Influence of surface preparation on the tool life of cathodic arc PVD coated twist drills

Cutting tool micro-geometry and surface integrity have been critical aspects to be considered for successful application of PVD thin films for cutting tool life enhancement. The present study examines in detail the role of pre-coating surface preparation (micro-blasting and drag finishing) on the tool life of coated cutting tools. TiN coating was deposited on different kinds of pre-treated (Micro blasting, Edge rounding and a combination of both) HSS and WC drills using cylindrical cathodic arc deposition method. They were subsequently characterized for surface roughness (Ra), adhesion strength and machining performance on EN 24 material. Pre-coating surface roughness (developed due to pretreatment) has a major influence on the adhesion strength of the coating. A lower pre-coating surface roughness with optimized edge rounding led to higher adhesion and edge strength which in turn resulted in a notable increase in tool life. Further underlining the importance of the present study, commercial TiN coatings deposited on HSS substrates were tested. The tool life obtained in the current study prolonged the tool life by a factor of 3 in comparison to the commercially available tools in the present day market.