Comparative tool wear study on drilling of CFRP/Ti stacks using TiAlN and AlTiSiN coated drill bits

Drilling of Carbon Fiber Reinforced Plastic (CFRP) and Ti-6Al-4V stacks presents significant challenges due to their contrasting material properties, leading to tool wear, delamination, and increased thrust force. This study evaluates the drilling performance of TiAlN and AlTiSiN-coated solid carbide tools under dry cutting conditions. Experiments were conducted at cutting speeds between 15 and 30 m/min and feed rates from 0.025 to 0.1 mm/rev. The effects of speed and feed on the thrust force variation of CFRP and Ti-6Al-4V were studied using an online dynamometer, and chip morphology was analyzed to assess machining efficiency. The results showed that higher cutting speeds and feed rates contributed to improved chip fragmentation and surface finish, particularly in stack drilling. TiAlN-coated drills exhibited superior wear resistance, demonstrating reduced flank wear over 100 holes. However, AlTiSiN-coated drills outperformed TiAlN in terms of lower burr formation and improved surface finish, which can be attributed to their enhanced thermal resistance and higher oxidation stability. TiAlN coated tool provided a 15% lower thrust force in CFRP and 10% reduction in titanium compared to AlTiSiN at 30 m/min & 0.075 mm/rev. AlTiSiN achieved a 20% lower maximum burr height relative to TiAlN under identical conditions. These findings suggest that TiAlN-coated drills provide longer tool life, whereas AlTiSiN-coated drills offer superior hole quality in terms of reduced burr formation, making them a preferred choice for applications where surface finish is critical.