Papers by Keyword: Polycrystalline Diamond (PCD)

Abstract: Polycrystalline diamond (PCD), is a tool material and widely used in nonferrous metal processing due to its excellent properties, such as high hardness, high wear resistance, high thermal conductivity and low friction coefficient. Considering the friction between the cutter and the workpiece, the heat generated by the elastic-plastic deformation and the heat transfer between the cutter and the workpiece. The finite element analysis software ABAQUS was used to study the effect of different processing parameters on the temperature field distribution and cutting force of the cutter, in the case of welded PCD double-edge end milling copper. The temperature distribution of cutting tools and the changing trend of cutting force with milling parameters was obtained. These technological parameters include the milling rotation speed n, the axial milling depth a_p, and the feed rate f. The simulation results show that the tool temperature increases with the increase of milling depth, feed per revolution and rotation speed. However, the tool temperature has little effect on the tool life. Under the condition of satisfying the work-piece surface quality and machining efficiency, low speed, small milling depth and small feed should be selected as far as possible. Milling depth has a great influence on cutting force. When milling speed is about 2400 r/min, the axial milling depth is 0.3 mm, and the feed is 0.2 mm/r, which can obtain small milling force and lower tool temperature, and further extend the life of PCD tool.

Abstract: With the demand of modern cutting technology for ‘high efficiency, precise, flexibility and green manufacturing’, polycrystalline diamond materials as cutting tools have been widely used in automobile, aerospace and non-metal processing. Electro-spark erosion is one of the most effective ways to machine polycrystalline diamond materials. Single pulse discharge is one of the research foundations of micro-EDM. Using 2 micron granularity polycrystalline diamond as experiment material, the influence of single pulse discharge technology on the removal efficiency of materials was studied, such as pit radius, pit depth and radius-depth ratio, etc. The experimental results show that, with the extension of the pulse duration, the radius of the discharge pit begins to increase rapidly, then slowly increases, and finally to slow down; while the radius of thermal influence zone increases rapidly and then continues to increase slowly. With the extension of pulse duration, the ratio of pit depth to radius changes within the range of 0.05 ~ 0.25, which shows a downward trend basically.

Abstract: In this paper, nanocrystalline diamond with the average grain size of 50nm was prepared under different sintering pressure, temperature and sintering time. The microstructure of the sample was analyzed by SEM, EDS and XRD, and the mechanical properties tested by micro-hardness tester and wear ratio instrument. The results show that the sample sintered under the optimum conditions of oil pressure 87MPa, heating power 4000W and sintering time 120s possessed hardness of 706.41HV and wear ratio of 3280. It indicated that high performance n-PCD sintered from nanodiamond and silicon system can be formed hardly with diamond to diamond bonding but can be formed with diamond to silicon carbide bonding. The poor mechanical properties of the samples were due to the surface adsorption groups and surface graphitization of nanodiamond during high pressure sintering.

Abstract: Some typical kinds of PCD and PCBN compacts are selected to be machined by WEDM, and a series of processing tests are taken. After machining, the surface roughness of cutting section, the processing quality of cobalt-rich interface layer and the edge of superhard material layer are measured by surface profiler and 3D microscope. The results show that processing quality is affected by superhard particle size and concentration greatly, and better processing quality can be obtained after several cutting of WEDM. The minimum sharpening allowance of PCD cutting tools can be controlled within 4~15μm after WEDM, and within 10μm for PCBN BNX20, while BZN6000 needs larger follow-up workload of sharpening.

Abstract: The electrode material plays a very important role in the electric discharge machining, affects the electrical discharge machining efficiency and machining surface quality. Experiment testing and materials analysis as the primary method, affect layer thickness and workpiece surface roughness value as evaluation indexes. PCD cutting tool samples were electrical discharge machined using copper electrodes and graphite electrodes respectively. After machining, the PCD cutting tool samples' surfaces were analyzed by X ray diffraction, the surfaces appearances were observed under the scanning electron microscope, and the surface roughness values were measured by roughness measuring instrument. PCD samples' surface effect layer thickness values and surface roughness values, affect layer distribution structure was statically analyzed in typical EDM process conditions with different electrode materials. Summary electrode material effect on PCD cutting tools in EDM processing. Provides an important experimental basis for designing technics of precision and highly efficient electrical discharge machining PCD cutting tools.

Abstract: PCD is the combination of diamond particles that are sintered together under high temperature and high pressure conditions in the presence of catalytic metal. Due to its superior properties, this material has been widely used for cutting tool. However, magnitude and direction of residual stress obtained from the fabrication process believe to affect the tool performance during application. Furthermore, high temperature generated by the process might also contribute to the structure alteration that finally reduces the strength of PCD. This paper revealed that the residual stress due to EDL is more dominant in tensile direction which is vice versa to the conventional process. Analysis on the spectrum indicated that there is a relationship between the tensile stress value and the composition of graphite on the Raman laser spot location.

Abstract: In this paper, three types of polycrystalline diamond (PCD) tools marked as PCD 030, PCD 010 and PCD 005 (equivalent to 30, 10, and 5μm average grain size of original diamond) were tested, and their wear behaviors was studied. The wear of PCD cutting tools in machining granite bars was invested by a turning process. The experiments were carried out under wet condition. Wear volume was measured by optical microscopy and wear morphology was examined by scanning election microscopy (SEM) and optical microscopy. By comparing the flank face, the experiments results show that the PCD tools with coarse original diamond grain size have long life at three cutting speeds, and the tool life of the three PCD tools decreases with the increase of cutting speed. SEM morphology by secondary electron image analysis indicates that the dominant wear mechanism for PCD 010 and PCD 005 is abrasive wear. While for PCD 030, the abrasive wear mechanism is predominant wear in the machining, occasionally some cleavage wear are also observed.

Abstract: The performance and wear mechanisms of two types of polycrystalline diamond (PCD) cutting tools (marked as PCD 010 and PCD 030) have been investigated in this paper. Continuous turning of round granite bars has been selected as the test method. The Taylor equation has been developed to describe the tool performance. The experimental results indicate that PCD 010 has a greater thermal wear resistance than PCD 030 at high cutting speeds. Scanning electron microscopy (SEM) was used to evaluate wear mechanisms of PCD tools, our results show that the dominant wear mechanisms for PCD 010 is abrasion wear while that for PCD 030 is inter-granular and cleavage wear.

Abstract: Laser polishing is a surface finishing technology for polycrystalline diamond (PCD) tools by removing uneven diamond particles from the diamond film through graphitization, melting and sublimation. While various types of lasers are used for the polishing of PCD tools, pulsed excimer and Nd: YAG lasers are among the most commonly used ones. The current development in laser polishing of PCD tools is reviewed. The reported experimental and modelling studies to improve the process performance are discussed. It reveals that there is a severe dearth of understanding of the process and the associated models for the efficient and effective use of the technology. The direction of future research in laser polishing is finally discussed.

Abstract: The residual stresses on the top surface and side face of the diamond layer of PDC with 25.4mm in diameter and 3.2mm in thickness were measured using Micro-Raman Spectroscopy, thus the stresses and their radial and vertical distributions were obtained. To evaluate the magnitude of the thermal residual microstress in the diamond layer of PDC, the tungsten carbide substrate of PDC was cut by electric discharge machining (EDM), and several Raman measurements were performed on the top surface of the diamond layer. The results show that 1) the stresses in the central part of the diamond surface are compressive, the biggest stress is about 600 MPa, the magnitude of the stress decreases from the center to the edge of PDC, and at about 2mm near the edge of PDC, the stress becomes tensile; 2) the stresses on the side face of the diamond layer are tensile, the maximum is about 580 MPa near the interface. These tensile stresses are thought to be one of the main factors to cause delamination of PDC used for cutting tools; 3) the measured value of the microstress in the diamond layer is 62.5MPa.