strength and wear ratio, which are 584 MPa and 6 873 MPa, respectively. The pull-out and bridging effects of carbon nanotubes improve the mechanical properties of PcBN composites.
Abstract: To improve the machining effect of cemented carbide ball valves, pore-forming agents were introduced into resin diamond wheels. The mechanical properties, microstructures, and grinding performances of the wheels were analyzed, and the effects of hollow glass ball pore-forming agent and plastic ball pore-forming agent on the performances of resin diamond wheels were studied. The results show that the bending strength of the grinding wheel decreases gradually with the increase in the content of pore-forming agent, and the influence of the two pore-forming agents on bending strength is basically the same. The hardness of the grinding wheel also decreases with the increase in pore-forming agent content, but the influence of the hollow glass ball pore-forming agent on the hardness of the grinding wheel is significantly greater than that of the plastic ball. The addition of pore-forming agent significantly improves the sharpness of the grinding wheel. The comprehensive performance of the grinding wheels is best when the volume fraction of hollow glass balls is 15% and the volume fraction of plastic balls is 20%, but the latter has better overall performance than the former.
Abstract: The preparation of functional surfaces is one of the important methods to enhance the therapeutic performance and safety of medical devices. Currently, the fabrication of functional surface microstructures based on laser processing is widely used in the optimizing medical device surface properties. This paper reviews the current research status of functional microstructures for laser processing of medical implantable and surgical devices in terms of cell function regulation, antimicrobial properties, corrosion resistance, frictional properties, and anti-adhesion, etc. It analyzes the advantages and limitations of laser processing of functional surfaces for medical devices and outlines the development prospects of laser processing technology for functional surfaces for medical devices.
Abstract: The nano and micro diamond film coated tools were prepared by the hot wire CVD method.The surface morphology of the film was characterized by field emission scanning electron microscopy. The prepared CVD diamond coated tools were used to end mill the aluminum alloy surface forward and backward at high speed under the condition of dry cutting without lubrication. It studies the characteristics and size of edge burrs during high-speed end milling of aluminum alloy using CVD diamond coated tools. It carries out orthogonal tests on cutting process parameters to explore the cutting parameters and processes with little or no cutting burr when nano-diamonds coated tools are used for high-speed forward milling. The results show that the distribution of burrs on the edges of the workpiece is uneven after milling, and the burrs during forward milling are sparse and small in size. Among them, the average height of burrs on the edges during forward milling with nano diamond coated tools is 32.08 μm, only 46.5% of the forward milling burr height of micrometer diamond coated tools. When nano diamond coated tools are used for high-speed forward milling of flat surfaces, vc has the greatest impact on edge burrs, followed by vf, and ae has the weakest impact. The optimal parameter combination for high-speed milling is ae=4 mm, vf=2 000 mm/min, and vc=400 m/min. The average burr height after milling is 21.29 μm. When the diamond coated tool is used to end mill the aluminum alloy plane, in order to obtain a small burr, the nano diamonds coated tool is selected, the cutting method of forward milling and the corresponding high-speed cutting parameters are adopted.
Abstract: To ensure the uniformity of material removal during surface grinding of screw rotors, a mathematical model for the material removal depth of screw rotors is established, considering the impact of abrasive wear on grinding removal depth. Based on the theory of elastic-plastic deformation and the wear pattern of abrasive particles during grinding, a theoretical model for the removal rate of single abrasive material is established. The wear of abrasive particles is divided into two stages: the rapid wear stage and the stable wear stage. Based on the number of abrasive particles per unit contact area and the rule of abrasive cutting edge, the maximum cutting depth of abrasive particles is calculated by numerical integration and contact pressure, and the mathematical model of macroscopic material removal rate based on abrasive belt wear is established. The model consideres the wear of the sand belt. The maximum error of the predicted value is 9.6%, and the minimum error is 4.1% compared with the experimental value. The experimental data fully verify the effectiveness of the model, and can provide a theoretical basis for ensuring the profile accuracy of the screw rotor.
Abstract: A tool passivation method called the rotating abrasive flow passivation method is proposed as a means to improve tool performance and processing quality. Experiments were conducted to compare the passivation of a carbide end milling cutter by vertical rotating passivation and rotating abrasive flow passivation, revealing the changing law of the tool edge. The results show that the original tool's edge has the smallest radius, characterized by a sharp edge with numerous defects. After vertical rotating passivation, there is slight change in the edge, but defects persist, and the blade shape remains unevenly blunt and circular. In contrast, As the edge after rotating abrasive flow passivation shows the most significant radius change, with some edge defects removed, resulting in a uniformly blunt circular edge shape. The rotating abrasive flow passivation method can not only eliminates edge defects but also presents higher passivation efficiency and a greater rate of change in the cutting edge radius. This method can significantly enhance tool performance, reduce tool wear, and improve machining quality.
Abstract: To explore the dynamic behavior of magnetic abrasive particles in the grinding process of pipe fittings, the grinding process of magnetic abrasive particles was simulated using discrete elements. The changes in motion trajectory and grinding force with the speed of pipe fittings and the processing gap were analyzed. Single abrasive particle ball motion and magnetic particle grinding test were conducted to verify the accuracy of the magnetic field force model and the feasibility of visualizing the particle kinematic behavior. The results show that as the speed of the pipe fittings increases, the magnetic abrasive particles move outside the processing area due to centrifugal force, and the larger the processing gap, the easier they are "thrown away". Before reaching the critical rotation speed, the grinding force decreases, and material removal efficiency increases with the increase in pipe rotation speed. When the pipe rotation speed increases from 400 r/min to the critical rotation speed and the machining gaps are 2 mm and 4 mm, the grinding forces decrease by 5.4 μN and 2.3 μN respectively, leading to a significant improvement in material removal efficiency. However, with a machining gap of 6 mm, the grinding force changes little, and when the rotation speed exceeds the critical rotation speed of 650 r/min, material removal efficiency decreases. Additionally, the material removal amount increases with the increase in pipe rotation speed before reaching the critical rotation speed, but increasing the processing gap reduces the critical rotation speed. The change in material removal amount aligns with the simulation results, validating the reliability of the simulation analysis.
Abstract: The wetting ratio of PDC drill bit matrix has a great influence on its mechanical properties and microstructure. To explore the influences of maceration alloys on the performance of PDC drill bit matrix, two kinds of maceration alloys, Cu-Ni-Mn-Zn and Cu-Ni-Mn-Sn, were used to make the working layer and the non-working layer test blocks with different heights. The differences in wetting ratio and mechanical properties between the working layer and the non-working layer of the matrix bit under different maceration alloys were obtained. At the same time, scanning electron microscopy was used to analyze the microstructure and the element content of the blocks. The results show that the wetting ratio of the test block is a constant value. The wetting ratio of the working layer of the bit matrix is smaller than that of the non-working layer. The microstructures show that the island structure of the maceration alloy in the working layer is large and dispersed, while the island structure in the non-working layer is small and dense. For the same type of test block, the higher the wetting ratio, the higher the density. The hardness of the test block obtained by Cu-Ni-Mn-Sn is higher than that of Cu-Ni-Mn-Zn, but its bending strength and impact toughness are much lower than that of Cu-Ni-Mn-Zn.
Abstract: When the rusted diamond circular saw blade works, there will be some problems such as reduced sawing stability. In response to this phenomenon, models are established through the structural parameters of saw blades with different corrosion degrees, and modal analysis of saw blades with different corrosion degrees is carried out. This analysis takes sawing vibration as a reference index of stability and studies the influence of saw blade corrosion on stability. Experiments verify the accuracy of the results. The results show that the vibration modes of the corroded saw blade more are more than 6 orders different from those of the original saw blade, and the difference in adjacent natural frequencies reduces by 8.56 % in the frequency range of 640 to 1,280 Hz. With the increase of corrosion degree, the saw blade is more prone to resonance. Corrosion at the important position has a great influence on the sawing stability of the saw blade. Reducing surface defects can reduce corrosion and its influence on the sawing stability of the saw blade. This study provides guidance for the practical use and rust prevention technology of diamond circular saw blades.
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