HIP Sintering of Diamond-Silicon Carbide Composite and its Application to the Carbide Tools

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Diamond and Si mixtures were HIPed under temperatures from 1,300° to 1500° and pressure at 50 Mpa for 30 min. When the temperatures were above 1350℃, the products were hardly sintered compacts. The highest density of 3.3g/cm^3 and the highest bending strength of 750 Mpa were obtained. The photomicrograph of polished surface of the product revealed that it mainly consisted of two kinds of substances. The XRD showed the coexistence of diamond and SiC. No trace of conversion reaction to graphite was seen although the sample was treated under the condition where diamond was thermodynamically metastable.An application of the compact to high pressure anvils was attempted. Cubes of the composites were used as the second stage anvils in Kawai-type high pressure apparatus. Because the diamond/SiC composites are transparent to X-ray, X-ray diffraction patterns of NaCl powder compressed in the high pressure apparatus were successfully recorded through the anvil and thereby generated pressures were determined using the equation of state of NaCl. The anvils were proved to be hard enough for the generation of pressure up to 30 Gpa. The present anvil will be applicable not only to X-ray diffraction experiments but also to radiographic studies under pressure.The result of this study indicates the possibility of the treatment of the diamond in the metastable pressure region and contributes to various materials processings in the thermodynamic metastable region.