Comparative experimental study of machining quality of polycrystalline diamond
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摘要: 为解决聚晶金刚石(PCD)表面加工成型和抛光难题,提高PCD加工效率和表面加工质量,采用电火花粗、精放电加工工艺及金刚石砂轮磨削加工工艺对PCD表面进行加工,并采用SEM、EDS、XRD和Raman等观察分析不同加工方式下PCD的表面形貌、表层组织及结构,对不同加工方式下PCD的显微硬度和耐磨性进行测试,考察不同加工方式对PCD表层微结构与力学性能的影响。结果表明:电火花加工后PCD表面会发生金刚石石墨化,而机械磨削加工后则不会;电火花精加工后PCD的显微硬度和耐磨性分别是5 613 HV 10和Q 5.8×104,机械磨削加工后则分别是5 727 HV 10和Q 5.4×104,二者相比变化不大,而电火花粗加工后的则是4 604 HV 10和Q 4.7×104,性能降低明显。同时提出放电加工后PCD表面变质层的概念,并讨论其变质层产生的原因。Abstract: In order to solve the problems of surface forming and polishing of polycrystalline diamond (PCD), and improve PCD processing efficiency and surface quality, the PCD surface was machined by EDM coarse/fine discharge or diamond grinding wheel. The surface morphology, composition and microstructure of PCD were observed and analyzed by SEM, EDS, XRD and Raman spectroscopy. The microhardness and wear resistance of PCD in different processing modes were tested and analyzed. The influences of different processing methods and modes on microstructures and mechanical properties of PCD surface were investigated. Experimental results show that there are graphitizations on the PCD surface after EDM, but none on that after mechanical grinding. The microhardness and wear resistance of EDM precision machined PCD are 5 613 HV 10 and Q 5.8×104while those of mechanically ground PCD are 5 727 HV 10 and Q 5.4×104. There is limited difference between them. As with the EDM rough machining, the values are 4 604 HV 10 and Q 4.7×104, respectively. The performance is significantly reduced.The concept of the surface metamorphic layer of PCD after discharge machining is proposed, the reasons of which are discussed.
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