Research On Synthesis And Mechanism Of Boron-doped Polycrystalline Diamond(PDC) Compacts

Compared with ordinary diamond, boron-doped diamond is with a strong antioxidant high resistance, good chemical inertness, impact toughness and good nerpormance characteristics of the semiconductor. It is more widely used in the polvcrystalline diamond compacts, so that polycrystalline diamona compacts using boron-doped diamond with high impact toughness and heat resistance, improving their service life, while contributing to the device using the electric arc process.In this paper, the growth style Φ19mm boron-doped polycrystalline diamonu compacts used for oil drilling were successfully synthesized on domestic cubic press with the method of Co infiltration-catalytic.The wear resistance, impact toughness, heat resistance, flexural strength and other properties of the synthetic samples were tested. The sample microstructure, the melt infiltration behavior and distribution of hand Co in the synthesis process of high-temperature high-pressure, the binding mechanism of polycrystalline diamond compacts,were analysed by meaning of SEM, EDS, XRD, DSC-TG and other analytical tools. Ultimately, the synthesis parameters for stable production were determined.The result showed that the purity of diamond powder was99.89%or more, and the main impurity elements were Fe, Ni, Mn, Si, Mg, Al, Ca, etc. The pretreatment process of the diamond powder was heated in high vacuum furnace for550-600℃,5h. and the integrate surface of WC-16Co matrix was needed sandblasting and ultrasonic cleaning in analytically pure alcohol for10min.The indirect heating assembled structure was self-designed. Conductive steel cap with large diameter thin-walled plug reduced transferring the heat to the direction of both heating hammers, which in order to achieve both ends of the insulation and to avoid burning hammer. Polycrystalline diamond layers were relative placement, between which the2-3salt films were placed, around which used the tube with high purity salt, to ensure that the process of synthesis was in stable pressure and temperature surrounding.The appropriate process parameters were established:(1) Φ460Press:synthesis pressure (cylinder pressure) of101MPa, the heating power of10728W, sintering time for9-11min.(2)Φ500press:synthesis pressure (cylinder pressure) of95MPa, the heating power12028W, sintering time10-12min. The binding mechanism of the PDC was studied. The results show that:(1) The binding of WC-Co substrate and diamond layer was essentially a combination of WC-Co-D.(2) In the polycrystalline diamond layer, diamond particles formed strong D-D and D-Co-D combination of the compact structure, in which cobalt along the grain boundary grid distribution.The relationship between the amount of the boron-doped diamond and the performance of synthesized boron-doped PDC. The results show that when the ratio of boron-doped diamond powder by adding20%～30%, the synthesis of the boron-doped PDC demonstrated best overall performance.