UnitTwo-汉英双语翻译版..doc

Unit Two Advances in the development of ultrahard cutting tool materials Introduction Natural diamonds have been used as defined edge cutting tools for hundreds of years.　Following the introduction of synthetic diamond grit in the 1950s, the 1970s yielded a second diamond-based cutting tool material, also based on high pressure synthesis technology, namely polycrystalline diamond (PCD). Until the late 1980s these two products were the only commercial diamond materials available for the manufacture of defined edge cutting tools. Tooling based on these natural and synthetic diamond materials clearly complement each other with little or no overlap the PCD suited to general purpose machining operations and all but the most demanding and specialised finishing operations, such as in the production of aluminium mirrors, where single-point natural diamond cutting tools are essential in order to achieve the required surface finish and dimensional tolerances. 1. 引言 天然金刚石作为切削刀具已有几百年的历史了。在本世纪五十年代人工合成金刚石磨粒的出现之后，七十年代制造出了第二类金刚石基的切削刀具，即采用高压合成技术制备出的聚晶金刚石（PCD）。直到八十年代末，这两类金刚石还是仅有的应用于制造有特定刃口的切削刀具的切削刀具的商用金刚石材料。天然和人工合成的金刚石材料的刀具加工之间相互交叉很少，不能相互补充利用。PCD适用于所有通常的机械加工，但对一些有特殊要求的抛光工艺，如制备Al2O3镜面时，往往不能满足要求，在这种场合下只有使用单晶天然金刚石刀具才能达到所需要的表面光洁度的尺寸公差。 Today, more options are available due to the arrival on the scene of new ultrahard cutting tool products. These include large synthetic single-crystal diamond, polycrystalline diamond coating by chemical vapour deposition, often referred to as thin film, and free-standing, often referred to as thick film. Where do these products fit into the overall diamond tooling picture? These are early days, but certain trends are evident. 如今，随着新型超硬刀具产品的出现，可以选择的余地也更大了。这些新产品包括：合成金刚石大颗粒单晶、由化学气相沉积制备的聚晶金刚石薄膜和无衬底的金刚石厚膜。这些产品在整个金刚石刀具材料尚处于发展的初期阶段，但从中可以明显看出今后的发展趋势。 This paper describes the variety of options that now faces the user of diamond cutting tool materials and seeks to clarify their areas of application. The following nomenclature is used: PCD - synthesised (high