Improving mechanical characteristics of an aluminum cutting tool by depositing multilayer amorphous carbon with assistance of plasma immersion ion implantation

An amorphous carbon (a-C:H) film formed by plasma chemical vapor deposition (CVD) combined with plasma immersion ion implantation (PIII) is known to have both high hardness and low friction at the same time. These properties are useful in some cases for cutting tools and sliding parts of machines. In order to improve the machining process for aluminum a cutting tool has been tried to be coated with such a carbonic deposition. There have been many reports about a monolayer a-C:H film for the purpose. On the other hand, we have developed a multilayer a-C:H film, i.e., a hybrid-nano-diamond (HND) film which is made by accumulating a-C:H films of different hardness on a same substrate [1]. We succeeded in improving the mechanical characteristics for cutting aluminum by coating the tool edge with the HND deposition [2]. In this research we studied about a triple-layer a-C:H coating in detail. As a result we found that the hardness of middle layer of multilayer film plays an important role in improving the machining characteristic for aluminum, i.e., that the middle-layer hardness enhances the total hardness of the multilayer film while the surface friction being kept low.