Ambient and elevated temperature properties of TiN, TiAlN and TiSiN PVD films and their impact on the cutting performance of coated carbide tools

The cutting performance of hardmetal inserts coated with PVD TiN, TiAlN and TiSiN films was investigated by innovative analytical-experimental methods, for explaining the effect of coating properties on coated tool wear in milling. Nanoindentation results were evaluated by FEM-supported algorithms for determining the stress-strain constitutive laws of the applied films. According to these laws, the TiSiN films possess enhanced mechanical properties in comparison to TiAlN and TiN coatings. Moreover, in perpendicular impact experiments at various temperatures, the TiSiN films exhibited the best resistance and fatigue behaviour. Additionally, Rockwell C indentations and inclined impact tests were performed to assess qualitatively and quantitatively the films' adhesion on the substrate. These tests revealed a deteriorated adhesion of the TiSiN coating compared to the corresponding ones of the other two films. Finally, by FEM-supported calculations of the material removal process in milling, the mechanical and thermal loadings of the cutting edge were estimated and insight was provided concerning the effect of coating adhesion, mechanical properties and fatigue on the cutting performance. The deterioration of the adhesion of the TiSiN films on the substrate led to a cutting performance reduction in milling compared to the one achieved with TiAlN coated hardmetal inserts.