Electron microscopy studies of hard coatings deposited on sharp edges by combined cathodic arc/unbalanced magnetron PVD

Protective wear resistant coatings deposited by PVD can substantially prolong cutting tool lifetime. However, in the edge region, crucial for cutting applications, the coating is strongly curved and can, thus, have different properties and hence performance compared to the flat coating. In our study we focused on TiAlCrYN deposited on SS wedge-shaped samples with different wedge angles (30, 45 and 60°) and with different radii of curvature (2 μm and 100 μm). The films were deposited by combined cathodic arc/unbalanced magnetron PVD process using production scale deposition system. The concentration of the two key elements — Al and Ti — was studied using scanning electron microscopy, combined with energy-dispersive X-ray spectroscopy. The concentration of the ion flux on the edges during the deposition resulted in a decrease of Al/Ti relative concentration in the edge region due to the enhanced preferential sputtering of Al. The change in Al/Ti relative concentration between curved and flat coating (up to −14% at the distance 0.5 μm from the substrate–coating interface) was found to be dependent on the substrate geometry, being more pronounced for geometries with narrower angles and smaller radii of curvature. Additionally, an increase in the coating thickness at the edge was observed, depending again on the substrate geometry.