Advanced Materials Research Vol. 797

Abstract: Polycrystalline diamond compacts (PCD) has high hardness, good anti abrasion property. The precision processing technology of PCD is key technology in applications. This article introduces a new combination machining method of polycrystalline diamond (PCD). This machining method combines diffusion machining with free abrasive milling. In the processing polycrystalline diamonds in PCD were removed by the diffusing; binders in PCD were removed by grinding. The two main factors in the processing were described. The results of the experiment indicate that grinding speed, abrasives particle - size are factors of the significant impact.

Abstract: The conventional diamond powders (< 10 μm) are generally produced from crushing the large-sized diamonds synthesized by high-pressure and high-temperature (HPHT) technique, whereas they have many morphological imperfections. In the present work, the hot filament chemical vapour deposition (HFCVD) technique is employed for synthesizing such diamond powders. A great many of micron diamonds are grown simultaneously but independently onto a large-area substrate. First, the seeds with an appropriate density approximately 1.3×10¹⁰ m^-2 are dispersed evenly onto a mirror-polished silicon wafer by using a spin coater machine. Afterwards, the regrowth mechanism of seeds is mainly discussed. The results demonstrate that the unwanted spontaneous and secondary nucleation play a determinant role in keeping well in the morphology of crystals and inhibiting the poly-crystals growth.

Abstract: For ultra-high-speed grinding, the deformation of grinding wheel has a greater impact on the machining accuracy. Finite element method was used to study the radial deformation of the CBN grinding wheel considering centrifugal force and grinding heat. The study shows that the effects of centrifugal force and grinding heat are same magnitude, and the proportion changes with the change of grinding speed and grinding force. By finite element analysis, it is possible to solve the grinding wheel the radial deformation and grinding temperature under different grinding speed and grinding force, and it also provides theoretical support for predicting the machining accuracy, compensating precision and avoiding grinding burn.

Abstract: As one of the important input parameters in the grinding process, the surface topography characteristic of grinding wheel has a decisive impact on the grinding performance. To evaluate and analyze the microscopic surface topography, the premise must be able to detect the microscopic surface topography accurately. Based on the measurement of detection device and its spatial position, the surface topography detection methods have been classified, the principle has been specifically analyzed for some typical detection methods, and the research work done by domestic and foreign scholars in the area. Finally, the current problems and future research direction in the field have been analyzed.

Abstract: This article studies the performance of ceramic grinding wheel made of micro-crystalline alumina in the creep feed grinding of nickel-based superalloy Inconel 718. The effects of abrasives and specific pore volume on the performance of wheels are experimentally discussed. Grinding force and temperature were measured and analyzed during grinding tests. The surface roughness was used to describe the quality of ground surfaces. The results indicate that the micro-crystalline alumina SG abrasive wheel with large specific volume has good grinding properties when grinding Inconel 718 in comparison of the wheels with PA abrasives or SG abrasives of small specific pore volume.

Abstract: Based on the orderly distribution alumina bubbles in working layer the porous composite-bonded CBN wheels were fabricated and grinding experiments of nickel-based alloy were carried out in comparison of the vitrified counterpart. Results show that the grinding force decreases and increases respectively with the increasing wheel velocity and depth of cut. The specific grinding energy reduces graduately from 465 to 93 J/mm³ when the maximun underformed chip thickness increases from 0.4 to 1.7 μm. Compared to the vitrified CBN wheel, the grinding forces, temperatures and specific grinding energy of the porous composite-bonded CBN wheel are always lower than that of the vitrified one. Its attributed to the graphite lubricating and alumina bubbles pore-forming effects. The larger chip storage space, sharper grit edge and less adhesion on the wheel surface surpport the advantages of the porous CBN wheel.

Abstract: In the grinding operation, grinding wheels are deformed by grinding forces, so that residual stock removal of the workpiece takes place. Since this residual stock removal of the workpiece causes low machining efficiency and deterioration of machining accuracy, high hardness grinding wheels may be selected in order to obtain high machining efficiency and/or high quality machining accuracy. On the other hand, when grinding operations used by low hardness grinding wheels are carried out, it is well known that ground surface roughness is smaller than in case of higher hardness grinding wheels. From such a viewpoint, this study aims to investigate experimentally the effect of the contact stiffness of grinding wheel on the ground surface roughness and the residual stock removal of the workpiece. Grinding operations were carried out using three grinding wheels which are different hardness type, and ground surface roughness and residual stock removal of the workpiece were measured. The contact stiffness of grinding wheel was calculated by a support stiffness of single abrasive grain and a contact area between grinding wheel and workpiece. Comparing the contact stiffness of grinding wheel with the ground surface roughness and the residual stock removal of the workpiece, it was known that ground surface roughness increases and residual stock removal of workpiece decreases with increaseing the contact stiffness of grinding wheel. From these results, since elastic deformation of the grinding wheel changed depending on the suppot stiffness of single abrasive grain, it was clarified that the ground surface roughness and the residual stock removal of the workpiece were changed by the contact stiffness of grinding wheel.

Abstract: In order to improve the efficiency of ultra-precision processing, the self-sharpening fine super-hard abrasive tool is presented to reduce or eliminate the surface and subsurface defects and improve the process efficiency. In the study of efficient experimental research of self-sharpening fine super-hard abrasive tool, base on single factor experiments such as additives composition, grinding speed, grinding pressure and processing liquid. The results showed that the wear rate of the self-sharpening fine super-hard abrasive tool can reach appropriate rate when the additive concentration 30wt%, grinding pressure 45N, grinding speed 60rpm and processing liquid 1wt%.

Abstract: Heat pipe grinding wheel (HPGW) is a new grinding wheel which can improves heat transfer enhancement with the contact zone by means of the heat pipe technology. In this paper, the heat transfer principle and making process about heat pipe grinding wheel is illustrated. After then, grinding experiments with HPGW were carried out to verify the effect of heat transfer in the grinding titanium alloy Ti-6Al-4V. Results showed that using HPGW could significantly reduce grinding temperature and prevent the burnout in the grinding.

Abstract: According to the limited measurement range of specific coordinate measuring machine (CMM), a reverse test method was put forward, and an auxiliary measuring equipment for tiny hole was developed. A measuring method for tiny hole was formulated, which using gauge head trigger signal of CMM as the test signal. The principle which was the tiny hole moving but not moving gauge head was used and the corresponding measurement software was designed so that the small measurement range was expanded. The measurement precision influence factors were analyzed and the measurement scheme was optimized. The results indicate that: then the measurement range of tiny hole is expanded to 1.0mm based on the combination of auxiliary equipment and CMM. The precision error is 0.004 mm which meets the measurement requirements.