Performance and Durability Enhancement of Tungsten Carbide Micro-Drills by Ti/ta-C Coatings

Abstract

This paper presents results of the application of Ti/ta-C films to micro drilling operation for machining. Tetrahedral amorphous carbon (ta-C) films were successfully deposited on WC-Co substrates by a filtered cathodic vacuum arc (FCVA) system. The mechanical and flexion properties of Ti/ta-C films were systematically investigated. The experimental results show that the Ti/ta-C coated micro drills have the excellent microhardness, adhesion and flexion properties and represent the optimal coatings for micro drilling applications. The role of the Ti –sublayer on a sintered powder tungsten carbide substrate is not only limited by the adhesion improvement, but it is mainly used to neutralise the grain boundary microcracks on a surface. The results of drilling tests carried out on PCB boards showed that the durability and drilling efficiency of tools coated by Ti/ta-C films are significantly higher than that of uncoated ones.