Abstract: Ultrasonic machining, as an effective method to regulate the input external energy, is widely used in surface generation and modification. It can fabricate the microstructure through the precise regulation of interface energy. In order to promote the application of ultrasonic machining for fabricating surface micro-texture and enhancing the part's serviceability, firstly, the current processing methods for surface micro-texture are compared, and the focus is on the comprehensive review of ultrasonic vibration-assisted machining. The characteristics of ultrasonic vibration-assisted turning, milling, grinding, and ultrasonic reinforcement surface micro-texture are analyzed in terms of different vibration forms and ultrasonic dimensions, and the limitations of each process application and the key problems that need to be solved are summarized. Secondly, based on the surface micro-texture fabricated by each process, the serviceability such as friction, wetting, and structural color regulation is analyzed. The analysis mainly elaborates on the friction and wear, friction coefficient, bearing capacity, contact performance, and optical property regulation of surface micro-texture. The results show that surface micro-texture can improve the part’s wear resistance, hydrophobic characteristics, and optical functional characteristics to a certain extent. Finally, considering the issues to be further investigated, the surface micro-texture and serviceability in ultrasonic vibration-assisted machining are discussed for future prospects.
Abstract: A survey on main economic indicators of Chinese superhard industry is conducted to reflect its development. Considering China’s macroeconomic data and the import and export trade of superhard commodities, the development situation of Chinese superhard industry is concluded. It is found that the overall development of the industry is benign, with 23.8% increase in operating revenue and 52.8% increase in operating profit, which are the highest in the past decade. The sales profit margin has reached 23.7, obviously higher than the average one of national enterprises above designated size. As with the imports and exports, the superhard industry has lower increase rates than the national average, more manifesting an internal circulation.
In order to solve the problems of low hardness in the grinding phase material of magnetic abrasive particles prepared by the existing sintering method, the grinding effects on high-hardness and poor magnetic conductivity materials, such as titanium alloys, were found to be poor. Additionally, the hardest diamond material could not be used as the grinding phase to prepare magnetic abrasive particles by the sintering method. In this study, the cBN-Fe magnetic abrasive particles were prepared by sintering with Fe powder as the matrix and cBN powder as the grinding phase. The study focused on using Ti-6A1-4V (TC4) plates as the grinding objects, and the effects of sintering time, heating rate and raw material ratio on the grinding performances of cBN-Fe magnetic abrasive particles were explored using a control variable method. The aim was to determine the optimal preparation process parameters of cBN-Fe magnetic abrasive particles. Taking 45# steel and 202 stainless steel as grinding workpieces, the performance of cBN-Fe magnetic abrasive particles were compared with that of Al2O3-Fe and SiC-Fe magnetic abrasive particles, both prepared by the sintering method. The surface roughness and morphology of the workpieces before and after grinding with three kinds of magnetic abrasive particles were compared. Moreover, the grinding performance and service life of different magnetic abrasive particles were investigated. The results show that the best grinding performances for cBN-Fe magnetic abrasive particles was achieved when using a mass ratio of Fe powder to cBN powder of 3∶1, a sintering temperature of 1150 ℃, a sintering time of 6 h, a holding time of 2 h and a heating rate of 3.19 ℃/min. Furthermore, it is found that the grinding performance of cBN-Fe magnetic abrasive particles is better than that of Al2O3-Fe and SiC-Fe magnetic abrasive particles prepared by sintering. The service life of cBN-Fe magnetic abrasive particles is 1.6 times and 1.3 times longer than that of Al2O3-Fe and SiC-Fe magnetic abrasive particles, respectively.
Abstract: To solve the problem of high sintering temperature of vitrified bond, a novel low- temperature vitrified bond based on Bi2O3-B2O3 glass system was proposed. The effect of nano-SiC and nano-ZrO2 on the phase composition, fluidity and mechanical properties of the vitrified bond were analyzed. Additionally, the effect of adding walnut shell powder as a pore-forming agent on the microstructure of the vitrified bond diamond grinding wheel was explored. A vitrified bond diamond cup grinding wheel based on Bi2O3-B2O3 glass system was prepared, and its grinding performance on monocrystalline silicon wafer was tested. The results show that adding nano-SiC powder leads to the formation of Bi in the vitrified bond and destroys the [BiO4] glass network of vitrified bond. The fluidity of the vitrified bond decreases with the addition of nano-SiC and nano- ZrO2. Furthermore, the fluidity, flexural strength and hardness of the vitrified bond increase as the sintering temperature increases. The flexural strength and the hardness of the vitrified bond reach to their highest value at 560 ℃. With the increase of the content of the pore-forming agent, the amount of large pores in the grinding wheel increases significantly and the size becomes larger. The prepared Bi2O3-B2O3 vitrified bond diamond cup grinding wheel (800 mesh or M10/20) was used to grind monocrystalline silicon wafer under specific conditions (linear speed: 12.56 m/s, workpiece speed: 5.23 m/s, and feed speed: 0.1 μm/s). The grinding ratio reaches 790, and the surface roughness of the monocrystalline silicon wafer is 0.16 μm.
Abstract: To improve the density of polycrystalline diamond, a study was conducted to investigate the changes in diamond powder under different pressure conditions, including initial loading, cold isostatic pressing, and six-sided die pressing. The study focused on the particle size distribution, powder density, and microstructural rearrangement before and after applying pressure to different diamond powder sizes and ratios. The process involved the initial random arrangement of particles, followed by the filling of fine particles into voids and rearrangement at 220 MPa during cold isostatic pressing. Subsequently, under ultra-high pressure, large particles (G20～30) were crushed and gradually filled the voids. The buffering effect of fine particles resulted in fewer fractures in the dual particle size formula (G2～4 and G20～30) compared to the single particle size formula (G20～30), which facilitated higher stacking density of the diamond powder. These findings provide valuable data support for optimizing the particle size and ratio design of diamond powders for the high-temperature high-pressure (HPHT) synthesis of high-performance polycrystalline diamond composite.
Abstract: In order to improve the surface roughness and roundness of the outer cylindrical surface of the spindle after precision grinding, a novel vertical precision grinding method was proposed, and a vertical grinding device was developed. This paper analyzes the influence of cylinder pressure, grit size, and spindle speed on the machining accuracy of shaft parts in the vertical lashing mode. Firstly, the standard L9(34) orthogonal table was designed based on the orthogonal experiment, and the experimental workpiece was processed strictly according to the experimental numbers in the orthogonal table. Then, the data of the processing results were analyzed by the S/N response method and ANOVA variance method, and the optimal combination of process parameters was obtained. Finally, based on the combination of optimized process parameters, the grinding experiment was conducted on the outer cylinder surface of the spindle made of 40Cr material, with the size of 50 mm × 160 mm. The results show that the average material removal rate is 7 μm/h, the average roundness error decreases from 4.12 μm to 1.47 μm, and the surface roughness reduces from 326 nm to 41 nm.
Abstract: The ceramic CBN grinding wheels are widely used in the fields of forming and precision machining, and the research on them is of great significance in improving the machining quality and efficiency of workpieces. The research progress of ceramic CBN grinding wheels in recent years is summarized from various aspects, including CBN abrasive grains, modifier addition, preparation and grinding performances. Additionally, the future development prospects are also discussed. Regarding CBN abrasive grains, the synthesis of CBN single crystal is explored, and the surface treatment of CBN abrasive grains, as well as the treatment methods when adding a strong magnetic field, are introduced. Concerning modifier, the influences of adding pore forming agents, oxides, metal materials and nano-materials on the performances of ceramic CBN grinding wheels are discussed. In the preparation of ceramic CBN grinding wheels, the methods of forming and sintering are described. Moreover, the grinding applications of ceramic CBN grinding wheels on difficult-to-machine materials such as steel, nickel base alloy and titanium alloy are introduced, and the factors affecting the grinding performances of CBN grinding wheels are proposed.
Abstract: To investigate the strengthening effect of calcium sulfate whiskers as a reinforcing filler for resin grinding tablets, experimental splines and resin grinding tablets were prepared by the hot pressing method. The effects of different whisker lengths and mass fraction on the hardness, bending strength and microstructures of the splines were examined, and the grinding performances of the grinding tablets on artificial granite were studied. The results show that when the mass fraction of the whisker is constant, the bending strength of the spline decreases with the increase of the whisker length, while the hardness remains relatively unchanged. One the other hand, when the whisker length keeps constant, the bending strength of the spline shows a trend of increasing and then decreasing with the increase of the whisker mass fraction. Using the grinding tablet to grind artificial granite, the best abrasion resistance of 1.973 min/% and good sharpness of 76.8 cm3/min are achieved when the length of calcium sulfate whisker ranges from 10 to 60 μm and the mass fraction is 10%.
Abstract: Using the layered design concept of fine-grained diamond in the upper layer and the coarse-fine diamond in contact with the cemented carbide layer in the lower layer, the polycrystalline diamond compact (PDC) with multiple diamond layers for drilling was prepared. The differences in microstructure and performance between the single-layer diamond PDC and the multi-layer diamond PDC with different particle sizes were compared. The internal defects and surface morphology of the PDC were characterized using ultrasonic scanning and scanning electron microscopy (SEM), and the heat resistance, impact resistance and wear resistance of the PDC were tested, respectively. The results show that the comprehensive performance of the multi-layer diamond PDC is good. The surface layer is wear-resistant, while the lower layer is more impact-resistant. The PDC exhibits a more balanced combination of heat resistance, impact resistance and wear resistance. Specifically, the fine-grained diamond layer PDC demonstrates higher wear resistance but lower heat and impact resistance; while the coarse-grained diamond layer PDC exhibits better heat and impact resistance, but poor wear resistance.
Abstract: Spherical and whisker-like cobalt particles were doped into the diamond powders to synthesize the PDC compacts under the HPHT conditions, to investigate the effect of their morphology on the properties of PDC. It was found that the two morphologies of cobalt powder have significant differences in physical characteristics, such as microstructure, porosity, magnetic properties, and crystallinity. When they were used to synthesize PDC samples, it was found that there were noticeable differences in interface bonding morphology, abnormal growth of interface WC, impact strength, and wear resistance. PDC synthesized with spherical cobalt powder had better comprehensive performance than PDC synthesized with whisker-like cobalt powder.
Abstract: To enhance the chemical mechanical polishing (CMP) efficiency of flexible display substrates, a polishing slurry based on ferric chloride and oxalic acid was proposed for polishing 304 stainless steel substrates. An orthogonal optimization test was designed to determine the significance order of the influence of abrasive size, abrasive content, oxalic acid content and ferric chloride content on the material removal rate (MRR) and surface roughness (surface arithmetical mean height of area, Sa). The aim was to investigate the effects of ferric chloride and oxalic acid on MRR. An optimized polishing slurry capable of achieving an MRR of over 560 nm/min and a Sa as low as 8 nm after 30 min was obtain. Compared with the conventional polishing slurry, whose MRR is 226.56 nm/min, the novel slurry has doubled its polishing efficiency or more.
Abstract: As the core component of magnetorheological polishing equipment, the key factor determining the success of magnetorheological polishing is whether the excitation device can generate a stable and uniform high gradient magnetic field. The sector permanent magnet was used to design the excitation device of the magnetorheological polishing wheel. The ANSYS Electronics Desktop and other softwares were used to simulate and analyze the excitation device various aspects, including the number of permanent magnets, magnetization modes, arrangement modes, and air gap widths. The magnetic induction lines and magnetic induction intensity distribution under different working conditions were obtained. The results show that when the air gap width is 4 mm, the magnetic induction intensity produced by axial magnetization of a single permanent magnet is the largest, reaching 358.4 mT. Theoretically, a polishing ribbon with a width of 26 mm and a height of 6.0 mm can be formed on the surface of the polishing wheel.
Abstract: The surface of 10 to 30 μm fine-grained diamond was plated with Cr, and the Cr- plated diamond was mixed with Ni-Cr-B-Si powder and placed on the surface of carbon steel. The wear-resistant coating was prepared by using a laser heat source to melt the preset powder on the surface of carbon steel. The results show that the thickened Cr coating on the diamond surface can effectively protect the diamond in the laser high-temperature thermal field, avoids oxidation and graphitization of the diamond at high temperatures, and achieves metallurgical bonding between the diamond and the metal matrix. The metallography, phase and morphology of the coating are analyzed, and it is found that the diamond can significantly improve the cooling rate of the coating, refine the condensing structure, increase the hardness, and enhance the wear resistance of the coating. The wear resistance of the cladding coating with a mass fraction of 20% Cr-plated diamond is 4.6 times higher than that of without diamond, and the corresponding friction coefficient is nearly 50% lower.
Abstract: Cubic press is the primary equipment for diamond production in China. Its key component, the hinge beam, bears continuous alternating loads in the working environment and is prone to failure and breakage. In this paper, a method combining response surface method (RSM) and multi-objective genetic algorithms (MOGA) is proposed to optimize the hinge beam of the new hexagon top press. Firstly, the parametric model of the hinge beam is established, with the dimensions of key parts as design parameters, the maximum stress and displacement as objective functions, and the maximum mass is constrained. Then, the optimal space-filling design (OSF) is used as the design of experiments (DOE) to obtain the design experimental points. The proxy model is obtained by the response surface method. Afterward, the global optimum solution is searched using the MOGA method, and the optimal result of the hinge beam is evaluated. The results show that the stiffness and strength of the optimized hinge beam are effectively improved with a slight increase in weight, and the stress concentration is also significantly reduced, providing a useful reference for the design and development of the press.