Study on Polycrystalline Diamond for Rock Drilling Application Utilizing Shock Consolidation Technique

该项目于1995-79财政年度进行，作为利用冲击固结技术用于凿岩应用的多晶金刚石工业化的可行性研究。凿岩钻头由硬质合金体和多晶金刚石层组成，通过冲击波固结处理而成。最严重的问题是在冲击过程中金刚石层产生裂纹。在金刚石粉中加入硅，金刚石层中产生的宏观和微观裂纹数量大大减少。对于岩石钻头应用，硅的合适含量为3-7%。主要研究结果如下：（1）用高分辨电子显微镜观察了复合片中金刚石颗粒间的晶界。金刚石颗粒由金刚石转变成具有Sp^3化学键的玻碳，并以高密度结合在一起。碳层中分散着极细的碳化硅颗粒。(2)金刚石复合片中的上述界面层具有纳米复合结构，可望起到机械增韧的作用。(3)在金刚石层中观察到几微米尺寸的粗碳化硅和石墨颗粒。这些较大尺寸的颗粒使其机械性能变差，这两种微米尺寸颗粒的产生是由于硅和金刚石颗粒混合不均匀造成的。(4)采用等离子体硅涂层技术，在2-4 μ m金刚石颗粒表面形成了均匀的硅涂层。然而，在涂覆过程中形成粗硅颗粒。该技术的产业化是通过开发硅极均匀包覆金刚石颗粒的方法实现的。

This project has been conducted in Fy 1995-79 as a feasibility study for industrialization of polycrystalline diamond for rock drilling application utilizing shock consolidation technique. The rock drilling bit consists of tungsten carbide alloy body and polycrystalline diamond layr, which formed by shock wave consolidation processing. The most serious problem is crack generation in the diamond layr during shock processing. Number of macro and micro cracks generated in the daiamond layr were decreased drastically by addition of silicon to diamond powder. Suitable contents of silicon is 3-7% for rock drilling bit application. Results of this study is summarized as following ;(1) Grain boundary between diamond particles in the compact was observed by high resolution electron microscope. Diamond particles are bonded with high dense from glassy carbon having Sp^3 chemical bond transformed from diamond. Very fine silicon carbide particles dispersed in the carbon layr.(2) The above boundary layr in the diamond compact has a kind of nano composite structure and it is expected a kind of mechanical toughening effect.(3) A few micron size coarse silicon carbide and graphite particles were observed in the diamond layr. these particles with comparatively large size deteriorate its mechanical property.Generation of both micron size particles is caused by lack of uniform mixing of silicon and diamond particles.(4) A plasma silicon coating technique was applied to form homogeneous coating to diamond particles with 2-4 micron. However coarse silicon particles were formed during the coating process. Industrialization of this technology is realized by development of extreme uniform coating method of silicon to diamond particles.