Diffusion across PVD coated cermet tool/workpiece interface

According to the limitations in improving the mechanical properties of cermet cutting tools, further possibilities seem to exist to improve tool performance on the basis of reducing thermo-chemical wear, which is a result of diffusion process. This is possible by choosing a favourable combination between the substratum and PVD coating in which the process of diffusion wear is slowed down as much as possible or is not detrimental for the mechanical properties of the substratum — the basic material of the tool. In this work the diffusion across the coated cermet tools/workpiece interface has been studied. Recently, the diffusion couple method was used to study the thermochemical wear of Ti(C, N)-based cermets coated with TiN (PVD) and TiZrN (PVD) coatings as a diffusion barrier. The result of the diffusion process of the element from the tool and the workpiece through the interface is a change in the composition of the boundary layers of the tool, which increases the possibility of mechanical damage of the cutting edge. In the case of cutting with coated tools, these phenomena occur after a longer time of service in comparison to uncoated ones.