George P. Grab

Comparison of the steel-milling performance of carbide inserts with MTCVD and PVD TiCN coatings

This study is a comparison of the performance of PVD-TiN-, PVD-TiCN-, and MTCVD-TiCN-coated milling inserts. It is shown that metal-cutting conditions and insert geometry dictate the optimum performance for each type of coating. The importance of compressive residual stress in PVD coatings in delaying the initiation of damaging cracks at the edge is evident in these results. Conditions in which thermal shock is not severe, such as dry milling or lower-speed wet milling and the use of sharp cutting edges, are shown to maximize the performance of the PVD-TiCN-coated tool. On the other hand, the MTCVD coating necessitates a strong cutting edge geometry on a tough substrate to obtain good performance, in wet milling. Practical productivity implications, including environmental concerns, are considered.