Studies on CVD diamond coating technologies and applications in machining abrasive materials

摘要

Diamond's extreme strength and hardness, good abrasive resistance, low friction coefficient, high thermal conductivity and chemical stability, make it vastly superior to cemented tungsten carbide in the machining of very abrasive, non-ferrousmaterials, such as Al-Si alloys and metal-matrix composite, etc. Diamond films were deposited using a hot-filament-assisted chemical vapor deposition system on tungsten carbide inserts and solid carbide drill (6% Co binder) in this paper. The propertechniques of substrate surface pretreatment and synthesis of diamond films were introduced, which were essential for good film growth and adhesion. A series of cutting tests were carried out by using the diamond-oated tools to cut Al-Si alloys andmetal-matrix composites. The mechanisms of the cutting tool wear out were studied systematically. The results show that the adhesion strength of the diamond films on the substrates is the most important factor for promoting the cutting performance of thetools, and which is depend upon the surface Co content and the surface roughness of the pretreated substrate as well as the CVD diamond coating technologies . The wear mechanism in machining Al-Si alloys and metal-matrix composite is abrasive wear ratherthan chemical wear. The wear rate and cutting force increased dramatically once the diamond was worn away and the tungsten carbide was exposed The availability of multiple cutting edges on diamond-coated tools with complex shape will result in decreasedmanufacturing cost and increased productivity in a broad range of abrasive materials cutting areas. With the development of technologies of CVD, the diamond-coated tools are increasingly being used in automotive industry and will take advantage overpolycrystalline diamond (PCD) tools which have inherent limitations on the fabrication costs, ability to form desired shapes and sizes.