Optimizing the tribological properties and high-speed drilling performance of a-C:H coatings via nitrogen addition

a-C:H:Nx% coatings with various levels of nitrogen addition ranging from 0 to 29 at.% are deposited on high-speed steel substrates and micro-drills utilizing a Closed Field Unbalanced Magnetron (CFUBM) sputtering technique. The tribological properties of the various coatings are evaluated by performing reciprocating sliding wear tests against an AISI 1045 steel cylinder under an applied load of 100 N. Additionally, the machining performance of the coated micro-drills is investigated by conducting high-speed through-hole drilling tests utilizing Printed Circuit Board (PCB) specimens. The experimental results reveal that the a-C:H:N8% coating possesses the best tribological properties, namely the lowest wear depth, the lowest friction coefficient and the longest lifetime. In addition, it is shown that the a-C:H:N8% coating increases the lifetime of the micro-drill by a factor of three compared to that of an uncoated micro-drill.