A new class of high performance PVD coatings for carbide cutting tools

A number of advanced PVD coating designs based on Ti–Al–N–C–B were evaluated in metalcutting. Monolayer PVD TiN, TiAlN, TiB2 and different variants of TiAlN multilayer coatings were deposited on WC-6 wt.% Co hardmetal inserts. The coatings were applied either by cathodic arc processes or a high-ionization magnetron sputtering process. The coated tools were evaluated in milling of ductile and gray cast irons with and without coolant, and in turning of Inconel 718 and a hypereutectic AlSi alloy. The TiAlN-multilayer coated tools showed the best performance in dry milling applications; the TiAlN-monolayer coated tools performed better under wet milling. The observed results are consistent with a model that takes into consideration the inherent residual stresses within the coating, the stresses during machining, and the bonding strength of the coating layers to the substrate. In Inconel 718 turning, the TiAlN-multilayer coating showed some performance advantage over the TiAlN-monolayer and the TiN/TiCN/TiAlN-multilayer coating particularly at higher speed. In the turning of the aluminum alloy, PVD TiB2 had performance advantage over PVD TiAlN and PVD TiN, which could be correlated with their relative hardness values.