TOOL WEAR OF SUPERHARD CERAMIC COATED TOOLS IN DRILLING OF CFRP/TI STACKS

This paper aims to investigate the effectiveness of several superhard ceramic coatings on carbide drills when drilling carbon fiber reinforced plastics (CFRP) composite/Ti-6Al-4V alloy (titanium or Ti) stacks. The drilling experiments of CFRP/Ti stack are conducted with diamond-like coating (DLC) coated, alternating layers of the nanocomposite of AlCrN & Si3N4 and TiN or (AlCrSi/TON coated, and uncoated tungsten carbide drills. Tool wear evolution of each drill is measured qualitatively as well as quantitatively using the scanning electron and confocal laser scanning microscopes (CLSM) by interrupting after making certain numbers of hole. Based on our drilling experiments, the performance of each coating when drilling CFRP/Ti stack are discussed. Among these coated and uncoated drills, uncoated and DLC coated drills failed before making 5 holes while (AlCrSi/TON coated drills performed the best making more than 80 holes. The DLC coating, despite of high hardness of DLC coating, does not provide any significant protection especially when drilling Ti layer.