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

在温度从1300°到1500°，压力在50 Mpa下进行30分钟的HIPed。当温度高于1350℃时，产物几乎没有烧结致密。其最高密度为3.3g/cm^3，最高抗弯强度为750 Mpa。产品抛光表面的显微照片显示其主要由两种物质组成。XRD分析表明，金刚石和碳化硅共存。虽然样品在金刚石热力学亚稳态条件下处理，但没有发现转化为石墨的痕迹。尝试将压实机应用于高压砧。在kawai型高压装置中，将复合材料的立方体作为二级顶砧。由于金刚石/碳化硅复合材料对x射线是透明的，因此通过压砧成功记录了高压装置中NaCl粉末的x射线衍射图，并利用NaCl的状态方程确定了产生的压力。这些砧被证明足够坚硬，可以产生高达30gpa的压力。这种铁砧不仅适用于x射线衍射实验，也适用于压力下的射线照相研究。该研究结果表明了在亚稳压力区处理金刚石的可能性，并有助于在热力学亚稳区处理各种材料。

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.