CVD diamond coating technologies and application in cutting abrasive materials

The extreme strength and hardness, good abrasive resistance, low friction c oefficient, high thermal conductivity and chemical stability have made diam ond vastly superior to cemented tungsten carbide in the machining of very a brasive, non-ferrous materials, such as AI-Si alloys and metal-matrix compo site. In this study, diamond films were deposited using a hot-filament-assi sted chemical vapor deposition system on tungsten carbide inserts and solid carbide drill (6% Co binder). The proper techniques of substrate surface p retreatment and synthesis of diamond films were introduced, which were esse ntial for good film growth and adhesion. A series of cutting tests were car ried out using the diamond-coated tools to cut AI-Si alloys and metal-matri x composites. The mechanisms of the cutting tool wear out were studied syst ematically. The results show that the adhesion strength of the diamond film s on the substrates is the most important factor for promoting the cutting performance of the tools and is dependent upon the surface Co content, the surface roughness of the pretreated substrate and the CVD diamond coating t echnologies. The wear mechanism in machining Al-Si alloys and metal-matrix composite is abrasive wear rather than chemical wear. The wear rate and cut ting force increased dramatically once the diamond was worn away and the tu ngsten carbide was exposed. The availability of multiple cutting edges on d iamond-coated tools with complex shape will result in decreased manufacturi ng cost and increased productivity in a broad range of abrasive materials c utting areas.