Diamond-coated tools

Industrial interests have focused on exploiting the special characteristics of diamond coatings as protection for parts which must resist high wear forces or extreme pressures. Such parts are generally fabricated from sintered tungsten carbide. Despite its hardness and toughness, tungsten carbide, even when coated with traditional protective films, does not hold up in certain applications where parts are subjected to very high wear forces. For example, the machining of new, ultrahard materials such as silicon alloys, abrasive materials, synthetic materials or composites can only be performed with tools coated with diamond. The main problem with these tools is the weakness of their cutting edge. When cutting tools are new, their edges are so thin that they become rounded when the tool touches the material. If the tool was coated with diamond, this layer would break. To decrease the risk of breaking, a multilayer of a few mu m of TiC/TiN is applied on the tools before diamond coating. The presence of the interlayer provides a strengthening of both the cutting edge and the hardness gradient between the substrate and the diamond coating, which improves adhesion. To simulate the machining of tools, adhesion tests have been carried out on tungsten carbide samples. (C) 1999 Elsevier Science S.A. All rights reserved.