Diamond Coatings on Cutting Tools

对于加工许多难以加工的材料，如高硅铝硅合金和复合材料，使用高压(50 kbars) -高温（1500 C） （HP-HT）工艺制成的多晶金刚石工具。由于加工和精加工成本高，并且需要替代刀具材料，这些刀具价格昂贵。相比之下，低压化学气相沉积（CVD）金刚石合成相对简单和便宜，因此提供了生产金刚石涂层切削工具的潜力。该项目的主要目标是通过四种活性CVD金刚石合成技术，即燃烧合成、微波CVD、热丝CVD、和激光辅助CVD，重点是前两种。每种活化CVD金刚石涂层工艺的条件将基于良好的冶金涂层，其厚度和形貌来优化给定的刀具材料。这些工具将通过光学和扫描电子显微镜以及拉曼光谱进行表征。它们将以切削速度和切削长度为变量，在加工不同的工作材料时进行评估。将考虑各种表面处理，包括表面蚀刻，不同的表面处理条件，基材的表面层间涂层。将金刚石涂层刀具的刀具磨损机制、刀具寿命和工件材料的光洁度与未涂层刀具和/或聚晶金刚石刀具进行比较。

For machining many difficult-to-machine materials, such as high silicon aluminum-silicon alloys and composites, polycrystalline diamond tools made by the high pressure (50 kbars) -- high temperature (1500 C) (HP-HT) process are used. These tools are expensive because of the high cost of processing and finishing and need exists for an alternate tool material. The low pressure chemical vapor desposition (CVD) diamond synthesis, in contrast, is relatively simple and inexpensive, thus offering a potential for producing diamond coated cutting tools. The primary goal of this project is to develop the science base for strongly adherent diamond coatings on various cutting tool materials, including, cemented carbide (coated and uncoated) and ceramics (silicon nitride and SiAION) by the four activated CVD diamond synthesis techniques, namely, combustion synthesis, microwave CVD, hot filament CVD, and laser assisted CVD with emphasis on the first two. The conditions for each of the activated CVD diamond coating processes will be optimized for a given tool material based on good metallurgical coating, its thickness and morphology. These tools will be characterized by optical and scanning electron microscopy, and Raman spectroscopy. They will be evaluated in machining different work materials with the cutting speed and length of cut as variables. Various surface treatments including etching of the surface, different surface finishing conditions, surface interlayer coatings for the substrate will be considered. Tool wear mechanisms, tool life, and finish of the work material with diamond coated tools will be compared with that of the uncoated tools and/or polycrystalline diamond tools.